<?xml version="1.0" encoding="US-ASCII"?>
<!--XBRL Document Created with Wdesk from Workiva-->
<!-- -->
<linkbase xsi:schemaLocation="http://www.xbrl.org/2003/linkbase http://www.xbrl.org/2003/xbrl-linkbase-2003-12-31.xsd" xmlns="http://www.xbrl.org/2003/linkbase" xmlns:xbrldt="http://xbrl.org/2005/xbrldt" xmlns:xlink="http://www.w3.org/1999/xlink" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance">
  <roleRef roleURI="http://www.astrotechcorp.com/role/AccruedLiabilitiesAndOtherLiabilities" xlink:href="astc-20160630.xsd#AccruedLiabilitiesAndOtherLiabilities" xlink:type="simple" />
  <roleRef roleURI="http://www.astrotechcorp.com/role/AccruedLiabilitiesAndOtherLiabilitiesDetails" xlink:href="astc-20160630.xsd#AccruedLiabilitiesAndOtherLiabilitiesDetails" xlink:type="simple" />
  <roleRef roleURI="http://www.astrotechcorp.com/role/AccruedLiabilitiesAndOtherLiabilitiesTables" xlink:href="astc-20160630.xsd#AccruedLiabilitiesAndOtherLiabilitiesTables" xlink:type="simple" />
  <roleRef roleURI="http://www.astrotechcorp.com/role/BusinessRiskAndCreditRiskConcentrationInvolvingCash" xlink:href="astc-20160630.xsd#BusinessRiskAndCreditRiskConcentrationInvolvingCash" xlink:type="simple" />
  <roleRef roleURI="http://www.astrotechcorp.com/role/BusinessRiskAndCreditRiskConcentrationInvolvingCashDetailTextuals" xlink:href="astc-20160630.xsd#BusinessRiskAndCreditRiskConcentrationInvolvingCashDetailTextuals" xlink:type="simple" />
  <roleRef roleURI="http://www.astrotechcorp.com/role/BusinessRiskAndCreditRiskConcentrationInvolvingCashDetails" xlink:href="astc-20160630.xsd#BusinessRiskAndCreditRiskConcentrationInvolvingCashDetails" xlink:type="simple" />
  <roleRef roleURI="http://www.astrotechcorp.com/role/BusinessRiskAndCreditRiskConcentrationInvolvingCashTables" xlink:href="astc-20160630.xsd#BusinessRiskAndCreditRiskConcentrationInvolvingCashTables" xlink:type="simple" />
  <roleRef roleURI="http://www.astrotechcorp.com/role/CommitmentsAndContingencies" xlink:href="astc-20160630.xsd#CommitmentsAndContingencies" xlink:type="simple" />
  <roleRef roleURI="http://www.astrotechcorp.com/role/CommitmentsAndContingenciesDetailTextuals" xlink:href="astc-20160630.xsd#CommitmentsAndContingenciesDetailTextuals" xlink:type="simple" />
  <roleRef roleURI="http://www.astrotechcorp.com/role/CommitmentsAndContingenciesDetails" xlink:href="astc-20160630.xsd#CommitmentsAndContingenciesDetails" xlink:type="simple" />
  <roleRef roleURI="http://www.astrotechcorp.com/role/CommitmentsAndContingenciesTables" xlink:href="astc-20160630.xsd#CommitmentsAndContingenciesTables" xlink:type="simple" />
  <roleRef roleURI="http://www.astrotechcorp.com/role/CommonStockIncentiveStockPurchasePlansAndOtherCompensationPlans" xlink:href="astc-20160630.xsd#CommonStockIncentiveStockPurchasePlansAndOtherCompensationPlans" xlink:type="simple" />
  <roleRef roleURI="http://www.astrotechcorp.com/role/CommonStockIncentiveStockPurchasePlansAndOtherCompensationPlansDetailTextuals" xlink:href="astc-20160630.xsd#CommonStockIncentiveStockPurchasePlansAndOtherCompensationPlansDetailTextuals" xlink:type="simple" />
  <roleRef roleURI="http://www.astrotechcorp.com/role/CommonStockIncentiveStockPurchasePlansAndOtherCompensationPlansDetails" xlink:href="astc-20160630.xsd#CommonStockIncentiveStockPurchasePlansAndOtherCompensationPlansDetails" xlink:type="simple" />
  <roleRef roleURI="http://www.astrotechcorp.com/role/CommonStockIncentiveStockPurchasePlansAndOtherCompensationPlansDetails1" xlink:href="astc-20160630.xsd#CommonStockIncentiveStockPurchasePlansAndOtherCompensationPlansDetails1" xlink:type="simple" />
  <roleRef roleURI="http://www.astrotechcorp.com/role/CommonStockIncentiveStockPurchasePlansAndOtherCompensationPlansDetails2" xlink:href="astc-20160630.xsd#CommonStockIncentiveStockPurchasePlansAndOtherCompensationPlansDetails2" xlink:type="simple" />
  <roleRef roleURI="http://www.astrotechcorp.com/role/CommonStockIncentiveStockPurchasePlansAndOtherCompensationPlansDetails3" xlink:href="astc-20160630.xsd#CommonStockIncentiveStockPurchasePlansAndOtherCompensationPlansDetails3" xlink:type="simple" />
  <roleRef roleURI="http://www.astrotechcorp.com/role/CommonStockIncentiveStockPurchasePlansAndOtherCompensationPlansTables" xlink:href="astc-20160630.xsd#CommonStockIncentiveStockPurchasePlansAndOtherCompensationPlansTables" xlink:type="simple" />
  <roleRef roleURI="http://www.astrotechcorp.com/role/ConsolidatedBalanceSheets" xlink:href="astc-20160630.xsd#ConsolidatedBalanceSheets" xlink:type="simple" />
  <roleRef roleURI="http://www.astrotechcorp.com/role/ConsolidatedBalanceSheetsParentheticals" xlink:href="astc-20160630.xsd#ConsolidatedBalanceSheetsParentheticals" xlink:type="simple" />
  <roleRef roleURI="http://www.astrotechcorp.com/role/ConsolidatedStatementOfChangesInStockholdersEquity" xlink:href="astc-20160630.xsd#ConsolidatedStatementOfChangesInStockholdersEquity" xlink:type="simple" />
  <roleRef roleURI="http://www.astrotechcorp.com/role/ConsolidatedStatementsOfCashFlows" xlink:href="astc-20160630.xsd#ConsolidatedStatementsOfCashFlows" xlink:type="simple" />
  <roleRef roleURI="http://www.astrotechcorp.com/role/ConsolidatedStatementsOfOperationsAndComprehensiveIncomeLoss" xlink:href="astc-20160630.xsd#ConsolidatedStatementsOfOperationsAndComprehensiveIncomeLoss" xlink:type="simple" />
  <roleRef roleURI="http://www.astrotechcorp.com/role/ConsolidatedStatementsOfOperationsAndComprehensiveIncomeLossParenthetical" xlink:href="astc-20160630.xsd#ConsolidatedStatementsOfOperationsAndComprehensiveIncomeLossParenthetical" xlink:type="simple" />
  <roleRef roleURI="http://www.astrotechcorp.com/role/Debt" xlink:href="astc-20160630.xsd#Debt" xlink:type="simple" />
  <roleRef roleURI="http://www.astrotechcorp.com/role/DebtDetailTextuals" xlink:href="astc-20160630.xsd#DebtDetailTextuals" xlink:type="simple" />
  <roleRef roleURI="http://www.astrotechcorp.com/role/DescriptionOfCompanyAndOperatingEnvironment" xlink:href="astc-20160630.xsd#DescriptionOfCompanyAndOperatingEnvironment" xlink:type="simple" />
  <roleRef roleURI="http://www.astrotechcorp.com/role/DescriptionOfCompanyAndOperatingEnvironmentDetails" xlink:href="astc-20160630.xsd#DescriptionOfCompanyAndOperatingEnvironmentDetails" xlink:type="simple" />
  <roleRef roleURI="http://www.astrotechcorp.com/role/DiscontinuedOperationsGainOnSaleOfAsoBusinessUnit" xlink:href="astc-20160630.xsd#DiscontinuedOperationsGainOnSaleOfAsoBusinessUnit" xlink:type="simple" />
  <roleRef roleURI="http://www.astrotechcorp.com/role/DiscontinuedOperationsGainOnSaleOfAsoBusinessUnitDetailTextuals" xlink:href="astc-20160630.xsd#DiscontinuedOperationsGainOnSaleOfAsoBusinessUnitDetailTextuals" xlink:type="simple" />
  <roleRef roleURI="http://www.astrotechcorp.com/role/DiscontinuedOperationsGainOnSaleOfAsoBusinessUnitDetails" xlink:href="astc-20160630.xsd#DiscontinuedOperationsGainOnSaleOfAsoBusinessUnitDetails" xlink:type="simple" />
  <roleRef roleURI="http://www.astrotechcorp.com/role/DiscontinuedOperationsGainOnSaleOfAsoBusinessUnitDetails2" xlink:href="astc-20160630.xsd#DiscontinuedOperationsGainOnSaleOfAsoBusinessUnitDetails2" xlink:type="simple" />
  <roleRef roleURI="http://www.astrotechcorp.com/role/DiscontinuedOperationsGainOnSaleOfAsoBusinessUnitTables" xlink:href="astc-20160630.xsd#DiscontinuedOperationsGainOnSaleOfAsoBusinessUnitTables" xlink:type="simple" />
  <roleRef roleURI="http://www.astrotechcorp.com/role/DocumentAndEntityInformation" xlink:href="astc-20160630.xsd#DocumentAndEntityInformation" xlink:type="simple" />
  <roleRef roleURI="http://www.astrotechcorp.com/role/EmployeeBenefitPlans" xlink:href="astc-20160630.xsd#EmployeeBenefitPlans" xlink:type="simple" />
  <roleRef roleURI="http://www.astrotechcorp.com/role/EmployeeBenefitPlansDetailTextuals" xlink:href="astc-20160630.xsd#EmployeeBenefitPlansDetailTextuals" xlink:type="simple" />
  <roleRef roleURI="http://www.astrotechcorp.com/role/FairValueOfFinancialInstruments" xlink:href="astc-20160630.xsd#FairValueOfFinancialInstruments" xlink:type="simple" />
  <roleRef roleURI="http://www.astrotechcorp.com/role/FairValueOfFinancialInstrumentsDetails" xlink:href="astc-20160630.xsd#FairValueOfFinancialInstrumentsDetails" xlink:type="simple" />
  <roleRef roleURI="http://www.astrotechcorp.com/role/FairValueOfFinancialInstrumentsTables" xlink:href="astc-20160630.xsd#FairValueOfFinancialInstrumentsTables" xlink:type="simple" />
  <roleRef roleURI="http://www.astrotechcorp.com/role/IncomeTaxes" xlink:href="astc-20160630.xsd#IncomeTaxes" xlink:type="simple" />
  <roleRef roleURI="http://www.astrotechcorp.com/role/IncomeTaxesDetailTextuals" xlink:href="astc-20160630.xsd#IncomeTaxesDetailTextuals" xlink:type="simple" />
  <roleRef roleURI="http://www.astrotechcorp.com/role/IncomeTaxesDetails" xlink:href="astc-20160630.xsd#IncomeTaxesDetails" xlink:type="simple" />
  <roleRef roleURI="http://www.astrotechcorp.com/role/IncomeTaxesDetails2" xlink:href="astc-20160630.xsd#IncomeTaxesDetails2" xlink:type="simple" />
  <roleRef roleURI="http://www.astrotechcorp.com/role/IncomeTaxesDetails3" xlink:href="astc-20160630.xsd#IncomeTaxesDetails3" xlink:type="simple" />
  <roleRef roleURI="http://www.astrotechcorp.com/role/IncomeTaxesDetails4" xlink:href="astc-20160630.xsd#IncomeTaxesDetails4" xlink:type="simple" />
  <roleRef roleURI="http://www.astrotechcorp.com/role/IncomeTaxesIncomeTaxesDetails1" xlink:href="astc-20160630.xsd#IncomeTaxesIncomeTaxesDetails1" xlink:type="simple" />
  <roleRef roleURI="http://www.astrotechcorp.com/role/IncomeTaxesTables" xlink:href="astc-20160630.xsd#IncomeTaxesTables" xlink:type="simple" />
  <roleRef roleURI="http://www.astrotechcorp.com/role/Investments" xlink:href="astc-20160630.xsd#Investments" xlink:type="simple" />
  <roleRef roleURI="http://www.astrotechcorp.com/role/InvestmentsAvailableForSaleSecuritiesDetails" xlink:href="astc-20160630.xsd#InvestmentsAvailableForSaleSecuritiesDetails" xlink:type="simple" />
  <roleRef roleURI="http://www.astrotechcorp.com/role/InvestmentsCarryingValueDetails" xlink:href="astc-20160630.xsd#InvestmentsCarryingValueDetails" xlink:type="simple" />
  <roleRef roleURI="http://www.astrotechcorp.com/role/InvestmentsHeldToMaturitySecuritiesDetails" xlink:href="astc-20160630.xsd#InvestmentsHeldToMaturitySecuritiesDetails" xlink:type="simple" />
  <roleRef roleURI="http://www.astrotechcorp.com/role/InvestmentsTables" xlink:href="astc-20160630.xsd#InvestmentsTables" xlink:type="simple" />
  <roleRef roleURI="http://www.astrotechcorp.com/role/NetLossIncomePerShare" xlink:href="astc-20160630.xsd#NetLossIncomePerShare" xlink:type="simple" />
  <roleRef roleURI="http://www.astrotechcorp.com/role/NetLossIncomePerShareDetailTextuals" xlink:href="astc-20160630.xsd#NetLossIncomePerShareDetailTextuals" xlink:type="simple" />
  <roleRef roleURI="http://www.astrotechcorp.com/role/NetLossIncomePerShareDetails" xlink:href="astc-20160630.xsd#NetLossIncomePerShareDetails" xlink:type="simple" />
  <roleRef roleURI="http://www.astrotechcorp.com/role/NetLossIncomePerShareTables" xlink:href="astc-20160630.xsd#NetLossIncomePerShareTables" xlink:type="simple" />
  <roleRef roleURI="http://www.astrotechcorp.com/role/NoncontrollingInterest" xlink:href="astc-20160630.xsd#NoncontrollingInterest" xlink:type="simple" />
  <roleRef roleURI="http://www.astrotechcorp.com/role/NoncontrollingInterestDetailTextuals" xlink:href="astc-20160630.xsd#NoncontrollingInterestDetailTextuals" xlink:type="simple" />
  <roleRef roleURI="http://www.astrotechcorp.com/role/NoncontrollingInterestDetails" xlink:href="astc-20160630.xsd#NoncontrollingInterestDetails" xlink:type="simple" />
  <roleRef roleURI="http://www.astrotechcorp.com/role/NoncontrollingInterestInterestHeldDetails" xlink:href="astc-20160630.xsd#NoncontrollingInterestInterestHeldDetails" xlink:type="simple" />
  <roleRef roleURI="http://www.astrotechcorp.com/role/NoncontrollingInterestTables" xlink:href="astc-20160630.xsd#NoncontrollingInterestTables" xlink:type="simple" />
  <roleRef roleURI="http://www.astrotechcorp.com/role/PropertyAndEquipment" xlink:href="astc-20160630.xsd#PropertyAndEquipment" xlink:type="simple" />
  <roleRef roleURI="http://www.astrotechcorp.com/role/PropertyAndEquipmentDetailTextuals" xlink:href="astc-20160630.xsd#PropertyAndEquipmentDetailTextuals" xlink:type="simple" />
  <roleRef roleURI="http://www.astrotechcorp.com/role/PropertyAndEquipmentDetails" xlink:href="astc-20160630.xsd#PropertyAndEquipmentDetails" xlink:type="simple" />
  <roleRef roleURI="http://www.astrotechcorp.com/role/PropertyAndEquipmentTables" xlink:href="astc-20160630.xsd#PropertyAndEquipmentTables" xlink:type="simple" />
  <roleRef roleURI="http://www.astrotechcorp.com/role/SegmentInformation" xlink:href="astc-20160630.xsd#SegmentInformation" xlink:type="simple" />
  <roleRef roleURI="http://www.astrotechcorp.com/role/SegmentInformationDetailTextuals" xlink:href="astc-20160630.xsd#SegmentInformationDetailTextuals" xlink:type="simple" />
  <roleRef roleURI="http://www.astrotechcorp.com/role/SegmentInformationDetails" xlink:href="astc-20160630.xsd#SegmentInformationDetails" xlink:type="simple" />
  <roleRef roleURI="http://www.astrotechcorp.com/role/SegmentInformationTables" xlink:href="astc-20160630.xsd#SegmentInformationTables" xlink:type="simple" />
  <roleRef roleURI="http://www.astrotechcorp.com/role/StateOfTexasFunding" xlink:href="astc-20160630.xsd#StateOfTexasFunding" xlink:type="simple" />
  <roleRef roleURI="http://www.astrotechcorp.com/role/StateOfTexasFundingDetailTextuals" xlink:href="astc-20160630.xsd#StateOfTexasFundingDetailTextuals" xlink:type="simple" />
  <roleRef roleURI="http://www.astrotechcorp.com/role/SubsequentEvents" xlink:href="astc-20160630.xsd#SubsequentEvents" xlink:type="simple" />
  <roleRef roleURI="http://www.astrotechcorp.com/role/SubsequentEventsDetails" xlink:href="astc-20160630.xsd#SubsequentEventsDetails" xlink:type="simple" />
  <roleRef roleURI="http://www.astrotechcorp.com/role/SummaryOfSignificantAccountingPolicies" xlink:href="astc-20160630.xsd#SummaryOfSignificantAccountingPolicies" xlink:type="simple" />
  <roleRef roleURI="http://www.astrotechcorp.com/role/SummaryOfSignificantAccountingPoliciesDetailTextuals" xlink:href="astc-20160630.xsd#SummaryOfSignificantAccountingPoliciesDetailTextuals" xlink:type="simple" />
  <roleRef roleURI="http://www.astrotechcorp.com/role/SummaryOfSignificantAccountingPoliciesPolicies" xlink:href="astc-20160630.xsd#SummaryOfSignificantAccountingPoliciesPolicies" xlink:type="simple" />
  <arcroleRef arcroleURI="http://xbrl.org/int/dim/arcrole/all" xlink:href="http://www.xbrl.org/2005/xbrldt-2005.xsd#all" xlink:type="simple" />
  <arcroleRef arcroleURI="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:href="http://www.xbrl.org/2005/xbrldt-2005.xsd#dimension-default" xlink:type="simple" />
  <arcroleRef arcroleURI="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:href="http://www.xbrl.org/2005/xbrldt-2005.xsd#dimension-domain" xlink:type="simple" />
  <arcroleRef arcroleURI="http://xbrl.org/int/dim/arcrole/domain-member" xlink:href="http://www.xbrl.org/2005/xbrldt-2005.xsd#domain-member" xlink:type="simple" />
  <arcroleRef arcroleURI="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:href="http://www.xbrl.org/2005/xbrldt-2005.xsd#hypercube-dimension" xlink:type="simple" />
  <definitionLink xlink:role="http://www.astrotechcorp.com/role/AccruedLiabilitiesAndOtherLiabilities" xlink:type="extended" />
  <definitionLink xlink:role="http://www.astrotechcorp.com/role/AccruedLiabilitiesAndOtherLiabilitiesDetails" xlink:type="extended" />
  <definitionLink xlink:role="http://www.astrotechcorp.com/role/AccruedLiabilitiesAndOtherLiabilitiesTables" xlink:type="extended" />
  <definitionLink xlink:role="http://www.astrotechcorp.com/role/BusinessRiskAndCreditRiskConcentrationInvolvingCash" xlink:type="extended" />
  <definitionLink xlink:role="http://www.astrotechcorp.com/role/BusinessRiskAndCreditRiskConcentrationInvolvingCashDetailTextuals" xlink:type="extended">
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_ConcentrationRiskLineItems" xlink:label="loc_us-gaap_ConcentrationRiskLineItems_B1E790BDD80A3A457E8E1FD5403C7330" xlink:type="locator" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_ConcentrationRiskTable" xlink:label="loc_us-gaap_ConcentrationRiskTable_D5F2687D21391D8211021FD5403A8F2A" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_ConcentrationRiskLineItems_B1E790BDD80A3A457E8E1FD5403C7330" xlink:to="loc_us-gaap_ConcentrationRiskTable_D5F2687D21391D8211021FD5403A8F2A" xlink:type="arc" xbrldt:closed="true" xbrldt:contextElement="segment" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_ConcentrationRiskByBenchmarkAxis" xlink:label="loc_us-gaap_ConcentrationRiskByBenchmarkAxis_16BEFAF57BEEBFA94C481FD5403B13B6" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ConcentrationRiskTable_D5F2687D21391D8211021FD5403A8F2A" xlink:to="loc_us-gaap_ConcentrationRiskByBenchmarkAxis_16BEFAF57BEEBFA94C481FD5403B13B6" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_ConcentrationRiskBenchmarkDomain" xlink:label="loc_us-gaap_ConcentrationRiskBenchmarkDomain_D15C0BEFCCC0BD4E360A1FD5403B8283_default" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_ConcentrationRiskByBenchmarkAxis_16BEFAF57BEEBFA94C481FD5403B13B6" xlink:to="loc_us-gaap_ConcentrationRiskBenchmarkDomain_D15C0BEFCCC0BD4E360A1FD5403B8283_default" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_ConcentrationRiskBenchmarkDomain" xlink:label="loc_us-gaap_ConcentrationRiskBenchmarkDomain_D15C0BEFCCC0BD4E360A1FD5403B8283" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_ConcentrationRiskByBenchmarkAxis_16BEFAF57BEEBFA94C481FD5403B13B6" xlink:to="loc_us-gaap_ConcentrationRiskBenchmarkDomain_D15C0BEFCCC0BD4E360A1FD5403B8283" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_SalesRevenueNetMember" xlink:label="loc_us-gaap_SalesRevenueNetMember_6C860CD915B586C9E1951FD5406C1085" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ConcentrationRiskBenchmarkDomain_D15C0BEFCCC0BD4E360A1FD5403B8283" xlink:to="loc_us-gaap_SalesRevenueNetMember_6C860CD915B586C9E1951FD5406C1085" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_ConcentrationRiskByTypeAxis" xlink:label="loc_us-gaap_ConcentrationRiskByTypeAxis_8C62E409B3B35AC387601FD5403CA41E" xlink:type="locator" />
    <definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ConcentrationRiskTable_D5F2687D21391D8211021FD5403A8F2A" xlink:to="loc_us-gaap_ConcentrationRiskByTypeAxis_8C62E409B3B35AC387601FD5403CA41E" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_ConcentrationRiskTypeDomain" xlink:label="loc_us-gaap_ConcentrationRiskTypeDomain_F030C81B816D28D97B601FD5403CA2BA_default" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_ConcentrationRiskByTypeAxis_8C62E409B3B35AC387601FD5403CA41E" xlink:to="loc_us-gaap_ConcentrationRiskTypeDomain_F030C81B816D28D97B601FD5403CA2BA_default" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_ConcentrationRiskTypeDomain" xlink:label="loc_us-gaap_ConcentrationRiskTypeDomain_F030C81B816D28D97B601FD5403CA2BA" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_ConcentrationRiskByTypeAxis_8C62E409B3B35AC387601FD5403CA41E" xlink:to="loc_us-gaap_ConcentrationRiskTypeDomain_F030C81B816D28D97B601FD5403CA2BA" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_CustomerConcentrationRiskMember" xlink:label="loc_us-gaap_CustomerConcentrationRiskMember_68DD61411BB3BC0E08A31FD54060E04D" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ConcentrationRiskTypeDomain_F030C81B816D28D97B601FD5403CA2BA" xlink:to="loc_us-gaap_CustomerConcentrationRiskMember_68DD61411BB3BC0E08A31FD54060E04D" xlink:type="arc" />
    <loc xlink:href="astc-20160630.xsd#astc_ConcentrationRiskNumberOfCustomers" xlink:label="loc_astc_ConcentrationRiskNumberOfCustomers_469F2958DA9507BCCA3F1FD5404857B3" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ConcentrationRiskLineItems_B1E790BDD80A3A457E8E1FD5403C7330" xlink:to="loc_astc_ConcentrationRiskNumberOfCustomers_469F2958DA9507BCCA3F1FD5404857B3" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_ConcentrationRiskPercentage1" xlink:label="loc_us-gaap_ConcentrationRiskPercentage1_245B63483EC34430712C1FD5405478DA" xlink:type="locator" />
    <definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ConcentrationRiskLineItems_B1E790BDD80A3A457E8E1FD5403C7330" xlink:to="loc_us-gaap_ConcentrationRiskPercentage1_245B63483EC34430712C1FD5405478DA" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_CashFDICInsuredAmount" xlink:label="loc_us-gaap_CashFDICInsuredAmount_2F3281C1BD6A050CCF681FBFE6EEEAA2" xlink:type="locator" />
    <definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ConcentrationRiskLineItems_B1E790BDD80A3A457E8E1FD5403C7330" xlink:to="loc_us-gaap_CashFDICInsuredAmount_2F3281C1BD6A050CCF681FBFE6EEEAA2" xlink:type="arc" />
  </definitionLink>
  <definitionLink xlink:role="http://www.astrotechcorp.com/role/BusinessRiskAndCreditRiskConcentrationInvolvingCashDetails" xlink:type="extended">
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_ConcentrationRiskLineItems" xlink:label="loc_us-gaap_ConcentrationRiskLineItems_2907D2939375A955B1F270EB714B5F7B" xlink:type="locator" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_ConcentrationRiskTable" xlink:label="loc_us-gaap_ConcentrationRiskTable_82357396FED0DD7C753770EB7146237E" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_ConcentrationRiskLineItems_2907D2939375A955B1F270EB714B5F7B" xlink:to="loc_us-gaap_ConcentrationRiskTable_82357396FED0DD7C753770EB7146237E" xlink:type="arc" xbrldt:closed="true" xbrldt:contextElement="segment" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_CounterpartyNameAxis" xlink:label="loc_us-gaap_CounterpartyNameAxis_6ABAD89C01FA87C1A80370EB714760D2" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ConcentrationRiskTable_82357396FED0DD7C753770EB7146237E" xlink:to="loc_us-gaap_CounterpartyNameAxis_6ABAD89C01FA87C1A80370EB714760D2" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_RepurchaseAgreementCounterpartyNameDomain" xlink:label="loc_us-gaap_RepurchaseAgreementCounterpartyNameDomain_D43DE848629903AB8FAE70EB71476FD3_default" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_CounterpartyNameAxis_6ABAD89C01FA87C1A80370EB714760D2" xlink:to="loc_us-gaap_RepurchaseAgreementCounterpartyNameDomain_D43DE848629903AB8FAE70EB71476FD3_default" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_RepurchaseAgreementCounterpartyNameDomain" xlink:label="loc_us-gaap_RepurchaseAgreementCounterpartyNameDomain_D43DE848629903AB8FAE70EB71476FD3" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_CounterpartyNameAxis_6ABAD89C01FA87C1A80370EB714760D2" xlink:to="loc_us-gaap_RepurchaseAgreementCounterpartyNameDomain_D43DE848629903AB8FAE70EB71476FD3" xlink:type="arc" />
    <loc xlink:href="astc-20160630.xsd#astc_BattelleMemorialInstituteMember" xlink:label="loc_astc_BattelleMemorialInstituteMember_37675DB81B879BCD940A70EB7147B3FD" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RepurchaseAgreementCounterpartyNameDomain_D43DE848629903AB8FAE70EB71476FD3" xlink:to="loc_astc_BattelleMemorialInstituteMember_37675DB81B879BCD940A70EB7147B3FD" xlink:type="arc" />
    <loc xlink:href="astc-20160630.xsd#astc_IncumbentProviderOfIMSInstrumentationMember" xlink:label="loc_astc_IncumbentProviderOfIMSInstrumentationMember_493B051227B751BF74DC70EC489A503B" xlink:type="locator" />
    <definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RepurchaseAgreementCounterpartyNameDomain_D43DE848629903AB8FAE70EB71476FD3" xlink:to="loc_astc_IncumbentProviderOfIMSInstrumentationMember_493B051227B751BF74DC70EC489A503B" xlink:type="arc" />
    <loc xlink:href="astc-20160630.xsd#astc_AJapaneseAerospaceCompanyMember" xlink:label="loc_astc_AJapaneseAerospaceCompanyMember_C6C09E943A1B31DECCDD70EB714AEFAD" xlink:type="locator" />
    <definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RepurchaseAgreementCounterpartyNameDomain_D43DE848629903AB8FAE70EB71476FD3" xlink:to="loc_astc_AJapaneseAerospaceCompanyMember_C6C09E943A1B31DECCDD70EB714AEFAD" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_ConcentrationRiskByBenchmarkAxis" xlink:label="loc_us-gaap_ConcentrationRiskByBenchmarkAxis_70E306725EF3A81FC9B170EB714AAA4C" xlink:type="locator" />
    <definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ConcentrationRiskTable_82357396FED0DD7C753770EB7146237E" xlink:to="loc_us-gaap_ConcentrationRiskByBenchmarkAxis_70E306725EF3A81FC9B170EB714AAA4C" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_ConcentrationRiskBenchmarkDomain" xlink:label="loc_us-gaap_ConcentrationRiskBenchmarkDomain_A5DF406205F86BFE498270EB714AFC3A_default" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_ConcentrationRiskByBenchmarkAxis_70E306725EF3A81FC9B170EB714AAA4C" xlink:to="loc_us-gaap_ConcentrationRiskBenchmarkDomain_A5DF406205F86BFE498270EB714AFC3A_default" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_ConcentrationRiskBenchmarkDomain" xlink:label="loc_us-gaap_ConcentrationRiskBenchmarkDomain_A5DF406205F86BFE498270EB714AFC3A" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_ConcentrationRiskByBenchmarkAxis_70E306725EF3A81FC9B170EB714AAA4C" xlink:to="loc_us-gaap_ConcentrationRiskBenchmarkDomain_A5DF406205F86BFE498270EB714AFC3A" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_SalesRevenueNetMember" xlink:label="loc_us-gaap_SalesRevenueNetMember_F78F3F777A69B033C76F70EB714BF73F" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ConcentrationRiskBenchmarkDomain_A5DF406205F86BFE498270EB714AFC3A" xlink:to="loc_us-gaap_SalesRevenueNetMember_F78F3F777A69B033C76F70EB714BF73F" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_AccountsReceivableMember" xlink:label="loc_us-gaap_AccountsReceivableMember_DB27B7F484609933379E70EB714B4832" xlink:type="locator" />
    <definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ConcentrationRiskBenchmarkDomain_A5DF406205F86BFE498270EB714AFC3A" xlink:to="loc_us-gaap_AccountsReceivableMember_DB27B7F484609933379E70EB714B4832" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_ConcentrationRiskByTypeAxis" xlink:label="loc_us-gaap_ConcentrationRiskByTypeAxis_431BC5FB4B325A38787D70EB714B68AB" xlink:type="locator" />
    <definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ConcentrationRiskTable_82357396FED0DD7C753770EB7146237E" xlink:to="loc_us-gaap_ConcentrationRiskByTypeAxis_431BC5FB4B325A38787D70EB714B68AB" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_ConcentrationRiskTypeDomain" xlink:label="loc_us-gaap_ConcentrationRiskTypeDomain_AF04C3B23BB4E648ED1C70EB714B3353_default" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_ConcentrationRiskByTypeAxis_431BC5FB4B325A38787D70EB714B68AB" xlink:to="loc_us-gaap_ConcentrationRiskTypeDomain_AF04C3B23BB4E648ED1C70EB714B3353_default" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_ConcentrationRiskTypeDomain" xlink:label="loc_us-gaap_ConcentrationRiskTypeDomain_AF04C3B23BB4E648ED1C70EB714B3353" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_ConcentrationRiskByTypeAxis_431BC5FB4B325A38787D70EB714B68AB" xlink:to="loc_us-gaap_ConcentrationRiskTypeDomain_AF04C3B23BB4E648ED1C70EB714B3353" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_CustomerConcentrationRiskMember" xlink:label="loc_us-gaap_CustomerConcentrationRiskMember_D393E112C5097F7011F170EB714B85AC" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ConcentrationRiskTypeDomain_AF04C3B23BB4E648ED1C70EB714B3353" xlink:to="loc_us-gaap_CustomerConcentrationRiskMember_D393E112C5097F7011F170EB714B85AC" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_ConcentrationRiskPercentage1" xlink:label="loc_us-gaap_ConcentrationRiskPercentage1_E6E371FC70BDAE984D3470EB714CFC15" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ConcentrationRiskLineItems_2907D2939375A955B1F270EB714B5F7B" xlink:to="loc_us-gaap_ConcentrationRiskPercentage1_E6E371FC70BDAE984D3470EB714CFC15" xlink:type="arc" />
  </definitionLink>
  <definitionLink xlink:role="http://www.astrotechcorp.com/role/BusinessRiskAndCreditRiskConcentrationInvolvingCashTables" xlink:type="extended" />
  <definitionLink xlink:role="http://www.astrotechcorp.com/role/CommitmentsAndContingencies" xlink:type="extended" />
  <definitionLink xlink:role="http://www.astrotechcorp.com/role/CommitmentsAndContingenciesDetailTextuals" xlink:type="extended">
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_OperatingLeasedAssetsLineItems" xlink:label="loc_us-gaap_OperatingLeasedAssetsLineItems_FCDB9AC11661E9F21919216513E19B88" xlink:type="locator" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_ScheduleOfOperatingLeasedAssetsTable" xlink:label="loc_us-gaap_ScheduleOfOperatingLeasedAssetsTable_0AD16F3278033621162C216513E0D8C6" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_OperatingLeasedAssetsLineItems_FCDB9AC11661E9F21919216513E19B88" xlink:to="loc_us-gaap_ScheduleOfOperatingLeasedAssetsTable_0AD16F3278033621162C216513E0D8C6" xlink:type="arc" xbrldt:closed="true" xbrldt:contextElement="segment" />
    <loc xlink:href="http://xbrl.sec.gov/dei/2014/dei-2014-01-31.xsd#dei_LegalEntityAxis" xlink:label="loc_dei_LegalEntityAxis_67FB046981E794CBEA3C216513E0425E" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfOperatingLeasedAssetsTable_0AD16F3278033621162C216513E0D8C6" xlink:to="loc_dei_LegalEntityAxis_67FB046981E794CBEA3C216513E0425E" xlink:type="arc" />
    <loc xlink:href="http://xbrl.sec.gov/dei/2014/dei-2014-01-31.xsd#dei_EntityDomain" xlink:label="loc_dei_EntityDomain_206D94724AEBE1E13F39216513E0723D_default" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_dei_LegalEntityAxis_67FB046981E794CBEA3C216513E0425E" xlink:to="loc_dei_EntityDomain_206D94724AEBE1E13F39216513E0723D_default" xlink:type="arc" />
    <loc xlink:href="http://xbrl.sec.gov/dei/2014/dei-2014-01-31.xsd#dei_EntityDomain" xlink:label="loc_dei_EntityDomain_206D94724AEBE1E13F39216513E0723D" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_dei_LegalEntityAxis_67FB046981E794CBEA3C216513E0425E" xlink:to="loc_dei_EntityDomain_206D94724AEBE1E13F39216513E0723D" xlink:type="arc" />
    <loc xlink:href="astc-20160630.xsd#astc_AstralImagesIncMember" xlink:label="loc_astc_AstralImagesIncMember_6A5F267308574C0A2F16216513E0D463" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_EntityDomain_206D94724AEBE1E13F39216513E0723D" xlink:to="loc_astc_AstralImagesIncMember_6A5F267308574C0A2F16216513E0D463" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_StatementGeographicalAxis" xlink:label="loc_us-gaap_StatementGeographicalAxis_A5CDDEAC13A0F0B46955216513E09FF4" xlink:type="locator" />
    <definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfOperatingLeasedAssetsTable_0AD16F3278033621162C216513E0D8C6" xlink:to="loc_us-gaap_StatementGeographicalAxis_A5CDDEAC13A0F0B46955216513E09FF4" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_SegmentGeographicalDomain" xlink:label="loc_us-gaap_SegmentGeographicalDomain_B930BB2E87EE4FC308D8216513E06C40_default" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementGeographicalAxis_A5CDDEAC13A0F0B46955216513E09FF4" xlink:to="loc_us-gaap_SegmentGeographicalDomain_B930BB2E87EE4FC308D8216513E06C40_default" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_SegmentGeographicalDomain" xlink:label="loc_us-gaap_SegmentGeographicalDomain_B930BB2E87EE4FC308D8216513E06C40" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementGeographicalAxis_A5CDDEAC13A0F0B46955216513E09FF4" xlink:to="loc_us-gaap_SegmentGeographicalDomain_B930BB2E87EE4FC308D8216513E06C40" xlink:type="arc" />
    <loc xlink:href="astc-20160630.xsd#astc_AustinTexasMember" xlink:label="loc_astc_AustinTexasMember_0A203C42AC4A68D795A0216513E00BC0" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentGeographicalDomain_B930BB2E87EE4FC308D8216513E06C40" xlink:to="loc_astc_AustinTexasMember_0A203C42AC4A68D795A0216513E00BC0" xlink:type="arc" />
    <loc xlink:href="astc-20160630.xsd#astc_WebsterTexasPropertyOneMember" xlink:label="loc_astc_WebsterTexasPropertyOneMember_9DDAAEFD1E6FDFCEBDB5216513E0939E" xlink:type="locator" />
    <definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentGeographicalDomain_B930BB2E87EE4FC308D8216513E06C40" xlink:to="loc_astc_WebsterTexasPropertyOneMember_9DDAAEFD1E6FDFCEBDB5216513E0939E" xlink:type="arc" />
    <loc xlink:href="astc-20160630.xsd#astc_WebsterTexasPropertyTwoMember" xlink:label="loc_astc_WebsterTexasPropertyTwoMember_5D989B042DAB25EB7C81216513E1EBF6" xlink:type="locator" />
    <definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentGeographicalDomain_B930BB2E87EE4FC308D8216513E06C40" xlink:to="loc_astc_WebsterTexasPropertyTwoMember_5D989B042DAB25EB7C81216513E1EBF6" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_RelatedPartyTransactionsByRelatedPartyAxis" xlink:label="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_50F2F188E3C3A5DD07C6216513E179E4" xlink:type="locator" />
    <definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfOperatingLeasedAssetsTable_0AD16F3278033621162C216513E0D8C6" xlink:to="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_50F2F188E3C3A5DD07C6216513E179E4" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_RelatedPartyDomain" xlink:label="loc_us-gaap_RelatedPartyDomain_19CB5116E3BBA3F45745216513E1C052_default" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_50F2F188E3C3A5DD07C6216513E179E4" xlink:to="loc_us-gaap_RelatedPartyDomain_19CB5116E3BBA3F45745216513E1C052_default" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_RelatedPartyDomain" xlink:label="loc_us-gaap_RelatedPartyDomain_19CB5116E3BBA3F45745216513E1C052" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_50F2F188E3C3A5DD07C6216513E179E4" xlink:to="loc_us-gaap_RelatedPartyDomain_19CB5116E3BBA3F45745216513E1C052" xlink:type="arc" />
    <loc xlink:href="astc-20160630.xsd#astc_FirstDetectMember" xlink:label="loc_astc_FirstDetectMember_AC6AED32B253E38F5B5D216513E13197" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyDomain_19CB5116E3BBA3F45745216513E1C052" xlink:to="loc_astc_FirstDetectMember_AC6AED32B253E38F5B5D216513E13197" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_LeaseAndRentalExpense" xlink:label="loc_us-gaap_LeaseAndRentalExpense_D55B0C4DBA8DB8B440AC216513E28458" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_OperatingLeasedAssetsLineItems_FCDB9AC11661E9F21919216513E19B88" xlink:to="loc_us-gaap_LeaseAndRentalExpense_D55B0C4DBA8DB8B440AC216513E28458" xlink:type="arc" />
    <loc xlink:href="astc-20160630.xsd#astc_OperatingLeasesRentExpenseAreaOfSubleaseRental" xlink:label="loc_astc_OperatingLeasesRentExpenseAreaOfSubleaseRental_A3E4FC5DBF7F2C803416216513E2924A" xlink:type="locator" />
    <definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_OperatingLeasedAssetsLineItems_FCDB9AC11661E9F21919216513E19B88" xlink:to="loc_astc_OperatingLeasesRentExpenseAreaOfSubleaseRental_A3E4FC5DBF7F2C803416216513E2924A" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_AreaOfLand" xlink:label="loc_us-gaap_AreaOfLand_BBC859B636D5C356889E216513E2172C" xlink:type="locator" />
    <definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_OperatingLeasedAssetsLineItems_FCDB9AC11661E9F21919216513E19B88" xlink:to="loc_us-gaap_AreaOfLand_BBC859B636D5C356889E216513E2172C" xlink:type="arc" />
    <loc xlink:href="astc-20160630.xsd#astc_NumberOfRenewalTerms" xlink:label="loc_astc_NumberOfRenewalTerms_2E24F1CC8E95BEFF8B0F216513E2B46D" xlink:type="locator" />
    <definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_OperatingLeasedAssetsLineItems_FCDB9AC11661E9F21919216513E19B88" xlink:to="loc_astc_NumberOfRenewalTerms_2E24F1CC8E95BEFF8B0F216513E2B46D" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_LesseeLeasingArrangementsOperatingLeasesRenewalTerm" xlink:label="loc_us-gaap_LesseeLeasingArrangementsOperatingLeasesRenewalTerm_6AA3B1711F55D63FCD6D216513E28769" xlink:type="locator" />
    <definitionArc order="5" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_OperatingLeasedAssetsLineItems_FCDB9AC11661E9F21919216513E19B88" xlink:to="loc_us-gaap_LesseeLeasingArrangementsOperatingLeasesRenewalTerm_6AA3B1711F55D63FCD6D216513E28769" xlink:type="arc" />
    <loc xlink:href="astc-20160630.xsd#astc_LesseeLeasingArrangementsOperatingLeasesRenewalNotificationPeriod" xlink:label="loc_astc_LesseeLeasingArrangementsOperatingLeasesRenewalNotificationPeriod_24BDA032A5206CE0ECBE216513E2F1E5" xlink:type="locator" />
    <definitionArc order="6" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_OperatingLeasedAssetsLineItems_FCDB9AC11661E9F21919216513E19B88" xlink:to="loc_astc_LesseeLeasingArrangementsOperatingLeasesRenewalNotificationPeriod_24BDA032A5206CE0ECBE216513E2F1E5" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_LitigationSettlementAmount" xlink:label="loc_us-gaap_LitigationSettlementAmount_836B7619CED221BCDCBA216513E2F9BC" xlink:type="locator" />
    <definitionArc order="7" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_OperatingLeasedAssetsLineItems_FCDB9AC11661E9F21919216513E19B88" xlink:to="loc_us-gaap_LitigationSettlementAmount_836B7619CED221BCDCBA216513E2F9BC" xlink:type="arc" />
  </definitionLink>
  <definitionLink xlink:role="http://www.astrotechcorp.com/role/CommitmentsAndContingenciesDetails" xlink:type="extended" />
  <definitionLink xlink:role="http://www.astrotechcorp.com/role/CommitmentsAndContingenciesTables" xlink:type="extended" />
  <definitionLink xlink:role="http://www.astrotechcorp.com/role/CommonStockIncentiveStockPurchasePlansAndOtherCompensationPlans" xlink:type="extended" />
  <definitionLink xlink:role="http://www.astrotechcorp.com/role/CommonStockIncentiveStockPurchasePlansAndOtherCompensationPlansDetailTextuals" xlink:type="extended">
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_0FFFCE08C7481A5F37941FBFE6CFA93F" xlink:type="locator" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable" xlink:label="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_A9C37C8D523B55AA978B1FBFE6CDBD2B" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_0FFFCE08C7481A5F37941FBFE6CFA93F" xlink:to="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_A9C37C8D523B55AA978B1FBFE6CDBD2B" xlink:type="arc" xbrldt:closed="true" xbrldt:contextElement="segment" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_ShareRepurchaseProgramAxis" xlink:label="loc_us-gaap_ShareRepurchaseProgramAxis_2C5691748F2200E399AF1FF794EBBBEF" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_A9C37C8D523B55AA978B1FBFE6CDBD2B" xlink:to="loc_us-gaap_ShareRepurchaseProgramAxis_2C5691748F2200E399AF1FF794EBBBEF" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_ShareRepurchaseProgramDomain" xlink:label="loc_us-gaap_ShareRepurchaseProgramDomain_79A92DF84BCA1AD275B41FF87C4C1C76_default" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_ShareRepurchaseProgramAxis_2C5691748F2200E399AF1FF794EBBBEF" xlink:to="loc_us-gaap_ShareRepurchaseProgramDomain_79A92DF84BCA1AD275B41FF87C4C1C76_default" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_ShareRepurchaseProgramDomain" xlink:label="loc_us-gaap_ShareRepurchaseProgramDomain_79A92DF84BCA1AD275B41FF87C4C1C76" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_ShareRepurchaseProgramAxis_2C5691748F2200E399AF1FF794EBBBEF" xlink:to="loc_us-gaap_ShareRepurchaseProgramDomain_79A92DF84BCA1AD275B41FF87C4C1C76" xlink:type="arc" />
    <loc xlink:href="astc-20160630.xsd#astc_AmendedSecuritiesRepurchaseProgramMember" xlink:label="loc_astc_AmendedSecuritiesRepurchaseProgramMember_1EDD9A2BA6C959D85A981FF8357F5634" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareRepurchaseProgramDomain_79A92DF84BCA1AD275B41FF87C4C1C76" xlink:to="loc_astc_AmendedSecuritiesRepurchaseProgramMember_1EDD9A2BA6C959D85A981FF8357F5634" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_AwardTypeAxis" xlink:label="loc_us-gaap_AwardTypeAxis_0B948AC134C3B32134271FBFE6CDB6CD" xlink:type="locator" />
    <definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_A9C37C8D523B55AA978B1FBFE6CDBD2B" xlink:to="loc_us-gaap_AwardTypeAxis_0B948AC134C3B32134271FBFE6CDB6CD" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_030BE29E5919DE3715081FBFE6CDC3CB_default" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_AwardTypeAxis_0B948AC134C3B32134271FBFE6CDB6CD" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_030BE29E5919DE3715081FBFE6CDC3CB_default" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_030BE29E5919DE3715081FBFE6CDC3CB" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_AwardTypeAxis_0B948AC134C3B32134271FBFE6CDB6CD" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_030BE29E5919DE3715081FBFE6CDC3CB" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_EmployeeStockOptionMember" xlink:label="loc_us-gaap_EmployeeStockOptionMember_B3BE05B4696CDC9906391FBFE6CD5269" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_030BE29E5919DE3715081FBFE6CDC3CB" xlink:to="loc_us-gaap_EmployeeStockOptionMember_B3BE05B4696CDC9906391FBFE6CD5269" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_RestrictedStockMember" xlink:label="loc_us-gaap_RestrictedStockMember_F5BFB972A827DFCAC0371FE6D37D636C" xlink:type="locator" />
    <definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_030BE29E5919DE3715081FBFE6CDC3CB" xlink:to="loc_us-gaap_RestrictedStockMember_F5BFB972A827DFCAC0371FE6D37D636C" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_RelatedPartyTransactionsByRelatedPartyAxis" xlink:label="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_9E9516B7F8DD4A6292AB1FBFE6CE9C26" xlink:type="locator" />
    <definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_A9C37C8D523B55AA978B1FBFE6CDBD2B" xlink:to="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_9E9516B7F8DD4A6292AB1FBFE6CE9C26" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_RelatedPartyDomain" xlink:label="loc_us-gaap_RelatedPartyDomain_88D99FB2F6EB182C29461FBFE6CE79BF_default" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_9E9516B7F8DD4A6292AB1FBFE6CE9C26" xlink:to="loc_us-gaap_RelatedPartyDomain_88D99FB2F6EB182C29461FBFE6CE79BF_default" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_RelatedPartyDomain" xlink:label="loc_us-gaap_RelatedPartyDomain_88D99FB2F6EB182C29461FBFE6CE79BF" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_9E9516B7F8DD4A6292AB1FBFE6CE9C26" xlink:to="loc_us-gaap_RelatedPartyDomain_88D99FB2F6EB182C29461FBFE6CE79BF" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_DirectorMember" xlink:label="loc_us-gaap_DirectorMember_41D3F0BCDE14810FE95C1FBFE6CE6723" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyDomain_88D99FB2F6EB182C29461FBFE6CE79BF" xlink:to="loc_us-gaap_DirectorMember_41D3F0BCDE14810FE95C1FBFE6CE6723" xlink:type="arc" />
    <loc xlink:href="astc-20160630.xsd#astc_BoardOfDirectorsChiefExecutiveOfficerandChiefFinancialOfficerMember" xlink:label="loc_astc_BoardOfDirectorsChiefExecutiveOfficerandChiefFinancialOfficerMember_003FB969CB6C38675DE11FBFE6CECD2F" xlink:type="locator" />
    <definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyDomain_88D99FB2F6EB182C29461FBFE6CE79BF" xlink:to="loc_astc_BoardOfDirectorsChiefExecutiveOfficerandChiefFinancialOfficerMember_003FB969CB6C38675DE11FBFE6CECD2F" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_ChiefOperatingOfficerMember" xlink:label="loc_us-gaap_ChiefOperatingOfficerMember_A6B20658496F06D9B8041FF645A5E5A1" xlink:type="locator" />
    <definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyDomain_88D99FB2F6EB182C29461FBFE6CE79BF" xlink:to="loc_us-gaap_ChiefOperatingOfficerMember_A6B20658496F06D9B8041FF645A5E5A1" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_PlanNameAxis" xlink:label="loc_us-gaap_PlanNameAxis_C11E1A4C507FE4B3B90F1FBFE6CE7558" xlink:type="locator" />
    <definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_A9C37C8D523B55AA978B1FBFE6CDBD2B" xlink:to="loc_us-gaap_PlanNameAxis_C11E1A4C507FE4B3B90F1FBFE6CE7558" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_PlanNameDomain" xlink:label="loc_us-gaap_PlanNameDomain_A7377140329C32ECC0411FBFE6CE8F15_default" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_PlanNameAxis_C11E1A4C507FE4B3B90F1FBFE6CE7558" xlink:to="loc_us-gaap_PlanNameDomain_A7377140329C32ECC0411FBFE6CE8F15_default" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_PlanNameDomain" xlink:label="loc_us-gaap_PlanNameDomain_A7377140329C32ECC0411FBFE6CE8F15" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_PlanNameAxis_C11E1A4C507FE4B3B90F1FBFE6CE7558" xlink:to="loc_us-gaap_PlanNameDomain_A7377140329C32ECC0411FBFE6CE8F15" xlink:type="arc" />
    <loc xlink:href="astc-20160630.xsd#astc_StockIncentivePlan2008Member" xlink:label="loc_astc_StockIncentivePlan2008Member_9E7944BD990BC8923D211FBFE6CE45E0" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PlanNameDomain_A7377140329C32ECC0411FBFE6CE8F15" xlink:to="loc_astc_StockIncentivePlan2008Member_9E7944BD990BC8923D211FBFE6CE45E0" xlink:type="arc" />
    <loc xlink:href="astc-20160630.xsd#astc_StockIncentivePlan2011Member" xlink:label="loc_astc_StockIncentivePlan2011Member_066FDD24EE2A13FF7C6E1FBFE6CE1BB8" xlink:type="locator" />
    <definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PlanNameDomain_A7377140329C32ECC0411FBFE6CE8F15" xlink:to="loc_astc_StockIncentivePlan2011Member_066FDD24EE2A13FF7C6E1FBFE6CE1BB8" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_CommonStockCapitalSharesReservedForFutureIssuance" xlink:label="loc_us-gaap_CommonStockCapitalSharesReservedForFutureIssuance_82E0732F8328EB33ABEA1FBFE6CFE969" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_0FFFCE08C7481A5F37941FBFE6CFA93F" xlink:to="loc_us-gaap_CommonStockCapitalSharesReservedForFutureIssuance_82E0732F8328EB33ABEA1FBFE6CFE969" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodGross" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodGross_B7121AB4E892DC4B399D1FBFE6CF70F2" xlink:type="locator" />
    <definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_0FFFCE08C7481A5F37941FBFE6CFA93F" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodGross_B7121AB4E892DC4B399D1FBFE6CF70F2" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAvailableForGrant" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAvailableForGrant_16B57A997979D9F77A361FBFE6CF2065" xlink:type="locator" />
    <definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_0FFFCE08C7481A5F37941FBFE6CFA93F" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAvailableForGrant_16B57A997979D9F77A361FBFE6CF2065" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsExercisableIntrinsicValue1" xlink:label="loc_us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsExercisableIntrinsicValue1_1D45FC8E02781500724B1FBFE6CF0B3E" xlink:type="locator" />
    <definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_0FFFCE08C7481A5F37941FBFE6CFA93F" xlink:to="loc_us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsExercisableIntrinsicValue1_1D45FC8E02781500724B1FBFE6CF0B3E" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingIntrinsicValue" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingIntrinsicValue_C2A63724538E7B390DAC1FBFE6CF5EA6" xlink:type="locator" />
    <definitionArc order="5" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_0FFFCE08C7481A5F37941FBFE6CFA93F" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingIntrinsicValue_C2A63724538E7B390DAC1FBFE6CF5EA6" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_AllocatedShareBasedCompensationExpense" xlink:label="loc_us-gaap_AllocatedShareBasedCompensationExpense_2F42B5787E46AEC437BF1FBFE6CFD3B9" xlink:type="locator" />
    <definitionArc order="6" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_0FFFCE08C7481A5F37941FBFE6CFA93F" xlink:to="loc_us-gaap_AllocatedShareBasedCompensationExpense_2F42B5787E46AEC437BF1FBFE6CFD3B9" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognizedStockOptions" xlink:label="loc_us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognizedStockOptions_2A716D65442C816D48251FBFE6CFAE8A" xlink:type="locator" />
    <definitionArc order="7" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_0FFFCE08C7481A5F37941FBFE6CFA93F" xlink:to="loc_us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognizedStockOptions_2A716D65442C816D48251FBFE6CFAE8A" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognizedPeriodForRecognition1" xlink:label="loc_us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognizedPeriodForRecognition1_88955FF2E6A7F6F739E81FBFE6CFC8AD" xlink:type="locator" />
    <definitionArc order="8" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_0FFFCE08C7481A5F37941FBFE6CFA93F" xlink:to="loc_us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognizedPeriodForRecognition1_88955FF2E6A7F6F739E81FBFE6CFC8AD" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognizedShareBasedAwardsOtherThanOptions" xlink:label="loc_us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognizedShareBasedAwardsOtherThanOptions_7FCA93C33A6A43776D521FEDBFC4DE5B" xlink:type="locator" />
    <definitionArc order="9" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_0FFFCE08C7481A5F37941FBFE6CFA93F" xlink:to="loc_us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognizedShareBasedAwardsOtherThanOptions_7FCA93C33A6A43776D521FEDBFC4DE5B" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedDividendRate" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedDividendRate_FB877997DD0043484DA41FBFE6CFDD96" xlink:type="locator" />
    <definitionArc order="10" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_0FFFCE08C7481A5F37941FBFE6CFA93F" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardFairValueAssumptionsExpectedDividendRate_FB877997DD0043484DA41FBFE6CFDD96" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_StockRepurchaseProgramAuthorizedAmount1" xlink:label="loc_us-gaap_StockRepurchaseProgramAuthorizedAmount1_CFAA9F1AE97A4FF8896A1FBFE6D09183" xlink:type="locator" />
    <definitionArc order="11" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_0FFFCE08C7481A5F37941FBFE6CFA93F" xlink:to="loc_us-gaap_StockRepurchaseProgramAuthorizedAmount1_CFAA9F1AE97A4FF8896A1FBFE6D09183" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_TreasuryStockSharesAcquired" xlink:label="loc_us-gaap_TreasuryStockSharesAcquired_3149D42FB4BA75D3F3B01FBFE6D0CE7B" xlink:type="locator" />
    <definitionArc order="12" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_0FFFCE08C7481A5F37941FBFE6CFA93F" xlink:to="loc_us-gaap_TreasuryStockSharesAcquired_3149D42FB4BA75D3F3B01FBFE6D0CE7B" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_TreasuryStockValueAcquiredCostMethod" xlink:label="loc_us-gaap_TreasuryStockValueAcquiredCostMethod_336ABD35B8A5E31A57E91FBFE6D0DA90" xlink:type="locator" />
    <definitionArc order="13" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_0FFFCE08C7481A5F37941FBFE6CFA93F" xlink:to="loc_us-gaap_TreasuryStockValueAcquiredCostMethod_336ABD35B8A5E31A57E91FBFE6D0DA90" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_TreasuryStockAcquiredAverageCostPerShare" xlink:label="loc_us-gaap_TreasuryStockAcquiredAverageCostPerShare_05397F00752A37DABFBB1FBFE6D0E515" xlink:type="locator" />
    <definitionArc order="14" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_0FFFCE08C7481A5F37941FBFE6CFA93F" xlink:to="loc_us-gaap_TreasuryStockAcquiredAverageCostPerShare_05397F00752A37DABFBB1FBFE6D0E515" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_StockRepurchaseProgramRemainingAuthorizedRepurchaseAmount1" xlink:label="loc_us-gaap_StockRepurchaseProgramRemainingAuthorizedRepurchaseAmount1_9FE9FD465144E6440F281FBFE6D0CFFB" xlink:type="locator" />
    <definitionArc order="15" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_0FFFCE08C7481A5F37941FBFE6CFA93F" xlink:to="loc_us-gaap_StockRepurchaseProgramRemainingAuthorizedRepurchaseAmount1_9FE9FD465144E6440F281FBFE6D0CFFB" xlink:type="arc" />
  </definitionLink>
  <definitionLink xlink:role="http://www.astrotechcorp.com/role/CommonStockIncentiveStockPurchasePlansAndOtherCompensationPlansDetails" xlink:type="extended" />
  <definitionLink xlink:role="http://www.astrotechcorp.com/role/CommonStockIncentiveStockPurchasePlansAndOtherCompensationPlansDetails1" xlink:type="extended">
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_ShareBasedCompensationSharesAuthorizedUnderStockOptionPlansExercisePriceRangeLineItems" xlink:label="loc_us-gaap_ShareBasedCompensationSharesAuthorizedUnderStockOptionPlansExercisePriceRangeLineItems_5D26BAD1C1023F7FB4DE2973DA83FA11" xlink:type="locator" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_ScheduleOfShareBasedCompensationSharesAuthorizedUnderStockOptionPlansByExercisePriceRangeTable" xlink:label="loc_us-gaap_ScheduleOfShareBasedCompensationSharesAuthorizedUnderStockOptionPlansByExercisePriceRangeTable_A0600DD3713FA9F26C2A2973DA822E19" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_ShareBasedCompensationSharesAuthorizedUnderStockOptionPlansExercisePriceRangeLineItems_5D26BAD1C1023F7FB4DE2973DA83FA11" xlink:to="loc_us-gaap_ScheduleOfShareBasedCompensationSharesAuthorizedUnderStockOptionPlansByExercisePriceRangeTable_A0600DD3713FA9F26C2A2973DA822E19" xlink:type="arc" xbrldt:closed="true" xbrldt:contextElement="segment" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_ShareBasedCompensationSharesAuthorizedUnderStockOptionPlansByExercisePriceRangeAxis" xlink:label="loc_us-gaap_ShareBasedCompensationSharesAuthorizedUnderStockOptionPlansByExercisePriceRangeAxis_25B17791948F0CF450462973DA82D128" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfShareBasedCompensationSharesAuthorizedUnderStockOptionPlansByExercisePriceRangeTable_A0600DD3713FA9F26C2A2973DA822E19" xlink:to="loc_us-gaap_ShareBasedCompensationSharesAuthorizedUnderStockOptionPlansByExercisePriceRangeAxis_25B17791948F0CF450462973DA82D128" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_ShareBasedCompensationSharesAuthorizedUnderStockOptionPlansExercisePriceRangeDomain" xlink:label="loc_us-gaap_ShareBasedCompensationSharesAuthorizedUnderStockOptionPlansExercisePriceRangeDomain_F7700FA1DF6E258CCAEB2973DA8271DC_default" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_ShareBasedCompensationSharesAuthorizedUnderStockOptionPlansByExercisePriceRangeAxis_25B17791948F0CF450462973DA82D128" xlink:to="loc_us-gaap_ShareBasedCompensationSharesAuthorizedUnderStockOptionPlansExercisePriceRangeDomain_F7700FA1DF6E258CCAEB2973DA8271DC_default" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_ShareBasedCompensationSharesAuthorizedUnderStockOptionPlansExercisePriceRangeDomain" xlink:label="loc_us-gaap_ShareBasedCompensationSharesAuthorizedUnderStockOptionPlansExercisePriceRangeDomain_F7700FA1DF6E258CCAEB2973DA8271DC" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_ShareBasedCompensationSharesAuthorizedUnderStockOptionPlansByExercisePriceRangeAxis_25B17791948F0CF450462973DA82D128" xlink:to="loc_us-gaap_ShareBasedCompensationSharesAuthorizedUnderStockOptionPlansExercisePriceRangeDomain_F7700FA1DF6E258CCAEB2973DA8271DC" xlink:type="arc" />
    <loc xlink:href="astc-20160630.xsd#astc_ExercisePriceRangeOneMember" xlink:label="loc_astc_ExercisePriceRangeOneMember_9826BAA79A79710F68272973DA829561" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationSharesAuthorizedUnderStockOptionPlansExercisePriceRangeDomain_F7700FA1DF6E258CCAEB2973DA8271DC" xlink:to="loc_astc_ExercisePriceRangeOneMember_9826BAA79A79710F68272973DA829561" xlink:type="arc" />
    <loc xlink:href="astc-20160630.xsd#astc_ExercisePriceRangeTwoMember" xlink:label="loc_astc_ExercisePriceRangeTwoMember_DED0FD3CC48233D4810E2973DA825FFA" xlink:type="locator" />
    <definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationSharesAuthorizedUnderStockOptionPlansExercisePriceRangeDomain_F7700FA1DF6E258CCAEB2973DA8271DC" xlink:to="loc_astc_ExercisePriceRangeTwoMember_DED0FD3CC48233D4810E2973DA825FFA" xlink:type="arc" />
    <loc xlink:href="astc-20160630.xsd#astc_ExercisePriceRangeThreeMember" xlink:label="loc_astc_ExercisePriceRangeThreeMember_2C97D796EC97B1DF0A992973DA82FA9D" xlink:type="locator" />
    <definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationSharesAuthorizedUnderStockOptionPlansExercisePriceRangeDomain_F7700FA1DF6E258CCAEB2973DA8271DC" xlink:to="loc_astc_ExercisePriceRangeThreeMember_2C97D796EC97B1DF0A992973DA82FA9D" xlink:type="arc" />
    <loc xlink:href="astc-20160630.xsd#astc_ExercisePriceRangeFourMember" xlink:label="loc_astc_ExercisePriceRangeFourMember_6E64B33B13AF7537E56F2973DA8226C4" xlink:type="locator" />
    <definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationSharesAuthorizedUnderStockOptionPlansExercisePriceRangeDomain_F7700FA1DF6E258CCAEB2973DA8271DC" xlink:to="loc_astc_ExercisePriceRangeFourMember_6E64B33B13AF7537E56F2973DA8226C4" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_ShareBasedCompensationSharesAuthorizedUnderStockOptionPlansExercisePriceRangeNumberOfOutstandingOptions" xlink:label="loc_us-gaap_ShareBasedCompensationSharesAuthorizedUnderStockOptionPlansExercisePriceRangeNumberOfOutstandingOptions_4766B0287B190B7AE7172973DA8369C4" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationSharesAuthorizedUnderStockOptionPlansExercisePriceRangeLineItems_5D26BAD1C1023F7FB4DE2973DA83FA11" xlink:to="loc_us-gaap_ShareBasedCompensationSharesAuthorizedUnderStockOptionPlansExercisePriceRangeNumberOfOutstandingOptions_4766B0287B190B7AE7172973DA8369C4" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_SharebasedCompensationSharesAuthorizedUnderStockOptionPlansExercisePriceRangeOutstandingOptionsWeightedAverageRemainingContractualTerm2" xlink:label="loc_us-gaap_SharebasedCompensationSharesAuthorizedUnderStockOptionPlansExercisePriceRangeOutstandingOptionsWeightedAverageRemainingContractualTerm2_6103132A4257C06EF0FE2973DA83D53D" xlink:type="locator" />
    <definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationSharesAuthorizedUnderStockOptionPlansExercisePriceRangeLineItems_5D26BAD1C1023F7FB4DE2973DA83FA11" xlink:to="loc_us-gaap_SharebasedCompensationSharesAuthorizedUnderStockOptionPlansExercisePriceRangeOutstandingOptionsWeightedAverageRemainingContractualTerm2_6103132A4257C06EF0FE2973DA83D53D" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_SharebasedCompensationSharesAuthorizedUnderStockOptionPlansExercisePriceRangeOutstandingOptionsWeightedAverageExercisePriceBeginningBalance1" xlink:label="loc_us-gaap_SharebasedCompensationSharesAuthorizedUnderStockOptionPlansExercisePriceRangeOutstandingOptionsWeightedAverageExercisePriceBeginningBalance1_4862E8E863F28EB842252973DA836E92" xlink:type="locator" />
    <definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationSharesAuthorizedUnderStockOptionPlansExercisePriceRangeLineItems_5D26BAD1C1023F7FB4DE2973DA83FA11" xlink:to="loc_us-gaap_SharebasedCompensationSharesAuthorizedUnderStockOptionPlansExercisePriceRangeOutstandingOptionsWeightedAverageExercisePriceBeginningBalance1_4862E8E863F28EB842252973DA836E92" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_ShareBasedCompensationSharesAuthorizedUnderStockOptionPlansExercisePriceRangeNumberOfExercisableOptions" xlink:label="loc_us-gaap_ShareBasedCompensationSharesAuthorizedUnderStockOptionPlansExercisePriceRangeNumberOfExercisableOptions_C004C3114B9F153982EE2973DA83C762" xlink:type="locator" />
    <definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationSharesAuthorizedUnderStockOptionPlansExercisePriceRangeLineItems_5D26BAD1C1023F7FB4DE2973DA83FA11" xlink:to="loc_us-gaap_ShareBasedCompensationSharesAuthorizedUnderStockOptionPlansExercisePriceRangeNumberOfExercisableOptions_C004C3114B9F153982EE2973DA83C762" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_SharebasedCompensationSharesAuthorizedUnderStockOptionPlansExercisePriceRangeExercisableOptionsWeightedAverageExercisePrice1" xlink:label="loc_us-gaap_SharebasedCompensationSharesAuthorizedUnderStockOptionPlansExercisePriceRangeExercisableOptionsWeightedAverageExercisePrice1_97FE8AD32CDBB06771932973DA839853" xlink:type="locator" />
    <definitionArc order="5" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationSharesAuthorizedUnderStockOptionPlansExercisePriceRangeLineItems_5D26BAD1C1023F7FB4DE2973DA83FA11" xlink:to="loc_us-gaap_SharebasedCompensationSharesAuthorizedUnderStockOptionPlansExercisePriceRangeExercisableOptionsWeightedAverageExercisePrice1_97FE8AD32CDBB06771932973DA839853" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_ShareBasedCompensationSharesAuthorizedUnderStockOptionPlansExercisePriceRangeLowerRangeLimit" xlink:label="loc_us-gaap_ShareBasedCompensationSharesAuthorizedUnderStockOptionPlansExercisePriceRangeLowerRangeLimit_8DCEBF56AA8B65D95F892982DB02E6CB" xlink:type="locator" />
    <definitionArc order="6" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationSharesAuthorizedUnderStockOptionPlansExercisePriceRangeLineItems_5D26BAD1C1023F7FB4DE2973DA83FA11" xlink:to="loc_us-gaap_ShareBasedCompensationSharesAuthorizedUnderStockOptionPlansExercisePriceRangeLowerRangeLimit_8DCEBF56AA8B65D95F892982DB02E6CB" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_ShareBasedCompensationSharesAuthorizedUnderStockOptionPlansExercisePriceRangeUpperRangeLimit" xlink:label="loc_us-gaap_ShareBasedCompensationSharesAuthorizedUnderStockOptionPlansExercisePriceRangeUpperRangeLimit_6B3C39164E5268A66588298305DA1438" xlink:type="locator" />
    <definitionArc order="7" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationSharesAuthorizedUnderStockOptionPlansExercisePriceRangeLineItems_5D26BAD1C1023F7FB4DE2973DA83FA11" xlink:to="loc_us-gaap_ShareBasedCompensationSharesAuthorizedUnderStockOptionPlansExercisePriceRangeUpperRangeLimit_6B3C39164E5268A66588298305DA1438" xlink:type="arc" />
  </definitionLink>
  <definitionLink xlink:role="http://www.astrotechcorp.com/role/CommonStockIncentiveStockPurchasePlansAndOtherCompensationPlansDetails2" xlink:type="extended">
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_ACA7A89497611EA144291FBFE6DA3E30" xlink:type="locator" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable" xlink:label="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_5C6CE7F46F35909E95551FBFE6DAB552" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_ACA7A89497611EA144291FBFE6DA3E30" xlink:to="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_5C6CE7F46F35909E95551FBFE6DAB552" xlink:type="arc" xbrldt:closed="true" xbrldt:contextElement="segment" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_AwardTypeAxis" xlink:label="loc_us-gaap_AwardTypeAxis_8C4B939952D5EFA4D09D1FBFE6DA9976" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_5C6CE7F46F35909E95551FBFE6DAB552" xlink:to="loc_us-gaap_AwardTypeAxis_8C4B939952D5EFA4D09D1FBFE6DA9976" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_3E5FA245F193BED209531FBFE6DA745F_default" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_AwardTypeAxis_8C4B939952D5EFA4D09D1FBFE6DA9976" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_3E5FA245F193BED209531FBFE6DA745F_default" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_3E5FA245F193BED209531FBFE6DA745F" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_AwardTypeAxis_8C4B939952D5EFA4D09D1FBFE6DA9976" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_3E5FA245F193BED209531FBFE6DA745F" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_RestrictedStockMember" xlink:label="loc_us-gaap_RestrictedStockMember_45A6A0BF4AA0A9DA1D181FBFE6DA4D56" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_3E5FA245F193BED209531FBFE6DA745F" xlink:to="loc_us-gaap_RestrictedStockMember_45A6A0BF4AA0A9DA1D181FBFE6DA4D56" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedRollForward" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedRollForward_17ECB7DB69C12E95E9A01FBFE6DB04BB" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_ACA7A89497611EA144291FBFE6DA3E30" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedRollForward_17ECB7DB69C12E95E9A01FBFE6DB04BB" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber_03696109875038A30DEF1FBFE6DB3A78" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedRollForward_17ECB7DB69C12E95E9A01FBFE6DB04BB" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber_03696109875038A30DEF1FBFE6DB3A78" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod_FECFD0E57751E59A923D1FBFE6DB65B8" xlink:type="locator" />
    <definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedRollForward_17ECB7DB69C12E95E9A01FBFE6DB04BB" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod_FECFD0E57751E59A923D1FBFE6DB65B8" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriod" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriod_7690DF17CE240757D95C1FBFE6DB40EC" xlink:type="locator" />
    <definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedRollForward_17ECB7DB69C12E95E9A01FBFE6DB04BB" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriod_7690DF17CE240757D95C1FBFE6DB40EC" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeitedInPeriod" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeitedInPeriod_6F296C3D7975EF50A6F61FBFE6DB1711" xlink:type="locator" />
    <definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedRollForward_17ECB7DB69C12E95E9A01FBFE6DB04BB" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeitedInPeriod_6F296C3D7975EF50A6F61FBFE6DB1711" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValueRollForward" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValueRollForward_6BD2C32B9DD0BC2447FC1FBFE6DB0367" xlink:type="locator" />
    <definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_ACA7A89497611EA144291FBFE6DA3E30" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValueRollForward_6BD2C32B9DD0BC2447FC1FBFE6DB0367" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValue" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValue_2ABA109989C07C4B72481FBFE6DB1A65" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValueRollForward_6BD2C32B9DD0BC2447FC1FBFE6DB0367" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValue_2ABA109989C07C4B72481FBFE6DB1A65" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriodWeightedAverageGrantDateFairValue" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriodWeightedAverageGrantDateFairValue_6F235704ACBDAEC758791FBFE6DBF732" xlink:type="locator" />
    <definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValueRollForward_6BD2C32B9DD0BC2447FC1FBFE6DB0367" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriodWeightedAverageGrantDateFairValue_6F235704ACBDAEC758791FBFE6DBF732" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriodWeightedAverageGrantDateFairValue" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriodWeightedAverageGrantDateFairValue_0E8863ED5F07F472065B1FBFE6DBECD0" xlink:type="locator" />
    <definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValueRollForward_6BD2C32B9DD0BC2447FC1FBFE6DB0367" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriodWeightedAverageGrantDateFairValue_0E8863ED5F07F472065B1FBFE6DBECD0" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeituresWeightedAverageGrantDateFairValue" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeituresWeightedAverageGrantDateFairValue_70E1BA13DC93BF00255E1FBFE6DBB26B" xlink:type="locator" />
    <definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedWeightedAverageGrantDateFairValueRollForward_6BD2C32B9DD0BC2447FC1FBFE6DB0367" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeituresWeightedAverageGrantDateFairValue_70E1BA13DC93BF00255E1FBFE6DBB26B" xlink:type="arc" />
  </definitionLink>
  <definitionLink xlink:role="http://www.astrotechcorp.com/role/CommonStockIncentiveStockPurchasePlansAndOtherCompensationPlansDetails3" xlink:type="extended" />
  <definitionLink xlink:role="http://www.astrotechcorp.com/role/CommonStockIncentiveStockPurchasePlansAndOtherCompensationPlansTables" xlink:type="extended" />
  <definitionLink xlink:role="http://www.astrotechcorp.com/role/ConsolidatedBalanceSheets" xlink:type="extended" />
  <definitionLink xlink:role="http://www.astrotechcorp.com/role/ConsolidatedBalanceSheetsParentheticals" xlink:type="extended" />
  <definitionLink xlink:role="http://www.astrotechcorp.com/role/ConsolidatedStatementOfChangesInStockholdersEquity" xlink:type="extended">
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_StatementLineItems" xlink:label="loc_us-gaap_StatementLineItems_D6C59D71D199373110DE1EEF4BA0D85B" xlink:type="locator" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_StatementTable" xlink:label="loc_us-gaap_StatementTable_1070943B656AA49292FA1EEF4BA056A0" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_StatementLineItems_D6C59D71D199373110DE1EEF4BA0D85B" xlink:to="loc_us-gaap_StatementTable_1070943B656AA49292FA1EEF4BA056A0" xlink:type="arc" xbrldt:closed="true" xbrldt:contextElement="segment" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_StatementEquityComponentsAxis" xlink:label="loc_us-gaap_StatementEquityComponentsAxis_F9B65CD5897B69CCF6D41EEF4BA0C808" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_StatementTable_1070943B656AA49292FA1EEF4BA056A0" xlink:to="loc_us-gaap_StatementEquityComponentsAxis_F9B65CD5897B69CCF6D41EEF4BA0C808" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_EquityComponentDomain" xlink:label="loc_us-gaap_EquityComponentDomain_4F29049D421508FB9E8E1EEF4BA053EC_default" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementEquityComponentsAxis_F9B65CD5897B69CCF6D41EEF4BA0C808" xlink:to="loc_us-gaap_EquityComponentDomain_4F29049D421508FB9E8E1EEF4BA053EC_default" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_EquityComponentDomain" xlink:label="loc_us-gaap_EquityComponentDomain_4F29049D421508FB9E8E1EEF4BA053EC" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementEquityComponentsAxis_F9B65CD5897B69CCF6D41EEF4BA0C808" xlink:to="loc_us-gaap_EquityComponentDomain_4F29049D421508FB9E8E1EEF4BA053EC" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_CommonStockMember" xlink:label="loc_us-gaap_CommonStockMember_1D8E097C176932A3991A1EEF4BA0D0CE" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_4F29049D421508FB9E8E1EEF4BA053EC" xlink:to="loc_us-gaap_CommonStockMember_1D8E097C176932A3991A1EEF4BA0D0CE" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_TreasuryStockMember" xlink:label="loc_us-gaap_TreasuryStockMember_3C49F7000618EABC81B41EEF4BA07E5B" xlink:type="locator" />
    <definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_4F29049D421508FB9E8E1EEF4BA053EC" xlink:to="loc_us-gaap_TreasuryStockMember_3C49F7000618EABC81B41EEF4BA07E5B" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_AdditionalPaidInCapitalMember" xlink:label="loc_us-gaap_AdditionalPaidInCapitalMember_0D1CD2C8C18C77EF8B6B1EEF4BA0B400" xlink:type="locator" />
    <definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_4F29049D421508FB9E8E1EEF4BA053EC" xlink:to="loc_us-gaap_AdditionalPaidInCapitalMember_0D1CD2C8C18C77EF8B6B1EEF4BA0B400" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_RetainedEarningsMember" xlink:label="loc_us-gaap_RetainedEarningsMember_982BC302F645DA3803511EEF4BA02725" xlink:type="locator" />
    <definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_4F29049D421508FB9E8E1EEF4BA053EC" xlink:to="loc_us-gaap_RetainedEarningsMember_982BC302F645DA3803511EEF4BA02725" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_AccumulatedOtherComprehensiveIncomeMember" xlink:label="loc_us-gaap_AccumulatedOtherComprehensiveIncomeMember_9FB23D2F83566262D7A41EEF4BA0B59B" xlink:type="locator" />
    <definitionArc order="5" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_4F29049D421508FB9E8E1EEF4BA053EC" xlink:to="loc_us-gaap_AccumulatedOtherComprehensiveIncomeMember_9FB23D2F83566262D7A41EEF4BA0B59B" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_NoncontrollingInterestMember" xlink:label="loc_us-gaap_NoncontrollingInterestMember_A06B74309575B22941AC1EEF4BA0CD9D" xlink:type="locator" />
    <definitionArc order="6" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_4F29049D421508FB9E8E1EEF4BA053EC" xlink:to="loc_us-gaap_NoncontrollingInterestMember_A06B74309575B22941AC1EEF4BA0CD9D" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_IncreaseDecreaseInStockholdersEquityRollForward" xlink:label="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_54999D35B5EB56B1996D1EEF4BA0096D" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_StatementLineItems_D6C59D71D199373110DE1EEF4BA0D85B" xlink:to="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_54999D35B5EB56B1996D1EEF4BA0096D" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_SharesOutstanding" xlink:label="loc_us-gaap_SharesOutstanding_8B438C3DA9A6154BEC0A1EEF4BA10221" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_54999D35B5EB56B1996D1EEF4BA0096D" xlink:to="loc_us-gaap_SharesOutstanding_8B438C3DA9A6154BEC0A1EEF4BA10221" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest" xlink:label="loc_us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest_EF0D26EF24E7992E6B091EEF4BA18892" xlink:type="locator" />
    <definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_54999D35B5EB56B1996D1EEF4BA0096D" xlink:to="loc_us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest_EF0D26EF24E7992E6B091EEF4BA18892" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_OtherComprehensiveIncomeLossAvailableForSaleSecuritiesAdjustmentBeforeTax" xlink:label="loc_us-gaap_OtherComprehensiveIncomeLossAvailableForSaleSecuritiesAdjustmentBeforeTax_3C59A0ABC7E19B48D12A1EEF4BA6FCFA" xlink:type="locator" />
    <definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_54999D35B5EB56B1996D1EEF4BA0096D" xlink:to="loc_us-gaap_OtherComprehensiveIncomeLossAvailableForSaleSecuritiesAdjustmentBeforeTax_3C59A0ABC7E19B48D12A1EEF4BA6FCFA" xlink:type="arc" />
    <loc xlink:href="astc-20160630.xsd#astc_AdjustmentsToAdditionalPaidInCapitalSharesSharebasedCompensationAndExerciseOfStockOptions" xlink:label="loc_astc_AdjustmentsToAdditionalPaidInCapitalSharesSharebasedCompensationAndExerciseOfStockOptions_641D74031868076083A71EEF4BA60F09" xlink:type="locator" />
    <definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_54999D35B5EB56B1996D1EEF4BA0096D" xlink:to="loc_astc_AdjustmentsToAdditionalPaidInCapitalSharesSharebasedCompensationAndExerciseOfStockOptions_641D74031868076083A71EEF4BA60F09" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_AdjustmentsToAdditionalPaidInCapitalSharebasedCompensationAndExerciseOfStockOptions" xlink:label="loc_us-gaap_AdjustmentsToAdditionalPaidInCapitalSharebasedCompensationAndExerciseOfStockOptions_6E718E6A1A443812029F1EEF4BA63E94" xlink:type="locator" />
    <definitionArc order="5" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_54999D35B5EB56B1996D1EEF4BA0096D" xlink:to="loc_us-gaap_AdjustmentsToAdditionalPaidInCapitalSharebasedCompensationAndExerciseOfStockOptions_6E718E6A1A443812029F1EEF4BA63E94" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_StockIssuedDuringPeriodSharesShareBasedCompensationForfeited" xlink:label="loc_us-gaap_StockIssuedDuringPeriodSharesShareBasedCompensationForfeited_8372226E100B865578551EEF4BA6E233" xlink:type="locator" />
    <definitionArc order="6" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_54999D35B5EB56B1996D1EEF4BA0096D" xlink:to="loc_us-gaap_StockIssuedDuringPeriodSharesShareBasedCompensationForfeited_8372226E100B865578551EEF4BA6E233" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_StockIssuedDuringPeriodValueShareBasedCompensationForfeited" xlink:label="loc_us-gaap_StockIssuedDuringPeriodValueShareBasedCompensationForfeited_E060C24F054ABFA331CE1EEF4BA63780" xlink:type="locator" />
    <definitionArc order="7" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_54999D35B5EB56B1996D1EEF4BA0096D" xlink:to="loc_us-gaap_StockIssuedDuringPeriodValueShareBasedCompensationForfeited_E060C24F054ABFA331CE1EEF4BA63780" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_StockIssuedDuringPeriodSharesShareBasedCompensation" xlink:label="loc_us-gaap_StockIssuedDuringPeriodSharesShareBasedCompensation_69FC395CF09A70DE01521EEF4BA6EAC4" xlink:type="locator" />
    <definitionArc order="8" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_54999D35B5EB56B1996D1EEF4BA0096D" xlink:to="loc_us-gaap_StockIssuedDuringPeriodSharesShareBasedCompensation_69FC395CF09A70DE01521EEF4BA6EAC4" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_StockIssuedDuringPeriodValueStockOptionsExercised" xlink:label="loc_us-gaap_StockIssuedDuringPeriodValueStockOptionsExercised_9C47FD554740B29765141EEF4BA62778" xlink:type="locator" />
    <definitionArc order="9" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_54999D35B5EB56B1996D1EEF4BA0096D" xlink:to="loc_us-gaap_StockIssuedDuringPeriodValueStockOptionsExercised_9C47FD554740B29765141EEF4BA62778" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_TreasuryStockSharesAcquired" xlink:label="loc_us-gaap_TreasuryStockSharesAcquired_C48106395C481F3402A91EEF4BA69B07" xlink:type="locator" />
    <definitionArc order="10" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_54999D35B5EB56B1996D1EEF4BA0096D" xlink:to="loc_us-gaap_TreasuryStockSharesAcquired_C48106395C481F3402A91EEF4BA69B07" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_TreasuryStockValueAcquiredCostMethod" xlink:label="loc_us-gaap_TreasuryStockValueAcquiredCostMethod_E7626B5975D1C8D6023F1EEF4BA6890F" xlink:type="locator" />
    <definitionArc order="11" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_54999D35B5EB56B1996D1EEF4BA0096D" xlink:to="loc_us-gaap_TreasuryStockValueAcquiredCostMethod_E7626B5975D1C8D6023F1EEF4BA6890F" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_StockIssuedDuringPeriodSharesRestrictedStockAwardGross" xlink:label="loc_us-gaap_StockIssuedDuringPeriodSharesRestrictedStockAwardGross_232FA260A7F8B4048E0F1EEF4BA6CE64" xlink:type="locator" />
    <definitionArc order="12" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_54999D35B5EB56B1996D1EEF4BA0096D" xlink:to="loc_us-gaap_StockIssuedDuringPeriodSharesRestrictedStockAwardGross_232FA260A7F8B4048E0F1EEF4BA6CE64" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_StockIssuedDuringPeriodValueRestrictedStockAwardGross" xlink:label="loc_us-gaap_StockIssuedDuringPeriodValueRestrictedStockAwardGross_943343A87CDECCBDC0141EEF4BA68F47" xlink:type="locator" />
    <definitionArc order="13" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_54999D35B5EB56B1996D1EEF4BA0096D" xlink:to="loc_us-gaap_StockIssuedDuringPeriodValueRestrictedStockAwardGross_943343A87CDECCBDC0141EEF4BA68F47" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_NoncontrollingInterestIncreaseFromSubsidiaryEquityIssuance" xlink:label="loc_us-gaap_NoncontrollingInterestIncreaseFromSubsidiaryEquityIssuance_3C94468FBFA430C60A861EEF4BA657AB" xlink:type="locator" />
    <definitionArc order="14" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_54999D35B5EB56B1996D1EEF4BA0096D" xlink:to="loc_us-gaap_NoncontrollingInterestIncreaseFromSubsidiaryEquityIssuance_3C94468FBFA430C60A861EEF4BA657AB" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_ProfitLoss" xlink:label="loc_us-gaap_ProfitLoss_EF3410BB24C54FFB045A1EEF4BA7EBE9" xlink:type="locator" />
    <definitionArc order="15" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_54999D35B5EB56B1996D1EEF4BA0096D" xlink:to="loc_us-gaap_ProfitLoss_EF3410BB24C54FFB045A1EEF4BA7EBE9" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_MinorityInterestDecreaseFromDistributionsToNoncontrollingInterestHolders" xlink:label="loc_us-gaap_MinorityInterestDecreaseFromDistributionsToNoncontrollingInterestHolders_CCD1E33585BC4C11830B1EEF4BA76E59" xlink:type="locator" />
    <definitionArc order="16" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_54999D35B5EB56B1996D1EEF4BA0096D" xlink:to="loc_us-gaap_MinorityInterestDecreaseFromDistributionsToNoncontrollingInterestHolders_CCD1E33585BC4C11830B1EEF4BA76E59" xlink:type="arc" />
  </definitionLink>
  <definitionLink xlink:role="http://www.astrotechcorp.com/role/ConsolidatedStatementsOfCashFlows" xlink:type="extended" />
  <definitionLink xlink:role="http://www.astrotechcorp.com/role/ConsolidatedStatementsOfOperationsAndComprehensiveIncomeLoss" xlink:type="extended" />
  <definitionLink xlink:role="http://www.astrotechcorp.com/role/ConsolidatedStatementsOfOperationsAndComprehensiveIncomeLossParenthetical" xlink:type="extended" />
  <definitionLink xlink:role="http://www.astrotechcorp.com/role/Debt" xlink:type="extended" />
  <definitionLink xlink:role="http://www.astrotechcorp.com/role/DebtDetailTextuals" xlink:type="extended">
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_LineOfCreditFacilityLineItems" xlink:label="loc_us-gaap_LineOfCreditFacilityLineItems_3E0AE59652955EB7A5FB1F87DE76DFDF" xlink:type="locator" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_LineOfCreditFacilityTable" xlink:label="loc_us-gaap_LineOfCreditFacilityTable_00D035F332B117964E571F87DE764EFF" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_LineOfCreditFacilityLineItems_3E0AE59652955EB7A5FB1F87DE76DFDF" xlink:to="loc_us-gaap_LineOfCreditFacilityTable_00D035F332B117964E571F87DE764EFF" xlink:type="arc" xbrldt:closed="true" xbrldt:contextElement="segment" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_CreditFacilityAxis" xlink:label="loc_us-gaap_CreditFacilityAxis_B6A00232E911CF8978F31F87DE76A2F0" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_LineOfCreditFacilityTable_00D035F332B117964E571F87DE764EFF" xlink:to="loc_us-gaap_CreditFacilityAxis_B6A00232E911CF8978F31F87DE76A2F0" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_CreditFacilityDomain" xlink:label="loc_us-gaap_CreditFacilityDomain_D2B90791AC56EE772A1F1F87DE765DB4_default" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_CreditFacilityAxis_B6A00232E911CF8978F31F87DE76A2F0" xlink:to="loc_us-gaap_CreditFacilityDomain_D2B90791AC56EE772A1F1F87DE765DB4_default" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_CreditFacilityDomain" xlink:label="loc_us-gaap_CreditFacilityDomain_D2B90791AC56EE772A1F1F87DE765DB4" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_CreditFacilityAxis_B6A00232E911CF8978F31F87DE76A2F0" xlink:to="loc_us-gaap_CreditFacilityDomain_D2B90791AC56EE772A1F1F87DE765DB4" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_SecuredDebtMember" xlink:label="loc_us-gaap_SecuredDebtMember_DDE1E606A4C971CF372D1F87DE76D5DD" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CreditFacilityDomain_D2B90791AC56EE772A1F1F87DE765DB4" xlink:to="loc_us-gaap_SecuredDebtMember_DDE1E606A4C971CF372D1F87DE76D5DD" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_RevolvingCreditFacilityMember" xlink:label="loc_us-gaap_RevolvingCreditFacilityMember_B8A0BA9EDF9B2F1B35521F87DE766350" xlink:type="locator" />
    <definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CreditFacilityDomain_D2B90791AC56EE772A1F1F87DE765DB4" xlink:to="loc_us-gaap_RevolvingCreditFacilityMember_B8A0BA9EDF9B2F1B35521F87DE766350" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_LineOfCreditFacilityMaximumBorrowingCapacity" xlink:label="loc_us-gaap_LineOfCreditFacilityMaximumBorrowingCapacity_4F113DBF9016BA424D541F87DE762238" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LineOfCreditFacilityLineItems_3E0AE59652955EB7A5FB1F87DE76DFDF" xlink:to="loc_us-gaap_LineOfCreditFacilityMaximumBorrowingCapacity_4F113DBF9016BA424D541F87DE762238" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_LineOfCredit" xlink:label="loc_us-gaap_LineOfCredit_4435A0077A43562766D01F87DE7633F6" xlink:type="locator" />
    <definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LineOfCreditFacilityLineItems_3E0AE59652955EB7A5FB1F87DE76DFDF" xlink:to="loc_us-gaap_LineOfCredit_4435A0077A43562766D01F87DE7633F6" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_LongTermDebt" xlink:label="loc_us-gaap_LongTermDebt_75FE49770E667D72F6AD1FB7C2D16930" xlink:type="locator" />
    <definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LineOfCreditFacilityLineItems_3E0AE59652955EB7A5FB1F87DE76DFDF" xlink:to="loc_us-gaap_LongTermDebt_75FE49770E667D72F6AD1FB7C2D16930" xlink:type="arc" />
  </definitionLink>
  <definitionLink xlink:role="http://www.astrotechcorp.com/role/DescriptionOfCompanyAndOperatingEnvironment" xlink:type="extended" />
  <definitionLink xlink:role="http://www.astrotechcorp.com/role/DescriptionOfCompanyAndOperatingEnvironmentDetails" xlink:type="extended" />
  <definitionLink xlink:role="http://www.astrotechcorp.com/role/DiscontinuedOperationsGainOnSaleOfAsoBusinessUnit" xlink:type="extended" />
  <definitionLink xlink:role="http://www.astrotechcorp.com/role/DiscontinuedOperationsGainOnSaleOfAsoBusinessUnitDetailTextuals" xlink:type="extended">
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsLineItems" xlink:label="loc_us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsLineItems_336F4C148A8648EA434E216DFBCE2572" xlink:type="locator" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsTable" xlink:label="loc_us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsTable_7212D530DA4BB18D46B7216DFBCE6C13" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsLineItems_336F4C148A8648EA434E216DFBCE2572" xlink:to="loc_us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsTable_7212D530DA4BB18D46B7216DFBCE6C13" xlink:type="arc" xbrldt:closed="true" xbrldt:contextElement="segment" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsAxis" xlink:label="loc_us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsAxis_7580761E5468452440C5216DFBCE00C2" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsTable_7212D530DA4BB18D46B7216DFBCE6C13" xlink:to="loc_us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsAxis_7580761E5468452440C5216DFBCE00C2" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_DisposalGroupsIncludingDiscontinuedOperationsNameDomain" xlink:label="loc_us-gaap_DisposalGroupsIncludingDiscontinuedOperationsNameDomain_BF755689E0E79976A417216DFBCEE7F8_default" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsAxis_7580761E5468452440C5216DFBCE00C2" xlink:to="loc_us-gaap_DisposalGroupsIncludingDiscontinuedOperationsNameDomain_BF755689E0E79976A417216DFBCEE7F8_default" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_DisposalGroupsIncludingDiscontinuedOperationsNameDomain" xlink:label="loc_us-gaap_DisposalGroupsIncludingDiscontinuedOperationsNameDomain_BF755689E0E79976A417216DFBCEE7F8" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsAxis_7580761E5468452440C5216DFBCE00C2" xlink:to="loc_us-gaap_DisposalGroupsIncludingDiscontinuedOperationsNameDomain_BF755689E0E79976A417216DFBCEE7F8" xlink:type="arc" />
    <loc xlink:href="astc-20160630.xsd#astc_AstrotechSpaceOperationsMember" xlink:label="loc_astc_AstrotechSpaceOperationsMember_E3DCBB3BE78A7D2E73BA216DFBCE1B6C" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DisposalGroupsIncludingDiscontinuedOperationsNameDomain_BF755689E0E79976A417216DFBCEE7F8" xlink:to="loc_astc_AstrotechSpaceOperationsMember_E3DCBB3BE78A7D2E73BA216DFBCE1B6C" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_CreditFacilityAxis" xlink:label="loc_us-gaap_CreditFacilityAxis_C7F8AE146A89F86654DA216DFBCE267E" xlink:type="locator" />
    <definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsTable_7212D530DA4BB18D46B7216DFBCE6C13" xlink:to="loc_us-gaap_CreditFacilityAxis_C7F8AE146A89F86654DA216DFBCE267E" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_CreditFacilityDomain" xlink:label="loc_us-gaap_CreditFacilityDomain_81D80E37442CE6E8A630216DFBCEC3D2_default" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_CreditFacilityAxis_C7F8AE146A89F86654DA216DFBCE267E" xlink:to="loc_us-gaap_CreditFacilityDomain_81D80E37442CE6E8A630216DFBCEC3D2_default" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_CreditFacilityDomain" xlink:label="loc_us-gaap_CreditFacilityDomain_81D80E37442CE6E8A630216DFBCEC3D2" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_CreditFacilityAxis_C7F8AE146A89F86654DA216DFBCE267E" xlink:to="loc_us-gaap_CreditFacilityDomain_81D80E37442CE6E8A630216DFBCEC3D2" xlink:type="arc" />
    <loc xlink:href="astc-20160630.xsd#astc_TermLoanMember" xlink:label="loc_astc_TermLoanMember_C80720551092EBCBA3A9216DFBCE07FE" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CreditFacilityDomain_81D80E37442CE6E8A630216DFBCEC3D2" xlink:to="loc_astc_TermLoanMember_C80720551092EBCBA3A9216DFBCE07FE" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_ProceedsFromDivestitureOfBusinesses" xlink:label="loc_us-gaap_ProceedsFromDivestitureOfBusinesses_DD133AB45137950BAEAB216DFBCFB04A" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsLineItems_336F4C148A8648EA434E216DFBCE2572" xlink:to="loc_us-gaap_ProceedsFromDivestitureOfBusinesses_DD133AB45137950BAEAB216DFBCFB04A" xlink:type="arc" />
    <loc xlink:href="astc-20160630.xsd#astc_WorkingCapitalSurplusDeficit" xlink:label="loc_astc_WorkingCapitalSurplusDeficit_1065E80D2E8456A171B5216DFBCFE8B0" xlink:type="locator" />
    <definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsLineItems_336F4C148A8648EA434E216DFBCE2572" xlink:to="loc_astc_WorkingCapitalSurplusDeficit_1065E80D2E8456A171B5216DFBCFE8B0" xlink:type="arc" />
    <loc xlink:href="astc-20160630.xsd#astc_IndemnnityHoldbackCurrent" xlink:label="loc_astc_IndemnnityHoldbackCurrent_2E91A7988F756526B52F216DFBCFEB21" xlink:type="locator" />
    <definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsLineItems_336F4C148A8648EA434E216DFBCE2572" xlink:to="loc_astc_IndemnnityHoldbackCurrent_2E91A7988F756526B52F216DFBCFEB21" xlink:type="arc" />
    <loc xlink:href="astc-20160630.xsd#astc_IndemnityHoldbackReleasedPercent" xlink:label="loc_astc_IndemnityHoldbackReleasedPercent_6FA7E9A7C11CD0271049216DFBCF2E5D" xlink:type="locator" />
    <definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsLineItems_336F4C148A8648EA434E216DFBCE2572" xlink:to="loc_astc_IndemnityHoldbackReleasedPercent_6FA7E9A7C11CD0271049216DFBCF2E5D" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_RepaymentsOfDebt" xlink:label="loc_us-gaap_RepaymentsOfDebt_C36834352875402AFD14216DFBCF4AFC" xlink:type="locator" />
    <definitionArc order="5" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsLineItems_336F4C148A8648EA434E216DFBCE2572" xlink:to="loc_us-gaap_RepaymentsOfDebt_C36834352875402AFD14216DFBCF4AFC" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_InterestExpenseDebt" xlink:label="loc_us-gaap_InterestExpenseDebt_3DB4639998EAE7FC92D4216DFBCFE051" xlink:type="locator" />
    <definitionArc order="6" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsLineItems_336F4C148A8648EA434E216DFBCE2572" xlink:to="loc_us-gaap_InterestExpenseDebt_3DB4639998EAE7FC92D4216DFBCFE051" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_DiscontinuedOperationGainLossFromDisposalOfDiscontinuedOperationBeforeIncomeTax" xlink:label="loc_us-gaap_DiscontinuedOperationGainLossFromDisposalOfDiscontinuedOperationBeforeIncomeTax_2AA9CD6F70C8402C4A8C216DFBCF32F4" xlink:type="locator" />
    <definitionArc order="7" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsLineItems_336F4C148A8648EA434E216DFBCE2572" xlink:to="loc_us-gaap_DiscontinuedOperationGainLossFromDisposalOfDiscontinuedOperationBeforeIncomeTax_2AA9CD6F70C8402C4A8C216DFBCF32F4" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_DiscontinuedOperationGainLossOnDisposalOfDiscontinuedOperationNetOfTax" xlink:label="loc_us-gaap_DiscontinuedOperationGainLossOnDisposalOfDiscontinuedOperationNetOfTax_8FC747BD57E7A9C312CE216DFBCF24C2" xlink:type="locator" />
    <definitionArc order="8" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsLineItems_336F4C148A8648EA434E216DFBCE2572" xlink:to="loc_us-gaap_DiscontinuedOperationGainLossOnDisposalOfDiscontinuedOperationNetOfTax_8FC747BD57E7A9C312CE216DFBCF24C2" xlink:type="arc" />
  </definitionLink>
  <definitionLink xlink:role="http://www.astrotechcorp.com/role/DiscontinuedOperationsGainOnSaleOfAsoBusinessUnitDetails" xlink:type="extended">
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsLineItems" xlink:label="loc_us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsLineItems_E26C704CC9068CA888F900B9D12C4AA3" xlink:type="locator" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsTable" xlink:label="loc_us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsTable_FD38E9F31972F30D016000B9D12C371E" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsLineItems_E26C704CC9068CA888F900B9D12C4AA3" xlink:to="loc_us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsTable_FD38E9F31972F30D016000B9D12C371E" xlink:type="arc" xbrldt:closed="true" xbrldt:contextElement="segment" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsAxis" xlink:label="loc_us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsAxis_D524561D5F5A69BAAED000B9D12CFC62" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsTable_FD38E9F31972F30D016000B9D12C371E" xlink:to="loc_us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsAxis_D524561D5F5A69BAAED000B9D12CFC62" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_DisposalGroupsIncludingDiscontinuedOperationsNameDomain" xlink:label="loc_us-gaap_DisposalGroupsIncludingDiscontinuedOperationsNameDomain_5164E0DD67B828B023C600B9D12C857D_default" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsAxis_D524561D5F5A69BAAED000B9D12CFC62" xlink:to="loc_us-gaap_DisposalGroupsIncludingDiscontinuedOperationsNameDomain_5164E0DD67B828B023C600B9D12C857D_default" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_DisposalGroupsIncludingDiscontinuedOperationsNameDomain" xlink:label="loc_us-gaap_DisposalGroupsIncludingDiscontinuedOperationsNameDomain_5164E0DD67B828B023C600B9D12C857D" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsAxis_D524561D5F5A69BAAED000B9D12CFC62" xlink:to="loc_us-gaap_DisposalGroupsIncludingDiscontinuedOperationsNameDomain_5164E0DD67B828B023C600B9D12C857D" xlink:type="arc" />
    <loc xlink:href="astc-20160630.xsd#astc_AstrotechSpaceOperationsMember" xlink:label="loc_astc_AstrotechSpaceOperationsMember_F12B1609DCED2F8BCD6B00B9D12CAF80" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DisposalGroupsIncludingDiscontinuedOperationsNameDomain_5164E0DD67B828B023C600B9D12C857D" xlink:to="loc_astc_AstrotechSpaceOperationsMember_F12B1609DCED2F8BCD6B00B9D12CAF80" xlink:type="arc" />
    <loc xlink:href="astc-20160630.xsd#astc_DiscontinuedOperationProceedsFromSaleOfBusiness" xlink:label="loc_astc_DiscontinuedOperationProceedsFromSaleOfBusiness_EAD37C1B96DFB0859DC100B9D12C05B6" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsLineItems_E26C704CC9068CA888F900B9D12C4AA3" xlink:to="loc_astc_DiscontinuedOperationProceedsFromSaleOfBusiness_EAD37C1B96DFB0859DC100B9D12C05B6" xlink:type="arc" />
    <loc xlink:href="astc-20160630.xsd#astc_IndemnnityHoldbackCurrent" xlink:label="loc_astc_IndemnnityHoldbackCurrent_72409CEA6B3335ABBED900B9D12CBE35" xlink:type="locator" />
    <definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsLineItems_E26C704CC9068CA888F900B9D12C4AA3" xlink:to="loc_astc_IndemnnityHoldbackCurrent_72409CEA6B3335ABBED900B9D12CBE35" xlink:type="arc" />
    <loc xlink:href="astc-20160630.xsd#astc_LiabilitiesAssumedOfDisposalGroupIncludingDiscontinuedOperation" xlink:label="loc_astc_LiabilitiesAssumedOfDisposalGroupIncludingDiscontinuedOperation_612816F2120B063ACB1B00B9D12CCDEC" xlink:type="locator" />
    <definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsLineItems_E26C704CC9068CA888F900B9D12C4AA3" xlink:to="loc_astc_LiabilitiesAssumedOfDisposalGroupIncludingDiscontinuedOperation_612816F2120B063ACB1B00B9D12CCDEC" xlink:type="arc" />
    <loc xlink:href="astc-20160630.xsd#astc_DisposalGroupIncludingDiscontinuedNetBookValueOfAssetsSold" xlink:label="loc_astc_DisposalGroupIncludingDiscontinuedNetBookValueOfAssetsSold_FF1CD0A7E78D7F46BC4800B9D12C2FC6" xlink:type="locator" />
    <definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsLineItems_E26C704CC9068CA888F900B9D12C4AA3" xlink:to="loc_astc_DisposalGroupIncludingDiscontinuedNetBookValueOfAssetsSold_FF1CD0A7E78D7F46BC4800B9D12C2FC6" xlink:type="arc" />
    <loc xlink:href="astc-20160630.xsd#astc_DisposalGroupIncludingDiscontinuedOperationOther" xlink:label="loc_astc_DisposalGroupIncludingDiscontinuedOperationOther_AC72CA9CE91FB3A002A000B9D12CD6AA" xlink:type="locator" />
    <definitionArc order="5" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsLineItems_E26C704CC9068CA888F900B9D12C4AA3" xlink:to="loc_astc_DisposalGroupIncludingDiscontinuedOperationOther_AC72CA9CE91FB3A002A000B9D12CD6AA" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_DiscontinuedOperationGainLossFromDisposalOfDiscontinuedOperationBeforeIncomeTax" xlink:label="loc_us-gaap_DiscontinuedOperationGainLossFromDisposalOfDiscontinuedOperationBeforeIncomeTax_52A3CA116D2CE95CBFBE00B9D12CFC19" xlink:type="locator" />
    <definitionArc order="6" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsLineItems_E26C704CC9068CA888F900B9D12C4AA3" xlink:to="loc_us-gaap_DiscontinuedOperationGainLossFromDisposalOfDiscontinuedOperationBeforeIncomeTax_52A3CA116D2CE95CBFBE00B9D12CFC19" xlink:type="arc" />
  </definitionLink>
  <definitionLink xlink:role="http://www.astrotechcorp.com/role/DiscontinuedOperationsGainOnSaleOfAsoBusinessUnitDetails2" xlink:type="extended">
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsLineItems" xlink:label="loc_us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsLineItems_839E6D126B7F25FD12FAA6DCD6A1507C" xlink:type="locator" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsTable" xlink:label="loc_us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsTable_419F21A175438651B572A6DCD6A12B3E" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsLineItems_839E6D126B7F25FD12FAA6DCD6A1507C" xlink:to="loc_us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsTable_419F21A175438651B572A6DCD6A12B3E" xlink:type="arc" xbrldt:closed="true" xbrldt:contextElement="segment" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsAxis" xlink:label="loc_us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsAxis_6D7ADECCC99BCB796FAEA6DCD6A1FDD0" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsTable_419F21A175438651B572A6DCD6A12B3E" xlink:to="loc_us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsAxis_6D7ADECCC99BCB796FAEA6DCD6A1FDD0" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_DisposalGroupsIncludingDiscontinuedOperationsNameDomain" xlink:label="loc_us-gaap_DisposalGroupsIncludingDiscontinuedOperationsNameDomain_6DEC160AA843CB2797E2A6DCD6A1883A_default" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsAxis_6D7ADECCC99BCB796FAEA6DCD6A1FDD0" xlink:to="loc_us-gaap_DisposalGroupsIncludingDiscontinuedOperationsNameDomain_6DEC160AA843CB2797E2A6DCD6A1883A_default" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_DisposalGroupsIncludingDiscontinuedOperationsNameDomain" xlink:label="loc_us-gaap_DisposalGroupsIncludingDiscontinuedOperationsNameDomain_6DEC160AA843CB2797E2A6DCD6A1883A" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsAxis_6D7ADECCC99BCB796FAEA6DCD6A1FDD0" xlink:to="loc_us-gaap_DisposalGroupsIncludingDiscontinuedOperationsNameDomain_6DEC160AA843CB2797E2A6DCD6A1883A" xlink:type="arc" />
    <loc xlink:href="astc-20160630.xsd#astc_AstrotechSpaceOperationsMember" xlink:label="loc_astc_AstrotechSpaceOperationsMember_A3635E462DCF9A504FD9A6DCD6A115F0" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DisposalGroupsIncludingDiscontinuedOperationsNameDomain_6DEC160AA843CB2797E2A6DCD6A1883A" xlink:to="loc_astc_AstrotechSpaceOperationsMember_A3635E462DCF9A504FD9A6DCD6A115F0" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_DisposalGroupIncludingDiscontinuedOperationRevenue" xlink:label="loc_us-gaap_DisposalGroupIncludingDiscontinuedOperationRevenue_B9AA68A875C3880D8523A6DCD6A19387" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsLineItems_839E6D126B7F25FD12FAA6DCD6A1507C" xlink:to="loc_us-gaap_DisposalGroupIncludingDiscontinuedOperationRevenue_B9AA68A875C3880D8523A6DCD6A19387" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_DisposalGroupIncludingDiscontinuedOperationCostsOfGoodsSold" xlink:label="loc_us-gaap_DisposalGroupIncludingDiscontinuedOperationCostsOfGoodsSold_0FD22208CDB953A7593AA6DCD6A1A4F5" xlink:type="locator" />
    <definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsLineItems_839E6D126B7F25FD12FAA6DCD6A1507C" xlink:to="loc_us-gaap_DisposalGroupIncludingDiscontinuedOperationCostsOfGoodsSold_0FD22208CDB953A7593AA6DCD6A1A4F5" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_DisposalGroupIncludingDiscontinuedOperationGeneralAndAdministrativeExpense" xlink:label="loc_us-gaap_DisposalGroupIncludingDiscontinuedOperationGeneralAndAdministrativeExpense_9EC6EE9FEF5875C68B38A6DCD6A17E5E" xlink:type="locator" />
    <definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsLineItems_839E6D126B7F25FD12FAA6DCD6A1507C" xlink:to="loc_us-gaap_DisposalGroupIncludingDiscontinuedOperationGeneralAndAdministrativeExpense_9EC6EE9FEF5875C68B38A6DCD6A17E5E" xlink:type="arc" />
    <loc xlink:href="astc-20160630.xsd#astc_DisposalGroupIncludingDiscontinuedOperationInterestExpenseAndOtherExpenses" xlink:label="loc_astc_DisposalGroupIncludingDiscontinuedOperationInterestExpenseAndOtherExpenses_9482D55B037FF4734C97A6DCD6A1CDA5" xlink:type="locator" />
    <definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsLineItems_839E6D126B7F25FD12FAA6DCD6A1507C" xlink:to="loc_astc_DisposalGroupIncludingDiscontinuedOperationInterestExpenseAndOtherExpenses_9482D55B037FF4734C97A6DCD6A1CDA5" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_DiscontinuedOperationGainLossFromDisposalOfDiscontinuedOperationBeforeIncomeTax" xlink:label="loc_us-gaap_DiscontinuedOperationGainLossFromDisposalOfDiscontinuedOperationBeforeIncomeTax_5F91B4999315D0D425C4A6DCD6A1E08E" xlink:type="locator" />
    <definitionArc order="5" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsLineItems_839E6D126B7F25FD12FAA6DCD6A1507C" xlink:to="loc_us-gaap_DiscontinuedOperationGainLossFromDisposalOfDiscontinuedOperationBeforeIncomeTax_5F91B4999315D0D425C4A6DCD6A1E08E" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_DiscontinuedOperationTaxEffectOfIncomeLossFromDisposalOfDiscontinuedOperation" xlink:label="loc_us-gaap_DiscontinuedOperationTaxEffectOfIncomeLossFromDisposalOfDiscontinuedOperation_0B0FCE093F238EB0CC55A6DCD6A1A3DB" xlink:type="locator" />
    <definitionArc order="6" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsLineItems_839E6D126B7F25FD12FAA6DCD6A1507C" xlink:to="loc_us-gaap_DiscontinuedOperationTaxEffectOfIncomeLossFromDisposalOfDiscontinuedOperation_0B0FCE093F238EB0CC55A6DCD6A1A3DB" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_IncomeLossFromDiscontinuedOperationsNetOfTax" xlink:label="loc_us-gaap_IncomeLossFromDiscontinuedOperationsNetOfTax_52A448ECE4883AE452A6A6DCD6A16411" xlink:type="locator" />
    <definitionArc order="7" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsLineItems_839E6D126B7F25FD12FAA6DCD6A1507C" xlink:to="loc_us-gaap_IncomeLossFromDiscontinuedOperationsNetOfTax_52A448ECE4883AE452A6A6DCD6A16411" xlink:type="arc" />
  </definitionLink>
  <definitionLink xlink:role="http://www.astrotechcorp.com/role/DiscontinuedOperationsGainOnSaleOfAsoBusinessUnitTables" xlink:type="extended" />
  <definitionLink xlink:role="http://www.astrotechcorp.com/role/DocumentAndEntityInformation" xlink:type="extended" />
  <definitionLink xlink:role="http://www.astrotechcorp.com/role/EmployeeBenefitPlans" xlink:type="extended" />
  <definitionLink xlink:role="http://www.astrotechcorp.com/role/EmployeeBenefitPlansDetailTextuals" xlink:type="extended" />
  <definitionLink xlink:role="http://www.astrotechcorp.com/role/FairValueOfFinancialInstruments" xlink:type="extended" />
  <definitionLink xlink:role="http://www.astrotechcorp.com/role/FairValueOfFinancialInstrumentsDetails" xlink:type="extended">
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems" xlink:label="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_7246FEDF61BEC42C88CF1FBFE6F7C689" xlink:type="locator" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_FairValueByBalanceSheetGroupingTable" xlink:label="loc_us-gaap_FairValueByBalanceSheetGroupingTable_5067189F88546B3C80421FBFE6F631DA" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_7246FEDF61BEC42C88CF1FBFE6F7C689" xlink:to="loc_us-gaap_FairValueByBalanceSheetGroupingTable_5067189F88546B3C80421FBFE6F631DA" xlink:type="arc" xbrldt:closed="true" xbrldt:contextElement="segment" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_FairValueByFairValueHierarchyLevelAxis" xlink:label="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_8D39643468A394247A071FBFE6F6D3C9" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValueByBalanceSheetGroupingTable_5067189F88546B3C80421FBFE6F631DA" xlink:to="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_8D39643468A394247A071FBFE6F6D3C9" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_FairValueMeasurementsFairValueHierarchyDomain" xlink:label="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_8FDF2AE54B30758EC9CA1FBFE6F6EF17_default" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_8D39643468A394247A071FBFE6F6D3C9" xlink:to="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_8FDF2AE54B30758EC9CA1FBFE6F6EF17_default" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_FairValueMeasurementsFairValueHierarchyDomain" xlink:label="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_8FDF2AE54B30758EC9CA1FBFE6F6EF17" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_8D39643468A394247A071FBFE6F6D3C9" xlink:to="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_8FDF2AE54B30758EC9CA1FBFE6F6EF17" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_FairValueInputsLevel1Member" xlink:label="loc_us-gaap_FairValueInputsLevel1Member_2F3EBD78C2F4A132F34D1FBFE6F6AD79" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_8FDF2AE54B30758EC9CA1FBFE6F6EF17" xlink:to="loc_us-gaap_FairValueInputsLevel1Member_2F3EBD78C2F4A132F34D1FBFE6F6AD79" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_FairValueInputsLevel2Member" xlink:label="loc_us-gaap_FairValueInputsLevel2Member_701A4D34D2D55F9A87AF1FBFE6F7D55A" xlink:type="locator" />
    <definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_8FDF2AE54B30758EC9CA1FBFE6F6EF17" xlink:to="loc_us-gaap_FairValueInputsLevel2Member_701A4D34D2D55F9A87AF1FBFE6F7D55A" xlink:type="arc" />
    <loc xlink:href="astc-20160630.xsd#astc_MutualFundsCarringValue" xlink:label="loc_astc_MutualFundsCarringValue_C17611004C5B8F4CB2891FBFE6F79FCC" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_7246FEDF61BEC42C88CF1FBFE6F7C689" xlink:to="loc_astc_MutualFundsCarringValue_C17611004C5B8F4CB2891FBFE6F79FCC" xlink:type="arc" />
    <loc xlink:href="astc-20160630.xsd#astc_MutualFundsFairValue" xlink:label="loc_astc_MutualFundsFairValue_ED484745E7A35DE698001FBFE6F74C05" xlink:type="locator" />
    <definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_7246FEDF61BEC42C88CF1FBFE6F7C689" xlink:to="loc_astc_MutualFundsFairValue_ED484745E7A35DE698001FBFE6F74C05" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_HeldToMaturitySecuritiesDebtMaturitiesWithinOneYearNetCarryingAmount" xlink:label="loc_us-gaap_HeldToMaturitySecuritiesDebtMaturitiesWithinOneYearNetCarryingAmount_5F28952041A00AEF9EC51FBFE6F797FA" xlink:type="locator" />
    <definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_7246FEDF61BEC42C88CF1FBFE6F7C689" xlink:to="loc_us-gaap_HeldToMaturitySecuritiesDebtMaturitiesWithinOneYearNetCarryingAmount_5F28952041A00AEF9EC51FBFE6F797FA" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_HeldToMaturitySecuritiesDebtMaturitiesWithinOneYearFairValue" xlink:label="loc_us-gaap_HeldToMaturitySecuritiesDebtMaturitiesWithinOneYearFairValue_27F72947471EF6E6F9991FBFE6F70D26" xlink:type="locator" />
    <definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_7246FEDF61BEC42C88CF1FBFE6F7C689" xlink:to="loc_us-gaap_HeldToMaturitySecuritiesDebtMaturitiesWithinOneYearFairValue_27F72947471EF6E6F9991FBFE6F70D26" xlink:type="arc" />
    <loc xlink:href="astc-20160630.xsd#astc_HeldtomaturitySecuritiesDebtMaturitiesafterOneThroughThreeYearsNetCarryingAmount" xlink:label="loc_astc_HeldtomaturitySecuritiesDebtMaturitiesafterOneThroughThreeYearsNetCarryingAmount_BA0B3CD95193E00B60C61FBFE6F7344E" xlink:type="locator" />
    <definitionArc order="5" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_7246FEDF61BEC42C88CF1FBFE6F7C689" xlink:to="loc_astc_HeldtomaturitySecuritiesDebtMaturitiesafterOneThroughThreeYearsNetCarryingAmount_BA0B3CD95193E00B60C61FBFE6F7344E" xlink:type="arc" />
    <loc xlink:href="astc-20160630.xsd#astc_HeldtomaturitySecuritiesDebtMaturitiesafterOneThroughThreeYearsFairValue" xlink:label="loc_astc_HeldtomaturitySecuritiesDebtMaturitiesafterOneThroughThreeYearsFairValue_2034093B028E2003EFD11FBFE6F72AB7" xlink:type="locator" />
    <definitionArc order="6" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_7246FEDF61BEC42C88CF1FBFE6F7C689" xlink:to="loc_astc_HeldtomaturitySecuritiesDebtMaturitiesafterOneThroughThreeYearsFairValue_2034093B028E2003EFD11FBFE6F72AB7" xlink:type="arc" />
    <loc xlink:href="astc-20160630.xsd#astc_HeldtomaturitySecuritiesDebtMaturitiesafterThreeThroughFiveYearsNetCarryingAmount" xlink:label="loc_astc_HeldtomaturitySecuritiesDebtMaturitiesafterThreeThroughFiveYearsNetCarryingAmount_B6690B81F62EF5FB7B2C1FBFE6F71A88" xlink:type="locator" />
    <definitionArc order="7" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_7246FEDF61BEC42C88CF1FBFE6F7C689" xlink:to="loc_astc_HeldtomaturitySecuritiesDebtMaturitiesafterThreeThroughFiveYearsNetCarryingAmount_B6690B81F62EF5FB7B2C1FBFE6F71A88" xlink:type="arc" />
    <loc xlink:href="astc-20160630.xsd#astc_HeldtomaturitySecuritiesDebtMaturitiesafterThreeThroughFiveYearsFairValue" xlink:label="loc_astc_HeldtomaturitySecuritiesDebtMaturitiesafterThreeThroughFiveYearsFairValue_F947847AB21E7F0978291FBFE6F7B907" xlink:type="locator" />
    <definitionArc order="8" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_7246FEDF61BEC42C88CF1FBFE6F7C689" xlink:to="loc_astc_HeldtomaturitySecuritiesDebtMaturitiesafterThreeThroughFiveYearsFairValue_F947847AB21E7F0978291FBFE6F7B907" xlink:type="arc" />
    <loc xlink:href="astc-20160630.xsd#astc_HeldToMaturitySecuritiesDebtMaturities1To90DaysNetCarryingAmount" xlink:label="loc_astc_HeldToMaturitySecuritiesDebtMaturities1To90DaysNetCarryingAmount_1E01CDD88CAB0B53BE181FBFE6F768C4" xlink:type="locator" />
    <definitionArc order="9" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_7246FEDF61BEC42C88CF1FBFE6F7C689" xlink:to="loc_astc_HeldToMaturitySecuritiesDebtMaturities1To90DaysNetCarryingAmount_1E01CDD88CAB0B53BE181FBFE6F768C4" xlink:type="arc" />
    <loc xlink:href="astc-20160630.xsd#astc_HeldToMaturitySecuritiesDebtMaturities1To90DaysFairValue" xlink:label="loc_astc_HeldToMaturitySecuritiesDebtMaturities1To90DaysFairValue_A5E1CE5FFDA54E5C205A1FBFE6F72C5F" xlink:type="locator" />
    <definitionArc order="10" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_7246FEDF61BEC42C88CF1FBFE6F7C689" xlink:to="loc_astc_HeldToMaturitySecuritiesDebtMaturities1To90DaysFairValue_A5E1CE5FFDA54E5C205A1FBFE6F72C5F" xlink:type="arc" />
    <loc xlink:href="astc-20160630.xsd#astc_HeldToMaturitySecuritiesDebtMaturities91To360DaysNetCarryingAmount" xlink:label="loc_astc_HeldToMaturitySecuritiesDebtMaturities91To360DaysNetCarryingAmount_DFBC6716F95AF5E65D851FBFE6F7569D" xlink:type="locator" />
    <definitionArc order="11" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_7246FEDF61BEC42C88CF1FBFE6F7C689" xlink:to="loc_astc_HeldToMaturitySecuritiesDebtMaturities91To360DaysNetCarryingAmount_DFBC6716F95AF5E65D851FBFE6F7569D" xlink:type="arc" />
    <loc xlink:href="astc-20160630.xsd#astc_HeldToMaturitySecuritiesDebtMaturities91To360DaysFairValue" xlink:label="loc_astc_HeldToMaturitySecuritiesDebtMaturities91To360DaysFairValue_EC4C5431F0F1989BEF001FBFE6F755FB" xlink:type="locator" />
    <definitionArc order="12" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_7246FEDF61BEC42C88CF1FBFE6F7C689" xlink:to="loc_astc_HeldToMaturitySecuritiesDebtMaturities91To360DaysFairValue_EC4C5431F0F1989BEF001FBFE6F755FB" xlink:type="arc" />
    <loc xlink:href="astc-20160630.xsd#astc_HeldToMaturitySecuritiesDebtMaturitiesOver360DaysNetCarryingAmount" xlink:label="loc_astc_HeldToMaturitySecuritiesDebtMaturitiesOver360DaysNetCarryingAmount_27A1974C7205AE6B32791FBFE6F7FC4B" xlink:type="locator" />
    <definitionArc order="13" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_7246FEDF61BEC42C88CF1FBFE6F7C689" xlink:to="loc_astc_HeldToMaturitySecuritiesDebtMaturitiesOver360DaysNetCarryingAmount_27A1974C7205AE6B32791FBFE6F7FC4B" xlink:type="arc" />
    <loc xlink:href="astc-20160630.xsd#astc_HeldToMaturitySecuritiesDebtMaturitiesOver360DaysFairValue" xlink:label="loc_astc_HeldToMaturitySecuritiesDebtMaturitiesOver360DaysFairValue_4708CEA9E6F2E32CA0901FBFE6F83C5C" xlink:type="locator" />
    <definitionArc order="14" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_7246FEDF61BEC42C88CF1FBFE6F7C689" xlink:to="loc_astc_HeldToMaturitySecuritiesDebtMaturitiesOver360DaysFairValue_4708CEA9E6F2E32CA0901FBFE6F83C5C" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_Investments" xlink:label="loc_us-gaap_Investments_9226203076D560EF6B921FBFE6F80AB5" xlink:type="locator" />
    <definitionArc order="15" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_7246FEDF61BEC42C88CF1FBFE6F7C689" xlink:to="loc_us-gaap_Investments_9226203076D560EF6B921FBFE6F80AB5" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_InvestmentsFairValueDisclosure" xlink:label="loc_us-gaap_InvestmentsFairValueDisclosure_6F8CDD00904AE950D3C51FBFE6F839B7" xlink:type="locator" />
    <definitionArc order="16" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_7246FEDF61BEC42C88CF1FBFE6F7C689" xlink:to="loc_us-gaap_InvestmentsFairValueDisclosure_6F8CDD00904AE950D3C51FBFE6F839B7" xlink:type="arc" />
  </definitionLink>
  <definitionLink xlink:role="http://www.astrotechcorp.com/role/FairValueOfFinancialInstrumentsTables" xlink:type="extended" />
  <definitionLink xlink:role="http://www.astrotechcorp.com/role/IncomeTaxes" xlink:type="extended" />
  <definitionLink xlink:role="http://www.astrotechcorp.com/role/IncomeTaxesDetailTextuals" xlink:type="extended" />
  <definitionLink xlink:role="http://www.astrotechcorp.com/role/IncomeTaxesDetails" xlink:type="extended" />
  <definitionLink xlink:role="http://www.astrotechcorp.com/role/IncomeTaxesDetails2" xlink:type="extended" />
  <definitionLink xlink:role="http://www.astrotechcorp.com/role/IncomeTaxesDetails3" xlink:type="extended" />
  <definitionLink xlink:role="http://www.astrotechcorp.com/role/IncomeTaxesDetails4" xlink:type="extended" />
  <definitionLink xlink:role="http://www.astrotechcorp.com/role/IncomeTaxesIncomeTaxesDetails1" xlink:type="extended" />
  <definitionLink xlink:role="http://www.astrotechcorp.com/role/IncomeTaxesTables" xlink:type="extended" />
  <definitionLink xlink:role="http://www.astrotechcorp.com/role/Investments" xlink:type="extended" />
  <definitionLink xlink:role="http://www.astrotechcorp.com/role/InvestmentsAvailableForSaleSecuritiesDetails" xlink:type="extended">
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_ScheduleOfAvailableForSaleSecuritiesLineItems" xlink:label="loc_us-gaap_ScheduleOfAvailableForSaleSecuritiesLineItems_DB22FB6771B60CDCB5FC1EEF4A9FF550" xlink:type="locator" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_ScheduleOfAvailableForSaleSecuritiesTable" xlink:label="loc_us-gaap_ScheduleOfAvailableForSaleSecuritiesTable_108C0C21227ED9ADD42C1EEF4A994541" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_ScheduleOfAvailableForSaleSecuritiesLineItems_DB22FB6771B60CDCB5FC1EEF4A9FF550" xlink:to="loc_us-gaap_ScheduleOfAvailableForSaleSecuritiesTable_108C0C21227ED9ADD42C1EEF4A994541" xlink:type="arc" xbrldt:closed="true" xbrldt:contextElement="segment" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_InvestmentTypeAxis" xlink:label="loc_us-gaap_InvestmentTypeAxis_0C681B7845E7DAD1DB231EEF4A99C263" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfAvailableForSaleSecuritiesTable_108C0C21227ED9ADD42C1EEF4A994541" xlink:to="loc_us-gaap_InvestmentTypeAxis_0C681B7845E7DAD1DB231EEF4A99C263" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_InvestmentTypeCategorizationMember" xlink:label="loc_us-gaap_InvestmentTypeCategorizationMember_28C3BE59A2A5CCFACC4D1EEF4A9A341F_default" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_InvestmentTypeAxis_0C681B7845E7DAD1DB231EEF4A99C263" xlink:to="loc_us-gaap_InvestmentTypeCategorizationMember_28C3BE59A2A5CCFACC4D1EEF4A9A341F_default" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_InvestmentTypeCategorizationMember" xlink:label="loc_us-gaap_InvestmentTypeCategorizationMember_28C3BE59A2A5CCFACC4D1EEF4A9A341F" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_InvestmentTypeAxis_0C681B7845E7DAD1DB231EEF4A99C263" xlink:to="loc_us-gaap_InvestmentTypeCategorizationMember_28C3BE59A2A5CCFACC4D1EEF4A9A341F" xlink:type="arc" />
    <loc xlink:href="astc-20160630.xsd#astc_MutualFundsMember" xlink:label="loc_astc_MutualFundsMember_31858D73BAE4DD0A26791EEF4A9A2883" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_InvestmentTypeCategorizationMember_28C3BE59A2A5CCFACC4D1EEF4A9A341F" xlink:to="loc_astc_MutualFundsMember_31858D73BAE4DD0A26791EEF4A9A2883" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_AvailableForSaleSecuritiesAmortizedCost" xlink:label="loc_us-gaap_AvailableForSaleSecuritiesAmortizedCost_B4C1A8F8C8A7DDD52BFB1EEF4A9F4925" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfAvailableForSaleSecuritiesLineItems_DB22FB6771B60CDCB5FC1EEF4A9FF550" xlink:to="loc_us-gaap_AvailableForSaleSecuritiesAmortizedCost_B4C1A8F8C8A7DDD52BFB1EEF4A9F4925" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_AvailableForSaleSecuritiesAccumulatedGrossUnrealizedGainBeforeTax" xlink:label="loc_us-gaap_AvailableForSaleSecuritiesAccumulatedGrossUnrealizedGainBeforeTax_769D318B7F55E57004E21EEF4AA0C5C5" xlink:type="locator" />
    <definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfAvailableForSaleSecuritiesLineItems_DB22FB6771B60CDCB5FC1EEF4A9FF550" xlink:to="loc_us-gaap_AvailableForSaleSecuritiesAccumulatedGrossUnrealizedGainBeforeTax_769D318B7F55E57004E21EEF4AA0C5C5" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_AvailableForSaleSecuritiesAccumulatedGrossUnrealizedLossBeforeTax" xlink:label="loc_us-gaap_AvailableForSaleSecuritiesAccumulatedGrossUnrealizedLossBeforeTax_D505725887614A5EDFCA1EEF4AA07286" xlink:type="locator" />
    <definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfAvailableForSaleSecuritiesLineItems_DB22FB6771B60CDCB5FC1EEF4A9FF550" xlink:to="loc_us-gaap_AvailableForSaleSecuritiesAccumulatedGrossUnrealizedLossBeforeTax_D505725887614A5EDFCA1EEF4AA07286" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_AvailableForSaleSecurities" xlink:label="loc_us-gaap_AvailableForSaleSecurities_5F431A45064053CF86DC1EEF4AA0FD0A" xlink:type="locator" />
    <definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfAvailableForSaleSecuritiesLineItems_DB22FB6771B60CDCB5FC1EEF4A9FF550" xlink:to="loc_us-gaap_AvailableForSaleSecurities_5F431A45064053CF86DC1EEF4AA0FD0A" xlink:type="arc" />
  </definitionLink>
  <definitionLink xlink:role="http://www.astrotechcorp.com/role/InvestmentsCarryingValueDetails" xlink:type="extended">
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_ScheduleOfHeldToMaturitySecuritiesLineItems" xlink:label="loc_us-gaap_ScheduleOfHeldToMaturitySecuritiesLineItems_58B6C4005C24C35D171C48509ADDB04C" xlink:type="locator" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_ScheduleOfHeldToMaturitySecuritiesTable" xlink:label="loc_us-gaap_ScheduleOfHeldToMaturitySecuritiesTable_0F04C4DBEBA0A9677D0348509ADDBE8C" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_ScheduleOfHeldToMaturitySecuritiesLineItems_58B6C4005C24C35D171C48509ADDB04C" xlink:to="loc_us-gaap_ScheduleOfHeldToMaturitySecuritiesTable_0F04C4DBEBA0A9677D0348509ADDBE8C" xlink:type="arc" xbrldt:closed="true" xbrldt:contextElement="segment" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_InvestmentTypeAxis" xlink:label="loc_us-gaap_InvestmentTypeAxis_E95A259A8DA9F91CCDC048509ADDB5A6" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfHeldToMaturitySecuritiesTable_0F04C4DBEBA0A9677D0348509ADDBE8C" xlink:to="loc_us-gaap_InvestmentTypeAxis_E95A259A8DA9F91CCDC048509ADDB5A6" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_InvestmentTypeCategorizationMember" xlink:label="loc_us-gaap_InvestmentTypeCategorizationMember_E9175E966F21AEC3D90448509ADD4C55_default" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_InvestmentTypeAxis_E95A259A8DA9F91CCDC048509ADDB5A6" xlink:to="loc_us-gaap_InvestmentTypeCategorizationMember_E9175E966F21AEC3D90448509ADD4C55_default" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_InvestmentTypeCategorizationMember" xlink:label="loc_us-gaap_InvestmentTypeCategorizationMember_E9175E966F21AEC3D90448509ADD4C55" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_InvestmentTypeAxis_E95A259A8DA9F91CCDC048509ADDB5A6" xlink:to="loc_us-gaap_InvestmentTypeCategorizationMember_E9175E966F21AEC3D90448509ADD4C55" xlink:type="arc" />
    <loc xlink:href="astc-20160630.xsd#astc_MutualFundsMember" xlink:label="loc_astc_MutualFundsMember_A678378B337C305969AF48509ADDAE27" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_InvestmentTypeCategorizationMember_E9175E966F21AEC3D90448509ADD4C55" xlink:to="loc_astc_MutualFundsMember_A678378B337C305969AF48509ADDAE27" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_BankTimeDepositsMember" xlink:label="loc_us-gaap_BankTimeDepositsMember_33CAA199750031DBFDA948509ADDB52B" xlink:type="locator" />
    <definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_InvestmentTypeCategorizationMember_E9175E966F21AEC3D90448509ADD4C55" xlink:to="loc_us-gaap_BankTimeDepositsMember_33CAA199750031DBFDA948509ADDB52B" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_FixedIncomeInvestmentsMember" xlink:label="loc_us-gaap_FixedIncomeInvestmentsMember_5737A7D835DCA68E264748509ADDF1D8" xlink:type="locator" />
    <definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_InvestmentTypeCategorizationMember_E9175E966F21AEC3D90448509ADD4C55" xlink:to="loc_us-gaap_FixedIncomeInvestmentsMember_5737A7D835DCA68E264748509ADDF1D8" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_BalanceSheetLocationAxis" xlink:label="loc_us-gaap_BalanceSheetLocationAxis_D36EB8013EEA52A68DF048509ADDBC0C" xlink:type="locator" />
    <definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfHeldToMaturitySecuritiesTable_0F04C4DBEBA0A9677D0348509ADDBE8C" xlink:to="loc_us-gaap_BalanceSheetLocationAxis_D36EB8013EEA52A68DF048509ADDBC0C" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_BalanceSheetLocationDomain" xlink:label="loc_us-gaap_BalanceSheetLocationDomain_3090D9C63BCDCF7FE9DA48509ADDCAAA_default" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_BalanceSheetLocationAxis_D36EB8013EEA52A68DF048509ADDBC0C" xlink:to="loc_us-gaap_BalanceSheetLocationDomain_3090D9C63BCDCF7FE9DA48509ADDCAAA_default" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_BalanceSheetLocationDomain" xlink:label="loc_us-gaap_BalanceSheetLocationDomain_3090D9C63BCDCF7FE9DA48509ADDCAAA" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_BalanceSheetLocationAxis_D36EB8013EEA52A68DF048509ADDBC0C" xlink:to="loc_us-gaap_BalanceSheetLocationDomain_3090D9C63BCDCF7FE9DA48509ADDCAAA" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_ShortTermInvestmentsMember" xlink:label="loc_us-gaap_ShortTermInvestmentsMember_1D2132B55B482ECC480348509ADD760E" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BalanceSheetLocationDomain_3090D9C63BCDCF7FE9DA48509ADDCAAA" xlink:to="loc_us-gaap_ShortTermInvestmentsMember_1D2132B55B482ECC480348509ADD760E" xlink:type="arc" />
    <loc xlink:href="astc-20160630.xsd#astc_LongTermInvestmentsMember" xlink:label="loc_astc_LongTermInvestmentsMember_A160C66BE9F9A69870E948509ADD62A3" xlink:type="locator" />
    <definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BalanceSheetLocationDomain_3090D9C63BCDCF7FE9DA48509ADDCAAA" xlink:to="loc_astc_LongTermInvestmentsMember_A160C66BE9F9A69870E948509ADD62A3" xlink:type="arc" />
    <loc xlink:href="astc-20160630.xsd#astc_MutualFundsAbstract" xlink:label="loc_astc_MutualFundsAbstract_A155EE91EF59476CB4CB48516A69F617" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfHeldToMaturitySecuritiesLineItems_58B6C4005C24C35D171C48509ADDB04C" xlink:to="loc_astc_MutualFundsAbstract_A155EE91EF59476CB4CB48516A69F617" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_AvailableForSaleSecurities" xlink:label="loc_us-gaap_AvailableForSaleSecurities_8A0482B2FEF50F99163548509ADDA67C" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_astc_MutualFundsAbstract_A155EE91EF59476CB4CB48516A69F617" xlink:to="loc_us-gaap_AvailableForSaleSecurities_8A0482B2FEF50F99163548509ADDA67C" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_MaturitiesOfTimeDepositsAbstract" xlink:label="loc_us-gaap_MaturitiesOfTimeDepositsAbstract_8C98FB8A0F379F32009048521FF1C9D6" xlink:type="locator" />
    <definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfHeldToMaturitySecuritiesLineItems_58B6C4005C24C35D171C48509ADDB04C" xlink:to="loc_us-gaap_MaturitiesOfTimeDepositsAbstract_8C98FB8A0F379F32009048521FF1C9D6" xlink:type="arc" />
    <loc xlink:href="astc-20160630.xsd#astc_HeldToMaturitySecuritiesDebtMaturities1To90DaysNetCarryingAmount" xlink:label="loc_astc_HeldToMaturitySecuritiesDebtMaturities1To90DaysNetCarryingAmount_A6F2AC557E2B0CA8634548509ADE778F" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_MaturitiesOfTimeDepositsAbstract_8C98FB8A0F379F32009048521FF1C9D6" xlink:to="loc_astc_HeldToMaturitySecuritiesDebtMaturities1To90DaysNetCarryingAmount_A6F2AC557E2B0CA8634548509ADE778F" xlink:type="arc" />
    <loc xlink:href="astc-20160630.xsd#astc_HeldToMaturitySecuritiesDebtMaturities91To360DaysNetCarryingAmount" xlink:label="loc_astc_HeldToMaturitySecuritiesDebtMaturities91To360DaysNetCarryingAmount_AF5A3FC0D04D212B214848509ADE7949" xlink:type="locator" />
    <definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_MaturitiesOfTimeDepositsAbstract_8C98FB8A0F379F32009048521FF1C9D6" xlink:to="loc_astc_HeldToMaturitySecuritiesDebtMaturities91To360DaysNetCarryingAmount_AF5A3FC0D04D212B214848509ADE7949" xlink:type="arc" />
    <loc xlink:href="astc-20160630.xsd#astc_HeldToMaturitySecuritiesDebtMaturitiesOver360DaysNetCarryingAmount" xlink:label="loc_astc_HeldToMaturitySecuritiesDebtMaturitiesOver360DaysNetCarryingAmount_81903553F3908DC2C81648509ADEB9FF" xlink:type="locator" />
    <definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_MaturitiesOfTimeDepositsAbstract_8C98FB8A0F379F32009048521FF1C9D6" xlink:to="loc_astc_HeldToMaturitySecuritiesDebtMaturitiesOver360DaysNetCarryingAmount_81903553F3908DC2C81648509ADEB9FF" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_MarketableSecuritiesFixedMaturitiesAbstract" xlink:label="loc_us-gaap_MarketableSecuritiesFixedMaturitiesAbstract_206CFCFC251AADE231DD48529779C0CD" xlink:type="locator" />
    <definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfHeldToMaturitySecuritiesLineItems_58B6C4005C24C35D171C48509ADDB04C" xlink:to="loc_us-gaap_MarketableSecuritiesFixedMaturitiesAbstract_206CFCFC251AADE231DD48529779C0CD" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_HeldToMaturitySecuritiesDebtMaturitiesWithinOneYearNetCarryingAmount" xlink:label="loc_us-gaap_HeldToMaturitySecuritiesDebtMaturitiesWithinOneYearNetCarryingAmount_D525AFEB5BA69E3F6C7B48509ADE3E9C" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_MarketableSecuritiesFixedMaturitiesAbstract_206CFCFC251AADE231DD48529779C0CD" xlink:to="loc_us-gaap_HeldToMaturitySecuritiesDebtMaturitiesWithinOneYearNetCarryingAmount_D525AFEB5BA69E3F6C7B48509ADE3E9C" xlink:type="arc" />
    <loc xlink:href="astc-20160630.xsd#astc_HeldtomaturitySecuritiesDebtMaturitiesafterOneThroughThreeYearsNetCarryingAmount" xlink:label="loc_astc_HeldtomaturitySecuritiesDebtMaturitiesafterOneThroughThreeYearsNetCarryingAmount_ED85649435F24F3ACEFD48509ADE33CB" xlink:type="locator" />
    <definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_MarketableSecuritiesFixedMaturitiesAbstract_206CFCFC251AADE231DD48529779C0CD" xlink:to="loc_astc_HeldtomaturitySecuritiesDebtMaturitiesafterOneThroughThreeYearsNetCarryingAmount_ED85649435F24F3ACEFD48509ADE33CB" xlink:type="arc" />
    <loc xlink:href="astc-20160630.xsd#astc_HeldtomaturitySecuritiesDebtMaturitiesafterThreeThroughFiveYearsNetCarryingAmount" xlink:label="loc_astc_HeldtomaturitySecuritiesDebtMaturitiesafterThreeThroughFiveYearsNetCarryingAmount_FB9F5392713694EE37E848509ADE76FE" xlink:type="locator" />
    <definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_MarketableSecuritiesFixedMaturitiesAbstract_206CFCFC251AADE231DD48529779C0CD" xlink:to="loc_astc_HeldtomaturitySecuritiesDebtMaturitiesafterThreeThroughFiveYearsNetCarryingAmount_FB9F5392713694EE37E848509ADE76FE" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_AvailableForSaleSecuritiesAndHeldToMaturitySecurities" xlink:label="loc_us-gaap_AvailableForSaleSecuritiesAndHeldToMaturitySecurities_ADFD5C210135B593F86148509ADE2A55" xlink:type="locator" />
    <definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfHeldToMaturitySecuritiesLineItems_58B6C4005C24C35D171C48509ADDB04C" xlink:to="loc_us-gaap_AvailableForSaleSecuritiesAndHeldToMaturitySecurities_ADFD5C210135B593F86148509ADE2A55" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_HeldToMaturitySecurities" xlink:label="loc_us-gaap_HeldToMaturitySecurities_745E084D4A9AA631594948509ADE5A11" xlink:type="locator" />
    <definitionArc order="5" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfHeldToMaturitySecuritiesLineItems_58B6C4005C24C35D171C48509ADDB04C" xlink:to="loc_us-gaap_HeldToMaturitySecurities_745E084D4A9AA631594948509ADE5A11" xlink:type="arc" />
  </definitionLink>
  <definitionLink xlink:role="http://www.astrotechcorp.com/role/InvestmentsHeldToMaturitySecuritiesDetails" xlink:type="extended">
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_ScheduleOfHeldToMaturitySecuritiesLineItems" xlink:label="loc_us-gaap_ScheduleOfHeldToMaturitySecuritiesLineItems_70D6DD3B570E69FD872E1EEF4A843DAB" xlink:type="locator" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_ScheduleOfHeldToMaturitySecuritiesTable" xlink:label="loc_us-gaap_ScheduleOfHeldToMaturitySecuritiesTable_08F32030615CA78D32601EEF4A7FB249" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_ScheduleOfHeldToMaturitySecuritiesLineItems_70D6DD3B570E69FD872E1EEF4A843DAB" xlink:to="loc_us-gaap_ScheduleOfHeldToMaturitySecuritiesTable_08F32030615CA78D32601EEF4A7FB249" xlink:type="arc" xbrldt:closed="true" xbrldt:contextElement="segment" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_InvestmentTypeAxis" xlink:label="loc_us-gaap_InvestmentTypeAxis_3F7473F79E35A47A60E91EEF4A84A2CC" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfHeldToMaturitySecuritiesTable_08F32030615CA78D32601EEF4A7FB249" xlink:to="loc_us-gaap_InvestmentTypeAxis_3F7473F79E35A47A60E91EEF4A84A2CC" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_InvestmentTypeCategorizationMember" xlink:label="loc_us-gaap_InvestmentTypeCategorizationMember_6B615EC1C7D33211597A1EEF4A8422B8_default" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_InvestmentTypeAxis_3F7473F79E35A47A60E91EEF4A84A2CC" xlink:to="loc_us-gaap_InvestmentTypeCategorizationMember_6B615EC1C7D33211597A1EEF4A8422B8_default" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_InvestmentTypeCategorizationMember" xlink:label="loc_us-gaap_InvestmentTypeCategorizationMember_6B615EC1C7D33211597A1EEF4A8422B8" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_InvestmentTypeAxis_3F7473F79E35A47A60E91EEF4A84A2CC" xlink:to="loc_us-gaap_InvestmentTypeCategorizationMember_6B615EC1C7D33211597A1EEF4A8422B8" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_FixedIncomeInvestmentsMember" xlink:label="loc_us-gaap_FixedIncomeInvestmentsMember_AF66EDB62275679F8F091EEF4A84DDD6" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_InvestmentTypeCategorizationMember_6B615EC1C7D33211597A1EEF4A8422B8" xlink:to="loc_us-gaap_FixedIncomeInvestmentsMember_AF66EDB62275679F8F091EEF4A84DDD6" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_BankTimeDepositsMember" xlink:label="loc_us-gaap_BankTimeDepositsMember_ACF25A8C948466E1831D1EEF4A84185F" xlink:type="locator" />
    <definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_InvestmentTypeCategorizationMember_6B615EC1C7D33211597A1EEF4A8422B8" xlink:to="loc_us-gaap_BankTimeDepositsMember_ACF25A8C948466E1831D1EEF4A84185F" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_HeldToMaturitySecurities" xlink:label="loc_us-gaap_HeldToMaturitySecurities_B73E511FFD1AC14F4D041EEF4A855382" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfHeldToMaturitySecuritiesLineItems_70D6DD3B570E69FD872E1EEF4A843DAB" xlink:to="loc_us-gaap_HeldToMaturitySecurities_B73E511FFD1AC14F4D041EEF4A855382" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_HeldToMaturitySecuritiesAccumulatedUnrecognizedHoldingGain" xlink:label="loc_us-gaap_HeldToMaturitySecuritiesAccumulatedUnrecognizedHoldingGain_8BC17CF297ED331AA2801EEF4A85DAFD" xlink:type="locator" />
    <definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfHeldToMaturitySecuritiesLineItems_70D6DD3B570E69FD872E1EEF4A843DAB" xlink:to="loc_us-gaap_HeldToMaturitySecuritiesAccumulatedUnrecognizedHoldingGain_8BC17CF297ED331AA2801EEF4A85DAFD" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_HeldToMaturitySecuritiesAccumulatedUnrecognizedHoldingLoss" xlink:label="loc_us-gaap_HeldToMaturitySecuritiesAccumulatedUnrecognizedHoldingLoss_E4B662E2A48FB7AF9A5A1EEF4A8523D2" xlink:type="locator" />
    <definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfHeldToMaturitySecuritiesLineItems_70D6DD3B570E69FD872E1EEF4A843DAB" xlink:to="loc_us-gaap_HeldToMaturitySecuritiesAccumulatedUnrecognizedHoldingLoss_E4B662E2A48FB7AF9A5A1EEF4A8523D2" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_HeldToMaturitySecuritiesFairValue" xlink:label="loc_us-gaap_HeldToMaturitySecuritiesFairValue_47356B474225FC9BD11C1EEF4A85B4A7" xlink:type="locator" />
    <definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfHeldToMaturitySecuritiesLineItems_70D6DD3B570E69FD872E1EEF4A843DAB" xlink:to="loc_us-gaap_HeldToMaturitySecuritiesFairValue_47356B474225FC9BD11C1EEF4A85B4A7" xlink:type="arc" />
  </definitionLink>
  <definitionLink xlink:role="http://www.astrotechcorp.com/role/InvestmentsTables" xlink:type="extended" />
  <definitionLink xlink:role="http://www.astrotechcorp.com/role/NetLossIncomePerShare" xlink:type="extended" />
  <definitionLink xlink:role="http://www.astrotechcorp.com/role/NetLossIncomePerShareDetailTextuals" xlink:type="extended" />
  <definitionLink xlink:role="http://www.astrotechcorp.com/role/NetLossIncomePerShareDetails" xlink:type="extended" />
  <definitionLink xlink:role="http://www.astrotechcorp.com/role/NetLossIncomePerShareTables" xlink:type="extended" />
  <definitionLink xlink:role="http://www.astrotechcorp.com/role/NoncontrollingInterest" xlink:type="extended" />
  <definitionLink xlink:role="http://www.astrotechcorp.com/role/NoncontrollingInterestDetailTextuals" xlink:type="extended">
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_MinorityInterestLineItems" xlink:label="loc_us-gaap_MinorityInterestLineItems_8826BEE21664AC74C8C11EE10BBDD62A" xlink:type="locator" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_MinorityInterestTable" xlink:label="loc_us-gaap_MinorityInterestTable_D827454713E96935552A1EE10BBC2208" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_MinorityInterestLineItems_8826BEE21664AC74C8C11EE10BBDD62A" xlink:to="loc_us-gaap_MinorityInterestTable_D827454713E96935552A1EE10BBC2208" xlink:type="arc" xbrldt:closed="true" xbrldt:contextElement="segment" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_CounterpartyNameAxis" xlink:label="loc_us-gaap_CounterpartyNameAxis_200EC39660126F4073A71EEACF1C44A3" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_MinorityInterestTable_D827454713E96935552A1EE10BBC2208" xlink:to="loc_us-gaap_CounterpartyNameAxis_200EC39660126F4073A71EEACF1C44A3" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_RepurchaseAgreementCounterpartyNameDomain" xlink:label="loc_us-gaap_RepurchaseAgreementCounterpartyNameDomain_2F223839E635E6FEFC841EEAD0D23FD1_default" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_CounterpartyNameAxis_200EC39660126F4073A71EEACF1C44A3" xlink:to="loc_us-gaap_RepurchaseAgreementCounterpartyNameDomain_2F223839E635E6FEFC841EEAD0D23FD1_default" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_RepurchaseAgreementCounterpartyNameDomain" xlink:label="loc_us-gaap_RepurchaseAgreementCounterpartyNameDomain_2F223839E635E6FEFC841EEAD0D23FD1" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_CounterpartyNameAxis_200EC39660126F4073A71EEACF1C44A3" xlink:to="loc_us-gaap_RepurchaseAgreementCounterpartyNameDomain_2F223839E635E6FEFC841EEAD0D23FD1" xlink:type="arc" />
    <loc xlink:href="astc-20160630.xsd#astc_AstralImagesIncMember" xlink:label="loc_astc_AstralImagesIncMember_87C02A8BE32381AD5DE11EEB046F3355" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RepurchaseAgreementCounterpartyNameDomain_2F223839E635E6FEFC841EEAD0D23FD1" xlink:to="loc_astc_AstralImagesIncMember_87C02A8BE32381AD5DE11EEB046F3355" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_LeaseArrangementTypeAxis" xlink:label="loc_us-gaap_LeaseArrangementTypeAxis_0430F22E49ECEC59474A1EE10BBCE926" xlink:type="locator" />
    <definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_MinorityInterestTable_D827454713E96935552A1EE10BBC2208" xlink:to="loc_us-gaap_LeaseArrangementTypeAxis_0430F22E49ECEC59474A1EE10BBCE926" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_LeaseArrangementTypeDomain" xlink:label="loc_us-gaap_LeaseArrangementTypeDomain_B2B74F5F780CAA6551711EE10BBC14CF_default" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_LeaseArrangementTypeAxis_0430F22E49ECEC59474A1EE10BBCE926" xlink:to="loc_us-gaap_LeaseArrangementTypeDomain_B2B74F5F780CAA6551711EE10BBC14CF_default" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_LeaseArrangementTypeDomain" xlink:label="loc_us-gaap_LeaseArrangementTypeDomain_B2B74F5F780CAA6551711EE10BBC14CF" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_LeaseArrangementTypeAxis_0430F22E49ECEC59474A1EE10BBCE926" xlink:to="loc_us-gaap_LeaseArrangementTypeDomain_B2B74F5F780CAA6551711EE10BBC14CF" xlink:type="arc" />
    <loc xlink:href="astc-20160630.xsd#astc_TexasEmergingTechnologyFundMember" xlink:label="loc_astc_TexasEmergingTechnologyFundMember_2176BF4823D2D3101D771EE10BBCDDFA" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LeaseArrangementTypeDomain_B2B74F5F780CAA6551711EE10BBC14CF" xlink:to="loc_astc_TexasEmergingTechnologyFundMember_2176BF4823D2D3101D771EE10BBCDDFA" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_RelatedPartyTransactionsByRelatedPartyAxis" xlink:label="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_3EE93140667EA4392C381EE10BBDDBCD" xlink:type="locator" />
    <definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_MinorityInterestTable_D827454713E96935552A1EE10BBC2208" xlink:to="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_3EE93140667EA4392C381EE10BBDDBCD" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_RelatedPartyDomain" xlink:label="loc_us-gaap_RelatedPartyDomain_A8100FAE513160182F021EE10BBD3C90_default" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_3EE93140667EA4392C381EE10BBDDBCD" xlink:to="loc_us-gaap_RelatedPartyDomain_A8100FAE513160182F021EE10BBD3C90_default" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_RelatedPartyDomain" xlink:label="loc_us-gaap_RelatedPartyDomain_A8100FAE513160182F021EE10BBD3C90" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_3EE93140667EA4392C381EE10BBDDBCD" xlink:to="loc_us-gaap_RelatedPartyDomain_A8100FAE513160182F021EE10BBD3C90" xlink:type="arc" />
    <loc xlink:href="astc-20160630.xsd#astc_FirstDetectMember" xlink:label="loc_astc_FirstDetectMember_1EE44FDC431E95A6DFFC1EE10BBDE973" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyDomain_A8100FAE513160182F021EE10BBD3C90" xlink:to="loc_astc_FirstDetectMember_1EE44FDC431E95A6DFFC1EE10BBDE973" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_MinorityInterest" xlink:label="loc_us-gaap_MinorityInterest_6958614E615977A5F8491EE10BBD2D28" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_MinorityInterestLineItems_8826BEE21664AC74C8C11EE10BBDD62A" xlink:to="loc_us-gaap_MinorityInterest_6958614E615977A5F8491EE10BBD2D28" xlink:type="arc" />
    <loc xlink:href="astc-20160630.xsd#astc_PaymentOfCommonStockRepurchaseRight" xlink:label="loc_astc_PaymentOfCommonStockRepurchaseRight_AC2C46C15F08D55A9C891EE10BBD9ABC" xlink:type="locator" />
    <definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_MinorityInterestLineItems_8826BEE21664AC74C8C11EE10BBDD62A" xlink:to="loc_astc_PaymentOfCommonStockRepurchaseRight_AC2C46C15F08D55A9C891EE10BBD9ABC" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_MinorityInterestOwnershipPercentageByParent" xlink:label="loc_us-gaap_MinorityInterestOwnershipPercentageByParent_B93309B838C0285407BF1EE10BBD46C9" xlink:type="locator" />
    <definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_MinorityInterestLineItems_8826BEE21664AC74C8C11EE10BBDD62A" xlink:to="loc_us-gaap_MinorityInterestOwnershipPercentageByParent_B93309B838C0285407BF1EE10BBD46C9" xlink:type="arc" />
  </definitionLink>
  <definitionLink xlink:role="http://www.astrotechcorp.com/role/NoncontrollingInterestDetails" xlink:type="extended" />
  <definitionLink xlink:role="http://www.astrotechcorp.com/role/NoncontrollingInterestInterestHeldDetails" xlink:type="extended">
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_MinorityInterestLineItems" xlink:label="loc_us-gaap_MinorityInterestLineItems_753B610B7BD472EDF1F51EE42333397D" xlink:type="locator" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_MinorityInterestTable" xlink:label="loc_us-gaap_MinorityInterestTable_21F5770A1ACDB01466901EE4232CDE00" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_MinorityInterestLineItems_753B610B7BD472EDF1F51EE42333397D" xlink:to="loc_us-gaap_MinorityInterestTable_21F5770A1ACDB01466901EE4232CDE00" xlink:type="arc" xbrldt:closed="true" xbrldt:contextElement="segment" />
    <loc xlink:href="http://xbrl.sec.gov/dei/2014/dei-2014-01-31.xsd#dei_LegalEntityAxis" xlink:label="loc_dei_LegalEntityAxis_764BC1D52E327D08F4EE1EE4232E4346" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_MinorityInterestTable_21F5770A1ACDB01466901EE4232CDE00" xlink:to="loc_dei_LegalEntityAxis_764BC1D52E327D08F4EE1EE4232E4346" xlink:type="arc" />
    <loc xlink:href="http://xbrl.sec.gov/dei/2014/dei-2014-01-31.xsd#dei_EntityDomain" xlink:label="loc_dei_EntityDomain_FDC1BBABA3B4CA6AB2091EE4232E63CF_default" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_dei_LegalEntityAxis_764BC1D52E327D08F4EE1EE4232E4346" xlink:to="loc_dei_EntityDomain_FDC1BBABA3B4CA6AB2091EE4232E63CF_default" xlink:type="arc" />
    <loc xlink:href="http://xbrl.sec.gov/dei/2014/dei-2014-01-31.xsd#dei_EntityDomain" xlink:label="loc_dei_EntityDomain_FDC1BBABA3B4CA6AB2091EE4232E63CF" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_dei_LegalEntityAxis_764BC1D52E327D08F4EE1EE4232E4346" xlink:to="loc_dei_EntityDomain_FDC1BBABA3B4CA6AB2091EE4232E63CF" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_ParentCompanyMember" xlink:label="loc_us-gaap_ParentCompanyMember_C97AFEA4A5AE100955991EFBD25CCAC7" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_EntityDomain_FDC1BBABA3B4CA6AB2091EE4232E63CF" xlink:to="loc_us-gaap_ParentCompanyMember_C97AFEA4A5AE100955991EFBD25CCAC7" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_SubsidiariesMember" xlink:label="loc_us-gaap_SubsidiariesMember_C62CF1AFDFAC78EE0C051EFAD5B44C10" xlink:type="locator" />
    <definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_EntityDomain_FDC1BBABA3B4CA6AB2091EE4232E63CF" xlink:to="loc_us-gaap_SubsidiariesMember_C62CF1AFDFAC78EE0C051EFAD5B44C10" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_NoncontrollingInterestIncreaseFromSubsidiaryEquityIssuance" xlink:label="loc_us-gaap_NoncontrollingInterestIncreaseFromSubsidiaryEquityIssuance_4A869E76A828F69624ED1EE4D1A38D20" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_MinorityInterestLineItems_753B610B7BD472EDF1F51EE42333397D" xlink:to="loc_us-gaap_NoncontrollingInterestIncreaseFromSubsidiaryEquityIssuance_4A869E76A828F69624ED1EE4D1A38D20" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_MinorityInterestOwnershipPercentageByParent" xlink:label="loc_us-gaap_MinorityInterestOwnershipPercentageByParent_D391321944D01377EC9D1EE5024BD205" xlink:type="locator" />
    <definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_MinorityInterestLineItems_753B610B7BD472EDF1F51EE42333397D" xlink:to="loc_us-gaap_MinorityInterestOwnershipPercentageByParent_D391321944D01377EC9D1EE5024BD205" xlink:type="arc" />
  </definitionLink>
  <definitionLink xlink:role="http://www.astrotechcorp.com/role/NoncontrollingInterestTables" xlink:type="extended" />
  <definitionLink xlink:role="http://www.astrotechcorp.com/role/PropertyAndEquipment" xlink:type="extended" />
  <definitionLink xlink:role="http://www.astrotechcorp.com/role/PropertyAndEquipmentDetailTextuals" xlink:type="extended" />
  <definitionLink xlink:role="http://www.astrotechcorp.com/role/PropertyAndEquipmentDetails" xlink:type="extended">
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_PropertyPlantAndEquipmentLineItems" xlink:label="loc_us-gaap_PropertyPlantAndEquipmentLineItems_9083B50EFC853050C7B01F87DE93DAE4" xlink:type="locator" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_ScheduleOfPropertyPlantAndEquipmentTable" xlink:label="loc_us-gaap_ScheduleOfPropertyPlantAndEquipmentTable_755AD67B973BEA81CA331F87DE922F5E" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentLineItems_9083B50EFC853050C7B01F87DE93DAE4" xlink:to="loc_us-gaap_ScheduleOfPropertyPlantAndEquipmentTable_755AD67B973BEA81CA331F87DE922F5E" xlink:type="arc" xbrldt:closed="true" xbrldt:contextElement="segment" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_PropertyPlantAndEquipmentByTypeAxis" xlink:label="loc_us-gaap_PropertyPlantAndEquipmentByTypeAxis_61FCC46373901BDDA8041F87DE92D62B" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfPropertyPlantAndEquipmentTable_755AD67B973BEA81CA331F87DE922F5E" xlink:to="loc_us-gaap_PropertyPlantAndEquipmentByTypeAxis_61FCC46373901BDDA8041F87DE92D62B" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_PropertyPlantAndEquipmentTypeDomain" xlink:label="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_A081E706F89C618E935B1F87DE92E0FB_default" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentByTypeAxis_61FCC46373901BDDA8041F87DE92D62B" xlink:to="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_A081E706F89C618E935B1F87DE92E0FB_default" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_PropertyPlantAndEquipmentTypeDomain" xlink:label="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_A081E706F89C618E935B1F87DE92E0FB" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentByTypeAxis_61FCC46373901BDDA8041F87DE92D62B" xlink:to="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_A081E706F89C618E935B1F87DE92E0FB" xlink:type="arc" />
    <loc xlink:href="astc-20160630.xsd#astc_FurnitureFixturesEquipmentAndLeaseholdImprovementsMember" xlink:label="loc_astc_FurnitureFixturesEquipmentAndLeaseholdImprovementsMember_DEDB810B49A56613CC1C1F87DE938711" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_A081E706F89C618E935B1F87DE92E0FB" xlink:to="loc_astc_FurnitureFixturesEquipmentAndLeaseholdImprovementsMember_DEDB810B49A56613CC1C1F87DE938711" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_SoftwareAndSoftwareDevelopmentCostsMember" xlink:label="loc_us-gaap_SoftwareAndSoftwareDevelopmentCostsMember_638431FE2FE4FB3560F31F90A8542D54" xlink:type="locator" />
    <definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_A081E706F89C618E935B1F87DE92E0FB" xlink:to="loc_us-gaap_SoftwareAndSoftwareDevelopmentCostsMember_638431FE2FE4FB3560F31F90A8542D54" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_ConstructionInProgressMember" xlink:label="loc_us-gaap_ConstructionInProgressMember_2B40D88203C11E3632F31F87DE9393EB" xlink:type="locator" />
    <definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_A081E706F89C618E935B1F87DE92E0FB" xlink:to="loc_us-gaap_ConstructionInProgressMember_2B40D88203C11E3632F31F87DE9393EB" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_PropertyPlantAndEquipmentGross" xlink:label="loc_us-gaap_PropertyPlantAndEquipmentGross_ADC30C3414C2D08F5D371F87DE9302F4" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentLineItems_9083B50EFC853050C7B01F87DE93DAE4" xlink:to="loc_us-gaap_PropertyPlantAndEquipmentGross_ADC30C3414C2D08F5D371F87DE9302F4" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_AccumulatedDepreciationDepletionAndAmortizationPropertyPlantAndEquipment" xlink:label="loc_us-gaap_AccumulatedDepreciationDepletionAndAmortizationPropertyPlantAndEquipment_896C623AB33100BB14D61F87DE9318EC" xlink:type="locator" />
    <definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentLineItems_9083B50EFC853050C7B01F87DE93DAE4" xlink:to="loc_us-gaap_AccumulatedDepreciationDepletionAndAmortizationPropertyPlantAndEquipment_896C623AB33100BB14D61F87DE9318EC" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_PropertyPlantAndEquipmentNet" xlink:label="loc_us-gaap_PropertyPlantAndEquipmentNet_499E1BE4D1DE3D16E7741F87DE93C448" xlink:type="locator" />
    <definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentLineItems_9083B50EFC853050C7B01F87DE93DAE4" xlink:to="loc_us-gaap_PropertyPlantAndEquipmentNet_499E1BE4D1DE3D16E7741F87DE93C448" xlink:type="arc" />
  </definitionLink>
  <definitionLink xlink:role="http://www.astrotechcorp.com/role/PropertyAndEquipmentTables" xlink:type="extended" />
  <definitionLink xlink:role="http://www.astrotechcorp.com/role/SegmentInformation" xlink:type="extended" />
  <definitionLink xlink:role="http://www.astrotechcorp.com/role/SegmentInformationDetailTextuals" xlink:type="extended" />
  <definitionLink xlink:role="http://www.astrotechcorp.com/role/SegmentInformationDetails" xlink:type="extended">
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_SegmentReportingInformationLineItems" xlink:label="loc_us-gaap_SegmentReportingInformationLineItems_2E9AB0582129FE8ECEC033C8D08E8E40" xlink:type="locator" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable" xlink:label="loc_us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable_FAC34ECD0ADDFEB3EDF333C8D0890259" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_2E9AB0582129FE8ECEC033C8D08E8E40" xlink:to="loc_us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable_FAC34ECD0ADDFEB3EDF333C8D0890259" xlink:type="arc" xbrldt:closed="true" xbrldt:contextElement="segment" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_ConsolidationItemsAxis" xlink:label="loc_us-gaap_ConsolidationItemsAxis_DD58CE918EA09773F00A33C8D0899247" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable_FAC34ECD0ADDFEB3EDF333C8D0890259" xlink:to="loc_us-gaap_ConsolidationItemsAxis_DD58CE918EA09773F00A33C8D0899247" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_ConsolidationItemsDomain" xlink:label="loc_us-gaap_ConsolidationItemsDomain_64892AB8488DD3CC7D4533C8D0897A2E_default" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_ConsolidationItemsAxis_DD58CE918EA09773F00A33C8D0899247" xlink:to="loc_us-gaap_ConsolidationItemsDomain_64892AB8488DD3CC7D4533C8D0897A2E_default" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_ConsolidationItemsDomain" xlink:label="loc_us-gaap_ConsolidationItemsDomain_64892AB8488DD3CC7D4533C8D0897A2E" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_ConsolidationItemsAxis_DD58CE918EA09773F00A33C8D0899247" xlink:to="loc_us-gaap_ConsolidationItemsDomain_64892AB8488DD3CC7D4533C8D0897A2E" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_OperatingSegmentsMember" xlink:label="loc_us-gaap_OperatingSegmentsMember_3B96B0E35D9D1D84F02533C8D089E86C" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ConsolidationItemsDomain_64892AB8488DD3CC7D4533C8D0897A2E" xlink:to="loc_us-gaap_OperatingSegmentsMember_3B96B0E35D9D1D84F02533C8D089E86C" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_StatementBusinessSegmentsAxis" xlink:label="loc_us-gaap_StatementBusinessSegmentsAxis_CD0D4423AE729843923533C8D08E7D14" xlink:type="locator" />
    <definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfSegmentReportingInformationBySegmentTable_FAC34ECD0ADDFEB3EDF333C8D0890259" xlink:to="loc_us-gaap_StatementBusinessSegmentsAxis_CD0D4423AE729843923533C8D08E7D14" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_SegmentDomain" xlink:label="loc_us-gaap_SegmentDomain_F4C76C581348D8B7084433C8D08EB7C1_default" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementBusinessSegmentsAxis_CD0D4423AE729843923533C8D08E7D14" xlink:to="loc_us-gaap_SegmentDomain_F4C76C581348D8B7084433C8D08EB7C1_default" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_SegmentDomain" xlink:label="loc_us-gaap_SegmentDomain_F4C76C581348D8B7084433C8D08EB7C1" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementBusinessSegmentsAxis_CD0D4423AE729843923533C8D08E7D14" xlink:to="loc_us-gaap_SegmentDomain_F4C76C581348D8B7084433C8D08EB7C1" xlink:type="arc" />
    <loc xlink:href="astc-20160630.xsd#astc_AstralImagesIncMember" xlink:label="loc_astc_AstralImagesIncMember_4904AA8F58B5E9EFC34333C8D08EB682" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentDomain_F4C76C581348D8B7084433C8D08EB7C1" xlink:to="loc_astc_AstralImagesIncMember_4904AA8F58B5E9EFC34333C8D08EB682" xlink:type="arc" />
    <loc xlink:href="astc-20160630.xsd#astc_AstroScientificMember" xlink:label="loc_astc_AstroScientificMember_ACCC55CA110C36057DB633C8D08E8068" xlink:type="locator" />
    <definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentDomain_F4C76C581348D8B7084433C8D08EB7C1" xlink:to="loc_astc_AstroScientificMember_ACCC55CA110C36057DB633C8D08E8068" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_Revenues" xlink:label="loc_us-gaap_Revenues_20487C46CC5E4204229C33C8D08EE0B3" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_2E9AB0582129FE8ECEC033C8D08E8E40" xlink:to="loc_us-gaap_Revenues_20487C46CC5E4204229C33C8D08EE0B3" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest" xlink:label="loc_us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest_989C8169D9F9E313A55933C8D090E522" xlink:type="locator" />
    <definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_2E9AB0582129FE8ECEC033C8D08E8E40" xlink:to="loc_us-gaap_IncomeLossFromContinuingOperationsBeforeIncomeTaxesExtraordinaryItemsNoncontrollingInterest_989C8169D9F9E313A55933C8D090E522" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_PropertyPlantAndEquipmentNet" xlink:label="loc_us-gaap_PropertyPlantAndEquipmentNet_F16D6730CC651D4CA78433C8D0908500" xlink:type="locator" />
    <definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_2E9AB0582129FE8ECEC033C8D08E8E40" xlink:to="loc_us-gaap_PropertyPlantAndEquipmentNet_F16D6730CC651D4CA78433C8D0908500" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_Assets" xlink:label="loc_us-gaap_Assets_06B13656FBDB8688D3D133C8D0901300" xlink:type="locator" />
    <definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_2E9AB0582129FE8ECEC033C8D08E8E40" xlink:to="loc_us-gaap_Assets_06B13656FBDB8688D3D133C8D0901300" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_DepreciationDepletionAndAmortization" xlink:label="loc_us-gaap_DepreciationDepletionAndAmortization_6717737F1BC7AD847A8C33DFA0FA000C" xlink:type="locator" />
    <definitionArc order="5" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_2E9AB0582129FE8ECEC033C8D08E8E40" xlink:to="loc_us-gaap_DepreciationDepletionAndAmortization_6717737F1BC7AD847A8C33DFA0FA000C" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_OtherNonrecurringExpense" xlink:label="loc_us-gaap_OtherNonrecurringExpense_DABB360500B8A404036D33D54765D582" xlink:type="locator" />
    <definitionArc order="6" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentReportingInformationLineItems_2E9AB0582129FE8ECEC033C8D08E8E40" xlink:to="loc_us-gaap_OtherNonrecurringExpense_DABB360500B8A404036D33D54765D582" xlink:type="arc" />
  </definitionLink>
  <definitionLink xlink:role="http://www.astrotechcorp.com/role/SegmentInformationTables" xlink:type="extended" />
  <definitionLink xlink:role="http://www.astrotechcorp.com/role/StateOfTexasFunding" xlink:type="extended" />
  <definitionLink xlink:role="http://www.astrotechcorp.com/role/StateOfTexasFundingDetailTextuals" xlink:type="extended">
    <loc xlink:href="astc-20160630.xsd#astc_StateOfTexasFundingLineItems" xlink:label="loc_astc_StateOfTexasFundingLineItems_07AC27AB740874E264192098DABBB893" xlink:type="locator" />
    <loc xlink:href="astc-20160630.xsd#astc_StateOfTexasFundingTable" xlink:label="loc_astc_StateOfTexasFundingTable_8005FA723861D80FE3962098DABA791C" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_astc_StateOfTexasFundingLineItems_07AC27AB740874E264192098DABBB893" xlink:to="loc_astc_StateOfTexasFundingTable_8005FA723861D80FE3962098DABA791C" xlink:type="arc" xbrldt:closed="true" xbrldt:contextElement="segment" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_LeaseArrangementTypeAxis" xlink:label="loc_us-gaap_LeaseArrangementTypeAxis_CEAA0C36C3AFB5890DAA2098DABA10AC" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_astc_StateOfTexasFundingTable_8005FA723861D80FE3962098DABA791C" xlink:to="loc_us-gaap_LeaseArrangementTypeAxis_CEAA0C36C3AFB5890DAA2098DABA10AC" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_LeaseArrangementTypeDomain" xlink:label="loc_us-gaap_LeaseArrangementTypeDomain_F0A368D20A54FC80316A2098DABA7AEB_default" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_LeaseArrangementTypeAxis_CEAA0C36C3AFB5890DAA2098DABA10AC" xlink:to="loc_us-gaap_LeaseArrangementTypeDomain_F0A368D20A54FC80316A2098DABA7AEB_default" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_LeaseArrangementTypeDomain" xlink:label="loc_us-gaap_LeaseArrangementTypeDomain_F0A368D20A54FC80316A2098DABA7AEB" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_LeaseArrangementTypeAxis_CEAA0C36C3AFB5890DAA2098DABA10AC" xlink:to="loc_us-gaap_LeaseArrangementTypeDomain_F0A368D20A54FC80316A2098DABA7AEB" xlink:type="arc" />
    <loc xlink:href="astc-20160630.xsd#astc_TexasEmergingTechnologyFundMember" xlink:label="loc_astc_TexasEmergingTechnologyFundMember_0F76ACACCCF98FE48CE02098DABA27BA" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LeaseArrangementTypeDomain_F0A368D20A54FC80316A2098DABA7AEB" xlink:to="loc_astc_TexasEmergingTechnologyFundMember_0F76ACACCCF98FE48CE02098DABA27BA" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_RelatedPartyTransactionsByRelatedPartyAxis" xlink:label="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_A48922EC33096CAAF6AC2098DABA1AB5" xlink:type="locator" />
    <definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_astc_StateOfTexasFundingTable_8005FA723861D80FE3962098DABA791C" xlink:to="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_A48922EC33096CAAF6AC2098DABA1AB5" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_RelatedPartyDomain" xlink:label="loc_us-gaap_RelatedPartyDomain_67EDDBCB495D32794D752098DABBC95D_default" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_A48922EC33096CAAF6AC2098DABA1AB5" xlink:to="loc_us-gaap_RelatedPartyDomain_67EDDBCB495D32794D752098DABBC95D_default" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_RelatedPartyDomain" xlink:label="loc_us-gaap_RelatedPartyDomain_67EDDBCB495D32794D752098DABBC95D" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_A48922EC33096CAAF6AC2098DABA1AB5" xlink:to="loc_us-gaap_RelatedPartyDomain_67EDDBCB495D32794D752098DABBC95D" xlink:type="arc" />
    <loc xlink:href="astc-20160630.xsd#astc_FirstDetectMember" xlink:label="loc_astc_FirstDetectMember_B7AAA7DA9C57571AF7C62098DABB7FC6" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyDomain_67EDDBCB495D32794D752098DABBC95D" xlink:to="loc_astc_FirstDetectMember_B7AAA7DA9C57571AF7C62098DABB7FC6" xlink:type="arc" />
    <loc xlink:href="astc-20160630.xsd#astc_FundsAwardedForDevelopmentAndMarketing" xlink:label="loc_astc_FundsAwardedForDevelopmentAndMarketing_D148D0B6FB9C70D328AE2098DABB94F6" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_astc_StateOfTexasFundingLineItems_07AC27AB740874E264192098DABBB893" xlink:to="loc_astc_FundsAwardedForDevelopmentAndMarketing_D148D0B6FB9C70D328AE2098DABB94F6" xlink:type="arc" />
    <loc xlink:href="astc-20160630.xsd#astc_PaymentOfCommonStockRepurchaseRight" xlink:label="loc_astc_PaymentOfCommonStockRepurchaseRight_612F97B70F3E9E0178742098DABBC6DB" xlink:type="locator" />
    <definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_astc_StateOfTexasFundingLineItems_07AC27AB740874E264192098DABBB893" xlink:to="loc_astc_PaymentOfCommonStockRepurchaseRight_612F97B70F3E9E0178742098DABBC6DB" xlink:type="arc" />
  </definitionLink>
  <definitionLink xlink:role="http://www.astrotechcorp.com/role/SubsequentEvents" xlink:type="extended" />
  <definitionLink xlink:role="http://www.astrotechcorp.com/role/SubsequentEventsDetails" xlink:type="extended">
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_SubsequentEventLineItems" xlink:label="loc_us-gaap_SubsequentEventLineItems_85B9DF0C26069A3C3B68216DFAE8B01B" xlink:type="locator" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_SubsequentEventTable" xlink:label="loc_us-gaap_SubsequentEventTable_C6162B8633B2369C9E62216DFAE8546F" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_SubsequentEventLineItems_85B9DF0C26069A3C3B68216DFAE8B01B" xlink:to="loc_us-gaap_SubsequentEventTable_C6162B8633B2369C9E62216DFAE8546F" xlink:type="arc" xbrldt:closed="true" xbrldt:contextElement="segment" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_StatementGeographicalAxis" xlink:label="loc_us-gaap_StatementGeographicalAxis_C04B808887A347581D96216DFAE8AF5A" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_SubsequentEventTable_C6162B8633B2369C9E62216DFAE8546F" xlink:to="loc_us-gaap_StatementGeographicalAxis_C04B808887A347581D96216DFAE8AF5A" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_SegmentGeographicalDomain" xlink:label="loc_us-gaap_SegmentGeographicalDomain_511DC854A3FFFD560B5C216DFAE8D397_default" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementGeographicalAxis_C04B808887A347581D96216DFAE8AF5A" xlink:to="loc_us-gaap_SegmentGeographicalDomain_511DC854A3FFFD560B5C216DFAE8D397_default" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_SegmentGeographicalDomain" xlink:label="loc_us-gaap_SegmentGeographicalDomain_511DC854A3FFFD560B5C216DFAE8D397" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementGeographicalAxis_C04B808887A347581D96216DFAE8AF5A" xlink:to="loc_us-gaap_SegmentGeographicalDomain_511DC854A3FFFD560B5C216DFAE8D397" xlink:type="arc" />
    <loc xlink:href="astc-20160630.xsd#astc_AustinTexasMember" xlink:label="loc_astc_AustinTexasMember_64BEC0D8C37096447D16216DFAE8F2C6" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SegmentGeographicalDomain_511DC854A3FFFD560B5C216DFAE8D397" xlink:to="loc_astc_AustinTexasMember_64BEC0D8C37096447D16216DFAE8F2C6" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_SubsequentEventTypeAxis" xlink:label="loc_us-gaap_SubsequentEventTypeAxis_16E2F7464011B479FD32216DFAE8BF0E" xlink:type="locator" />
    <definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_SubsequentEventTable_C6162B8633B2369C9E62216DFAE8546F" xlink:to="loc_us-gaap_SubsequentEventTypeAxis_16E2F7464011B479FD32216DFAE8BF0E" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_SubsequentEventTypeDomain" xlink:label="loc_us-gaap_SubsequentEventTypeDomain_E877ED07693433F2B31C216DFAE87AEA_default" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_SubsequentEventTypeAxis_16E2F7464011B479FD32216DFAE8BF0E" xlink:to="loc_us-gaap_SubsequentEventTypeDomain_E877ED07693433F2B31C216DFAE87AEA_default" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_SubsequentEventTypeDomain" xlink:label="loc_us-gaap_SubsequentEventTypeDomain_E877ED07693433F2B31C216DFAE87AEA" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_SubsequentEventTypeAxis_16E2F7464011B479FD32216DFAE8BF0E" xlink:to="loc_us-gaap_SubsequentEventTypeDomain_E877ED07693433F2B31C216DFAE87AEA" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_SubsequentEventMember" xlink:label="loc_us-gaap_SubsequentEventMember_E114A24ED71083026495216DFAE813E7" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SubsequentEventTypeDomain_E877ED07693433F2B31C216DFAE87AEA" xlink:to="loc_us-gaap_SubsequentEventMember_E114A24ED71083026495216DFAE813E7" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_AreaOfLand" xlink:label="loc_us-gaap_AreaOfLand_64D4AFECCBC68F77A196216DFAE84A87" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SubsequentEventLineItems_85B9DF0C26069A3C3B68216DFAE8B01B" xlink:to="loc_us-gaap_AreaOfLand_64D4AFECCBC68F77A196216DFAE84A87" xlink:type="arc" />
    <loc xlink:href="astc-20160630.xsd#astc_OperatingLeasesMonthlyRentalExpense" xlink:label="loc_astc_OperatingLeasesMonthlyRentalExpense_7AEEC5A58D0D0AACE975216DFAE826BC" xlink:type="locator" />
    <definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_SubsequentEventLineItems_85B9DF0C26069A3C3B68216DFAE8B01B" xlink:to="loc_astc_OperatingLeasesMonthlyRentalExpense_7AEEC5A58D0D0AACE975216DFAE826BC" xlink:type="arc" />
  </definitionLink>
  <definitionLink xlink:role="http://www.astrotechcorp.com/role/SummaryOfSignificantAccountingPolicies" xlink:type="extended" />
  <definitionLink xlink:role="http://www.astrotechcorp.com/role/SummaryOfSignificantAccountingPoliciesDetailTextuals" xlink:type="extended">
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_PropertyPlantAndEquipmentLineItems" xlink:label="loc_us-gaap_PropertyPlantAndEquipmentLineItems_382BF61A0729E0DAB6544CFE3C1E381A" xlink:type="locator" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_ScheduleOfPropertyPlantAndEquipmentTable" xlink:label="loc_us-gaap_ScheduleOfPropertyPlantAndEquipmentTable_B560062BBE6814D719904CFE3C1D3190" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentLineItems_382BF61A0729E0DAB6544CFE3C1E381A" xlink:to="loc_us-gaap_ScheduleOfPropertyPlantAndEquipmentTable_B560062BBE6814D719904CFE3C1D3190" xlink:type="arc" xbrldt:closed="true" xbrldt:contextElement="segment" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_PropertyPlantAndEquipmentByTypeAxis" xlink:label="loc_us-gaap_PropertyPlantAndEquipmentByTypeAxis_A1ED9756DE3EBE0C9EA14CFE3C1D4EDE" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfPropertyPlantAndEquipmentTable_B560062BBE6814D719904CFE3C1D3190" xlink:to="loc_us-gaap_PropertyPlantAndEquipmentByTypeAxis_A1ED9756DE3EBE0C9EA14CFE3C1D4EDE" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_PropertyPlantAndEquipmentTypeDomain" xlink:label="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_A33FF6767A88B6AEB3FA4CFE3C1DCF0F_default" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentByTypeAxis_A1ED9756DE3EBE0C9EA14CFE3C1D4EDE" xlink:to="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_A33FF6767A88B6AEB3FA4CFE3C1DCF0F_default" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_PropertyPlantAndEquipmentTypeDomain" xlink:label="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_A33FF6767A88B6AEB3FA4CFE3C1DCF0F" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentByTypeAxis_A1ED9756DE3EBE0C9EA14CFE3C1D4EDE" xlink:to="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_A33FF6767A88B6AEB3FA4CFE3C1DCF0F" xlink:type="arc" />
    <loc xlink:href="astc-20160630.xsd#astc_PurchasedSoftwareMember" xlink:label="loc_astc_PurchasedSoftwareMember_C98FB5BBF833A30403264CFE3C1D5061" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentTypeDomain_A33FF6767A88B6AEB3FA4CFE3C1DCF0F" xlink:to="loc_astc_PurchasedSoftwareMember_C98FB5BBF833A30403264CFE3C1D5061" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_RangeAxis" xlink:label="loc_us-gaap_RangeAxis_8932F70ECEAA2D202EB04CFE3C1D9318" xlink:type="locator" />
    <definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfPropertyPlantAndEquipmentTable_B560062BBE6814D719904CFE3C1D3190" xlink:to="loc_us-gaap_RangeAxis_8932F70ECEAA2D202EB04CFE3C1D9318" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_RangeMember" xlink:label="loc_us-gaap_RangeMember_C395BAA81697FD7CE0AF4CFE3C1D46FB_default" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_RangeAxis_8932F70ECEAA2D202EB04CFE3C1D9318" xlink:to="loc_us-gaap_RangeMember_C395BAA81697FD7CE0AF4CFE3C1D46FB_default" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_RangeMember" xlink:label="loc_us-gaap_RangeMember_C395BAA81697FD7CE0AF4CFE3C1D46FB" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_RangeAxis_8932F70ECEAA2D202EB04CFE3C1D9318" xlink:to="loc_us-gaap_RangeMember_C395BAA81697FD7CE0AF4CFE3C1D46FB" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_MinimumMember" xlink:label="loc_us-gaap_MinimumMember_0BDF70572C1000CD85DF4CFE3C1DF643" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RangeMember_C395BAA81697FD7CE0AF4CFE3C1D46FB" xlink:to="loc_us-gaap_MinimumMember_0BDF70572C1000CD85DF4CFE3C1DF643" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_MaximumMember" xlink:label="loc_us-gaap_MaximumMember_0B1C09983B0614ABB8114CFE3C1D8FA0" xlink:type="locator" />
    <definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RangeMember_C395BAA81697FD7CE0AF4CFE3C1D46FB" xlink:to="loc_us-gaap_MaximumMember_0B1C09983B0614ABB8114CFE3C1D8FA0" xlink:type="arc" />
    <loc xlink:href="http://xbrl.sec.gov/dei/2014/dei-2014-01-31.xsd#dei_LegalEntityAxis" xlink:label="loc_dei_LegalEntityAxis_03DB16D51910E02813AD4CFE3C1D0C01" xlink:type="locator" />
    <definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfPropertyPlantAndEquipmentTable_B560062BBE6814D719904CFE3C1D3190" xlink:to="loc_dei_LegalEntityAxis_03DB16D51910E02813AD4CFE3C1D0C01" xlink:type="arc" />
    <loc xlink:href="http://xbrl.sec.gov/dei/2014/dei-2014-01-31.xsd#dei_EntityDomain" xlink:label="loc_dei_EntityDomain_98C1930326176D84B8B84CFE3C1D5DAA_default" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_dei_LegalEntityAxis_03DB16D51910E02813AD4CFE3C1D0C01" xlink:to="loc_dei_EntityDomain_98C1930326176D84B8B84CFE3C1D5DAA_default" xlink:type="arc" />
    <loc xlink:href="http://xbrl.sec.gov/dei/2014/dei-2014-01-31.xsd#dei_EntityDomain" xlink:label="loc_dei_EntityDomain_98C1930326176D84B8B84CFE3C1D5DAA" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_dei_LegalEntityAxis_03DB16D51910E02813AD4CFE3C1D0C01" xlink:to="loc_dei_EntityDomain_98C1930326176D84B8B84CFE3C1D5DAA" xlink:type="arc" />
    <loc xlink:href="astc-20160630.xsd#astc_AstralImagesIncMember" xlink:label="loc_astc_AstralImagesIncMember_299B44FFB618F23A700C4CFE3C1D5199" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_dei_EntityDomain_98C1930326176D84B8B84CFE3C1D5DAA" xlink:to="loc_astc_AstralImagesIncMember_299B44FFB618F23A700C4CFE3C1D5199" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_LeaseArrangementTypeAxis" xlink:label="loc_us-gaap_LeaseArrangementTypeAxis_D7255F67B3AEB2ABE7FD4CFE3C1D2FB7" xlink:type="locator" />
    <definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfPropertyPlantAndEquipmentTable_B560062BBE6814D719904CFE3C1D3190" xlink:to="loc_us-gaap_LeaseArrangementTypeAxis_D7255F67B3AEB2ABE7FD4CFE3C1D2FB7" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_LeaseArrangementTypeDomain" xlink:label="loc_us-gaap_LeaseArrangementTypeDomain_87317D5735E6421CDDF04CFE3C1D9DCD_default" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_LeaseArrangementTypeAxis_D7255F67B3AEB2ABE7FD4CFE3C1D2FB7" xlink:to="loc_us-gaap_LeaseArrangementTypeDomain_87317D5735E6421CDDF04CFE3C1D9DCD_default" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_LeaseArrangementTypeDomain" xlink:label="loc_us-gaap_LeaseArrangementTypeDomain_87317D5735E6421CDDF04CFE3C1D9DCD" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_LeaseArrangementTypeAxis_D7255F67B3AEB2ABE7FD4CFE3C1D2FB7" xlink:to="loc_us-gaap_LeaseArrangementTypeDomain_87317D5735E6421CDDF04CFE3C1D9DCD" xlink:type="arc" />
    <loc xlink:href="astc-20160630.xsd#astc_TexasEmergingTechnologyFundMember" xlink:label="loc_astc_TexasEmergingTechnologyFundMember_373EFBB802ABAA7E2D474CFE3C1D083C" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LeaseArrangementTypeDomain_87317D5735E6421CDDF04CFE3C1D9DCD" xlink:to="loc_astc_TexasEmergingTechnologyFundMember_373EFBB802ABAA7E2D474CFE3C1D083C" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_RelatedPartyTransactionsByRelatedPartyAxis" xlink:label="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_018661E8591ED1428B1D4CFE3C1EB719" xlink:type="locator" />
    <definitionArc order="5" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfPropertyPlantAndEquipmentTable_B560062BBE6814D719904CFE3C1D3190" xlink:to="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_018661E8591ED1428B1D4CFE3C1EB719" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_RelatedPartyDomain" xlink:label="loc_us-gaap_RelatedPartyDomain_D8AC77AFC96D462A4B364CFE3C1EB1E6_default" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_018661E8591ED1428B1D4CFE3C1EB719" xlink:to="loc_us-gaap_RelatedPartyDomain_D8AC77AFC96D462A4B364CFE3C1EB1E6_default" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_RelatedPartyDomain" xlink:label="loc_us-gaap_RelatedPartyDomain_D8AC77AFC96D462A4B364CFE3C1EB1E6" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_018661E8591ED1428B1D4CFE3C1EB719" xlink:to="loc_us-gaap_RelatedPartyDomain_D8AC77AFC96D462A4B364CFE3C1EB1E6" xlink:type="arc" />
    <loc xlink:href="astc-20160630.xsd#astc_FirstDetectMember" xlink:label="loc_astc_FirstDetectMember_F18B4342907A2413691C4CFE3C1E8820" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyDomain_D8AC77AFC96D462A4B364CFE3C1EB1E6" xlink:to="loc_astc_FirstDetectMember_F18B4342907A2413691C4CFE3C1E8820" xlink:type="arc" />
    <loc xlink:href="astc-20160630.xsd#astc_RevenueRecognitionFixedPriceSubcontractOnGovernmentProjectTerm" xlink:label="loc_astc_RevenueRecognitionFixedPriceSubcontractOnGovernmentProjectTerm_A37E6CEE61979604F9864CFE3C1E5451" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentLineItems_382BF61A0729E0DAB6544CFE3C1E381A" xlink:to="loc_astc_RevenueRecognitionFixedPriceSubcontractOnGovernmentProjectTerm_A37E6CEE61979604F9864CFE3C1E5451" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_ResearchAndDevelopmentExpense" xlink:label="loc_us-gaap_ResearchAndDevelopmentExpense_5B25C9FB9A7F7036EDBE4CFE3C1E4A12" xlink:type="locator" />
    <definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentLineItems_382BF61A0729E0DAB6544CFE3C1E381A" xlink:to="loc_us-gaap_ResearchAndDevelopmentExpense_5B25C9FB9A7F7036EDBE4CFE3C1E4A12" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_AllowanceForDoubtfulAccountsReceivable" xlink:label="loc_us-gaap_AllowanceForDoubtfulAccountsReceivable_DE13B24DB847D3F422204CFE3C1E7ADE" xlink:type="locator" />
    <definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentLineItems_382BF61A0729E0DAB6544CFE3C1E381A" xlink:to="loc_us-gaap_AllowanceForDoubtfulAccountsReceivable_DE13B24DB847D3F422204CFE3C1E7ADE" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_PropertyPlantAndEquipmentUsefulLife" xlink:label="loc_us-gaap_PropertyPlantAndEquipmentUsefulLife_F1744F5603FD562A28C84CFE3C1E8B3F" xlink:type="locator" />
    <definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentLineItems_382BF61A0729E0DAB6544CFE3C1E381A" xlink:to="loc_us-gaap_PropertyPlantAndEquipmentUsefulLife_F1744F5603FD562A28C84CFE3C1E8B3F" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_AssetImpairmentCharges" xlink:label="loc_us-gaap_AssetImpairmentCharges_B12FEA4CFDAF3474D4B44CFE3C1E5A6F" xlink:type="locator" />
    <definitionArc order="5" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentLineItems_382BF61A0729E0DAB6544CFE3C1E381A" xlink:to="loc_us-gaap_AssetImpairmentCharges_B12FEA4CFDAF3474D4B44CFE3C1E5A6F" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_MinorityInterest" xlink:label="loc_us-gaap_MinorityInterest_7E93D86F5BE69A0082224CFE3C1E4746" xlink:type="locator" />
    <definitionArc order="6" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentLineItems_382BF61A0729E0DAB6544CFE3C1E381A" xlink:to="loc_us-gaap_MinorityInterest_7E93D86F5BE69A0082224CFE3C1E4746" xlink:type="arc" />
    <loc xlink:href="astc-20160630.xsd#astc_DisbursementOfFundForDevelopmentAndMarketing" xlink:label="loc_astc_DisbursementOfFundForDevelopmentAndMarketing_618FD6AEA7902A390F254CFE3C1E2A28" xlink:type="locator" />
    <definitionArc order="7" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentLineItems_382BF61A0729E0DAB6544CFE3C1E381A" xlink:to="loc_astc_DisbursementOfFundForDevelopmentAndMarketing_618FD6AEA7902A390F254CFE3C1E2A28" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2016/elts/us-gaap-2016-01-31.xsd#us-gaap_DebtInstrumentFaceAmount" xlink:label="loc_us-gaap_DebtInstrumentFaceAmount_540EBE12C8398E8B7E3F4CFE3C1ED03C" xlink:type="locator" />
    <definitionArc order="8" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentLineItems_382BF61A0729E0DAB6544CFE3C1E381A" xlink:to="loc_us-gaap_DebtInstrumentFaceAmount_540EBE12C8398E8B7E3F4CFE3C1ED03C" xlink:type="arc" />
    <loc xlink:href="astc-20160630.xsd#astc_PaymentOfCommonStockRepurchaseRight" xlink:label="loc_astc_PaymentOfCommonStockRepurchaseRight_165DEBB12441893997D44CFE3C1EFE29" xlink:type="locator" />
    <definitionArc order="9" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PropertyPlantAndEquipmentLineItems_382BF61A0729E0DAB6544CFE3C1E381A" xlink:to="loc_astc_PaymentOfCommonStockRepurchaseRight_165DEBB12441893997D44CFE3C1EFE29" xlink:type="arc" />
  </definitionLink>
  <definitionLink xlink:role="http://www.astrotechcorp.com/role/SummaryOfSignificantAccountingPoliciesPolicies" xlink:type="extended" />
</linkbase>
