<?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/BusinessRiskAndCreditRiskConcentrationInvolvingCash" xlink:href="astc-20151231.xsd#BusinessRiskAndCreditRiskConcentrationInvolvingCash" xlink:type="simple" />
  <roleRef roleURI="http://www.astrotechcorp.com/role/BusinessRiskAndCreditRiskConcentrationInvolvingCashDetailTextuals" xlink:href="astc-20151231.xsd#BusinessRiskAndCreditRiskConcentrationInvolvingCashDetailTextuals" xlink:type="simple" />
  <roleRef roleURI="http://www.astrotechcorp.com/role/CommitmentsAndContingencies" xlink:href="astc-20151231.xsd#CommitmentsAndContingencies" xlink:type="simple" />
  <roleRef roleURI="http://www.astrotechcorp.com/role/CommitmentsAndContingenciesDetailTextuals" xlink:href="astc-20151231.xsd#CommitmentsAndContingenciesDetailTextuals" xlink:type="simple" />
  <roleRef roleURI="http://www.astrotechcorp.com/role/CommonStockIncentiveStockPurchasePlansAndOtherCompensationPlans" xlink:href="astc-20151231.xsd#CommonStockIncentiveStockPurchasePlansAndOtherCompensationPlans" xlink:type="simple" />
  <roleRef roleURI="http://www.astrotechcorp.com/role/CommonStockIncentiveStockPurchasePlansAndOtherCompensationPlansNarrativeDetails" xlink:href="astc-20151231.xsd#CommonStockIncentiveStockPurchasePlansAndOtherCompensationPlansNarrativeDetails" xlink:type="simple" />
  <roleRef roleURI="http://www.astrotechcorp.com/role/CommonStockIncentiveStockPurchasePlansAndOtherCompensationPlansStockOptionActivityDetails" xlink:href="astc-20151231.xsd#CommonStockIncentiveStockPurchasePlansAndOtherCompensationPlansStockOptionActivityDetails" xlink:type="simple" />
  <roleRef roleURI="http://www.astrotechcorp.com/role/CommonStockIncentiveStockPurchasePlansAndOtherCompensationPlansStockOptionsByExercisePriceDetails" xlink:href="astc-20151231.xsd#CommonStockIncentiveStockPurchasePlansAndOtherCompensationPlansStockOptionsByExercisePriceDetails" xlink:type="simple" />
  <roleRef roleURI="http://www.astrotechcorp.com/role/CommonStockIncentiveStockPurchasePlansAndOtherCompensationPlansTables" xlink:href="astc-20151231.xsd#CommonStockIncentiveStockPurchasePlansAndOtherCompensationPlansTables" xlink:type="simple" />
  <roleRef roleURI="http://www.astrotechcorp.com/role/CondensedConsolidatedBalanceSheetsUnaudited" xlink:href="astc-20151231.xsd#CondensedConsolidatedBalanceSheetsUnaudited" xlink:type="simple" />
  <roleRef roleURI="http://www.astrotechcorp.com/role/CondensedConsolidatedBalanceSheetsUnauditedParentheticals" xlink:href="astc-20151231.xsd#CondensedConsolidatedBalanceSheetsUnauditedParentheticals" xlink:type="simple" />
  <roleRef roleURI="http://www.astrotechcorp.com/role/CondensedConsolidatedStatementsOfCashFlowsUnaudited" xlink:href="astc-20151231.xsd#CondensedConsolidatedStatementsOfCashFlowsUnaudited" xlink:type="simple" />
  <roleRef roleURI="http://www.astrotechcorp.com/role/CondensedConsolidatedStatementsOfOperationsAndComprehensiveIncomeUnaudited" xlink:href="astc-20151231.xsd#CondensedConsolidatedStatementsOfOperationsAndComprehensiveIncomeUnaudited" xlink:type="simple" />
  <roleRef roleURI="http://www.astrotechcorp.com/role/CondensedConsolidatedStatementsOfOperationsUnauditedParentheticals" xlink:href="astc-20151231.xsd#CondensedConsolidatedStatementsOfOperationsUnauditedParentheticals" xlink:type="simple" />
  <roleRef roleURI="http://www.astrotechcorp.com/role/Debt" xlink:href="astc-20151231.xsd#Debt" xlink:type="simple" />
  <roleRef roleURI="http://www.astrotechcorp.com/role/DebtDetailTextuals" xlink:href="astc-20151231.xsd#DebtDetailTextuals" xlink:type="simple" />
  <roleRef roleURI="http://www.astrotechcorp.com/role/DiscontinuedOperationsGainOnSaleOfAsoBusinessUnit" xlink:href="astc-20151231.xsd#DiscontinuedOperationsGainOnSaleOfAsoBusinessUnit" xlink:type="simple" />
  <roleRef roleURI="http://www.astrotechcorp.com/role/DiscontinuedOperationsGainOnSaleOfAsoBusinessUnitDetailTextuals" xlink:href="astc-20151231.xsd#DiscontinuedOperationsGainOnSaleOfAsoBusinessUnitDetailTextuals" xlink:type="simple" />
  <roleRef roleURI="http://www.astrotechcorp.com/role/DiscontinuedOperationsGainOnSaleOfAsoBusinessUnitDetails" xlink:href="astc-20151231.xsd#DiscontinuedOperationsGainOnSaleOfAsoBusinessUnitDetails" xlink:type="simple" />
  <roleRef roleURI="http://www.astrotechcorp.com/role/DiscontinuedOperationsGainOnSaleOfAsoBusinessUnitDetails1" xlink:href="astc-20151231.xsd#DiscontinuedOperationsGainOnSaleOfAsoBusinessUnitDetails1" xlink:type="simple" />
  <roleRef roleURI="http://www.astrotechcorp.com/role/DiscontinuedOperationsGainOnSaleOfAsoBusinessUnitTables" xlink:href="astc-20151231.xsd#DiscontinuedOperationsGainOnSaleOfAsoBusinessUnitTables" xlink:type="simple" />
  <roleRef roleURI="http://www.astrotechcorp.com/role/DocumentAndEntityInformation" xlink:href="astc-20151231.xsd#DocumentAndEntityInformation" xlink:type="simple" />
  <roleRef roleURI="http://www.astrotechcorp.com/role/FairValueMeasurement" xlink:href="astc-20151231.xsd#FairValueMeasurement" xlink:type="simple" />
  <roleRef roleURI="http://www.astrotechcorp.com/role/FairValueMeasurementDetails" xlink:href="astc-20151231.xsd#FairValueMeasurementDetails" xlink:type="simple" />
  <roleRef roleURI="http://www.astrotechcorp.com/role/FairValueMeasurementTables" xlink:href="astc-20151231.xsd#FairValueMeasurementTables" xlink:type="simple" />
  <roleRef roleURI="http://www.astrotechcorp.com/role/GeneralInformation" xlink:href="astc-20151231.xsd#GeneralInformation" xlink:type="simple" />
  <roleRef roleURI="http://www.astrotechcorp.com/role/GeneralInformationDetailTextuals" xlink:href="astc-20151231.xsd#GeneralInformationDetailTextuals" xlink:type="simple" />
  <roleRef roleURI="http://www.astrotechcorp.com/role/IncomeTaxes" xlink:href="astc-20151231.xsd#IncomeTaxes" xlink:type="simple" />
  <roleRef roleURI="http://www.astrotechcorp.com/role/IncomeTaxesDetailTextuals" xlink:href="astc-20151231.xsd#IncomeTaxesDetailTextuals" xlink:type="simple" />
  <roleRef roleURI="http://www.astrotechcorp.com/role/Investments" xlink:href="astc-20151231.xsd#Investments" xlink:type="simple" />
  <roleRef roleURI="http://www.astrotechcorp.com/role/InvestmentsAvailableForSaleAndHeldToMaturitySecuritiesDetails" xlink:href="astc-20151231.xsd#InvestmentsAvailableForSaleAndHeldToMaturitySecuritiesDetails" xlink:type="simple" />
  <roleRef roleURI="http://www.astrotechcorp.com/role/InvestmentsCarryingValueDetails" xlink:href="astc-20151231.xsd#InvestmentsCarryingValueDetails" xlink:type="simple" />
  <roleRef roleURI="http://www.astrotechcorp.com/role/InvestmentsTables" xlink:href="astc-20151231.xsd#InvestmentsTables" xlink:type="simple" />
  <roleRef roleURI="http://www.astrotechcorp.com/role/NetLossIncomePerShare" xlink:href="astc-20151231.xsd#NetLossIncomePerShare" xlink:type="simple" />
  <roleRef roleURI="http://www.astrotechcorp.com/role/NetLossIncomePerShareDetailTextuals" xlink:href="astc-20151231.xsd#NetLossIncomePerShareDetailTextuals" xlink:type="simple" />
  <roleRef roleURI="http://www.astrotechcorp.com/role/NetLossIncomePerShareDetails" xlink:href="astc-20151231.xsd#NetLossIncomePerShareDetails" xlink:type="simple" />
  <roleRef roleURI="http://www.astrotechcorp.com/role/NetLossIncomePerShareTables" xlink:href="astc-20151231.xsd#NetLossIncomePerShareTables" xlink:type="simple" />
  <roleRef roleURI="http://www.astrotechcorp.com/role/NoncontrollingInterest" xlink:href="astc-20151231.xsd#NoncontrollingInterest" xlink:type="simple" />
  <roleRef roleURI="http://www.astrotechcorp.com/role/NoncontrollingInterestChangesInEquityDetails" xlink:href="astc-20151231.xsd#NoncontrollingInterestChangesInEquityDetails" xlink:type="simple" />
  <roleRef roleURI="http://www.astrotechcorp.com/role/NoncontrollingInterestDetailTextuals" xlink:href="astc-20151231.xsd#NoncontrollingInterestDetailTextuals" xlink:type="simple" />
  <roleRef roleURI="http://www.astrotechcorp.com/role/NoncontrollingInterestTables" xlink:href="astc-20151231.xsd#NoncontrollingInterestTables" xlink:type="simple" />
  <roleRef roleURI="http://www.astrotechcorp.com/role/OtherComprehensiveLossIncome" xlink:href="astc-20151231.xsd#OtherComprehensiveLossIncome" xlink:type="simple" />
  <roleRef roleURI="http://www.astrotechcorp.com/role/OtherComprehensiveLossIncomeDetails" xlink:href="astc-20151231.xsd#OtherComprehensiveLossIncomeDetails" xlink:type="simple" />
  <roleRef roleURI="http://www.astrotechcorp.com/role/OtherComprehensiveLossIncomeTables" xlink:href="astc-20151231.xsd#OtherComprehensiveLossIncomeTables" xlink:type="simple" />
  <roleRef roleURI="http://www.astrotechcorp.com/role/ReceivablesIndemnityHoldbackRelatedToAssetSale" xlink:href="astc-20151231.xsd#ReceivablesIndemnityHoldbackRelatedToAssetSale" xlink:type="simple" />
  <roleRef roleURI="http://www.astrotechcorp.com/role/ReceivablesIndemnityHoldbackRelatedToAssetSaleDetailTextuals" xlink:href="astc-20151231.xsd#ReceivablesIndemnityHoldbackRelatedToAssetSaleDetailTextuals" xlink:type="simple" />
  <roleRef roleURI="http://www.astrotechcorp.com/role/RevenueRecognition" xlink:href="astc-20151231.xsd#RevenueRecognition" xlink:type="simple" />
  <roleRef roleURI="http://www.astrotechcorp.com/role/RevenueRecognitionDetails" xlink:href="astc-20151231.xsd#RevenueRecognitionDetails" xlink:type="simple" />
  <roleRef roleURI="http://www.astrotechcorp.com/role/StateOfTexasFunding" xlink:href="astc-20151231.xsd#StateOfTexasFunding" xlink:type="simple" />
  <roleRef roleURI="http://www.astrotechcorp.com/role/StateOfTexasFundingDetailTextuals" xlink:href="astc-20151231.xsd#StateOfTexasFundingDetailTextuals" 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/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/2014/elts/us-gaap-2014-01-31.xsd#us-gaap_ConcentrationRiskLineItems" xlink:label="loc_us-gaap_ConcentrationRiskLineItems_C6147A6468711E9E47FD890F39B21307" xlink:type="locator" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2014/elts/us-gaap-2014-01-31.xsd#us-gaap_ConcentrationRiskTable" xlink:label="loc_us-gaap_ConcentrationRiskTable_A84AE84F3E0550D27994890F39AB9D20" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_ConcentrationRiskLineItems_C6147A6468711E9E47FD890F39B21307" xlink:to="loc_us-gaap_ConcentrationRiskTable_A84AE84F3E0550D27994890F39AB9D20" xlink:type="arc" xbrldt:closed="true" xbrldt:contextElement="segment" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2014/elts/us-gaap-2014-01-31.xsd#us-gaap_ConcentrationRiskByBenchmarkAxis" xlink:label="loc_us-gaap_ConcentrationRiskByBenchmarkAxis_012110F6AB63BF431F90890F39AC4BA9" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ConcentrationRiskTable_A84AE84F3E0550D27994890F39AB9D20" xlink:to="loc_us-gaap_ConcentrationRiskByBenchmarkAxis_012110F6AB63BF431F90890F39AC4BA9" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2014/elts/us-gaap-2014-01-31.xsd#us-gaap_ConcentrationRiskBenchmarkDomain" xlink:label="loc_us-gaap_ConcentrationRiskBenchmarkDomain_DDA94B6AA4C1E73A91CA890F39AE74D4_default" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_ConcentrationRiskByBenchmarkAxis_012110F6AB63BF431F90890F39AC4BA9" xlink:to="loc_us-gaap_ConcentrationRiskBenchmarkDomain_DDA94B6AA4C1E73A91CA890F39AE74D4_default" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2014/elts/us-gaap-2014-01-31.xsd#us-gaap_ConcentrationRiskBenchmarkDomain" xlink:label="loc_us-gaap_ConcentrationRiskBenchmarkDomain_DDA94B6AA4C1E73A91CA890F39AE74D4" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_ConcentrationRiskByBenchmarkAxis_012110F6AB63BF431F90890F39AC4BA9" xlink:to="loc_us-gaap_ConcentrationRiskBenchmarkDomain_DDA94B6AA4C1E73A91CA890F39AE74D4" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2014/elts/us-gaap-2014-01-31.xsd#us-gaap_SalesRevenueNetMember" xlink:label="loc_us-gaap_SalesRevenueNetMember_EC06497E5C16AFC490388910E0C8F059" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ConcentrationRiskBenchmarkDomain_DDA94B6AA4C1E73A91CA890F39AE74D4" xlink:to="loc_us-gaap_SalesRevenueNetMember_EC06497E5C16AFC490388910E0C8F059" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2014/elts/us-gaap-2014-01-31.xsd#us-gaap_ConcentrationRiskByTypeAxis" xlink:label="loc_us-gaap_ConcentrationRiskByTypeAxis_2DCF2B7C0F3335E323AA890F39AFDB40" xlink:type="locator" />
    <definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ConcentrationRiskTable_A84AE84F3E0550D27994890F39AB9D20" xlink:to="loc_us-gaap_ConcentrationRiskByTypeAxis_2DCF2B7C0F3335E323AA890F39AFDB40" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2014/elts/us-gaap-2014-01-31.xsd#us-gaap_ConcentrationRiskTypeDomain" xlink:label="loc_us-gaap_ConcentrationRiskTypeDomain_AC007A6372BA3534B5DB890F39B1988A_default" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_ConcentrationRiskByTypeAxis_2DCF2B7C0F3335E323AA890F39AFDB40" xlink:to="loc_us-gaap_ConcentrationRiskTypeDomain_AC007A6372BA3534B5DB890F39B1988A_default" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2014/elts/us-gaap-2014-01-31.xsd#us-gaap_ConcentrationRiskTypeDomain" xlink:label="loc_us-gaap_ConcentrationRiskTypeDomain_AC007A6372BA3534B5DB890F39B1988A" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_ConcentrationRiskByTypeAxis_2DCF2B7C0F3335E323AA890F39AFDB40" xlink:to="loc_us-gaap_ConcentrationRiskTypeDomain_AC007A6372BA3534B5DB890F39B1988A" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2014/elts/us-gaap-2014-01-31.xsd#us-gaap_CustomerConcentrationRiskMember" xlink:label="loc_us-gaap_CustomerConcentrationRiskMember_D5C3DD3BDB2AF215657D891173D66BA2" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ConcentrationRiskTypeDomain_AC007A6372BA3534B5DB890F39B1988A" xlink:to="loc_us-gaap_CustomerConcentrationRiskMember_D5C3DD3BDB2AF215657D891173D66BA2" xlink:type="arc" />
    <loc xlink:href="astc-20151231.xsd#astc_ConcentrationRiskNumberOfCustomers" xlink:label="loc_astc_ConcentrationRiskNumberOfCustomers_D3C04518446EDA6B4CC788EDB712E3BA" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ConcentrationRiskLineItems_C6147A6468711E9E47FD890F39B21307" xlink:to="loc_astc_ConcentrationRiskNumberOfCustomers_D3C04518446EDA6B4CC788EDB712E3BA" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2014/elts/us-gaap-2014-01-31.xsd#us-gaap_ConcentrationRiskPercentage1" xlink:label="loc_us-gaap_ConcentrationRiskPercentage1_5B802D9EC9ECA2C23EF6890EEC9980FB" xlink:type="locator" />
    <definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ConcentrationRiskLineItems_C6147A6468711E9E47FD890F39B21307" xlink:to="loc_us-gaap_ConcentrationRiskPercentage1_5B802D9EC9ECA2C23EF6890EEC9980FB" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2014/elts/us-gaap-2014-01-31.xsd#us-gaap_CashFDICInsuredAmount" xlink:label="loc_us-gaap_CashFDICInsuredAmount_355BD4D4F647D85DD6F788EDB71273A2" xlink:type="locator" />
    <definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ConcentrationRiskLineItems_C6147A6468711E9E47FD890F39B21307" xlink:to="loc_us-gaap_CashFDICInsuredAmount_355BD4D4F647D85DD6F788EDB71273A2" xlink:type="arc" />
  </definitionLink>
  <definitionLink xlink:role="http://www.astrotechcorp.com/role/CommitmentsAndContingencies" xlink:type="extended" />
  <definitionLink xlink:role="http://www.astrotechcorp.com/role/CommitmentsAndContingenciesDetailTextuals" xlink:type="extended" />
  <definitionLink xlink:role="http://www.astrotechcorp.com/role/CommonStockIncentiveStockPurchasePlansAndOtherCompensationPlans" xlink:type="extended" />
  <definitionLink xlink:role="http://www.astrotechcorp.com/role/CommonStockIncentiveStockPurchasePlansAndOtherCompensationPlansNarrativeDetails" xlink:type="extended">
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2014/elts/us-gaap-2014-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_431FCE1CAEE5F93721C888EDB6C23B11" xlink:type="locator" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2014/elts/us-gaap-2014-01-31.xsd#us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable" xlink:label="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_866DE99DD7CC02AF5C4888EDB6BC10EE" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_431FCE1CAEE5F93721C888EDB6C23B11" xlink:to="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_866DE99DD7CC02AF5C4888EDB6BC10EE" xlink:type="arc" xbrldt:closed="true" xbrldt:contextElement="segment" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2014/elts/us-gaap-2014-01-31.xsd#us-gaap_PlanNameAxis" xlink:label="loc_us-gaap_PlanNameAxis_F33FB45998CC3F0CDB8C88EDB6C11E04" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_866DE99DD7CC02AF5C4888EDB6BC10EE" xlink:to="loc_us-gaap_PlanNameAxis_F33FB45998CC3F0CDB8C88EDB6C11E04" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2014/elts/us-gaap-2014-01-31.xsd#us-gaap_PlanNameDomain" xlink:label="loc_us-gaap_PlanNameDomain_07B6CD64E8661A70BF4F88EDB6C1C2B7_default" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_PlanNameAxis_F33FB45998CC3F0CDB8C88EDB6C11E04" xlink:to="loc_us-gaap_PlanNameDomain_07B6CD64E8661A70BF4F88EDB6C1C2B7_default" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2014/elts/us-gaap-2014-01-31.xsd#us-gaap_PlanNameDomain" xlink:label="loc_us-gaap_PlanNameDomain_07B6CD64E8661A70BF4F88EDB6C1C2B7" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_PlanNameAxis_F33FB45998CC3F0CDB8C88EDB6C11E04" xlink:to="loc_us-gaap_PlanNameDomain_07B6CD64E8661A70BF4F88EDB6C1C2B7" xlink:type="arc" />
    <loc xlink:href="astc-20151231.xsd#astc_AstrotechSecuritiesRepurchaseProgramMember" xlink:label="loc_astc_AstrotechSecuritiesRepurchaseProgramMember_DAEA994D22A58377963E88EDB6C115A7" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_PlanNameDomain_07B6CD64E8661A70BF4F88EDB6C1C2B7" xlink:to="loc_astc_AstrotechSecuritiesRepurchaseProgramMember_DAEA994D22A58377963E88EDB6C115A7" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2014/elts/us-gaap-2014-01-31.xsd#us-gaap_AwardTypeAxis" xlink:label="loc_us-gaap_AwardTypeAxis_8974137CF0D5EB7E2D8088EDB6C1BD96" xlink:type="locator" />
    <definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfShareBasedCompensationArrangementsByShareBasedPaymentAwardTable_866DE99DD7CC02AF5C4888EDB6BC10EE" xlink:to="loc_us-gaap_AwardTypeAxis_8974137CF0D5EB7E2D8088EDB6C1BD96" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2014/elts/us-gaap-2014-01-31.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_047A76669AE8E0BFDFBE88EDB6C11C31_default" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_AwardTypeAxis_8974137CF0D5EB7E2D8088EDB6C1BD96" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_047A76669AE8E0BFDFBE88EDB6C11C31_default" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2014/elts/us-gaap-2014-01-31.xsd#us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_047A76669AE8E0BFDFBE88EDB6C11C31" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_AwardTypeAxis_8974137CF0D5EB7E2D8088EDB6C1BD96" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_047A76669AE8E0BFDFBE88EDB6C11C31" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2014/elts/us-gaap-2014-01-31.xsd#us-gaap_EmployeeStockOptionMember" xlink:label="loc_us-gaap_EmployeeStockOptionMember_480214DB85DC2A44750988EDB6C1ECF5" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_047A76669AE8E0BFDFBE88EDB6C11C31" xlink:to="loc_us-gaap_EmployeeStockOptionMember_480214DB85DC2A44750988EDB6C1ECF5" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2014/elts/us-gaap-2014-01-31.xsd#us-gaap_RestrictedStockMember" xlink:label="loc_us-gaap_RestrictedStockMember_7AA1392D2A0523174A9788EDB6C232C6" xlink:type="locator" />
    <definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementsByShareBasedPaymentAwardAwardTypeAndPlanNameDomain_047A76669AE8E0BFDFBE88EDB6C11C31" xlink:to="loc_us-gaap_RestrictedStockMember_7AA1392D2A0523174A9788EDB6C232C6" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2014/elts/us-gaap-2014-01-31.xsd#us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsExercisableIntrinsicValue1" xlink:label="loc_us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsExercisableIntrinsicValue1_A96221543A3B770F37AC88EDB6C2AF61" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_431FCE1CAEE5F93721C888EDB6C23B11" xlink:to="loc_us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsExercisableIntrinsicValue1_A96221543A3B770F37AC88EDB6C2AF61" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2014/elts/us-gaap-2014-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingIntrinsicValue" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingIntrinsicValue_90EFDB105F7AE5826AF388EDB6C29D8F" xlink:type="locator" />
    <definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_431FCE1CAEE5F93721C888EDB6C23B11" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingIntrinsicValue_90EFDB105F7AE5826AF388EDB6C29D8F" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2014/elts/us-gaap-2014-01-31.xsd#us-gaap_AllocatedShareBasedCompensationExpense" xlink:label="loc_us-gaap_AllocatedShareBasedCompensationExpense_4A6C137BE0FC5BACEFBD88EDB6C22627" xlink:type="locator" />
    <definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_431FCE1CAEE5F93721C888EDB6C23B11" xlink:to="loc_us-gaap_AllocatedShareBasedCompensationExpense_4A6C137BE0FC5BACEFBD88EDB6C22627" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2014/elts/us-gaap-2014-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodGross" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodGross_C522AE2BDE2DBA5CA2F688EDB6C21834" xlink:type="locator" />
    <definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_431FCE1CAEE5F93721C888EDB6C23B11" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodGross_C522AE2BDE2DBA5CA2F688EDB6C21834" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2014/elts/us-gaap-2014-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod_7C54E0251318AB580F8A88EDB6C2AEC5" xlink:type="locator" />
    <definitionArc order="5" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_431FCE1CAEE5F93721C888EDB6C23B11" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod_7C54E0251318AB580F8A88EDB6C2AEC5" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2014/elts/us-gaap-2014-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriod" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriod_9042D266F25E3DA01D0988EDB6C26718" xlink:type="locator" />
    <definitionArc order="6" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_431FCE1CAEE5F93721C888EDB6C23B11" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriod_9042D266F25E3DA01D0988EDB6C26718" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2014/elts/us-gaap-2014-01-31.xsd#us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeitedInPeriod" xlink:label="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeitedInPeriod_D9C743854CFA58B9CC7388EDB6C28F7B" xlink:type="locator" />
    <definitionArc order="7" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_431FCE1CAEE5F93721C888EDB6C23B11" xlink:to="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeitedInPeriod_D9C743854CFA58B9CC7388EDB6C28F7B" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2014/elts/us-gaap-2014-01-31.xsd#us-gaap_StockRepurchaseProgramAuthorizedAmount1" xlink:label="loc_us-gaap_StockRepurchaseProgramAuthorizedAmount1_22F1C556415B0A13078388EDB6C2EE8E" xlink:type="locator" />
    <definitionArc order="8" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_431FCE1CAEE5F93721C888EDB6C23B11" xlink:to="loc_us-gaap_StockRepurchaseProgramAuthorizedAmount1_22F1C556415B0A13078388EDB6C2EE8E" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2014/elts/us-gaap-2014-01-31.xsd#us-gaap_TreasuryStockSharesAcquired" xlink:label="loc_us-gaap_TreasuryStockSharesAcquired_B79EA8431429A359794B88EDB6C20136" xlink:type="locator" />
    <definitionArc order="9" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_431FCE1CAEE5F93721C888EDB6C23B11" xlink:to="loc_us-gaap_TreasuryStockSharesAcquired_B79EA8431429A359794B88EDB6C20136" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2014/elts/us-gaap-2014-01-31.xsd#us-gaap_TreasuryStockValueAcquiredCostMethod" xlink:label="loc_us-gaap_TreasuryStockValueAcquiredCostMethod_E4C4BC2C0D8839F18F7388EDB6C2A215" xlink:type="locator" />
    <definitionArc order="10" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems_431FCE1CAEE5F93721C888EDB6C23B11" xlink:to="loc_us-gaap_TreasuryStockValueAcquiredCostMethod_E4C4BC2C0D8839F18F7388EDB6C2A215" xlink:type="arc" />
  </definitionLink>
  <definitionLink xlink:role="http://www.astrotechcorp.com/role/CommonStockIncentiveStockPurchasePlansAndOtherCompensationPlansStockOptionActivityDetails" xlink:type="extended" />
  <definitionLink xlink:role="http://www.astrotechcorp.com/role/CommonStockIncentiveStockPurchasePlansAndOtherCompensationPlansStockOptionsByExercisePriceDetails" xlink:type="extended">
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2014/elts/us-gaap-2014-01-31.xsd#us-gaap_ShareBasedCompensationSharesAuthorizedUnderStockOptionPlansExercisePriceRangeLineItems" xlink:label="loc_us-gaap_ShareBasedCompensationSharesAuthorizedUnderStockOptionPlansExercisePriceRangeLineItems_09C8611BF2CF2E1E124CC62A1DB0376D" xlink:type="locator" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2014/elts/us-gaap-2014-01-31.xsd#us-gaap_ScheduleOfShareBasedCompensationSharesAuthorizedUnderStockOptionPlansByExercisePriceRangeTable" xlink:label="loc_us-gaap_ScheduleOfShareBasedCompensationSharesAuthorizedUnderStockOptionPlansByExercisePriceRangeTable_8DDE144BA6017748FEFEC62A1DB02B30" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_ShareBasedCompensationSharesAuthorizedUnderStockOptionPlansExercisePriceRangeLineItems_09C8611BF2CF2E1E124CC62A1DB0376D" xlink:to="loc_us-gaap_ScheduleOfShareBasedCompensationSharesAuthorizedUnderStockOptionPlansByExercisePriceRangeTable_8DDE144BA6017748FEFEC62A1DB02B30" xlink:type="arc" xbrldt:closed="true" xbrldt:contextElement="segment" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2014/elts/us-gaap-2014-01-31.xsd#us-gaap_ShareBasedCompensationSharesAuthorizedUnderStockOptionPlansByExercisePriceRangeAxis" xlink:label="loc_us-gaap_ShareBasedCompensationSharesAuthorizedUnderStockOptionPlansByExercisePriceRangeAxis_2337123E203402E755BDC62A1DB0AFED" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfShareBasedCompensationSharesAuthorizedUnderStockOptionPlansByExercisePriceRangeTable_8DDE144BA6017748FEFEC62A1DB02B30" xlink:to="loc_us-gaap_ShareBasedCompensationSharesAuthorizedUnderStockOptionPlansByExercisePriceRangeAxis_2337123E203402E755BDC62A1DB0AFED" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2014/elts/us-gaap-2014-01-31.xsd#us-gaap_ShareBasedCompensationSharesAuthorizedUnderStockOptionPlansExercisePriceRangeDomain" xlink:label="loc_us-gaap_ShareBasedCompensationSharesAuthorizedUnderStockOptionPlansExercisePriceRangeDomain_FE6FFF85B74778420849C62A1DB0774B_default" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_ShareBasedCompensationSharesAuthorizedUnderStockOptionPlansByExercisePriceRangeAxis_2337123E203402E755BDC62A1DB0AFED" xlink:to="loc_us-gaap_ShareBasedCompensationSharesAuthorizedUnderStockOptionPlansExercisePriceRangeDomain_FE6FFF85B74778420849C62A1DB0774B_default" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2014/elts/us-gaap-2014-01-31.xsd#us-gaap_ShareBasedCompensationSharesAuthorizedUnderStockOptionPlansExercisePriceRangeDomain" xlink:label="loc_us-gaap_ShareBasedCompensationSharesAuthorizedUnderStockOptionPlansExercisePriceRangeDomain_FE6FFF85B74778420849C62A1DB0774B" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_ShareBasedCompensationSharesAuthorizedUnderStockOptionPlansByExercisePriceRangeAxis_2337123E203402E755BDC62A1DB0AFED" xlink:to="loc_us-gaap_ShareBasedCompensationSharesAuthorizedUnderStockOptionPlansExercisePriceRangeDomain_FE6FFF85B74778420849C62A1DB0774B" xlink:type="arc" />
    <loc xlink:href="astc-20151231.xsd#astc_ExercisePriceRangeOneMember" xlink:label="loc_astc_ExercisePriceRangeOneMember_79D1127DE6FD00FE10E7C62A1DB08A45" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationSharesAuthorizedUnderStockOptionPlansExercisePriceRangeDomain_FE6FFF85B74778420849C62A1DB0774B" xlink:to="loc_astc_ExercisePriceRangeOneMember_79D1127DE6FD00FE10E7C62A1DB08A45" xlink:type="arc" />
    <loc xlink:href="astc-20151231.xsd#astc_ExercisePriceRangeTwoMember" xlink:label="loc_astc_ExercisePriceRangeTwoMember_4ACA118EDFF96D0C5C5CC62A1DB0E288" xlink:type="locator" />
    <definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationSharesAuthorizedUnderStockOptionPlansExercisePriceRangeDomain_FE6FFF85B74778420849C62A1DB0774B" xlink:to="loc_astc_ExercisePriceRangeTwoMember_4ACA118EDFF96D0C5C5CC62A1DB0E288" xlink:type="arc" />
    <loc xlink:href="astc-20151231.xsd#astc_ExercisePriceRangeThreeMember" xlink:label="loc_astc_ExercisePriceRangeThreeMember_54E8DE8D412254C77B9CC62A1DB06028" xlink:type="locator" />
    <definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationSharesAuthorizedUnderStockOptionPlansExercisePriceRangeDomain_FE6FFF85B74778420849C62A1DB0774B" xlink:to="loc_astc_ExercisePriceRangeThreeMember_54E8DE8D412254C77B9CC62A1DB06028" xlink:type="arc" />
    <loc xlink:href="astc-20151231.xsd#astc_ExercisePriceRangeFourMember" xlink:label="loc_astc_ExercisePriceRangeFourMember_2C9F44B270A0D7C49E20C62A1DB02A25" xlink:type="locator" />
    <definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationSharesAuthorizedUnderStockOptionPlansExercisePriceRangeDomain_FE6FFF85B74778420849C62A1DB0774B" xlink:to="loc_astc_ExercisePriceRangeFourMember_2C9F44B270A0D7C49E20C62A1DB02A25" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2014/elts/us-gaap-2014-01-31.xsd#us-gaap_ShareBasedCompensationSharesAuthorizedUnderStockOptionPlansExercisePriceRangeLowerRangeLimit" xlink:label="loc_us-gaap_ShareBasedCompensationSharesAuthorizedUnderStockOptionPlansExercisePriceRangeLowerRangeLimit_FC7CCF9B1DF22328D4EBC62A1DB07F5C" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationSharesAuthorizedUnderStockOptionPlansExercisePriceRangeLineItems_09C8611BF2CF2E1E124CC62A1DB0376D" xlink:to="loc_us-gaap_ShareBasedCompensationSharesAuthorizedUnderStockOptionPlansExercisePriceRangeLowerRangeLimit_FC7CCF9B1DF22328D4EBC62A1DB07F5C" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2014/elts/us-gaap-2014-01-31.xsd#us-gaap_ShareBasedCompensationSharesAuthorizedUnderStockOptionPlansExercisePriceRangeUpperRangeLimit" xlink:label="loc_us-gaap_ShareBasedCompensationSharesAuthorizedUnderStockOptionPlansExercisePriceRangeUpperRangeLimit_99161F516C90B8B7A457C62A1DB02B04" xlink:type="locator" />
    <definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationSharesAuthorizedUnderStockOptionPlansExercisePriceRangeLineItems_09C8611BF2CF2E1E124CC62A1DB0376D" xlink:to="loc_us-gaap_ShareBasedCompensationSharesAuthorizedUnderStockOptionPlansExercisePriceRangeUpperRangeLimit_99161F516C90B8B7A457C62A1DB02B04" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2014/elts/us-gaap-2014-01-31.xsd#us-gaap_ShareBasedCompensationSharesAuthorizedUnderStockOptionPlansExercisePriceRangeNumberOfOutstandingOptions" xlink:label="loc_us-gaap_ShareBasedCompensationSharesAuthorizedUnderStockOptionPlansExercisePriceRangeNumberOfOutstandingOptions_67769652A7CDA26854A2C62A1DB0ED1E" xlink:type="locator" />
    <definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationSharesAuthorizedUnderStockOptionPlansExercisePriceRangeLineItems_09C8611BF2CF2E1E124CC62A1DB0376D" xlink:to="loc_us-gaap_ShareBasedCompensationSharesAuthorizedUnderStockOptionPlansExercisePriceRangeNumberOfOutstandingOptions_67769652A7CDA26854A2C62A1DB0ED1E" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2014/elts/us-gaap-2014-01-31.xsd#us-gaap_SharebasedCompensationSharesAuthorizedUnderStockOptionPlansExercisePriceRangeOutstandingOptionsWeightedAverageRemainingContractualTerm2" xlink:label="loc_us-gaap_SharebasedCompensationSharesAuthorizedUnderStockOptionPlansExercisePriceRangeOutstandingOptionsWeightedAverageRemainingContractualTerm2_9372CC6BCF248AF69447C62A1DB0DD68" xlink:type="locator" />
    <definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationSharesAuthorizedUnderStockOptionPlansExercisePriceRangeLineItems_09C8611BF2CF2E1E124CC62A1DB0376D" xlink:to="loc_us-gaap_SharebasedCompensationSharesAuthorizedUnderStockOptionPlansExercisePriceRangeOutstandingOptionsWeightedAverageRemainingContractualTerm2_9372CC6BCF248AF69447C62A1DB0DD68" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2014/elts/us-gaap-2014-01-31.xsd#us-gaap_SharebasedCompensationSharesAuthorizedUnderStockOptionPlansExercisePriceRangeOutstandingOptionsWeightedAverageExercisePriceBeginningBalance1" xlink:label="loc_us-gaap_SharebasedCompensationSharesAuthorizedUnderStockOptionPlansExercisePriceRangeOutstandingOptionsWeightedAverageExercisePriceBeginningBalance1_014EC9DE585FC35CF3EEC62A1DB1ABFF" xlink:type="locator" />
    <definitionArc order="5" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationSharesAuthorizedUnderStockOptionPlansExercisePriceRangeLineItems_09C8611BF2CF2E1E124CC62A1DB0376D" xlink:to="loc_us-gaap_SharebasedCompensationSharesAuthorizedUnderStockOptionPlansExercisePriceRangeOutstandingOptionsWeightedAverageExercisePriceBeginningBalance1_014EC9DE585FC35CF3EEC62A1DB1ABFF" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2014/elts/us-gaap-2014-01-31.xsd#us-gaap_ShareBasedCompensationSharesAuthorizedUnderStockOptionPlansExercisePriceRangeNumberOfExercisableOptions" xlink:label="loc_us-gaap_ShareBasedCompensationSharesAuthorizedUnderStockOptionPlansExercisePriceRangeNumberOfExercisableOptions_B51B426FEB8F2B8B2537C62A1DB1EAF0" xlink:type="locator" />
    <definitionArc order="6" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationSharesAuthorizedUnderStockOptionPlansExercisePriceRangeLineItems_09C8611BF2CF2E1E124CC62A1DB0376D" xlink:to="loc_us-gaap_ShareBasedCompensationSharesAuthorizedUnderStockOptionPlansExercisePriceRangeNumberOfExercisableOptions_B51B426FEB8F2B8B2537C62A1DB1EAF0" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2014/elts/us-gaap-2014-01-31.xsd#us-gaap_SharebasedCompensationSharesAuthorizedUnderStockOptionPlansExercisePriceRangeExercisableOptionsWeightedAverageExercisePrice1" xlink:label="loc_us-gaap_SharebasedCompensationSharesAuthorizedUnderStockOptionPlansExercisePriceRangeExercisableOptionsWeightedAverageExercisePrice1_E8BBB31304A6CB68F298C62A1DB1178F" xlink:type="locator" />
    <definitionArc order="7" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ShareBasedCompensationSharesAuthorizedUnderStockOptionPlansExercisePriceRangeLineItems_09C8611BF2CF2E1E124CC62A1DB0376D" xlink:to="loc_us-gaap_SharebasedCompensationSharesAuthorizedUnderStockOptionPlansExercisePriceRangeExercisableOptionsWeightedAverageExercisePrice1_E8BBB31304A6CB68F298C62A1DB1178F" xlink:type="arc" />
  </definitionLink>
  <definitionLink xlink:role="http://www.astrotechcorp.com/role/CommonStockIncentiveStockPurchasePlansAndOtherCompensationPlansTables" xlink:type="extended" />
  <definitionLink xlink:role="http://www.astrotechcorp.com/role/CondensedConsolidatedBalanceSheetsUnaudited" xlink:type="extended" />
  <definitionLink xlink:role="http://www.astrotechcorp.com/role/CondensedConsolidatedBalanceSheetsUnauditedParentheticals" xlink:type="extended" />
  <definitionLink xlink:role="http://www.astrotechcorp.com/role/CondensedConsolidatedStatementsOfCashFlowsUnaudited" xlink:type="extended" />
  <definitionLink xlink:role="http://www.astrotechcorp.com/role/CondensedConsolidatedStatementsOfOperationsAndComprehensiveIncomeUnaudited" xlink:type="extended" />
  <definitionLink xlink:role="http://www.astrotechcorp.com/role/CondensedConsolidatedStatementsOfOperationsUnauditedParentheticals" 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/2014/elts/us-gaap-2014-01-31.xsd#us-gaap_LineOfCreditFacilityLineItems" xlink:label="loc_us-gaap_LineOfCreditFacilityLineItems_20BF9693935950B0968C6819A79473B3" xlink:type="locator" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2014/elts/us-gaap-2014-01-31.xsd#us-gaap_LineOfCreditFacilityTable" xlink:label="loc_us-gaap_LineOfCreditFacilityTable_4521DC3B713F5B96A7960D3AC4D99EB2" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_LineOfCreditFacilityLineItems_20BF9693935950B0968C6819A79473B3" xlink:to="loc_us-gaap_LineOfCreditFacilityTable_4521DC3B713F5B96A7960D3AC4D99EB2" xlink:type="arc" xbrldt:closed="true" xbrldt:contextElement="segment" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2014/elts/us-gaap-2014-01-31.xsd#us-gaap_CreditFacilityAxis" xlink:label="loc_us-gaap_CreditFacilityAxis_1CAB7A1215C6517693658F7E0AE980A0" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_LineOfCreditFacilityTable_4521DC3B713F5B96A7960D3AC4D99EB2" xlink:to="loc_us-gaap_CreditFacilityAxis_1CAB7A1215C6517693658F7E0AE980A0" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2014/elts/us-gaap-2014-01-31.xsd#us-gaap_CreditFacilityDomain" xlink:label="loc_us-gaap_CreditFacilityDomain_5C6FFD4351E22380C0F78FD9A4D71090_5DC86A9CC9775A9183529C3628FB6E75" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_CreditFacilityAxis_1CAB7A1215C6517693658F7E0AE980A0" xlink:to="loc_us-gaap_CreditFacilityDomain_5C6FFD4351E22380C0F78FD9A4D71090_5DC86A9CC9775A9183529C3628FB6E75" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2014/elts/us-gaap-2014-01-31.xsd#us-gaap_CreditFacilityDomain" xlink:label="loc_us-gaap_CreditFacilityDomain_BD68246B02C85510A74E59F9ABAF6A28" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_CreditFacilityAxis_1CAB7A1215C6517693658F7E0AE980A0" xlink:to="loc_us-gaap_CreditFacilityDomain_BD68246B02C85510A74E59F9ABAF6A28" xlink:type="arc" />
    <loc xlink:href="astc-20151231.xsd#astc_TermLoanMember" xlink:label="loc_astc_TermLoanMember_10D4FB439A5253489F7604654189DA42" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CreditFacilityDomain_BD68246B02C85510A74E59F9ABAF6A28" xlink:to="loc_astc_TermLoanMember_10D4FB439A5253489F7604654189DA42" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2014/elts/us-gaap-2014-01-31.xsd#us-gaap_RevolvingCreditFacilityMember" xlink:label="loc_us-gaap_RevolvingCreditFacilityMember_BF6E6AB08E355BF0B56AE77851A19A03" xlink:type="locator" />
    <definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CreditFacilityDomain_BD68246B02C85510A74E59F9ABAF6A28" xlink:to="loc_us-gaap_RevolvingCreditFacilityMember_BF6E6AB08E355BF0B56AE77851A19A03" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2014/elts/us-gaap-2014-01-31.xsd#us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsAxis" xlink:label="loc_us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsAxis_805B322278665EEAAB574C29C212BBC4" xlink:type="locator" />
    <definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_LineOfCreditFacilityTable_4521DC3B713F5B96A7960D3AC4D99EB2" xlink:to="loc_us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsAxis_805B322278665EEAAB574C29C212BBC4" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2014/elts/us-gaap-2014-01-31.xsd#us-gaap_DisposalGroupsIncludingDiscontinuedOperationsNameDomain" xlink:label="loc_us-gaap_DisposalGroupsIncludingDiscontinuedOperationsNameDomain_B3D8F1235C59973F3C7F8FD9A4D8BA05_5DC86A9CC9775A9183529C3628FB6E75" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsAxis_805B322278665EEAAB574C29C212BBC4" xlink:to="loc_us-gaap_DisposalGroupsIncludingDiscontinuedOperationsNameDomain_B3D8F1235C59973F3C7F8FD9A4D8BA05_5DC86A9CC9775A9183529C3628FB6E75" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2014/elts/us-gaap-2014-01-31.xsd#us-gaap_DisposalGroupsIncludingDiscontinuedOperationsNameDomain" xlink:label="loc_us-gaap_DisposalGroupsIncludingDiscontinuedOperationsNameDomain_DBB3BCD55A7D54A3B48F458ECD244DE0" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsAxis_805B322278665EEAAB574C29C212BBC4" xlink:to="loc_us-gaap_DisposalGroupsIncludingDiscontinuedOperationsNameDomain_DBB3BCD55A7D54A3B48F458ECD244DE0" xlink:type="arc" />
    <loc xlink:href="astc-20151231.xsd#astc_AstrotechSpaceOperationsMember" xlink:label="loc_astc_AstrotechSpaceOperationsMember_662C4E4A3BBD5ABCB0CD7EECB8926970" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DisposalGroupsIncludingDiscontinuedOperationsNameDomain_DBB3BCD55A7D54A3B48F458ECD244DE0" xlink:to="loc_astc_AstrotechSpaceOperationsMember_662C4E4A3BBD5ABCB0CD7EECB8926970" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2014/elts/us-gaap-2014-01-31.xsd#us-gaap_LineOfCreditFacilityMaximumBorrowingCapacity" xlink:label="loc_us-gaap_LineOfCreditFacilityMaximumBorrowingCapacity_A44C88AA1C35569D9C1B87D5C85525F6" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LineOfCreditFacilityLineItems_20BF9693935950B0968C6819A79473B3" xlink:to="loc_us-gaap_LineOfCreditFacilityMaximumBorrowingCapacity_A44C88AA1C35569D9C1B87D5C85525F6" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2014/elts/us-gaap-2014-01-31.xsd#us-gaap_LineOfCreditFacilityExpirationDate1" xlink:label="loc_us-gaap_LineOfCreditFacilityExpirationDate1_935009A875BE50CBB7953656B455517B" xlink:type="locator" />
    <definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LineOfCreditFacilityLineItems_20BF9693935950B0968C6819A79473B3" xlink:to="loc_us-gaap_LineOfCreditFacilityExpirationDate1_935009A875BE50CBB7953656B455517B" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2014/elts/us-gaap-2014-01-31.xsd#us-gaap_RepaymentsOfDebt" xlink:label="loc_us-gaap_RepaymentsOfDebt_7F84A826FE2B5357A60D718806A715D7" xlink:type="locator" />
    <definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LineOfCreditFacilityLineItems_20BF9693935950B0968C6819A79473B3" xlink:to="loc_us-gaap_RepaymentsOfDebt_7F84A826FE2B5357A60D718806A715D7" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2014/elts/us-gaap-2014-01-31.xsd#us-gaap_LongTermDebt" xlink:label="loc_us-gaap_LongTermDebt_936491D719BC54FF88C5EAF460903952" xlink:type="locator" />
    <definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LineOfCreditFacilityLineItems_20BF9693935950B0968C6819A79473B3" xlink:to="loc_us-gaap_LongTermDebt_936491D719BC54FF88C5EAF460903952" xlink:type="arc" />
  </definitionLink>
  <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/2014/elts/us-gaap-2014-01-31.xsd#us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsLineItems" xlink:label="loc_us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsLineItems_084EA1332FB4D7FE790688EDB7E5EE19" xlink:type="locator" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2014/elts/us-gaap-2014-01-31.xsd#us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsTable" xlink:label="loc_us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsTable_0A7A1DB9BC25EDF28E9188EDB7E43BCD" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsLineItems_084EA1332FB4D7FE790688EDB7E5EE19" xlink:to="loc_us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsTable_0A7A1DB9BC25EDF28E9188EDB7E43BCD" xlink:type="arc" xbrldt:closed="true" xbrldt:contextElement="segment" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2014/elts/us-gaap-2014-01-31.xsd#us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsAxis" xlink:label="loc_us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsAxis_907E72311B35CDC9030D88EDB7E418A6" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsTable_0A7A1DB9BC25EDF28E9188EDB7E43BCD" xlink:to="loc_us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsAxis_907E72311B35CDC9030D88EDB7E418A6" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2014/elts/us-gaap-2014-01-31.xsd#us-gaap_DisposalGroupsIncludingDiscontinuedOperationsNameDomain" xlink:label="loc_us-gaap_DisposalGroupsIncludingDiscontinuedOperationsNameDomain_D2AF86904296876A19E988EDB7E4712C_default" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsAxis_907E72311B35CDC9030D88EDB7E418A6" xlink:to="loc_us-gaap_DisposalGroupsIncludingDiscontinuedOperationsNameDomain_D2AF86904296876A19E988EDB7E4712C_default" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2014/elts/us-gaap-2014-01-31.xsd#us-gaap_DisposalGroupsIncludingDiscontinuedOperationsNameDomain" xlink:label="loc_us-gaap_DisposalGroupsIncludingDiscontinuedOperationsNameDomain_D2AF86904296876A19E988EDB7E4712C" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsAxis_907E72311B35CDC9030D88EDB7E418A6" xlink:to="loc_us-gaap_DisposalGroupsIncludingDiscontinuedOperationsNameDomain_D2AF86904296876A19E988EDB7E4712C" xlink:type="arc" />
    <loc xlink:href="astc-20151231.xsd#astc_AstrotechSpaceOperationsMember" xlink:label="loc_astc_AstrotechSpaceOperationsMember_E3DA11E412606D9BF77F88EDB7E4882B" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DisposalGroupsIncludingDiscontinuedOperationsNameDomain_D2AF86904296876A19E988EDB7E4712C" xlink:to="loc_astc_AstrotechSpaceOperationsMember_E3DA11E412606D9BF77F88EDB7E4882B" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2014/elts/us-gaap-2014-01-31.xsd#us-gaap_CreditFacilityAxis" xlink:label="loc_us-gaap_CreditFacilityAxis_FD2E4CA43D095967028288EDB7E5A293" xlink:type="locator" />
    <definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsTable_0A7A1DB9BC25EDF28E9188EDB7E43BCD" xlink:to="loc_us-gaap_CreditFacilityAxis_FD2E4CA43D095967028288EDB7E5A293" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2014/elts/us-gaap-2014-01-31.xsd#us-gaap_CreditFacilityDomain" xlink:label="loc_us-gaap_CreditFacilityDomain_4B7D5373E3A5CCF9AAA288EDB7E5B83D_default" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_CreditFacilityAxis_FD2E4CA43D095967028288EDB7E5A293" xlink:to="loc_us-gaap_CreditFacilityDomain_4B7D5373E3A5CCF9AAA288EDB7E5B83D_default" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2014/elts/us-gaap-2014-01-31.xsd#us-gaap_CreditFacilityDomain" xlink:label="loc_us-gaap_CreditFacilityDomain_4B7D5373E3A5CCF9AAA288EDB7E5B83D" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_CreditFacilityAxis_FD2E4CA43D095967028288EDB7E5A293" xlink:to="loc_us-gaap_CreditFacilityDomain_4B7D5373E3A5CCF9AAA288EDB7E5B83D" xlink:type="arc" />
    <loc xlink:href="astc-20151231.xsd#astc_TermLoanMember" xlink:label="loc_astc_TermLoanMember_E8F1F68D4B3541757FF688EDB7E5CF14" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_CreditFacilityDomain_4B7D5373E3A5CCF9AAA288EDB7E5B83D" xlink:to="loc_astc_TermLoanMember_E8F1F68D4B3541757FF688EDB7E5CF14" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2014/elts/us-gaap-2014-01-31.xsd#us-gaap_ProceedsFromDivestitureOfBusinesses" xlink:label="loc_us-gaap_ProceedsFromDivestitureOfBusinesses_216656E264D96738E3A488EDB7E6FCFE" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsLineItems_084EA1332FB4D7FE790688EDB7E5EE19" xlink:to="loc_us-gaap_ProceedsFromDivestitureOfBusinesses_216656E264D96738E3A488EDB7E6FCFE" xlink:type="arc" />
    <loc xlink:href="astc-20151231.xsd#astc_WorkingCapitalSurplusDeficit" xlink:label="loc_astc_WorkingCapitalSurplusDeficit_E8826D0809DE184F46C088EDB7E6124B" xlink:type="locator" />
    <definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsLineItems_084EA1332FB4D7FE790688EDB7E5EE19" xlink:to="loc_astc_WorkingCapitalSurplusDeficit_E8826D0809DE184F46C088EDB7E6124B" xlink:type="arc" />
    <loc xlink:href="astc-20151231.xsd#astc_DiscontinuedOperationProceedsFromSaleOfBusiness" xlink:label="loc_astc_DiscontinuedOperationProceedsFromSaleOfBusiness_671FED727C028A85EC5988EDB7E6833B" xlink:type="locator" />
    <definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsLineItems_084EA1332FB4D7FE790688EDB7E5EE19" xlink:to="loc_astc_DiscontinuedOperationProceedsFromSaleOfBusiness_671FED727C028A85EC5988EDB7E6833B" xlink:type="arc" />
    <loc xlink:href="astc-20151231.xsd#astc_IndemnnityHoldbackCurrent" xlink:label="loc_astc_IndemnnityHoldbackCurrent_EF4204A946BEDC4EDB8688EDB7E6B83F" xlink:type="locator" />
    <definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsLineItems_084EA1332FB4D7FE790688EDB7E5EE19" xlink:to="loc_astc_IndemnnityHoldbackCurrent_EF4204A946BEDC4EDB8688EDB7E6B83F" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2014/elts/us-gaap-2014-01-31.xsd#us-gaap_RepaymentsOfDebt" xlink:label="loc_us-gaap_RepaymentsOfDebt_98B89F40DDE12667B52B88EDB7E6331B" xlink:type="locator" />
    <definitionArc order="5" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsLineItems_084EA1332FB4D7FE790688EDB7E5EE19" xlink:to="loc_us-gaap_RepaymentsOfDebt_98B89F40DDE12667B52B88EDB7E6331B" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2014/elts/us-gaap-2014-01-31.xsd#us-gaap_InterestExpenseDebt" xlink:label="loc_us-gaap_InterestExpenseDebt_B879244102B1265A690288EDB7E6283A" xlink:type="locator" />
    <definitionArc order="6" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsLineItems_084EA1332FB4D7FE790688EDB7E5EE19" xlink:to="loc_us-gaap_InterestExpenseDebt_B879244102B1265A690288EDB7E6283A" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2014/elts/us-gaap-2014-01-31.xsd#us-gaap_DiscontinuedOperationGainLossFromDisposalOfDiscontinuedOperationBeforeIncomeTax" xlink:label="loc_us-gaap_DiscontinuedOperationGainLossFromDisposalOfDiscontinuedOperationBeforeIncomeTax_B99429C02049ADAB2F4188EDB7E60FB4" xlink:type="locator" />
    <definitionArc order="7" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsLineItems_084EA1332FB4D7FE790688EDB7E5EE19" xlink:to="loc_us-gaap_DiscontinuedOperationGainLossFromDisposalOfDiscontinuedOperationBeforeIncomeTax_B99429C02049ADAB2F4188EDB7E60FB4" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2014/elts/us-gaap-2014-01-31.xsd#us-gaap_DiscontinuedOperationGainLossOnDisposalOfDiscontinuedOperationNetOfTax" xlink:label="loc_us-gaap_DiscontinuedOperationGainLossOnDisposalOfDiscontinuedOperationNetOfTax_311F3A35538C06ABA7EE88EDB7E60820" xlink:type="locator" />
    <definitionArc order="8" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsLineItems_084EA1332FB4D7FE790688EDB7E5EE19" xlink:to="loc_us-gaap_DiscontinuedOperationGainLossOnDisposalOfDiscontinuedOperationNetOfTax_311F3A35538C06ABA7EE88EDB7E60820" 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/2014/elts/us-gaap-2014-01-31.xsd#us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsLineItems" xlink:label="loc_us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsLineItems_E222037953EDA1A4FA1A45CDA1F6DEE5" xlink:type="locator" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2014/elts/us-gaap-2014-01-31.xsd#us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsTable" xlink:label="loc_us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsTable_9B606955EF6CB96B3B2545CDA1F66CFB" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsLineItems_E222037953EDA1A4FA1A45CDA1F6DEE5" xlink:to="loc_us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsTable_9B606955EF6CB96B3B2545CDA1F66CFB" xlink:type="arc" xbrldt:closed="true" xbrldt:contextElement="segment" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2014/elts/us-gaap-2014-01-31.xsd#us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsAxis" xlink:label="loc_us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsAxis_76C5C2E12B7EDF6FB78A45CDA1F68524" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsTable_9B606955EF6CB96B3B2545CDA1F66CFB" xlink:to="loc_us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsAxis_76C5C2E12B7EDF6FB78A45CDA1F68524" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2014/elts/us-gaap-2014-01-31.xsd#us-gaap_DisposalGroupsIncludingDiscontinuedOperationsNameDomain" xlink:label="loc_us-gaap_DisposalGroupsIncludingDiscontinuedOperationsNameDomain_AF9C554B32CD6818B61F45CDA1F62588_default" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsAxis_76C5C2E12B7EDF6FB78A45CDA1F68524" xlink:to="loc_us-gaap_DisposalGroupsIncludingDiscontinuedOperationsNameDomain_AF9C554B32CD6818B61F45CDA1F62588_default" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2014/elts/us-gaap-2014-01-31.xsd#us-gaap_DisposalGroupsIncludingDiscontinuedOperationsNameDomain" xlink:label="loc_us-gaap_DisposalGroupsIncludingDiscontinuedOperationsNameDomain_AF9C554B32CD6818B61F45CDA1F62588" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsAxis_76C5C2E12B7EDF6FB78A45CDA1F68524" xlink:to="loc_us-gaap_DisposalGroupsIncludingDiscontinuedOperationsNameDomain_AF9C554B32CD6818B61F45CDA1F62588" xlink:type="arc" />
    <loc xlink:href="astc-20151231.xsd#astc_AstrotechSpaceOperationsMember" xlink:label="loc_astc_AstrotechSpaceOperationsMember_C914523CEA37C1CF87BB45CDA1F613E0" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DisposalGroupsIncludingDiscontinuedOperationsNameDomain_AF9C554B32CD6818B61F45CDA1F62588" xlink:to="loc_astc_AstrotechSpaceOperationsMember_C914523CEA37C1CF87BB45CDA1F613E0" xlink:type="arc" />
    <loc xlink:href="astc-20151231.xsd#astc_DiscontinuedOperationProceedsFromSaleOfBusiness" xlink:label="loc_astc_DiscontinuedOperationProceedsFromSaleOfBusiness_4223DB6B9DA4A5BDD1D545CDA1F626EF" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsLineItems_E222037953EDA1A4FA1A45CDA1F6DEE5" xlink:to="loc_astc_DiscontinuedOperationProceedsFromSaleOfBusiness_4223DB6B9DA4A5BDD1D545CDA1F626EF" xlink:type="arc" />
    <loc xlink:href="astc-20151231.xsd#astc_IndemnnityHoldbackCurrent" xlink:label="loc_astc_IndemnnityHoldbackCurrent_34947DF0CE2B32DEA50445CDA1F60ABD" xlink:type="locator" />
    <definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsLineItems_E222037953EDA1A4FA1A45CDA1F6DEE5" xlink:to="loc_astc_IndemnnityHoldbackCurrent_34947DF0CE2B32DEA50445CDA1F60ABD" xlink:type="arc" />
    <loc xlink:href="astc-20151231.xsd#astc_LiabilitiesAssumedOfDisposalGroupIncludingDiscontinuedOperation" xlink:label="loc_astc_LiabilitiesAssumedOfDisposalGroupIncludingDiscontinuedOperation_9B3B160BA87CFD1154F845CDA1F689B0" xlink:type="locator" />
    <definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsLineItems_E222037953EDA1A4FA1A45CDA1F6DEE5" xlink:to="loc_astc_LiabilitiesAssumedOfDisposalGroupIncludingDiscontinuedOperation_9B3B160BA87CFD1154F845CDA1F689B0" xlink:type="arc" />
    <loc xlink:href="astc-20151231.xsd#astc_DisposalGroupIncludingDiscontinuedNetBookValueOfAssetsSold" xlink:label="loc_astc_DisposalGroupIncludingDiscontinuedNetBookValueOfAssetsSold_07C515848F51DF43519F45CDA1F65EC1" xlink:type="locator" />
    <definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsLineItems_E222037953EDA1A4FA1A45CDA1F6DEE5" xlink:to="loc_astc_DisposalGroupIncludingDiscontinuedNetBookValueOfAssetsSold_07C515848F51DF43519F45CDA1F65EC1" xlink:type="arc" />
    <loc xlink:href="astc-20151231.xsd#astc_DisposalGroupIncludingDiscontinuedOperationOther" xlink:label="loc_astc_DisposalGroupIncludingDiscontinuedOperationOther_CE199BD398F40E4644BE45CDA1F651AB" xlink:type="locator" />
    <definitionArc order="5" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsLineItems_E222037953EDA1A4FA1A45CDA1F6DEE5" xlink:to="loc_astc_DisposalGroupIncludingDiscontinuedOperationOther_CE199BD398F40E4644BE45CDA1F651AB" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2014/elts/us-gaap-2014-01-31.xsd#us-gaap_DiscontinuedOperationGainLossFromDisposalOfDiscontinuedOperationBeforeIncomeTax" xlink:label="loc_us-gaap_DiscontinuedOperationGainLossFromDisposalOfDiscontinuedOperationBeforeIncomeTax_1C5D85C7CB50C910793E45CDA1F6FA6E" xlink:type="locator" />
    <definitionArc order="6" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsLineItems_E222037953EDA1A4FA1A45CDA1F6DEE5" xlink:to="loc_us-gaap_DiscontinuedOperationGainLossFromDisposalOfDiscontinuedOperationBeforeIncomeTax_1C5D85C7CB50C910793E45CDA1F6FA6E" xlink:type="arc" />
  </definitionLink>
  <definitionLink xlink:role="http://www.astrotechcorp.com/role/DiscontinuedOperationsGainOnSaleOfAsoBusinessUnitDetails1" xlink:type="extended">
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2014/elts/us-gaap-2014-01-31.xsd#us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsLineItems" xlink:label="loc_us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsLineItems_B5F9303CD4E1AF9EAC7888EDB7ED2A4E" xlink:type="locator" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2014/elts/us-gaap-2014-01-31.xsd#us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsTable" xlink:label="loc_us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsTable_2F70B325D52326FE90F588EDB7EDD420" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsLineItems_B5F9303CD4E1AF9EAC7888EDB7ED2A4E" xlink:to="loc_us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsTable_2F70B325D52326FE90F588EDB7EDD420" xlink:type="arc" xbrldt:closed="true" xbrldt:contextElement="segment" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2014/elts/us-gaap-2014-01-31.xsd#us-gaap_StatementScenarioAxis" xlink:label="loc_us-gaap_StatementScenarioAxis_685DDC1BA277CA0CA6A288EDB7EDCE40" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsTable_2F70B325D52326FE90F588EDB7EDD420" xlink:to="loc_us-gaap_StatementScenarioAxis_685DDC1BA277CA0CA6A288EDB7EDCE40" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2014/elts/us-gaap-2014-01-31.xsd#us-gaap_ScenarioUnspecifiedDomain" xlink:label="loc_us-gaap_ScenarioUnspecifiedDomain_070A79B34C5866A5DE1288EDB7ED14A0_default" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementScenarioAxis_685DDC1BA277CA0CA6A288EDB7EDCE40" xlink:to="loc_us-gaap_ScenarioUnspecifiedDomain_070A79B34C5866A5DE1288EDB7ED14A0_default" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2014/elts/us-gaap-2014-01-31.xsd#us-gaap_ScenarioUnspecifiedDomain" xlink:label="loc_us-gaap_ScenarioUnspecifiedDomain_070A79B34C5866A5DE1288EDB7ED14A0" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementScenarioAxis_685DDC1BA277CA0CA6A288EDB7EDCE40" xlink:to="loc_us-gaap_ScenarioUnspecifiedDomain_070A79B34C5866A5DE1288EDB7ED14A0" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2014/elts/us-gaap-2014-01-31.xsd#us-gaap_ScenarioAdjustmentMember" xlink:label="loc_us-gaap_ScenarioAdjustmentMember_614D1408E8AB6592C6F988EDB7ED1EE0" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScenarioUnspecifiedDomain_070A79B34C5866A5DE1288EDB7ED14A0" xlink:to="loc_us-gaap_ScenarioAdjustmentMember_614D1408E8AB6592C6F988EDB7ED1EE0" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2014/elts/us-gaap-2014-01-31.xsd#us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsAxis" xlink:label="loc_us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsAxis_03EFF6C520BD159B0D2F88EDB7EDFCFB" xlink:type="locator" />
    <definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsTable_2F70B325D52326FE90F588EDB7EDD420" xlink:to="loc_us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsAxis_03EFF6C520BD159B0D2F88EDB7EDFCFB" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2014/elts/us-gaap-2014-01-31.xsd#us-gaap_DisposalGroupsIncludingDiscontinuedOperationsNameDomain" xlink:label="loc_us-gaap_DisposalGroupsIncludingDiscontinuedOperationsNameDomain_86D3850EEE1808D8219B88EDB7EDC440_default" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsAxis_03EFF6C520BD159B0D2F88EDB7EDFCFB" xlink:to="loc_us-gaap_DisposalGroupsIncludingDiscontinuedOperationsNameDomain_86D3850EEE1808D8219B88EDB7EDC440_default" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2014/elts/us-gaap-2014-01-31.xsd#us-gaap_DisposalGroupsIncludingDiscontinuedOperationsNameDomain" xlink:label="loc_us-gaap_DisposalGroupsIncludingDiscontinuedOperationsNameDomain_86D3850EEE1808D8219B88EDB7EDC440" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsAxis_03EFF6C520BD159B0D2F88EDB7EDFCFB" xlink:to="loc_us-gaap_DisposalGroupsIncludingDiscontinuedOperationsNameDomain_86D3850EEE1808D8219B88EDB7EDC440" xlink:type="arc" />
    <loc xlink:href="astc-20151231.xsd#astc_AstrotechSpaceOperationsMember" xlink:label="loc_astc_AstrotechSpaceOperationsMember_E17B50E4B55C2ED6F88C88EDB7EDDAD7" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DisposalGroupsIncludingDiscontinuedOperationsNameDomain_86D3850EEE1808D8219B88EDB7EDC440" xlink:to="loc_astc_AstrotechSpaceOperationsMember_E17B50E4B55C2ED6F88C88EDB7EDDAD7" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2014/elts/us-gaap-2014-01-31.xsd#us-gaap_DisposalGroupIncludingDiscontinuedOperationRevenue" xlink:label="loc_us-gaap_DisposalGroupIncludingDiscontinuedOperationRevenue_40087B26A5A714657D6B88EDB7EECE08" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsLineItems_B5F9303CD4E1AF9EAC7888EDB7ED2A4E" xlink:to="loc_us-gaap_DisposalGroupIncludingDiscontinuedOperationRevenue_40087B26A5A714657D6B88EDB7EECE08" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2014/elts/us-gaap-2014-01-31.xsd#us-gaap_DisposalGroupIncludingDiscontinuedOperationCostsOfGoodsSold" xlink:label="loc_us-gaap_DisposalGroupIncludingDiscontinuedOperationCostsOfGoodsSold_B5CF77DF512CD1BA774A88EDB7EE2DB3" xlink:type="locator" />
    <definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsLineItems_B5F9303CD4E1AF9EAC7888EDB7ED2A4E" xlink:to="loc_us-gaap_DisposalGroupIncludingDiscontinuedOperationCostsOfGoodsSold_B5CF77DF512CD1BA774A88EDB7EE2DB3" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2014/elts/us-gaap-2014-01-31.xsd#us-gaap_DisposalGroupIncludingDiscontinuedOperationGeneralAndAdministrativeExpense" xlink:label="loc_us-gaap_DisposalGroupIncludingDiscontinuedOperationGeneralAndAdministrativeExpense_74CC63F9277253EE0B3E88EDB7EE2658" xlink:type="locator" />
    <definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsLineItems_B5F9303CD4E1AF9EAC7888EDB7ED2A4E" xlink:to="loc_us-gaap_DisposalGroupIncludingDiscontinuedOperationGeneralAndAdministrativeExpense_74CC63F9277253EE0B3E88EDB7EE2658" xlink:type="arc" />
    <loc xlink:href="astc-20151231.xsd#astc_DisposalGroupIncludingDiscontinuedOperationInterestExpenseAndOtherExpenses" xlink:label="loc_astc_DisposalGroupIncludingDiscontinuedOperationInterestExpenseAndOtherExpenses_73928F0A29311B3547BF88EDB7EE34FF" xlink:type="locator" />
    <definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsLineItems_B5F9303CD4E1AF9EAC7888EDB7ED2A4E" xlink:to="loc_astc_DisposalGroupIncludingDiscontinuedOperationInterestExpenseAndOtherExpenses_73928F0A29311B3547BF88EDB7EE34FF" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2014/elts/us-gaap-2014-01-31.xsd#us-gaap_DiscontinuedOperationGainLossFromDisposalOfDiscontinuedOperationBeforeIncomeTax" xlink:label="loc_us-gaap_DiscontinuedOperationGainLossFromDisposalOfDiscontinuedOperationBeforeIncomeTax_1FC2F60A1AA8F2C9DAEA88EDB7EEAA68" xlink:type="locator" />
    <definitionArc order="5" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsLineItems_B5F9303CD4E1AF9EAC7888EDB7ED2A4E" xlink:to="loc_us-gaap_DiscontinuedOperationGainLossFromDisposalOfDiscontinuedOperationBeforeIncomeTax_1FC2F60A1AA8F2C9DAEA88EDB7EEAA68" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2014/elts/us-gaap-2014-01-31.xsd#us-gaap_DiscontinuedOperationTaxEffectOfIncomeLossFromDisposalOfDiscontinuedOperation" xlink:label="loc_us-gaap_DiscontinuedOperationTaxEffectOfIncomeLossFromDisposalOfDiscontinuedOperation_C9CF01F560F07A4372BD88EDB7EEB0CA" xlink:type="locator" />
    <definitionArc order="6" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsLineItems_B5F9303CD4E1AF9EAC7888EDB7ED2A4E" xlink:to="loc_us-gaap_DiscontinuedOperationTaxEffectOfIncomeLossFromDisposalOfDiscontinuedOperation_C9CF01F560F07A4372BD88EDB7EEB0CA" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2014/elts/us-gaap-2014-01-31.xsd#us-gaap_IncomeLossFromDiscontinuedOperationsNetOfTax" xlink:label="loc_us-gaap_IncomeLossFromDiscontinuedOperationsNetOfTax_397BF6CBB742C8D27FF188EDB7EEDA34" xlink:type="locator" />
    <definitionArc order="7" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsLineItems_B5F9303CD4E1AF9EAC7888EDB7ED2A4E" xlink:to="loc_us-gaap_IncomeLossFromDiscontinuedOperationsNetOfTax_397BF6CBB742C8D27FF188EDB7EEDA34" 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/FairValueMeasurement" xlink:type="extended" />
  <definitionLink xlink:role="http://www.astrotechcorp.com/role/FairValueMeasurementDetails" xlink:type="extended">
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2014/elts/us-gaap-2014-01-31.xsd#us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems" xlink:label="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_D12C5E88CD544D6FEB80C62A1DD1BBE1" xlink:type="locator" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2014/elts/us-gaap-2014-01-31.xsd#us-gaap_FairValueByBalanceSheetGroupingTable" xlink:label="loc_us-gaap_FairValueByBalanceSheetGroupingTable_4129B20AAB071E3F04CAC62A1DD0C1BE" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_D12C5E88CD544D6FEB80C62A1DD1BBE1" xlink:to="loc_us-gaap_FairValueByBalanceSheetGroupingTable_4129B20AAB071E3F04CAC62A1DD0C1BE" xlink:type="arc" xbrldt:closed="true" xbrldt:contextElement="segment" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2014/elts/us-gaap-2014-01-31.xsd#us-gaap_FairValueByFairValueHierarchyLevelAxis" xlink:label="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_F8C3497944018DB2AA37C62A1DD01A0D" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_FairValueByBalanceSheetGroupingTable_4129B20AAB071E3F04CAC62A1DD0C1BE" xlink:to="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_F8C3497944018DB2AA37C62A1DD01A0D" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2014/elts/us-gaap-2014-01-31.xsd#us-gaap_FairValueMeasurementsFairValueHierarchyDomain" xlink:label="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_A2207AE17E463EF183DFC62A1DD1A34D_default" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_F8C3497944018DB2AA37C62A1DD01A0D" xlink:to="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_A2207AE17E463EF183DFC62A1DD1A34D_default" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2014/elts/us-gaap-2014-01-31.xsd#us-gaap_FairValueMeasurementsFairValueHierarchyDomain" xlink:label="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_A2207AE17E463EF183DFC62A1DD1A34D" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_FairValueByFairValueHierarchyLevelAxis_F8C3497944018DB2AA37C62A1DD01A0D" xlink:to="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_A2207AE17E463EF183DFC62A1DD1A34D" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2014/elts/us-gaap-2014-01-31.xsd#us-gaap_FairValueInputsLevel1Member" xlink:label="loc_us-gaap_FairValueInputsLevel1Member_D1C28E18D9A62AA8418AC62A1DD1B762" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_A2207AE17E463EF183DFC62A1DD1A34D" xlink:to="loc_us-gaap_FairValueInputsLevel1Member_D1C28E18D9A62AA8418AC62A1DD1B762" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2014/elts/us-gaap-2014-01-31.xsd#us-gaap_FairValueInputsLevel2Member" xlink:label="loc_us-gaap_FairValueInputsLevel2Member_D5906C1D98CB67BD3D1FC62A1DD1891D" xlink:type="locator" />
    <definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueMeasurementsFairValueHierarchyDomain_A2207AE17E463EF183DFC62A1DD1A34D" xlink:to="loc_us-gaap_FairValueInputsLevel2Member_D5906C1D98CB67BD3D1FC62A1DD1891D" xlink:type="arc" />
    <loc xlink:href="astc-20151231.xsd#astc_MutualFundsCarringValue" xlink:label="loc_astc_MutualFundsCarringValue_3DD46194D45B47D115FFC62A1DD14739" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_D12C5E88CD544D6FEB80C62A1DD1BBE1" xlink:to="loc_astc_MutualFundsCarringValue_3DD46194D45B47D115FFC62A1DD14739" xlink:type="arc" />
    <loc xlink:href="astc-20151231.xsd#astc_MutualFundsFairValue" xlink:label="loc_astc_MutualFundsFairValue_EC0A93992283E1A4158FC62A1DD1056E" xlink:type="locator" />
    <definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_D12C5E88CD544D6FEB80C62A1DD1BBE1" xlink:to="loc_astc_MutualFundsFairValue_EC0A93992283E1A4158FC62A1DD1056E" xlink:type="arc" />
    <loc xlink:href="astc-20151231.xsd#astc_HeldtomaturitySecuritiesDebtMaturitiesafterOneThroughThreeYearsNetCarryingAmount" xlink:label="loc_astc_HeldtomaturitySecuritiesDebtMaturitiesafterOneThroughThreeYearsNetCarryingAmount_76E6ECDF6F59728EA7C3C62A1DD1B9F5" xlink:type="locator" />
    <definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_D12C5E88CD544D6FEB80C62A1DD1BBE1" xlink:to="loc_astc_HeldtomaturitySecuritiesDebtMaturitiesafterOneThroughThreeYearsNetCarryingAmount_76E6ECDF6F59728EA7C3C62A1DD1B9F5" xlink:type="arc" />
    <loc xlink:href="astc-20151231.xsd#astc_HeldtomaturitySecuritiesDebtMaturitiesafterOneThroughThreeYearsFairValue" xlink:label="loc_astc_HeldtomaturitySecuritiesDebtMaturitiesafterOneThroughThreeYearsFairValue_CD18898BFEDF52FE8C7EC62A1DD12D7A" xlink:type="locator" />
    <definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_D12C5E88CD544D6FEB80C62A1DD1BBE1" xlink:to="loc_astc_HeldtomaturitySecuritiesDebtMaturitiesafterOneThroughThreeYearsFairValue_CD18898BFEDF52FE8C7EC62A1DD12D7A" xlink:type="arc" />
    <loc xlink:href="astc-20151231.xsd#astc_HeldtomaturitySecuritiesDebtMaturitiesafterThreeThroughFiveYearsNetCarryingAmount" xlink:label="loc_astc_HeldtomaturitySecuritiesDebtMaturitiesafterThreeThroughFiveYearsNetCarryingAmount_9C8102323D2AD29A404CC66D91AF4C08" xlink:type="locator" />
    <definitionArc order="5" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_D12C5E88CD544D6FEB80C62A1DD1BBE1" xlink:to="loc_astc_HeldtomaturitySecuritiesDebtMaturitiesafterThreeThroughFiveYearsNetCarryingAmount_9C8102323D2AD29A404CC66D91AF4C08" xlink:type="arc" />
    <loc xlink:href="astc-20151231.xsd#astc_HeldtomaturitySecuritiesDebtMaturitiesafterThreeThroughFiveYearsFairValue" xlink:label="loc_astc_HeldtomaturitySecuritiesDebtMaturitiesafterThreeThroughFiveYearsFairValue_390F90B986EAD2E7875DC62A1DD1516C" xlink:type="locator" />
    <definitionArc order="6" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_D12C5E88CD544D6FEB80C62A1DD1BBE1" xlink:to="loc_astc_HeldtomaturitySecuritiesDebtMaturitiesafterThreeThroughFiveYearsFairValue_390F90B986EAD2E7875DC62A1DD1516C" xlink:type="arc" />
    <loc xlink:href="astc-20151231.xsd#astc_HeldToMaturitySecuritiesDebtMaturities1To90DaysNetCarryingAmount" xlink:label="loc_astc_HeldToMaturitySecuritiesDebtMaturities1To90DaysNetCarryingAmount_9D638D44D3EB39EDAD38C66D9293BF1B" xlink:type="locator" />
    <definitionArc order="7" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_D12C5E88CD544D6FEB80C62A1DD1BBE1" xlink:to="loc_astc_HeldToMaturitySecuritiesDebtMaturities1To90DaysNetCarryingAmount_9D638D44D3EB39EDAD38C66D9293BF1B" xlink:type="arc" />
    <loc xlink:href="astc-20151231.xsd#astc_HeldToMaturitySecuritiesDebtMaturities1To90DaysFairValue" xlink:label="loc_astc_HeldToMaturitySecuritiesDebtMaturities1To90DaysFairValue_BE11E37A273E384E9F8CC62A1DD171BC" xlink:type="locator" />
    <definitionArc order="8" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_D12C5E88CD544D6FEB80C62A1DD1BBE1" xlink:to="loc_astc_HeldToMaturitySecuritiesDebtMaturities1To90DaysFairValue_BE11E37A273E384E9F8CC62A1DD171BC" xlink:type="arc" />
    <loc xlink:href="astc-20151231.xsd#astc_HeldToMaturitySecuritiesDebtMaturities91To360DaysNetCarryingAmount" xlink:label="loc_astc_HeldToMaturitySecuritiesDebtMaturities91To360DaysNetCarryingAmount_2C0CB6D7C7B68B30F20FC66D952D0C60" xlink:type="locator" />
    <definitionArc order="9" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_D12C5E88CD544D6FEB80C62A1DD1BBE1" xlink:to="loc_astc_HeldToMaturitySecuritiesDebtMaturities91To360DaysNetCarryingAmount_2C0CB6D7C7B68B30F20FC66D952D0C60" xlink:type="arc" />
    <loc xlink:href="astc-20151231.xsd#astc_HeldToMaturitySecuritiesDebtMaturities91To360DaysFairValue" xlink:label="loc_astc_HeldToMaturitySecuritiesDebtMaturities91To360DaysFairValue_BC485E20030E804A8E2DC62A1DD1468D" xlink:type="locator" />
    <definitionArc order="10" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_D12C5E88CD544D6FEB80C62A1DD1BBE1" xlink:to="loc_astc_HeldToMaturitySecuritiesDebtMaturities91To360DaysFairValue_BC485E20030E804A8E2DC62A1DD1468D" xlink:type="arc" />
    <loc xlink:href="astc-20151231.xsd#astc_HeldToMaturitySecuritiesDebtMaturitiesOver360DaysNetCarryingAmount" xlink:label="loc_astc_HeldToMaturitySecuritiesDebtMaturitiesOver360DaysNetCarryingAmount_C76DCBB148DD1B9915F1C66D96D615EA" xlink:type="locator" />
    <definitionArc order="11" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_D12C5E88CD544D6FEB80C62A1DD1BBE1" xlink:to="loc_astc_HeldToMaturitySecuritiesDebtMaturitiesOver360DaysNetCarryingAmount_C76DCBB148DD1B9915F1C66D96D615EA" xlink:type="arc" />
    <loc xlink:href="astc-20151231.xsd#astc_HeldToMaturitySecuritiesDebtMaturitiesOver360DaysFairValue" xlink:label="loc_astc_HeldToMaturitySecuritiesDebtMaturitiesOver360DaysFairValue_B4DA74D12D4FBD95213FC62A1DD1BD23" xlink:type="locator" />
    <definitionArc order="12" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_D12C5E88CD544D6FEB80C62A1DD1BBE1" xlink:to="loc_astc_HeldToMaturitySecuritiesDebtMaturitiesOver360DaysFairValue_B4DA74D12D4FBD95213FC62A1DD1BD23" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2014/elts/us-gaap-2014-01-31.xsd#us-gaap_Investments" xlink:label="loc_us-gaap_Investments_69B9327EE8A664CBAC99C672441E6175" xlink:type="locator" />
    <definitionArc order="13" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_D12C5E88CD544D6FEB80C62A1DD1BBE1" xlink:to="loc_us-gaap_Investments_69B9327EE8A664CBAC99C672441E6175" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2014/elts/us-gaap-2014-01-31.xsd#us-gaap_InvestmentsFairValueDisclosure" xlink:label="loc_us-gaap_InvestmentsFairValueDisclosure_18B589896E1075CA015EC62A1DD27D0C" xlink:type="locator" />
    <definitionArc order="14" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_FairValueAssetsAndLiabilitiesMeasuredOnRecurringAndNonrecurringBasisLineItems_D12C5E88CD544D6FEB80C62A1DD1BBE1" xlink:to="loc_us-gaap_InvestmentsFairValueDisclosure_18B589896E1075CA015EC62A1DD27D0C" xlink:type="arc" />
  </definitionLink>
  <definitionLink xlink:role="http://www.astrotechcorp.com/role/FairValueMeasurementTables" xlink:type="extended" />
  <definitionLink xlink:role="http://www.astrotechcorp.com/role/GeneralInformation" xlink:type="extended" />
  <definitionLink xlink:role="http://www.astrotechcorp.com/role/GeneralInformationDetailTextuals" xlink:type="extended">
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2014/elts/us-gaap-2014-01-31.xsd#us-gaap_RelatedPartyTransactionLineItems" xlink:label="loc_us-gaap_RelatedPartyTransactionLineItems_15261F9E2E0F77A4DDE745D156E469DF" xlink:type="locator" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2014/elts/us-gaap-2014-01-31.xsd#us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable" xlink:label="loc_us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable_F5A01D114FFE3A0BEF5045D156DC47DF" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_RelatedPartyTransactionLineItems_15261F9E2E0F77A4DDE745D156E469DF" xlink:to="loc_us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable_F5A01D114FFE3A0BEF5045D156DC47DF" xlink:type="arc" xbrldt:closed="true" xbrldt:contextElement="segment" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2014/elts/us-gaap-2014-01-31.xsd#us-gaap_RelatedPartyTransactionsByRelatedPartyAxis" xlink:label="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_B434F9D5C24F8AB35C0F45CDA20644F1" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfRelatedPartyTransactionsByRelatedPartyTable_F5A01D114FFE3A0BEF5045D156DC47DF" xlink:to="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_B434F9D5C24F8AB35C0F45CDA20644F1" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2014/elts/us-gaap-2014-01-31.xsd#us-gaap_RelatedPartyDomain" xlink:label="loc_us-gaap_RelatedPartyDomain_F6F28C6BA7CFCD62B9FD45CDA206F270_default" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_B434F9D5C24F8AB35C0F45CDA20644F1" xlink:to="loc_us-gaap_RelatedPartyDomain_F6F28C6BA7CFCD62B9FD45CDA206F270_default" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2014/elts/us-gaap-2014-01-31.xsd#us-gaap_RelatedPartyDomain" xlink:label="loc_us-gaap_RelatedPartyDomain_F6F28C6BA7CFCD62B9FD45CDA206F270" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_B434F9D5C24F8AB35C0F45CDA20644F1" xlink:to="loc_us-gaap_RelatedPartyDomain_F6F28C6BA7CFCD62B9FD45CDA206F270" xlink:type="arc" />
    <loc xlink:href="astc-20151231.xsd#astc_AstrogenetixMember" xlink:label="loc_astc_AstrogenetixMember_6AC1DC721C89BF271F2045CDA2062893" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyDomain_F6F28C6BA7CFCD62B9FD45CDA206F270" xlink:to="loc_astc_AstrogenetixMember_6AC1DC721C89BF271F2045CDA2062893" xlink:type="arc" />
    <loc xlink:href="astc-20151231.xsd#astc_MinimumNumberOfSpaceFlightsNegotiated" xlink:label="loc_astc_MinimumNumberOfSpaceFlightsNegotiated_7E3399C0CF58482713C445CDA2068291" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyTransactionLineItems_15261F9E2E0F77A4DDE745D156E469DF" xlink:to="loc_astc_MinimumNumberOfSpaceFlightsNegotiated_7E3399C0CF58482713C445CDA2068291" xlink:type="arc" />
  </definitionLink>
  <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/Investments" xlink:type="extended" />
  <definitionLink xlink:role="http://www.astrotechcorp.com/role/InvestmentsAvailableForSaleAndHeldToMaturitySecuritiesDetails" xlink:type="extended">
    <loc xlink:href="astc-20151231.xsd#astc_ShortTermInvestmentLineItems" xlink:label="loc_astc_ShortTermInvestmentLineItems_A85DDAC7AAC6349BD07888EDB803323D" xlink:type="locator" />
    <loc xlink:href="astc-20151231.xsd#astc_ShortTermInvestmentTable" xlink:label="loc_astc_ShortTermInvestmentTable_32F050F9D1C1B289AC4988EDB803CD4A" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_astc_ShortTermInvestmentLineItems_A85DDAC7AAC6349BD07888EDB803323D" xlink:to="loc_astc_ShortTermInvestmentTable_32F050F9D1C1B289AC4988EDB803CD4A" xlink:type="arc" xbrldt:closed="true" xbrldt:contextElement="segment" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2014/elts/us-gaap-2014-01-31.xsd#us-gaap_InvestmentTypeAxis" xlink:label="loc_us-gaap_InvestmentTypeAxis_9A8DCF611490E267C47188EDB8036C3C" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_astc_ShortTermInvestmentTable_32F050F9D1C1B289AC4988EDB803CD4A" xlink:to="loc_us-gaap_InvestmentTypeAxis_9A8DCF611490E267C47188EDB8036C3C" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2014/elts/us-gaap-2014-01-31.xsd#us-gaap_InvestmentTypeCategorizationMember" xlink:label="loc_us-gaap_InvestmentTypeCategorizationMember_5C377491DB75390F5B0688EDB8037F7C_default" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_InvestmentTypeAxis_9A8DCF611490E267C47188EDB8036C3C" xlink:to="loc_us-gaap_InvestmentTypeCategorizationMember_5C377491DB75390F5B0688EDB8037F7C_default" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2014/elts/us-gaap-2014-01-31.xsd#us-gaap_InvestmentTypeCategorizationMember" xlink:label="loc_us-gaap_InvestmentTypeCategorizationMember_5C377491DB75390F5B0688EDB8037F7C" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_InvestmentTypeAxis_9A8DCF611490E267C47188EDB8036C3C" xlink:to="loc_us-gaap_InvestmentTypeCategorizationMember_5C377491DB75390F5B0688EDB8037F7C" xlink:type="arc" />
    <loc xlink:href="astc-20151231.xsd#astc_MutualFundsMember" xlink:label="loc_astc_MutualFundsMember_AEF2070E3D6AE4A80EE288EDB803B125" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_InvestmentTypeCategorizationMember_5C377491DB75390F5B0688EDB8037F7C" xlink:to="loc_astc_MutualFundsMember_AEF2070E3D6AE4A80EE288EDB803B125" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2014/elts/us-gaap-2014-01-31.xsd#us-gaap_FixedIncomeInvestmentsMember" xlink:label="loc_us-gaap_FixedIncomeInvestmentsMember_FAE99A0663FD2F2D895788EDB803F52B" xlink:type="locator" />
    <definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_InvestmentTypeCategorizationMember_5C377491DB75390F5B0688EDB8037F7C" xlink:to="loc_us-gaap_FixedIncomeInvestmentsMember_FAE99A0663FD2F2D895788EDB803F52B" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2014/elts/us-gaap-2014-01-31.xsd#us-gaap_BankTimeDepositsMember" xlink:label="loc_us-gaap_BankTimeDepositsMember_5C7B51115C97895A257288EDB8035414" xlink:type="locator" />
    <definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_InvestmentTypeCategorizationMember_5C377491DB75390F5B0688EDB8037F7C" xlink:to="loc_us-gaap_BankTimeDepositsMember_5C7B51115C97895A257288EDB8035414" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2014/elts/us-gaap-2014-01-31.xsd#us-gaap_AvailableForSaleSecuritiesAbstract" xlink:label="loc_us-gaap_AvailableForSaleSecuritiesAbstract_C7DE88E7AF8D41FD1A1C88EDB8035C72" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_astc_ShortTermInvestmentLineItems_A85DDAC7AAC6349BD07888EDB803323D" xlink:to="loc_us-gaap_AvailableForSaleSecuritiesAbstract_C7DE88E7AF8D41FD1A1C88EDB8035C72" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2014/elts/us-gaap-2014-01-31.xsd#us-gaap_AvailableForSaleSecuritiesAmortizedCost" xlink:label="loc_us-gaap_AvailableForSaleSecuritiesAmortizedCost_8790399BB7982C6A7D6588EDB80430A7" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AvailableForSaleSecuritiesAbstract_C7DE88E7AF8D41FD1A1C88EDB8035C72" xlink:to="loc_us-gaap_AvailableForSaleSecuritiesAmortizedCost_8790399BB7982C6A7D6588EDB80430A7" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2014/elts/us-gaap-2014-01-31.xsd#us-gaap_AvailableForSaleSecuritiesAccumulatedGrossUnrealizedGainBeforeTax" xlink:label="loc_us-gaap_AvailableForSaleSecuritiesAccumulatedGrossUnrealizedGainBeforeTax_0CAC97A3A6428DB529D888EDB804B42F" xlink:type="locator" />
    <definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AvailableForSaleSecuritiesAbstract_C7DE88E7AF8D41FD1A1C88EDB8035C72" xlink:to="loc_us-gaap_AvailableForSaleSecuritiesAccumulatedGrossUnrealizedGainBeforeTax_0CAC97A3A6428DB529D888EDB804B42F" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2014/elts/us-gaap-2014-01-31.xsd#us-gaap_AvailableForSaleSecuritiesAccumulatedGrossUnrealizedLossBeforeTax" xlink:label="loc_us-gaap_AvailableForSaleSecuritiesAccumulatedGrossUnrealizedLossBeforeTax_7CB86CF7A0168457769C88EDB80463D4" xlink:type="locator" />
    <definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AvailableForSaleSecuritiesAbstract_C7DE88E7AF8D41FD1A1C88EDB8035C72" xlink:to="loc_us-gaap_AvailableForSaleSecuritiesAccumulatedGrossUnrealizedLossBeforeTax_7CB86CF7A0168457769C88EDB80463D4" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2014/elts/us-gaap-2014-01-31.xsd#us-gaap_AvailableForSaleSecurities" xlink:label="loc_us-gaap_AvailableForSaleSecurities_58808A5AB1C433DC9A1288EDB8041753" xlink:type="locator" />
    <definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_AvailableForSaleSecuritiesAbstract_C7DE88E7AF8D41FD1A1C88EDB8035C72" xlink:to="loc_us-gaap_AvailableForSaleSecurities_58808A5AB1C433DC9A1288EDB8041753" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2014/elts/us-gaap-2014-01-31.xsd#us-gaap_HeldToMaturitySecuritiesAbstract" xlink:label="loc_us-gaap_HeldToMaturitySecuritiesAbstract_A6BB03DF6314B01E7B7C88EDB8045A82" xlink:type="locator" />
    <definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_astc_ShortTermInvestmentLineItems_A85DDAC7AAC6349BD07888EDB803323D" xlink:to="loc_us-gaap_HeldToMaturitySecuritiesAbstract_A6BB03DF6314B01E7B7C88EDB8045A82" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2014/elts/us-gaap-2014-01-31.xsd#us-gaap_HeldToMaturitySecurities" xlink:label="loc_us-gaap_HeldToMaturitySecurities_72FEF5A817EE481F2E8388EDB804378D" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_HeldToMaturitySecuritiesAbstract_A6BB03DF6314B01E7B7C88EDB8045A82" xlink:to="loc_us-gaap_HeldToMaturitySecurities_72FEF5A817EE481F2E8388EDB804378D" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2014/elts/us-gaap-2014-01-31.xsd#us-gaap_HeldToMaturitySecuritiesAccumulatedUnrecognizedHoldingGain" xlink:label="loc_us-gaap_HeldToMaturitySecuritiesAccumulatedUnrecognizedHoldingGain_E0284D05EF35C83A153388EDB80452DE" xlink:type="locator" />
    <definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_HeldToMaturitySecuritiesAbstract_A6BB03DF6314B01E7B7C88EDB8045A82" xlink:to="loc_us-gaap_HeldToMaturitySecuritiesAccumulatedUnrecognizedHoldingGain_E0284D05EF35C83A153388EDB80452DE" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2014/elts/us-gaap-2014-01-31.xsd#us-gaap_HeldToMaturitySecuritiesAccumulatedUnrecognizedHoldingLoss" xlink:label="loc_us-gaap_HeldToMaturitySecuritiesAccumulatedUnrecognizedHoldingLoss_7C42CA2B5BE1DC19238C88EDB804C88F" xlink:type="locator" />
    <definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_HeldToMaturitySecuritiesAbstract_A6BB03DF6314B01E7B7C88EDB8045A82" xlink:to="loc_us-gaap_HeldToMaturitySecuritiesAccumulatedUnrecognizedHoldingLoss_7C42CA2B5BE1DC19238C88EDB804C88F" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2014/elts/us-gaap-2014-01-31.xsd#us-gaap_HeldToMaturitySecuritiesFairValue" xlink:label="loc_us-gaap_HeldToMaturitySecuritiesFairValue_C2BF9FEEEFE6C657168388EDB804F2CE" xlink:type="locator" />
    <definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_HeldToMaturitySecuritiesAbstract_A6BB03DF6314B01E7B7C88EDB8045A82" xlink:to="loc_us-gaap_HeldToMaturitySecuritiesFairValue_C2BF9FEEEFE6C657168388EDB804F2CE" 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/2014/elts/us-gaap-2014-01-31.xsd#us-gaap_ScheduleOfHeldToMaturitySecuritiesLineItems" xlink:label="loc_us-gaap_ScheduleOfHeldToMaturitySecuritiesLineItems_84765EB178D01D661B5288EDB7FD82BA" xlink:type="locator" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2014/elts/us-gaap-2014-01-31.xsd#us-gaap_ScheduleOfHeldToMaturitySecuritiesTable" xlink:label="loc_us-gaap_ScheduleOfHeldToMaturitySecuritiesTable_B0ACBBA14427DDCBE99788EDB7FD110E" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_ScheduleOfHeldToMaturitySecuritiesLineItems_84765EB178D01D661B5288EDB7FD82BA" xlink:to="loc_us-gaap_ScheduleOfHeldToMaturitySecuritiesTable_B0ACBBA14427DDCBE99788EDB7FD110E" xlink:type="arc" xbrldt:closed="true" xbrldt:contextElement="segment" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2014/elts/us-gaap-2014-01-31.xsd#us-gaap_InvestmentTypeAxis" xlink:label="loc_us-gaap_InvestmentTypeAxis_70FDA24453CDA13AA49A88EDB7FD8B3C" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfHeldToMaturitySecuritiesTable_B0ACBBA14427DDCBE99788EDB7FD110E" xlink:to="loc_us-gaap_InvestmentTypeAxis_70FDA24453CDA13AA49A88EDB7FD8B3C" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2014/elts/us-gaap-2014-01-31.xsd#us-gaap_InvestmentTypeCategorizationMember" xlink:label="loc_us-gaap_InvestmentTypeCategorizationMember_4BEF42E01A7763E6F0C188EDB7FD48FE_default" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_InvestmentTypeAxis_70FDA24453CDA13AA49A88EDB7FD8B3C" xlink:to="loc_us-gaap_InvestmentTypeCategorizationMember_4BEF42E01A7763E6F0C188EDB7FD48FE_default" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2014/elts/us-gaap-2014-01-31.xsd#us-gaap_InvestmentTypeCategorizationMember" xlink:label="loc_us-gaap_InvestmentTypeCategorizationMember_4BEF42E01A7763E6F0C188EDB7FD48FE" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_InvestmentTypeAxis_70FDA24453CDA13AA49A88EDB7FD8B3C" xlink:to="loc_us-gaap_InvestmentTypeCategorizationMember_4BEF42E01A7763E6F0C188EDB7FD48FE" xlink:type="arc" />
    <loc xlink:href="astc-20151231.xsd#astc_MutualFundsMember" xlink:label="loc_astc_MutualFundsMember_C85B6E001AAAE1332BBD88EDB7FD0154" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_InvestmentTypeCategorizationMember_4BEF42E01A7763E6F0C188EDB7FD48FE" xlink:to="loc_astc_MutualFundsMember_C85B6E001AAAE1332BBD88EDB7FD0154" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2014/elts/us-gaap-2014-01-31.xsd#us-gaap_BankTimeDepositsMember" xlink:label="loc_us-gaap_BankTimeDepositsMember_DD23D1DF03342E37666888EDB7FD33D7" xlink:type="locator" />
    <definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_InvestmentTypeCategorizationMember_4BEF42E01A7763E6F0C188EDB7FD48FE" xlink:to="loc_us-gaap_BankTimeDepositsMember_DD23D1DF03342E37666888EDB7FD33D7" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2014/elts/us-gaap-2014-01-31.xsd#us-gaap_FixedIncomeInvestmentsMember" xlink:label="loc_us-gaap_FixedIncomeInvestmentsMember_4839C81BF94EE135111088EDB7FD89B9" xlink:type="locator" />
    <definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_InvestmentTypeCategorizationMember_4BEF42E01A7763E6F0C188EDB7FD48FE" xlink:to="loc_us-gaap_FixedIncomeInvestmentsMember_4839C81BF94EE135111088EDB7FD89B9" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2014/elts/us-gaap-2014-01-31.xsd#us-gaap_BalanceSheetLocationAxis" xlink:label="loc_us-gaap_BalanceSheetLocationAxis_855CA4D463CA5AD9897088EDB7FDECFA" xlink:type="locator" />
    <definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_ScheduleOfHeldToMaturitySecuritiesTable_B0ACBBA14427DDCBE99788EDB7FD110E" xlink:to="loc_us-gaap_BalanceSheetLocationAxis_855CA4D463CA5AD9897088EDB7FDECFA" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2014/elts/us-gaap-2014-01-31.xsd#us-gaap_BalanceSheetLocationDomain" xlink:label="loc_us-gaap_BalanceSheetLocationDomain_E26F7E8DD5DA668BDF2888EDB7FD2267_default" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_BalanceSheetLocationAxis_855CA4D463CA5AD9897088EDB7FDECFA" xlink:to="loc_us-gaap_BalanceSheetLocationDomain_E26F7E8DD5DA668BDF2888EDB7FD2267_default" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2014/elts/us-gaap-2014-01-31.xsd#us-gaap_BalanceSheetLocationDomain" xlink:label="loc_us-gaap_BalanceSheetLocationDomain_E26F7E8DD5DA668BDF2888EDB7FD2267" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_BalanceSheetLocationAxis_855CA4D463CA5AD9897088EDB7FDECFA" xlink:to="loc_us-gaap_BalanceSheetLocationDomain_E26F7E8DD5DA668BDF2888EDB7FD2267" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2014/elts/us-gaap-2014-01-31.xsd#us-gaap_ShortTermInvestmentsMember" xlink:label="loc_us-gaap_ShortTermInvestmentsMember_5BC3C3F3F4898DAC27C288EDB7FDE562" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BalanceSheetLocationDomain_E26F7E8DD5DA668BDF2888EDB7FD2267" xlink:to="loc_us-gaap_ShortTermInvestmentsMember_5BC3C3F3F4898DAC27C288EDB7FDE562" xlink:type="arc" />
    <loc xlink:href="astc-20151231.xsd#astc_LongTermInvestmentsMember" xlink:label="loc_astc_LongTermInvestmentsMember_D0659D90D47E086895A288EDB7FD1A13" xlink:type="locator" />
    <definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_BalanceSheetLocationDomain_E26F7E8DD5DA668BDF2888EDB7FD2267" xlink:to="loc_astc_LongTermInvestmentsMember_D0659D90D47E086895A288EDB7FD1A13" xlink:type="arc" />
    <loc xlink:href="astc-20151231.xsd#astc_MutualFundsCarringValue" xlink:label="loc_astc_MutualFundsCarringValue_C5E501EF6C16D4E50194890C067D2044" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfHeldToMaturitySecuritiesLineItems_84765EB178D01D661B5288EDB7FD82BA" xlink:to="loc_astc_MutualFundsCarringValue_C5E501EF6C16D4E50194890C067D2044" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2014/elts/us-gaap-2014-01-31.xsd#us-gaap_AvailableForSaleSecurities" xlink:label="loc_us-gaap_AvailableForSaleSecurities_05D9B5AF672B14CEFA3F88EDB7FD5358" xlink:type="locator" />
    <definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfHeldToMaturitySecuritiesLineItems_84765EB178D01D661B5288EDB7FD82BA" xlink:to="loc_us-gaap_AvailableForSaleSecurities_05D9B5AF672B14CEFA3F88EDB7FD5358" xlink:type="arc" />
    <loc xlink:href="astc-20151231.xsd#astc_HeldToMaturitySecuritiesDebtMaturities1To90DaysNetCarryingAmount" xlink:label="loc_astc_HeldToMaturitySecuritiesDebtMaturities1To90DaysNetCarryingAmount_109D64831EF1EBE8053E88EDB7FD6B1C" xlink:type="locator" />
    <definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfHeldToMaturitySecuritiesLineItems_84765EB178D01D661B5288EDB7FD82BA" xlink:to="loc_astc_HeldToMaturitySecuritiesDebtMaturities1To90DaysNetCarryingAmount_109D64831EF1EBE8053E88EDB7FD6B1C" xlink:type="arc" />
    <loc xlink:href="astc-20151231.xsd#astc_HeldToMaturitySecuritiesDebtMaturities91To360DaysNetCarryingAmount" xlink:label="loc_astc_HeldToMaturitySecuritiesDebtMaturities91To360DaysNetCarryingAmount_8939A07CF3642541BAAB88EDB7FDC022" xlink:type="locator" />
    <definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfHeldToMaturitySecuritiesLineItems_84765EB178D01D661B5288EDB7FD82BA" xlink:to="loc_astc_HeldToMaturitySecuritiesDebtMaturities91To360DaysNetCarryingAmount_8939A07CF3642541BAAB88EDB7FDC022" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2014/elts/us-gaap-2014-01-31.xsd#us-gaap_AvailableForSaleSecuritiesAndHeldToMaturitySecurities" xlink:label="loc_us-gaap_AvailableForSaleSecuritiesAndHeldToMaturitySecurities_8D122F266D07A098DF6A88EDB7FDE7A4" xlink:type="locator" />
    <definitionArc order="5" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfHeldToMaturitySecuritiesLineItems_84765EB178D01D661B5288EDB7FD82BA" xlink:to="loc_us-gaap_AvailableForSaleSecuritiesAndHeldToMaturitySecurities_8D122F266D07A098DF6A88EDB7FDE7A4" xlink:type="arc" />
    <loc xlink:href="astc-20151231.xsd#astc_HeldToMaturitySecuritiesDebtMaturitiesOver360DaysNetCarryingAmount" xlink:label="loc_astc_HeldToMaturitySecuritiesDebtMaturitiesOver360DaysNetCarryingAmount_2D1299F39F2A3923BED488EDB7FED5CD" xlink:type="locator" />
    <definitionArc order="6" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfHeldToMaturitySecuritiesLineItems_84765EB178D01D661B5288EDB7FD82BA" xlink:to="loc_astc_HeldToMaturitySecuritiesDebtMaturitiesOver360DaysNetCarryingAmount_2D1299F39F2A3923BED488EDB7FED5CD" xlink:type="arc" />
    <loc xlink:href="astc-20151231.xsd#astc_HeldtomaturitySecuritiesDebtMaturitiesafterOneThroughThreeYearsNetCarryingAmount" xlink:label="loc_astc_HeldtomaturitySecuritiesDebtMaturitiesafterOneThroughThreeYearsNetCarryingAmount_A2548B378C534F91764888EDB7FE00C2" xlink:type="locator" />
    <definitionArc order="7" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfHeldToMaturitySecuritiesLineItems_84765EB178D01D661B5288EDB7FD82BA" xlink:to="loc_astc_HeldtomaturitySecuritiesDebtMaturitiesafterOneThroughThreeYearsNetCarryingAmount_A2548B378C534F91764888EDB7FE00C2" xlink:type="arc" />
    <loc xlink:href="astc-20151231.xsd#astc_HeldtomaturitySecuritiesDebtMaturitiesafterThreeThroughFiveYearsNetCarryingAmount" xlink:label="loc_astc_HeldtomaturitySecuritiesDebtMaturitiesafterThreeThroughFiveYearsNetCarryingAmount_EAA9AF826338C466722188EDB7FE2C51" xlink:type="locator" />
    <definitionArc order="8" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfHeldToMaturitySecuritiesLineItems_84765EB178D01D661B5288EDB7FD82BA" xlink:to="loc_astc_HeldtomaturitySecuritiesDebtMaturitiesafterThreeThroughFiveYearsNetCarryingAmount_EAA9AF826338C466722188EDB7FE2C51" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2014/elts/us-gaap-2014-01-31.xsd#us-gaap_HeldToMaturitySecurities" xlink:label="loc_us-gaap_HeldToMaturitySecurities_D14830D488FBE250C5DE88EDB7FE0D1A" xlink:type="locator" />
    <definitionArc order="9" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_ScheduleOfHeldToMaturitySecuritiesLineItems_84765EB178D01D661B5288EDB7FD82BA" xlink:to="loc_us-gaap_HeldToMaturitySecurities_D14830D488FBE250C5DE88EDB7FE0D1A" 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/NoncontrollingInterestChangesInEquityDetails" xlink:type="extended">
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2014/elts/us-gaap-2014-01-31.xsd#us-gaap_MinorityInterestLineItems" xlink:label="loc_us-gaap_MinorityInterestLineItems_FDCE71CAF497E9981232C4C975C967FA" xlink:type="locator" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2014/elts/us-gaap-2014-01-31.xsd#us-gaap_MinorityInterestTable" xlink:label="loc_us-gaap_MinorityInterestTable_C3D6840DB2772A25598CC4C975C85E02" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_MinorityInterestLineItems_FDCE71CAF497E9981232C4C975C967FA" xlink:to="loc_us-gaap_MinorityInterestTable_C3D6840DB2772A25598CC4C975C85E02" xlink:type="arc" xbrldt:closed="true" xbrldt:contextElement="segment" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2014/elts/us-gaap-2014-01-31.xsd#us-gaap_StatementEquityComponentsAxis" xlink:label="loc_us-gaap_StatementEquityComponentsAxis_C2E23C37A379D75DEB4FC4C975C8E0DE" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_MinorityInterestTable_C3D6840DB2772A25598CC4C975C85E02" xlink:to="loc_us-gaap_StatementEquityComponentsAxis_C2E23C37A379D75DEB4FC4C975C8E0DE" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2014/elts/us-gaap-2014-01-31.xsd#us-gaap_EquityComponentDomain" xlink:label="loc_us-gaap_EquityComponentDomain_C6BF724173A914685841C4C975C851C6_default" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_StatementEquityComponentsAxis_C2E23C37A379D75DEB4FC4C975C8E0DE" xlink:to="loc_us-gaap_EquityComponentDomain_C6BF724173A914685841C4C975C851C6_default" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2014/elts/us-gaap-2014-01-31.xsd#us-gaap_EquityComponentDomain" xlink:label="loc_us-gaap_EquityComponentDomain_C6BF724173A914685841C4C975C851C6" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_StatementEquityComponentsAxis_C2E23C37A379D75DEB4FC4C975C8E0DE" xlink:to="loc_us-gaap_EquityComponentDomain_C6BF724173A914685841C4C975C851C6" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2014/elts/us-gaap-2014-01-31.xsd#us-gaap_ParentMember" xlink:label="loc_us-gaap_ParentMember_DB8503DB96988F325A06C4C975C899CE" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_C6BF724173A914685841C4C975C851C6" xlink:to="loc_us-gaap_ParentMember_DB8503DB96988F325A06C4C975C899CE" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2014/elts/us-gaap-2014-01-31.xsd#us-gaap_NoncontrollingInterestMember" xlink:label="loc_us-gaap_NoncontrollingInterestMember_3BD00336E1822775886CC4C975C897AD" xlink:type="locator" />
    <definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_EquityComponentDomain_C6BF724173A914685841C4C975C851C6" xlink:to="loc_us-gaap_NoncontrollingInterestMember_3BD00336E1822775886CC4C975C897AD" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2014/elts/us-gaap-2014-01-31.xsd#us-gaap_IncreaseDecreaseInStockholdersEquityRollForward" xlink:label="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_1664506C9DA16F6D2220C4C975C98882" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_MinorityInterestLineItems_FDCE71CAF497E9981232C4C975C967FA" xlink:to="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_1664506C9DA16F6D2220C4C975C98882" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2014/elts/us-gaap-2014-01-31.xsd#us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest" xlink:label="loc_us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest_7DB8683E6E6221D708F1C4C975C9275B" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_1664506C9DA16F6D2220C4C975C98882" xlink:to="loc_us-gaap_StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest_7DB8683E6E6221D708F1C4C975C9275B" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2014/elts/us-gaap-2014-01-31.xsd#us-gaap_AdjustmentsToAdditionalPaidInCapitalSharebasedCompensationRequisiteServicePeriodRecognitionValue" xlink:label="loc_us-gaap_AdjustmentsToAdditionalPaidInCapitalSharebasedCompensationRequisiteServicePeriodRecognitionValue_5C99CB7F25E282312D51C4C975C9AFFE" xlink:type="locator" />
    <definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_1664506C9DA16F6D2220C4C975C98882" xlink:to="loc_us-gaap_AdjustmentsToAdditionalPaidInCapitalSharebasedCompensationRequisiteServicePeriodRecognitionValue_5C99CB7F25E282312D51C4C975C9AFFE" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2014/elts/us-gaap-2014-01-31.xsd#us-gaap_TreasuryStockValueAcquiredCostMethod" xlink:label="loc_us-gaap_TreasuryStockValueAcquiredCostMethod_0D4FBFF9C2DEBC3DB18EC4C975CE4953" xlink:type="locator" />
    <definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_1664506C9DA16F6D2220C4C975C98882" xlink:to="loc_us-gaap_TreasuryStockValueAcquiredCostMethod_0D4FBFF9C2DEBC3DB18EC4C975CE4953" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2014/elts/us-gaap-2014-01-31.xsd#us-gaap_OtherComprehensiveIncomeLossNetOfTax" xlink:label="loc_us-gaap_OtherComprehensiveIncomeLossNetOfTax_B1E25E1336D59B42D643C4C975CEC20A" xlink:type="locator" />
    <definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_1664506C9DA16F6D2220C4C975C98882" xlink:to="loc_us-gaap_OtherComprehensiveIncomeLossNetOfTax_B1E25E1336D59B42D643C4C975CEC20A" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2014/elts/us-gaap-2014-01-31.xsd#us-gaap_NetIncomeLoss" xlink:label="loc_us-gaap_NetIncomeLoss_9044B32346DF72CBAD16C4C975CEAE46" xlink:type="locator" />
    <definitionArc order="5" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_1664506C9DA16F6D2220C4C975C98882" xlink:to="loc_us-gaap_NetIncomeLoss_9044B32346DF72CBAD16C4C975CEAE46" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2014/elts/us-gaap-2014-01-31.xsd#us-gaap_NetIncomeLossAttributableToNoncontrollingInterest" xlink:label="loc_us-gaap_NetIncomeLossAttributableToNoncontrollingInterest_5A9702D937181C9B642DC4C975CE43B0" xlink:type="locator" />
    <definitionArc order="6" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncreaseDecreaseInStockholdersEquityRollForward_1664506C9DA16F6D2220C4C975C98882" xlink:to="loc_us-gaap_NetIncomeLossAttributableToNoncontrollingInterest_5A9702D937181C9B642DC4C975CE43B0" xlink:type="arc" />
  </definitionLink>
  <definitionLink xlink:role="http://www.astrotechcorp.com/role/NoncontrollingInterestDetailTextuals" xlink:type="extended">
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2014/elts/us-gaap-2014-01-31.xsd#us-gaap_MinorityInterestLineItems" xlink:label="loc_us-gaap_MinorityInterestLineItems_30C128708DD49DFD79C1B1D61C7F0684" xlink:type="locator" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2014/elts/us-gaap-2014-01-31.xsd#us-gaap_MinorityInterestTable" xlink:label="loc_us-gaap_MinorityInterestTable_2F344475AE2DD8307E5CB1D61C77CE8F" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_MinorityInterestLineItems_30C128708DD49DFD79C1B1D61C7F0684" xlink:to="loc_us-gaap_MinorityInterestTable_2F344475AE2DD8307E5CB1D61C77CE8F" xlink:type="arc" xbrldt:closed="true" xbrldt:contextElement="segment" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2014/elts/us-gaap-2014-01-31.xsd#us-gaap_CounterpartyNameAxis" xlink:label="loc_us-gaap_CounterpartyNameAxis_0BF4361DEEA51C356C9DB1D61C784238" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_MinorityInterestTable_2F344475AE2DD8307E5CB1D61C77CE8F" xlink:to="loc_us-gaap_CounterpartyNameAxis_0BF4361DEEA51C356C9DB1D61C784238" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2014/elts/us-gaap-2014-01-31.xsd#us-gaap_RepurchaseAgreementCounterpartyNameDomain" xlink:label="loc_us-gaap_RepurchaseAgreementCounterpartyNameDomain_F288958C8EDB53CDBBCEB1D61C78A813_default" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_CounterpartyNameAxis_0BF4361DEEA51C356C9DB1D61C784238" xlink:to="loc_us-gaap_RepurchaseAgreementCounterpartyNameDomain_F288958C8EDB53CDBBCEB1D61C78A813_default" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2014/elts/us-gaap-2014-01-31.xsd#us-gaap_RepurchaseAgreementCounterpartyNameDomain" xlink:label="loc_us-gaap_RepurchaseAgreementCounterpartyNameDomain_F288958C8EDB53CDBBCEB1D61C78A813" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_CounterpartyNameAxis_0BF4361DEEA51C356C9DB1D61C784238" xlink:to="loc_us-gaap_RepurchaseAgreementCounterpartyNameDomain_F288958C8EDB53CDBBCEB1D61C78A813" xlink:type="arc" />
    <loc xlink:href="astc-20151231.xsd#astc_AstralImagesIncMember" xlink:label="loc_astc_AstralImagesIncMember_8EC14496646432F14349B1D61C79DB95" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RepurchaseAgreementCounterpartyNameDomain_F288958C8EDB53CDBBCEB1D61C78A813" xlink:to="loc_astc_AstralImagesIncMember_8EC14496646432F14349B1D61C79DB95" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2014/elts/us-gaap-2014-01-31.xsd#us-gaap_RelatedPartyTransactionsByRelatedPartyAxis" xlink:label="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_1E4B7B452566FAD9ECD2B1D61C799296" xlink:type="locator" />
    <definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_MinorityInterestTable_2F344475AE2DD8307E5CB1D61C77CE8F" xlink:to="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_1E4B7B452566FAD9ECD2B1D61C799296" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2014/elts/us-gaap-2014-01-31.xsd#us-gaap_RelatedPartyDomain" xlink:label="loc_us-gaap_RelatedPartyDomain_1125056D79067950EC25B1D61C7987AC_default" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_1E4B7B452566FAD9ECD2B1D61C799296" xlink:to="loc_us-gaap_RelatedPartyDomain_1125056D79067950EC25B1D61C7987AC_default" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2014/elts/us-gaap-2014-01-31.xsd#us-gaap_RelatedPartyDomain" xlink:label="loc_us-gaap_RelatedPartyDomain_1125056D79067950EC25B1D61C7987AC" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_1E4B7B452566FAD9ECD2B1D61C799296" xlink:to="loc_us-gaap_RelatedPartyDomain_1125056D79067950EC25B1D61C7987AC" xlink:type="arc" />
    <loc xlink:href="astc-20151231.xsd#astc_FirstDetectMember" xlink:label="loc_astc_FirstDetectMember_FAF333036E5FAFDD6492B1D61C7AB2DD" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyDomain_1125056D79067950EC25B1D61C7987AC" xlink:to="loc_astc_FirstDetectMember_FAF333036E5FAFDD6492B1D61C7AB2DD" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2014/elts/us-gaap-2014-01-31.xsd#us-gaap_LeaseArrangementTypeAxis" xlink:label="loc_us-gaap_LeaseArrangementTypeAxis_5282743A6017FB23266CB1D61C7BD006" xlink:type="locator" />
    <definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_MinorityInterestTable_2F344475AE2DD8307E5CB1D61C77CE8F" xlink:to="loc_us-gaap_LeaseArrangementTypeAxis_5282743A6017FB23266CB1D61C7BD006" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2014/elts/us-gaap-2014-01-31.xsd#us-gaap_LeaseArrangementTypeDomain" xlink:label="loc_us-gaap_LeaseArrangementTypeDomain_B616C5C9F1D00173C22CB1D61C7C3B06_default" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_LeaseArrangementTypeAxis_5282743A6017FB23266CB1D61C7BD006" xlink:to="loc_us-gaap_LeaseArrangementTypeDomain_B616C5C9F1D00173C22CB1D61C7C3B06_default" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2014/elts/us-gaap-2014-01-31.xsd#us-gaap_LeaseArrangementTypeDomain" xlink:label="loc_us-gaap_LeaseArrangementTypeDomain_B616C5C9F1D00173C22CB1D61C7C3B06" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_LeaseArrangementTypeAxis_5282743A6017FB23266CB1D61C7BD006" xlink:to="loc_us-gaap_LeaseArrangementTypeDomain_B616C5C9F1D00173C22CB1D61C7C3B06" xlink:type="arc" />
    <loc xlink:href="astc-20151231.xsd#astc_TexasEmergingTechnologyFundMember" xlink:label="loc_astc_TexasEmergingTechnologyFundMember_91AAFDD888BEECCE123EB1D61C7DBD21" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LeaseArrangementTypeDomain_B616C5C9F1D00173C22CB1D61C7C3B06" xlink:to="loc_astc_TexasEmergingTechnologyFundMember_91AAFDD888BEECCE123EB1D61C7DBD21" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2014/elts/us-gaap-2014-01-31.xsd#us-gaap_MinorityInterestOwnershipPercentageByParent" xlink:label="loc_us-gaap_MinorityInterestOwnershipPercentageByParent_B6A3DD6A28BA9F1D563FB1D61C7F75B5" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_MinorityInterestLineItems_30C128708DD49DFD79C1B1D61C7F0684" xlink:to="loc_us-gaap_MinorityInterestOwnershipPercentageByParent_B6A3DD6A28BA9F1D563FB1D61C7F75B5" xlink:type="arc" />
    <loc xlink:href="astc-20151231.xsd#astc_PaymentOfCommonStockRepurchaseRight" xlink:label="loc_astc_PaymentOfCommonStockRepurchaseRight_A4E8B9DADB7FFA925347B1D61C801FFF" xlink:type="locator" />
    <definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_MinorityInterestLineItems_30C128708DD49DFD79C1B1D61C7F0684" xlink:to="loc_astc_PaymentOfCommonStockRepurchaseRight_A4E8B9DADB7FFA925347B1D61C801FFF" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2014/elts/us-gaap-2014-01-31.xsd#us-gaap_MinorityInterest" xlink:label="loc_us-gaap_MinorityInterest_BF0AEAF90FDE687E366BB1D61C80FC1B" xlink:type="locator" />
    <definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_MinorityInterestLineItems_30C128708DD49DFD79C1B1D61C7F0684" xlink:to="loc_us-gaap_MinorityInterest_BF0AEAF90FDE687E366BB1D61C80FC1B" xlink:type="arc" />
  </definitionLink>
  <definitionLink xlink:role="http://www.astrotechcorp.com/role/NoncontrollingInterestTables" xlink:type="extended" />
  <definitionLink xlink:role="http://www.astrotechcorp.com/role/OtherComprehensiveLossIncome" xlink:type="extended" />
  <definitionLink xlink:role="http://www.astrotechcorp.com/role/OtherComprehensiveLossIncomeDetails" xlink:type="extended" />
  <definitionLink xlink:role="http://www.astrotechcorp.com/role/OtherComprehensiveLossIncomeTables" xlink:type="extended" />
  <definitionLink xlink:role="http://www.astrotechcorp.com/role/ReceivablesIndemnityHoldbackRelatedToAssetSale" xlink:type="extended" />
  <definitionLink xlink:role="http://www.astrotechcorp.com/role/ReceivablesIndemnityHoldbackRelatedToAssetSaleDetailTextuals" xlink:type="extended">
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2014/elts/us-gaap-2014-01-31.xsd#us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsLineItems" xlink:label="loc_us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsLineItems_14247FEDA0C15612BDE1E5E604FE6644" xlink:type="locator" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2014/elts/us-gaap-2014-01-31.xsd#us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsTable" xlink:label="loc_us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsTable_1624A16F127059448500B8FEBA190C81" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsLineItems_14247FEDA0C15612BDE1E5E604FE6644" xlink:to="loc_us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsTable_1624A16F127059448500B8FEBA190C81" xlink:type="arc" xbrldt:closed="true" xbrldt:contextElement="segment" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2014/elts/us-gaap-2014-01-31.xsd#us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsAxis" xlink:label="loc_us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsAxis_7FEE45A16DFF5D7CA0295AC0880B1327" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsTable_1624A16F127059448500B8FEBA190C81" xlink:to="loc_us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsAxis_7FEE45A16DFF5D7CA0295AC0880B1327" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2014/elts/us-gaap-2014-01-31.xsd#us-gaap_DisposalGroupsIncludingDiscontinuedOperationsNameDomain" xlink:label="loc_us-gaap_DisposalGroupsIncludingDiscontinuedOperationsNameDomain_EBC195E19508C5F20DC033D604C1AB88_233FCA54C942517DA0692F7A30B2E478" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsAxis_7FEE45A16DFF5D7CA0295AC0880B1327" xlink:to="loc_us-gaap_DisposalGroupsIncludingDiscontinuedOperationsNameDomain_EBC195E19508C5F20DC033D604C1AB88_233FCA54C942517DA0692F7A30B2E478" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2014/elts/us-gaap-2014-01-31.xsd#us-gaap_DisposalGroupsIncludingDiscontinuedOperationsNameDomain" xlink:label="loc_us-gaap_DisposalGroupsIncludingDiscontinuedOperationsNameDomain_84C36EB894E756D1BCA7D96722218E7A" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsAxis_7FEE45A16DFF5D7CA0295AC0880B1327" xlink:to="loc_us-gaap_DisposalGroupsIncludingDiscontinuedOperationsNameDomain_84C36EB894E756D1BCA7D96722218E7A" xlink:type="arc" />
    <loc xlink:href="astc-20151231.xsd#astc_AstrotechSpaceOperationsMember" xlink:label="loc_astc_AstrotechSpaceOperationsMember_DAED8BBE91D85D4481AFD2D955700043" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_DisposalGroupsIncludingDiscontinuedOperationsNameDomain_84C36EB894E756D1BCA7D96722218E7A" xlink:to="loc_astc_AstrotechSpaceOperationsMember_DAED8BBE91D85D4481AFD2D955700043" xlink:type="arc" />
    <loc xlink:href="astc-20151231.xsd#astc_DisposalGroupIncludingDiscontinuedOperationEstimatedPurchasePrice" xlink:label="loc_astc_DisposalGroupIncludingDiscontinuedOperationEstimatedPurchasePrice_B3BDDD513A9F56DDB178F10BF5744107" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsLineItems_14247FEDA0C15612BDE1E5E604FE6644" xlink:to="loc_astc_DisposalGroupIncludingDiscontinuedOperationEstimatedPurchasePrice_B3BDDD513A9F56DDB178F10BF5744107" xlink:type="arc" />
    <loc xlink:href="astc-20151231.xsd#astc_WorkingCapitalSurplusDeficit" xlink:label="loc_astc_WorkingCapitalSurplusDeficit_BCEA4744E2E55504A654E684B0F9218A" xlink:type="locator" />
    <definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsLineItems_14247FEDA0C15612BDE1E5E604FE6644" xlink:to="loc_astc_WorkingCapitalSurplusDeficit_BCEA4744E2E55504A654E684B0F9218A" xlink:type="arc" />
    <loc xlink:href="astc-20151231.xsd#astc_DiscontinuedOperationProceedsFromSaleOfBusiness" xlink:label="loc_astc_DiscontinuedOperationProceedsFromSaleOfBusiness_1F9CB919C00957DB9A5E19C8041F181A" xlink:type="locator" />
    <definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsLineItems_14247FEDA0C15612BDE1E5E604FE6644" xlink:to="loc_astc_DiscontinuedOperationProceedsFromSaleOfBusiness_1F9CB919C00957DB9A5E19C8041F181A" xlink:type="arc" />
    <loc xlink:href="astc-20151231.xsd#astc_IndemnnityHoldbackCurrent" xlink:label="loc_astc_IndemnnityHoldbackCurrent_8983264416BC5319AAAF321364AF1F51" xlink:type="locator" />
    <definitionArc order="4" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsLineItems_14247FEDA0C15612BDE1E5E604FE6644" xlink:to="loc_astc_IndemnnityHoldbackCurrent_8983264416BC5319AAAF321364AF1F51" xlink:type="arc" />
  </definitionLink>
  <definitionLink xlink:role="http://www.astrotechcorp.com/role/RevenueRecognition" xlink:type="extended" />
  <definitionLink xlink:role="http://www.astrotechcorp.com/role/RevenueRecognitionDetails" xlink:type="extended">
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2014/elts/us-gaap-2014-01-31.xsd#us-gaap_RevenueRecognitionMultipleDeliverableArrangementsLineItems" xlink:label="loc_us-gaap_RevenueRecognitionMultipleDeliverableArrangementsLineItems_47C620A0681DA42B68B88907B97A6D30" xlink:type="locator" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2014/elts/us-gaap-2014-01-31.xsd#us-gaap_RevenueRecognitionMultipleDeliverableArrangementsTable" xlink:label="loc_us-gaap_RevenueRecognitionMultipleDeliverableArrangementsTable_A0F5D86A76156BA87D258907B9741F25" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_us-gaap_RevenueRecognitionMultipleDeliverableArrangementsLineItems_47C620A0681DA42B68B88907B97A6D30" xlink:to="loc_us-gaap_RevenueRecognitionMultipleDeliverableArrangementsTable_A0F5D86A76156BA87D258907B9741F25" xlink:type="arc" xbrldt:closed="true" xbrldt:contextElement="segment" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2014/elts/us-gaap-2014-01-31.xsd#us-gaap_RangeAxis" xlink:label="loc_us-gaap_RangeAxis_A9791C49E8748500770F8907CFB86956" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_us-gaap_RevenueRecognitionMultipleDeliverableArrangementsTable_A0F5D86A76156BA87D258907B9741F25" xlink:to="loc_us-gaap_RangeAxis_A9791C49E8748500770F8907CFB86956" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2014/elts/us-gaap-2014-01-31.xsd#us-gaap_RangeMember" xlink:label="loc_us-gaap_RangeMember_C45A476D89F2F9E39D858907CFBFB82E_default" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_RangeAxis_A9791C49E8748500770F8907CFB86956" xlink:to="loc_us-gaap_RangeMember_C45A476D89F2F9E39D858907CFBFB82E_default" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2014/elts/us-gaap-2014-01-31.xsd#us-gaap_RangeMember" xlink:label="loc_us-gaap_RangeMember_C45A476D89F2F9E39D858907CFBFB82E" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_RangeAxis_A9791C49E8748500770F8907CFB86956" xlink:to="loc_us-gaap_RangeMember_C45A476D89F2F9E39D858907CFBFB82E" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2014/elts/us-gaap-2014-01-31.xsd#us-gaap_MinimumMember" xlink:label="loc_us-gaap_MinimumMember_835D177C1F71786230488907F76FAB53" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RangeMember_C45A476D89F2F9E39D858907CFBFB82E" xlink:to="loc_us-gaap_MinimumMember_835D177C1F71786230488907F76FAB53" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2014/elts/us-gaap-2014-01-31.xsd#us-gaap_MaximumMember" xlink:label="loc_us-gaap_MaximumMember_3B87500237D8A90F5566890819C6AF8D" xlink:type="locator" />
    <definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RangeMember_C45A476D89F2F9E39D858907CFBFB82E" xlink:to="loc_us-gaap_MaximumMember_3B87500237D8A90F5566890819C6AF8D" xlink:type="arc" />
    <loc xlink:href="astc-20151231.xsd#astc_RevenueRecognitionFixedPriceSubcontractOnGovernmentProjectTerm" xlink:label="loc_astc_RevenueRecognitionFixedPriceSubcontractOnGovernmentProjectTerm_1A5426D743C20FD0073389065313DED7" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RevenueRecognitionMultipleDeliverableArrangementsLineItems_47C620A0681DA42B68B88907B97A6D30" xlink:to="loc_astc_RevenueRecognitionFixedPriceSubcontractOnGovernmentProjectTerm_1A5426D743C20FD0073389065313DED7" xlink:type="arc" />
  </definitionLink>
  <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-20151231.xsd#astc_StateOfTexasFundingLineItems" xlink:label="loc_astc_StateOfTexasFundingLineItems_F2A9F6655A6D51D19FBEBA3924FB8888" xlink:type="locator" />
    <loc xlink:href="astc-20151231.xsd#astc_StateOfTexasFundingTable" xlink:label="loc_astc_StateOfTexasFundingTable_DA884C0319355C6ABB1C7B5F27472849" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/all" xlink:from="loc_astc_StateOfTexasFundingLineItems_F2A9F6655A6D51D19FBEBA3924FB8888" xlink:to="loc_astc_StateOfTexasFundingTable_DA884C0319355C6ABB1C7B5F27472849" xlink:type="arc" xbrldt:closed="true" xbrldt:contextElement="segment" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2014/elts/us-gaap-2014-01-31.xsd#us-gaap_LeaseArrangementTypeAxis" xlink:label="loc_us-gaap_LeaseArrangementTypeAxis_ADA3F60175985DCAAD55F307827FC061" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_astc_StateOfTexasFundingTable_DA884C0319355C6ABB1C7B5F27472849" xlink:to="loc_us-gaap_LeaseArrangementTypeAxis_ADA3F60175985DCAAD55F307827FC061" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2014/elts/us-gaap-2014-01-31.xsd#us-gaap_LeaseArrangementTypeDomain" xlink:label="loc_us-gaap_LeaseArrangementTypeDomain_79FB391AF86EB6612282B9CF893300E0_5DC86A9CC9775A9183529C3628FB6E75" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_LeaseArrangementTypeAxis_ADA3F60175985DCAAD55F307827FC061" xlink:to="loc_us-gaap_LeaseArrangementTypeDomain_79FB391AF86EB6612282B9CF893300E0_5DC86A9CC9775A9183529C3628FB6E75" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2014/elts/us-gaap-2014-01-31.xsd#us-gaap_LeaseArrangementTypeDomain" xlink:label="loc_us-gaap_LeaseArrangementTypeDomain_BF934F0A77575CB4B1C11D21F99AC76E" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_LeaseArrangementTypeAxis_ADA3F60175985DCAAD55F307827FC061" xlink:to="loc_us-gaap_LeaseArrangementTypeDomain_BF934F0A77575CB4B1C11D21F99AC76E" xlink:type="arc" />
    <loc xlink:href="astc-20151231.xsd#astc_TexasEmergingTechnologyFundMember" xlink:label="loc_astc_TexasEmergingTechnologyFundMember_169720C4A8985829876468EFFF015EC9" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_LeaseArrangementTypeDomain_BF934F0A77575CB4B1C11D21F99AC76E" xlink:to="loc_astc_TexasEmergingTechnologyFundMember_169720C4A8985829876468EFFF015EC9" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2014/elts/us-gaap-2014-01-31.xsd#us-gaap_RelatedPartyTransactionsByRelatedPartyAxis" xlink:label="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_4F0F67A68A72539CBDF25292D072D941" xlink:type="locator" />
    <definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/hypercube-dimension" xlink:from="loc_astc_StateOfTexasFundingTable_DA884C0319355C6ABB1C7B5F27472849" xlink:to="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_4F0F67A68A72539CBDF25292D072D941" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2014/elts/us-gaap-2014-01-31.xsd#us-gaap_RelatedPartyDomain" xlink:label="loc_us-gaap_RelatedPartyDomain_512C7ECE7770D673E010B9CF89340EB2_5DC86A9CC9775A9183529C3628FB6E75" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-default" xlink:from="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_4F0F67A68A72539CBDF25292D072D941" xlink:to="loc_us-gaap_RelatedPartyDomain_512C7ECE7770D673E010B9CF89340EB2_5DC86A9CC9775A9183529C3628FB6E75" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2014/elts/us-gaap-2014-01-31.xsd#us-gaap_RelatedPartyDomain" xlink:label="loc_us-gaap_RelatedPartyDomain_494AF9361AB45649BB6EEAC0C015AC71" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/dimension-domain" xlink:from="loc_us-gaap_RelatedPartyTransactionsByRelatedPartyAxis_4F0F67A68A72539CBDF25292D072D941" xlink:to="loc_us-gaap_RelatedPartyDomain_494AF9361AB45649BB6EEAC0C015AC71" xlink:type="arc" />
    <loc xlink:href="astc-20151231.xsd#astc_FirstDetectMember" xlink:label="loc_astc_FirstDetectMember_EF2DE73DAB6A538EA5897D9808D27283" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_us-gaap_RelatedPartyDomain_494AF9361AB45649BB6EEAC0C015AC71" xlink:to="loc_astc_FirstDetectMember_EF2DE73DAB6A538EA5897D9808D27283" xlink:type="arc" />
    <loc xlink:href="astc-20151231.xsd#astc_FundsAwardedForDevelopmentAndMarketing" xlink:label="loc_astc_FundsAwardedForDevelopmentAndMarketing_540221E3090B5F90AC0353EFFBA8FCBD" xlink:type="locator" />
    <definitionArc order="1" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_astc_StateOfTexasFundingLineItems_F2A9F6655A6D51D19FBEBA3924FB8888" xlink:to="loc_astc_FundsAwardedForDevelopmentAndMarketing_540221E3090B5F90AC0353EFFBA8FCBD" xlink:type="arc" />
    <loc xlink:href="http://xbrl.fasb.org/us-gaap/2014/elts/us-gaap-2014-01-31.xsd#us-gaap_DebtInstrumentInterestRateStatedPercentage" xlink:label="loc_us-gaap_DebtInstrumentInterestRateStatedPercentage_EDD8CE1B26E85DF5B71D4533DC0281B9" xlink:type="locator" />
    <definitionArc order="2" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_astc_StateOfTexasFundingLineItems_F2A9F6655A6D51D19FBEBA3924FB8888" xlink:to="loc_us-gaap_DebtInstrumentInterestRateStatedPercentage_EDD8CE1B26E85DF5B71D4533DC0281B9" xlink:type="arc" />
    <loc xlink:href="astc-20151231.xsd#astc_PaymentOfCommonStockRepurchaseRight" xlink:label="loc_astc_PaymentOfCommonStockRepurchaseRight_EEF161C565305990BD7C011007A164D8" xlink:type="locator" />
    <definitionArc order="3" xlink:arcrole="http://xbrl.org/int/dim/arcrole/domain-member" xlink:from="loc_astc_StateOfTexasFundingLineItems_F2A9F6655A6D51D19FBEBA3924FB8888" xlink:to="loc_astc_PaymentOfCommonStockRepurchaseRight_EEF161C565305990BD7C011007A164D8" xlink:type="arc" />
  </definitionLink>
</linkbase>
