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      <TermEndowmentBalanceEOYPct>1.00000</TermEndowmentBalanceEOYPct>
      <EndowmentsHeldUnrelatedOrgInd>0</EndowmentsHeldUnrelatedOrgInd>
      <EndowmentsHeldRelatedOrgInd>0</EndowmentsHeldRelatedOrgInd>
      <TotalBookValueLandBuildingsAmt>0</TotalBookValueLandBuildingsAmt>
      <OtherLiabilitiesOrgGrp>
        <Desc>DUE TO LOWELL OBSERVATORY</Desc>
        <Amt>3514</Amt>
      </OtherLiabilitiesOrgGrp>
      <TotalLiabilityAmt>3514</TotalLiabilityAmt>
      <FootnoteTextInd>X</FootnoteTextInd>
      <SupplementalInformationDetail>
        <FormAndLineReferenceDesc>PART V, LINE 4:</FormAndLineReferenceDesc>
        <ExplanationTxt>THE ENDOWMENT FUNDS ARE USED FOR SUPPORT OF LOWELL OBSERVATORY AND FOR REINVESTMENT. DURING 2017, THE SOLE TRUSTEE SUCCESSFULLY PETITIONED THE COURTS TO REMOVE THE PERPETUAL RESTRICTIONS ON THE TRUST ASSETS. THE TRUST ASSETS WERE RECLASSIFIED TO TEMPORARILY RESTRICTED NET ASSETS.</ExplanationTxt>
      </SupplementalInformationDetail>
      <SupplementalInformationDetail>
        <FormAndLineReferenceDesc>PART X, LINE 2:</FormAndLineReferenceDesc>
        <ExplanationTxt>THE FOLLOWING DISCLOSURE IS RELATED TO THE COMBINED FINANCIAL STATEMENTS OF THE LOWELL OBSERVATORY, TRUST U/W OF PERCIVAL LOWELL, AND THE LOWELL OBSERVATORY FOUNDATION: THE OBSERVATORY AND THE FOUNDATION ARE EXEMPT FROM INCOME TAXES UNDER BOTH INTERNAL REVENUE CODE (IRC) SECTION 501(C)(3) AND ARIZONA INCOME TAX LAWS. THE OBSERVATORY IS CLASSIFIED AS OTHER THAN A PRIVATE FOUNDATION UNDER IRC SECTION 509(A)(1). THE FOUNDATION IS CLASSIFIED AS OTHER THAN A PRIVATE FOUNDATION UNDER IRC SECTION 509(A)(3) AS A SUPPORTING ORGANIZATION OF THE OBSERVATORY. THE TRUST QUALIFIES AS AN IRC SECTION 509(A)(3) SUPPORTING ORGANIZATION OF THE OBSERVATORY. NO PROVISION FOR FEDERAL AND STATE INCOME TAXES HAS BEEN MADE. INCOME FROM CERTAIN ACTIVITIES NOT DIRECTLY RELATED TO THE ORGANIZATION'S TAX-EXEMPT PURPOSE, HOWEVER, MAY BE SUBJECT TO TAXATION AS UNRELATED BUSINESS TAXABLE INCOME (UBTI). GAAP REQUIRES MANAGEMENT TO PERFORM AN EVALUATION OF ALL TAX POSITIONS TAKEN OR EXPECTED TO BE TAKEN IN THE COURSE OF PREPARING THE ORGANIZATION'S TAX RETURNS TO DETERMINE WHETHER THE TAX POSITIONS MEET A "MORE LIKELY THAN NOT" STANDARD OF BEING SUSTAINED UNDER EXAMINATION BY THE APPLICABLE TAXING AUTHORITIES. THIS EVALUATION IS REQUIRED TO BE PERFORMED FOR ALL OPEN TAX YEARS, AS DEFINED BY THE VARIOUS STATUTES OF LIMITATIONS, FOR FEDERAL AND STATE PURPOSES. THE ORGANIZATION IS ONLY SUBJECT TO INCOME TAXES ON UBTI AS APPLICABLE. THE ORGANIZATION IS REQUIRED TO FILE INFORMATIONAL RETURNS FOR FEDERAL AND STATE PURPOSES AND, IF IT HAS UBTI, FEDERAL AND STATE INCOME TAX RETURNS. MANAGEMENT HAS PERFORMED ITS EVALUATION OF TAX POSITIONS TAKEN ON ALL OPEN TAX RETURNS AND HAS DETERMINED THAT THERE WERE NO POSITIONS TAKEN THAT DO NOT MEET THE "MORE LIKELY THAN NOT" STANDARD. FROM TIME TO TIME, THE ORGANIZATION MAY BE SUBJECT TO PENALTIES AND INTEREST ASSESSED BY VARIOUS TAXING AUTHORITIES, WHICH ARE CLASSIFIED AS GENERAL AND ADMINISTRATIVE EXPENSES IF THEY OCCUR.</ExplanationTxt>
      </SupplementalInformationDetail>
      <SupplementalInformationDetail>
        <FormAndLineReferenceDesc>SCHEDULE D, PART V, LINE 1C, COLUMN A</FormAndLineReferenceDesc>
        <ExplanationTxt>CALCULATION OF CURRENT YEAR INVESTMENT GAINS/(LOSSES): NET UNREALIZED GAINS: 1,262,071 NET REALIZED GAINS: 1,568,382 INTEREST INCOME: 189,771 DIVIDEND INCOME: 885,602 NET INVESTMENT INCOME: 3,905,826</ExplanationTxt>
      </SupplementalInformationDetail>
    </IRS990ScheduleD>
    <IRS990ScheduleI documentId="RetDoc1041900001">
      <GrantRecordsMaintainedInd>0</GrantRecordsMaintainedInd>
      <RecipientTable>
        <RecipientBusinessName>
          <BusinessNameLine1Txt>LOWELL OBSERVATORY</BusinessNameLine1Txt>
        </RecipientBusinessName>
        <USAddress>
          <AddressLine1Txt>1400 W MARS HILL ROAD</AddressLine1Txt>
          <CityNm>FLAGSTAFF</CityNm>
          <StateAbbreviationCd>AZ</StateAbbreviationCd>
          <ZIPCd>860014470</ZIPCd>
        </USAddress>
        <RecipientEIN>860098918</RecipientEIN>
        <IRCSectionDesc>501(C)(3)</IRCSectionDesc>
        <CashGrantAmt>11650000</CashGrantAmt>
        <PurposeOfGrantTxt>GENERAL SUPPORT &amp; DEBT PAYMENTS ON OBSERVATORY'S BEHALF.</PurposeOfGrantTxt>
      </RecipientTable>
      <Total501c3OrgCnt>1</Total501c3OrgCnt>
      <SupplementalInformationDetail>
        <FormAndLineReferenceDesc>PART I, LINE I</FormAndLineReferenceDesc>
        <ExplanationTxt>THE TRUST EXISTS WITH THE SOLE PURPOSE OF SUPPORTING LOWELL OBSERVATORY, THEREFORE SELECTION CRITERIA AND ELIGIBILITY REQUIREMENTS ARE NOT APPLICABLE. SUBSTANTIATION FOR THE AMOUNTS OF GRANTS ARE KEPT WITHIN LOWELL'S INTERNAL ACCOUNTING DEPARTMENT.</ExplanationTxt>
      </SupplementalInformationDetail>
    </IRS990ScheduleI>
    <IRS990ScheduleO documentId="RetDoc1044400001">
      <SupplementalInformationDetail>
        <FormAndLineReferenceDesc>FORM 990, PART VI, SECTION A, LINE 4</FormAndLineReferenceDesc>
        <ExplanationTxt>THE PERCIVAL LOWELL TRUST UW (TRUST) WAS PREVIOUSLY CLASSIFIED AS A NON-EXEMPT TRUST WITH AN UNLIMITED EXCLUSION OF GROSS INCOME BECAUSE IT'S NET ASSETS WERE SET ASIDE FOR CHARITABLE AND SCIENTIFIC PURPOSES. DURING 2017, THE SOLE TRUSTEE SUCCESSFULLY PETITIONED THE COURT TO MODIFY THE TRUST DOCUMENT TO COMPLY WITH THE RULES GOVERNING CHARITABLE TRUSTS. AS A RESULT, IN 2017 THE TRUST FILED FORM 1023 TO APPLY FOR RECOGNITION OF EXEMPTION UNDER SECTION 501(C)(3). THE APPLICATION WAS APPROVED ON MARCH 22, 2018, WITH A RETROACTIVE EXEMPTION DATE OF MAY 8, 2017. THE TRUST IS OTHER THAN A PRIVATE FOUNDATION PURSUANT TO IRC SEC 509(A)(3), AND IS A TYPE II SUPPORT ORGANIZATION.</ExplanationTxt>
      </SupplementalInformationDetail>
      <SupplementalInformationDetail>
        <FormAndLineReferenceDesc>FORM 990, PART VI, SECTION A, LINE 7A</FormAndLineReferenceDesc>
        <ExplanationTxt>THE SOLE TRUSTEE IS RESPONSIBLE FOR NAMING THE SUCCESSOR TRUSTEE.</ExplanationTxt>
      </SupplementalInformationDetail>
      <SupplementalInformationDetail>
        <FormAndLineReferenceDesc>FORM 990, PART VI, SECTION A, LINE 8A</FormAndLineReferenceDesc>
        <ExplanationTxt>THE SOLE TRUSTEE WILL RECORD ACTIONS UNDERTAKEN FROM TIME TO TIME AS NEEDED.</ExplanationTxt>
      </SupplementalInformationDetail>
      <SupplementalInformationDetail>
        <FormAndLineReferenceDesc>FORM 990, PART VI, SECTION A, LINE 8B</FormAndLineReferenceDesc>
        <ExplanationTxt>THERE ARE NO COMMITTEES WITH AUTHORITY TO ACT ON BEHALF OF THE SOLE TRUSTEE/GOVERNING BODY.</ExplanationTxt>
      </SupplementalInformationDetail>
      <SupplementalInformationDetail>
        <FormAndLineReferenceDesc>FORM 990, PART VI, SECTION B, LINE 11B</FormAndLineReferenceDesc>
        <ExplanationTxt>THE FORM 990 DRAFT WILL BE FIRST REVIEWED BY THE DEPUTY DIRECTOR FOR ADMINISTRATION (DDA) FOR THE OBSERVATORY FOR ACCURACY. ONCE IT HAS BEEN DEEMED ACCURATE BY THE DDA IT WILL BE FORWARDED TO THE SOLE TRUSTEE AND AUDIT COMMITTEE FOR THEIR REVIEW AND COMMENTS. AFTER ANY QUESTIONS AND COMMENTS HAVE BEEN ADDRESSED IT WILL BE APPROVED AND A FINAL COPY WILL BE SIGNED BY THE SOLE TRUSTEE.</ExplanationTxt>
      </SupplementalInformationDetail>
      <SupplementalInformationDetail>
        <FormAndLineReferenceDesc>FORM 990, PART VI, SECTION C, LINE 19</FormAndLineReferenceDesc>
        <ExplanationTxt>THE TRUST IS GOVERNED BY THE WILL OF PERCIVAL LOWELL AND EXISTS EXCLUSIVELY FOR THE BENEFIT OF LOWELL OBSERVATORY. WHEN REQUESTED, DOCUMENTS REGARDING THE TRUST ARE PROVIDED BY THE LOWELL OBSERVATORY BUSINESS OFFICE. THE 990 IS ALSO AVAILABLE ON GUIDESTAR.</ExplanationTxt>
      </SupplementalInformationDetail>
    </IRS990ScheduleO>
    <IRS990ScheduleR documentId="RetDoc1043400001">
      <IdRelatedTaxExemptOrgGrp>
        <DisregardedEntityName>
          <BusinessNameLine1Txt>LOWELL OBSERVATORY</BusinessNameLine1Txt>
        </DisregardedEntityName>
        <USAddress>
          <AddressLine1Txt>1400 W MARS HILL ROAD</AddressLine1Txt>
          <CityNm>FLAGSTAFF</CityNm>
          <StateAbbreviationCd>AZ</StateAbbreviationCd>
          <ZIPCd>86001</ZIPCd>
        </USAddress>
        <EIN>860098918</EIN>
        <PrimaryActivitiesTxt>ASTRONOMICAL RESEARCH AND EDUCATION</PrimaryActivitiesTxt>
        <LegalDomicileStateCd>AZ</LegalDomicileStateCd>
        <ExemptCodeSectionTxt>501(C)(3)</ExemptCodeSectionTxt>
        <PublicCharityStatusTxt>LINE 7</PublicCharityStatusTxt>
        <DirectControllingEntityName>
          <BusinessNameLine1Txt>TRUST UW OF PERCIVAL LOWELL</BusinessNameLine1Txt>
        </DirectControllingEntityName>
        <ControlledOrganizationInd>1</ControlledOrganizationInd>
      </IdRelatedTaxExemptOrgGrp>
      <IdRelatedTaxExemptOrgGrp>
        <DisregardedEntityName>
          <BusinessNameLine1Txt>LOWELL OBSERVATORY FOUNDATION</BusinessNameLine1Txt>
        </DisregardedEntityName>
        <USAddress>
          <AddressLine1Txt>1400 W MARS HILL ROAD</AddressLine1Txt>
          <CityNm>FLAGSTAFF</CityNm>
          <StateAbbreviationCd>AZ</StateAbbreviationCd>
          <ZIPCd>86001</ZIPCd>
        </USAddress>
        <EIN>472052113</EIN>
        <PrimaryActivitiesTxt>FOUNDATION F/B/O LOWELL OBSERVATORY</PrimaryActivitiesTxt>
        <LegalDomicileStateCd>AZ</LegalDomicileStateCd>
        <ExemptCodeSectionTxt>501(C)(3)</ExemptCodeSectionTxt>
        <PublicCharityStatusTxt>LINE 12B, II</PublicCharityStatusTxt>
        <DirectControllingNACd>N/A</DirectControllingNACd>
        <ControlledOrganizationInd>0</ControlledOrganizationInd>
      </IdRelatedTaxExemptOrgGrp>
      <ReceiptOfIntAnntsRntsRyltsInd>0</ReceiptOfIntAnntsRntsRyltsInd>
      <GiftGrntOrCapContriToOthOrgInd>1</GiftGrntOrCapContriToOthOrgInd>
      <GiftGrntCapContriFromOthOrgInd>0</GiftGrntCapContriFromOthOrgInd>
      <LoansOrGuaranteesToOtherOrgInd>1</LoansOrGuaranteesToOtherOrgInd>
      <LoansOrGuaranteesFromOthOrgInd>1</LoansOrGuaranteesFromOthOrgInd>
      <DivRelatedOrganizationInd>0</DivRelatedOrganizationInd>
      <AssetSaleToOtherOrgInd>0</AssetSaleToOtherOrgInd>
      <AssetPurchaseFromOtherOrgInd>0</AssetPurchaseFromOtherOrgInd>
      <AssetExchangeInd>0</AssetExchangeInd>
      <RentalOfFacilitiesToOthOrgInd>0</RentalOfFacilitiesToOthOrgInd>
      <RentalOfFcltsFromOthOrgInd>0</RentalOfFcltsFromOthOrgInd>
      <PerformOfServicesForOthOrgInd>0</PerformOfServicesForOthOrgInd>
      <PerformOfServicesByOtherOrgInd>0</PerformOfServicesByOtherOrgInd>
      <SharingOfFacilitiesInd>0</SharingOfFacilitiesInd>
      <PaidEmployeesSharingInd>1</PaidEmployeesSharingInd>
      <ReimbursementPaidToOtherOrgInd>1</ReimbursementPaidToOtherOrgInd>
      <ReimbursementPaidByOtherOrgInd>0</ReimbursementPaidByOtherOrgInd>
      <TransferToOtherOrgInd>0</TransferToOtherOrgInd>
      <TransferFromOtherOrgInd>0</TransferFromOtherOrgInd>
      <TransactionsRelatedOrgGrp>
        <OtherOrganizationName>
          <BusinessNameLine1Txt>LOWELL OBSERVATORY</BusinessNameLine1Txt>
        </OtherOrganizationName>
        <TransactionTypeTxt>D</TransactionTypeTxt>
        <InvolvedAmt>750000</InvolvedAmt>
        <MethodOfAmountDeterminationTxt>END OF YEAR BALANCE</MethodOfAmountDeterminationTxt>
      </TransactionsRelatedOrgGrp>
      <TransactionsRelatedOrgGrp>
        <OtherOrganizationName>
          <BusinessNameLine1Txt>LOWELL OBSERVATORY</BusinessNameLine1Txt>
        </OtherOrganizationName>
        <TransactionTypeTxt>E</TransactionTypeTxt>
        <InvolvedAmt>3514</InvolvedAmt>
        <MethodOfAmountDeterminationTxt>END OF YEAR BALANCE</MethodOfAmountDeterminationTxt>
      </TransactionsRelatedOrgGrp>
      <TransactionsRelatedOrgGrp>
        <OtherOrganizationName>
          <BusinessNameLine1Txt>LOWELL OBSERVATORY</BusinessNameLine1Txt>
        </OtherOrganizationName>
        <TransactionTypeTxt>B</TransactionTypeTxt>
        <InvolvedAmt>11650000</InvolvedAmt>
        <MethodOfAmountDeterminationTxt>CASH VALUE</MethodOfAmountDeterminationTxt>
      </TransactionsRelatedOrgGrp>
    </IRS990ScheduleR>
  </ReturnData>
</Return>