1. LAT-PR-01967-01Section 8.2 – Structural Design1 GLAST LAT Project CDR/CD3 Review, May 12-16 2003 15 Apr 2003 Martin Nordbynordby@slac.stanford.edu With contributions from: Youssef IsmailJohn Ku Mike FossRich Bielawski Michael LoveletteJim Haughton Eric GawehnLarry Wai Gamma-ray Large Area Space Telescope LAT Structural Systems

2. LAT-PR-01967-01Section 8.2 – Structural Design2 GLAST LAT Project CDR/CD3 Review, May 12-16 2003 Agenda Design Overview –LAT design –Design and interface changes since Delta PDR –CCB actions, trade studies, and open issues Peer Review RFA’s and requirements Structural analysis model development Structural analysis results –LAT modal analysis –Distortion analysis –Interface loads extraction Environmental test plans –Integration and test flow –Modal survey testing –Sine vibe and sine burst testing –Acoustic testing –Optical and muon surveying Summary and conclusions UPDATE

3. LAT-PR-01967-01Section 8.2 – Structural Design3 GLAST LAT Project CDR/CD3 Review, May 12-16 2003 Mechanical Design Overview LAT Overview Anticoincidence Detector (ACD) Mass270.1 kg (Mar 2003 est) Size1806 mm w x 1081.5 mm h InterfacesGrid bolted joint, shear pins Electronics Mass199.3 kg (Mar 2003 est) Size1417 mm sq x 222 mm h InterfacesStand-off to CAL; thermal joint to X-LAT Plate Grid/X-LAT Plate/Radiators Mass329.3 kg (Mar 2003 est) Size1580 mm sq x 236 mm h InterfacesFour-point mount to SC flexures LAT Structural Design Parameters DesignSpec Mass2679.4 kg<3000 kg Center of Gravity149.3 mm<185 mm Width1806 mm<1820 mm Height1081.5 mm1100 mm LAT Mass Budget and Current Estimates (kg) EstimateBudget TKR504.9510.0 CAL1375.81440.0 ACD270.1280.0 Mech329.3345.0 Elec199.3220.0 LAT Total2679.43000 Source: LAT-TD-00564-6 “LAT Mass Status Report Mass Estimates for Mar 2003” Calorimeter (CAL) Mass1375.8 kg (Mar 2003 est) Size364 mm sq x 224 mm h InterfacesGrid bolted friction joint Tracker (TKR) Mass504.9 kg (Mar 2003 est) Size372 mm sq x 640 h InterfacesGrid Ti flexure mount and Cu strap UPDATE

4. LAT-PR-01967-01Section 8.2 – Structural Design4 GLAST LAT Project CDR/CD3 Review, May 12-16 2003 System Block Diagram TKR Module CFC tray, side walls Grid monolithic alum structure CAL Modules alum bottom plate Elec. Boxes alum electronics box MLI Insulation MLI surrounding underside of LAT ACD Base Elec Ass’y alum frame LAT Radiators on +/- Y sides of LAT Grid Spacecraft LAT mounting structure Spacecraft SC bus structure Solar Arrays S.A. mount MLI Surrounding ACD LAT Block Diagram X-LAT Plate monolithic alum structure Radiator Mnt Bkt Support Radiators at corners of Grid EMI Skirt Shields E-Boxes, supports X-LAT Pl Htr Switch Boxes Operate Radiator heaters

5. LAT-PR-01967-01Section 8.2 – Structural Design5 GLAST LAT Project CDR/CD3 Review, May 12-16 2003 LAT Design Details Grid corner detail showing heat pipes, purge grooves; corner chamfer and bottom flange for ACD Radiator Mount at Grid corners. Note mid-side Grid Wing Reverse-angle view of VCHP S-bends and DSHP connection TKR mid-side and corner flexures Copper thermal straps UPDATE

6. LAT-PR-01967-01Section 8.2 – Structural Design6 GLAST LAT Project CDR/CD3 Review, May 12-16 2003 LAT Interface Details Grid Wing with SC mount bracket EMI Skirt cut-outs around SC stay-clear LAT inside LV fairing static stay-clear PAF, per Boeing PPG SC proposed interface stay-clear on top of octagonal SC volume UPDATE

7. LAT-PR-01967-01Section 8.2 – Structural Design7 GLAST LAT Project CDR/CD3 Review, May 12-16 2003 LAT Underside Design Details Upside-down view of a Grid Y mid- side, showing DSHP’s, Grid Wing, and EMI Skirt Detail of TEM, TPS, and EPU box stack Empty boxes EPU boxes PDU box GASU box SIU boxes TPS (16x) TEM (16x) LAT Underside View of Electronics Boxes UPDATE

8. LAT-PR-01967-01Section 8.2 – Structural Design8 GLAST LAT Project CDR/CD3 Review, May 12-16 2003 LAT Design Changes Since Delta-PDR Subsystem changes affecting system performance –TKR bottom tray re-work: strengthens CC tray in high-stress corner regions –TKR flexure re-design: accommodates updated bottom tray design and provides for stiffer cantilever mode for TKR –ACD mass growth: accommodates larger tile overlaps and increase in structural stiffness and strength LAT internal interface changes –Integrated Grid Wing into bottom flange Incorporated Wing into machined Grid (no longer a bolt-on part) Tapered wing into a full bottom flange around Grid perimeter to reduce stress concentrations at SC mount and heat pipe cut-outs –Changed TKR thermal interface to thermal straps Copper straps provide compliant joint to Grid –Stiffened TKR flexure connection to Grid This was part of TKR bottom tray re-design Effect was to increase TKR first-mode natural frequency –Moved Electronics Box structural mount to CAL back plate Boxes now hard-mounted to CAL plate by way of moment-bearing stand-offs Cleaner structural design simplifies analysis and test plans for CAL and Electronics groups Forces on the X-LAT Plate are reduced to just inertial loads of the plate –X-LAT plate thermal connection changed to V-Therm cloth Test program underway –CAL-Grid bolted joint modified to include pins Development program underway to finalize pinned joint design Design incorporated into CDR analysis

9. LAT-PR-01967-01Section 8.2 – Structural Design9 GLAST LAT Project CDR/CD3 Review, May 12-16 2003 LAT External Interface Changes Since Delta-PDR Finalized Radiator dimensions and interface –Modified Radiator aspect ratio at request of Spectrum –Agreed on final width, based on reduction in spacing between Radiators that was requested by Spectrum –Agreed on final height, based on final positioning of LAT and PAF stay-clear agreements with Boeing –Resulting radiator area is 2.78 m 2 Finalized Radiator mount location to SC –Moved mount location down at request of Spectrum –This reduced Radiator first-mode natural frequency, but margin to 50 Hz requirements is still large Modified LAT-SC mount region –Finalized bolt pattern and pad size to accommodate Spectrum’s flexure design –Agreed to final LAT and SC stay-clear geometry around flexure

10. LAT-PR-01967-01Section 8.2 – Structural Design10 GLAST LAT Project CDR/CD3 Review, May 12-16 2003 Design Changes Since Delta PDR (cont) LAT Delta PDR Design July 2002 LAT CDR Design Mar 2003 Radiator panels widened and shortened, reducing thermal efficiency Panels cut-out locations fixed SC-LAT mount region still in work VCHP S-bends UPDATE

11. LAT-PR-01967-01Section 8.2 – Structural Design11 GLAST LAT Project CDR/CD3 Review, May 12-16 2003 Change Control Board Changes Since Delta-PDR ACD mass growth –Added structural mass to increase design margins –Added mass in scintillating tiles to increase size of tiles and overlap between tiles Mechanical Systems mass growth –Added mass for Grid box additions: Grid Wing, bottom flange, EMI Skirt stiffening, X-LAT thermal straps –Added mass for slightly increased Radiator area Calorimeter mass de-allocation –Decreased mass allocation to reflect reduction in size of CsI logs –Log size was reduced to accommodate tolerance stack-up within CFC box structure Power allocation update (pending) –Updated power allocations based on current measured values –Already using updated allocations in thermal analysis

12. LAT-PR-01967-01Section 8.2 – Structural Design12 GLAST LAT Project CDR/CD3 Review, May 12-16 2003 LAT Mechanical System Schematic Diagram LAT Schematic Diagram

13. LAT-PR-01967-01Section 8.2 – Structural Design13 GLAST LAT Project CDR/CD3 Review, May 12-16 2003 Trade Studies Since Delta PDR Moved Electronics Box structural mount to CAL back plate –Boxes now hard-mounted to CAL plate by way of moment-bearing stand-offs –Cleaner structural design simplifies analysis and test plans for CAL and Electronics groups –Forces on X-LAT Plate are reduced to just inertial loads of the plate Radiator panel top profile –Modified panel to a stepped top profile –Radiator area is maximized, while providing good access volume under the ACD

14. LAT-PR-01967-01Section 8.2 – Structural Design14 GLAST LAT Project CDR/CD3 Review, May 12-16 2003 Structural Interface Open Issues CAL-Grid structural joint –Issue: joint has recently been changed from an all-friction joint to a pinned joint, but analysis and development testing are not yet complete –Closure plan Structural analysis underway Joint testing is underway Process development work underway X-LAT Plate to Electronics box thermal joint –Issue: thermal strap design was recently abandoned in favor of V-Therm carbon fiber cloth, with much testing yet to be done –Closure plan Materials testing Contamination studies and testing Thermal properties testing Joint design and tolerance study Radiator-SC strut angle –Issue: Spectrum proposes to angle the Radiator support struts

15. LAT-PR-01967-01Section 8.2 – Structural Design15 GLAST LAT Project CDR/CD3 Review, May 12-16 2003 Structural RFA’s from Peer Review UPDATE

16. LAT-PR-01967-01Section 8.2 – Structural Design16 GLAST LAT Project CDR/CD3 Review, May 12-16 2003 LAT Requirements Flow-Down Legend GLAST Mission Spec’s LAT Spec’s Subsystem Spec’s

17. LAT-PR-01967-01Section 8.2 – Structural Design17 GLAST LAT Project CDR/CD3 Review, May 12-16 2003 Key LAT Configuration and Structural Requirements UPDATE: Origin of Req

18. LAT-PR-01967-01Section 8.2 – Structural Design18 GLAST LAT Project CDR/CD3 Review, May 12-16 2003 LAT Integrated Structural FEA Model LAT structural model moved to NASTRAN –Changed FEA software from ANSYS to NASTRAN to make it more compatible with GLAST project office –Re-built model to improve dynamic analysis capabilities –Model is used to generate system structural response and interface limit loads Subsystem models updated –New TKR model from Hytec—including bottom tray and flexure design modifications –Updated ACD model from GSFC—with new mass baseline –Incorporated reduced CAL model from NRL –New Radiator model from LM— including size and mount point modifications –Re-built electronics—new model based on current E-Box and interface designs –Grid Box model modified—integrated wing and X-LAT Plate modifications have been included LAT Finite Element Model NEW FEA Model

19. LAT-PR-01967-01Section 8.2 – Structural Design19 GLAST LAT Project CDR/CD3 Review, May 12-16 2003 Subsystem FEA Model Quality Checks Subsystem model evaluation –Review model—units, orientation/coordinate system, size, mesh resolution –Review delivery report—do the report and model agree FEA model check-runs –Free-free modal analysis—check model for mechanisms –Translation check—check model for inadvertent grounding –Gravity check—check that inertial loads are reacted only at boundaries –Temperature check—check that structure is free to expand/contract Analysis comparison runs –Mass, center of mass—compare with subsystem estimate –Modal analysis—check against subsystem detailed model and report UPDATE

20. LAT-PR-01967-01Section 8.2 – Structural Design20 GLAST LAT Project CDR/CD3 Review, May 12-16 2003 LAT FEA Model Boundary Conditions Accelerations –Used LAT center-of-mass accelerations from LAT Environmental Spec. for structural load cases SC mount boundary condition mimics flexure-type connection –X-Side SC mount: LAT restrained in the Y- and Z-directions –Y-Side SC mount: LAT restrained in the X- and Z-directions Radiator mounting –Radiators mounted to Grid through Radiator Mount Bracket beams –SC boundary condition fixed in Y- direction (out-of-plane) only LAT F.E.A. Properties and Current LAT Estimates Source: LAT-TD-00564-06 “LAT Mass Status Report, Mass Estimates for Mar 2003,” 7 Mar 2003 LAT Static-Equivalent Design Accelerations Source: LAT-SS-00778-01 “LAT Environmental Specification,” March 2003 LAT F.E.A. Model Metrics UPDATE

21. LAT-PR-01967-01Section 8.2 – Structural Design21 GLAST LAT Project CDR/CD3 Review, May 12-16 2003 LAT FEA Model Quality Checks FEA model check-runs –Free-free modal analysis—check model for mechanisms –Translation check—check model for inadvertent grounding –Gravity check—check that inertial loads are reacted only at boundaries –Temperature check—check that structure is free to expand/contract Analysis comparison runs –Mass—compare model mass with LAT estimate –Center of mass—compare model center of mass with LAT estimate –Modal analysis—compare subsystem modes in LAT model against fixed-base results

22. LAT-PR-01967-01Section 8.2 – Structural Design22 GLAST LAT Project CDR/CD3 Review, May 12-16 2003 Launch and Thermal Load Case Definitions LAT Structural Analysis Load Cases UPDATE

23. LAT-PR-01967-01Section 8.2 – Structural Design23 GLAST LAT Project CDR/CD3 Review, May 12-16 2003 Integration and Test Load Case Definitions UPDATE

24. LAT-PR-01967-01Section 8.2 – Structural Design24 GLAST LAT Project CDR/CD3 Review, May 12-16 2003 Modal Analysis Results 10 modes below 75 Hz –1 significant LAT modes –Multiple ACD panel, BEA vibration modes –Multiple Radiator modes and mode combinations LAT drumhead mode –65.9 Hz at 2679 kg estimate –63 Hz at 3000 kg allocation First 10 LAT Modes LAT Drumhead Mode UPDATE

25. LAT-PR-01967-01Section 8.2 – Structural Design25 GLAST LAT Project CDR/CD3 Review, May 12-16 2003 Deflections Due to Launch Loads Grid Deflection –6.8 g thrust load at MECO produces maximum Grid bowing –Grid deflections -0.41 mm at the center of the Grid -0.09 mm at corner of the Grid LAT Deflected Shape Plot UPDATE

26. LAT-PR-01967-01Section 8.2 – Structural Design26 GLAST LAT Project CDR/CD3 Review, May 12-16 2003 Interface Load Recovery The LAT Environmental Specification is the collection point for interface loads for subsystem design and test Current load tables in the LAT Environmental Specification contain results from the Delta-PDR structural model (also being used for the current CLA cycle) –Some interface limit loads were generated by LAT static-equivalent analyses –Some limit loads were gleaned from the preliminary CLA, completed in December, 2001 The goal of CDR analysis is to generate updated loads, based on the CDR design, and compare with Delta-PDR design values –Include results for all load cases to assure that worst-case loads have been captured –Identify interfaces and load cases where CDR analysis shows higher predicts than earlier analysis  develop action plan to resolve these issues –Identify interfaces where loads have come down considerably  investigate reducing limit loads in the Environmental Specification, to increase design margin LAT Mech PDR Structural Analysis Aug, 2001 LAT PDR Structural Analysis Jan, 2002 Prelim CLA Results Out Dec 2001-Mar, 2002 Deliver Mech PDR LAT FEA (Sep, 2001) LAT Delta-PDR Structural Analysis Aug, 2002 Deliver Delta- PDR LAT FEA (Sep, 2002) LAT CDR Structural Analysis May, 2003 LAT Env Spec Mar, 2003 SC Study II Struc Models Deliver CDR LAT FEA (Jun, 2003) Spectrum Proposal Struc Model Mission PDR CLA Results Out May, 2003 LAT Env Spec Jun, 2003 Spectrum PDR Struc Model Mission CDR CLA Results Out Sep, 2003 LAT Env Spec Oct, 2003 LAT Structural Analysis Flow-down Schedule

27. LAT-PR-01967-01Section 8.2 – Structural Design27 GLAST LAT Project CDR/CD3 Review, May 12-16 2003 TKR Interface Load Recovery TKR Flexure joint –Flexures isolate the carbon-fiber TKR structure from thermal strains of the Grid –All flexure normals point to the center of a TKR module –The 8 flexures are not a kinematic mount TKR Flexure force recovery –Nodal forces are retrieved by isolating nodal forces at the TKR Flexure beam elements –All forces are expressed in local cylindrical coordinates, with the module centerline the z axis –Shear forces in theta-increasing direction have the same sign. Shear forces sum to zero. –Design limit loads are the maxima of the TKR module loads Limit loads identified for peak compressive, tensile, and shear load Peak loads all occur in corner bays Flexure Limit Loads Delta PDR Analysis Model Source: LAT-SS-00778-01 “LAT Environmental Specification,” March 2003 UPDATE

28. LAT-PR-01967-01Section 8.2 – Structural Design28 GLAST LAT Project CDR/CD3 Review, May 12-16 2003 CAL Interface Load Recovery CAL-Grid tab joint –Pins carry all shear load at joint –Bolts carry pull-out and prying loads Load recovery –Tab loads separated into shear tabs and bolted tabs –All tabs designed to peak limit loads Tab Limit Loads Delta PDR Analysis Model Source: LAT-SS-00778-01 “LAT Environmental Specification,” March 2003 UPDATE

29. LAT-PR-01967-01Section 8.2 – Structural Design29 GLAST LAT Project CDR/CD3 Review, May 12-16 2003 ACD Interface Load Recovery ACD Base Electronics Assembly (BEA) to Grid Joint –Bolted connection at 4 corners of BEA carry z-direction (thrust) loads only –Bolted and pinned connections at the center of each of the 4 sides Interface load recovery –Interface loads evaluated by retrieving nodal forces at rigid extension from Grid to BEA –Loads shown are the maximum of predicts from ACD subsystem and LAT level analysis ACD Limit Loads Delta PDR Analysis Model Source: LAT-SS-00778-01 “LAT Environmental Specification,” March 2003 UPDATE

30. LAT-PR-01967-01Section 8.2 – Structural Design30 GLAST LAT Project CDR/CD3 Review, May 12-16 2003 Electronics Interface Load Recovery Electronics Box joints –Rigid stand-offs to the CAL carry z-direction (thrust) loads, and lateral loads and moments –Flexible connection to the X-LAT Plates allow transverse motion while providing compressive pre-load Interface load/deflection recovery –Limit loads extracted from model –Max relative motion at X-LAT Plate interface also tracked, for use in finalizing the bolted joint design Electronic Box Limit Loads Delta PDR Analysis Model Source: LAT-SS-00778-01 “LAT Environmental Specification,” March 2003 UPDATE

31. LAT-PR-01967-01Section 8.2 – Structural Design31 GLAST LAT Project CDR/CD3 Review, May 12-16 2003 Structural Analysis Summary and Further Work Summary –Subsystem structural models have been updated to reflect Peer Review designs –First look at mode shapes and frequency show that the LAT has margin with respect to its frequency requirement –Structural model re-work is still in process Further Work –Verify subsystem model integration –Complete all load cases with LAT CDR model –Update subsystem interface loads, based on CDR model –Deliver model to GLAST PO for next CLA cycle –Incorporate acoustic analysis results into limit load analyses –Revise “LAT Environmental Specification” with these results –Start pre-test analysis runs Dynamic analyses to size accelerometers STE structural analyses UPDATE

32. LAT-PR-01967-01Section 8.2 – Structural Design32 GLAST LAT Project CDR/CD3 Review, May 12-16 2003 Verification Test Outline Integration and Test flow Qualification and verification flow –Strength qualification test flow –Vibroacoustic test flow Dynamic test plans (see LAT-MD-01196, “Dynamics Test Plan”) –Modal survey –Sine vibration –Sine Burst –Acoustic LAT survey plans (see LAT-MD-00895, “LAT Instrument Survey Plan”) –Optical survey –Cosmic-ray muon survey

33. LAT-PR-01967-01Section 8.2 – Structural Design33 GLAST LAT Project CDR/CD3 Review, May 12-16 2003 Integration and Test Flow LAT Integration and Test Flow UPDATE

34. LAT-PR-01967-01Section 8.2 – Structural Design34 GLAST LAT Project CDR/CD3 Review, May 12-16 2003 Strength Qualification Test Flow ACD Sub-Ass’y Sine Burst A TKR QM Sine Burst, Static Load Q ACD Shell + BFA Sine Burst Q CAL QM Sine Burst Q TEM/TPS QM’s Sine Burst Q E-Box PF QM’s Sine Burst P Grid Box Ass’y Static Load P Radiator Static Load P LAT Ass’y Sine Burst P GLAST Obs Sine Burst P Subsystem Qual Tests Subsystem Acceptance Tests

35. LAT-PR-01967-01Section 8.2 – Structural Design35 GLAST LAT Project CDR/CD3 Review, May 12-16 2003 Vibroacoustic Test Flow LAT and GLAST vibroacoustic test plan –LAT modal survey—without Radiators, while at SLAC –LAT sine vibration—without Radiators; includes sine sweep signature –LAT acoustic—without Radiators –GLAST Observatory sine vibration—with Radiators but without solar arrays (TBR); includes sine sweep signature –GLAST Observatory acoustic—with Radiators but without solar arrays (TBR) –GLAST Observatory shock—shock event applied at PAF separation plane ACD Sub-Ass’y Sine Vibe, Random Vibe A ACD Sub-Ass’y Acoustic A TKR Qual Module Sine Vibe, Random Vibe Q TKR Flt Modules Sine Vibe, Random Vibe A ACD Shell + BFA Sine Vibe, Random Vibe Q ACD Shell + BFA Acoustic Q CAL QM’s Sine Vibe, Random Vibe Q CAL FM’s Random Vibe A TEM/TPS QM’s Sine Vibe, Random Vibe Q TEM/TPS FM’s Random Vibe A E-Box PF QM’s Sine Vibe, Random Vibe P Grid Box Ass’y P Radiator Sine Vibe P Radiator Acoustic P LAT Ass’y Modal Survey, Sine Vibe P LAT Ass’y Acoustic P GLAST Obs Sine Vibe P GLAST Obs Acoustic P Subsystem Qual Tests Subsystem Acceptance Tests GLAST Obs Shock P

36. LAT-PR-01967-01Section 8.2 – Structural Design36 GLAST LAT Project CDR/CD3 Review, May 12-16 2003 LAT Modal Survey Test goals –Validate the LAT structural finite element analysis (FEA) model by correlating with test results –Measure all primary modes of the LAT/Grid structure. –Measure the first mode, and all modes predicted to have high mass participation, for every subsystem –Measure as many natural frequencies of the LAT up to 150 Hz as practical –Test results will be used to evaluate the predicted expected modal frequencies and mode shapes, and used to modify the structural FEA, if needed. –Finalize test environments and notching plans for sine vibration testing Configuration –Fully integrated, except the Radiators are not mounted –Supported off of its spacecraft (SC) mount brackets, –+Z-axis point vertically up –LAT powered off during testing Specialized test equipment requirements –LAT supported by the Vibe Test Plate which provides a rigid support of each mount point –Vibe Test Plate sits on a massive base-isolated table, to damp high-frequency base noise being transmitted to the structure –Excited using two stingers, located under the LAT

37. LAT-PR-01967-01Section 8.2 – Structural Design37 GLAST LAT Project CDR/CD3 Review, May 12-16 2003 LAT Modal Survey (cont) Instrumentation –High-precision accelerometers mounted to the LAT and test stand Outstanding technical issues –Establish excitation levels –Finalize accelerometers for test, based on predicted test levels Source: LAT-MD-01196-01, “LAT Dynamics Test Plan,” March 2003 ACD Accelerometer Placement CAL Bottom and E-Box Accelerometer Placement TKR, CAL, and Grid Accelerometer Placement

38. LAT-PR-01967-01Section 8.2 – Structural Design38 GLAST LAT Project CDR/CD3 Review, May 12-16 2003 LAT Sine Vibration Test Test goals –Verify the LAT’s ability to survive the low frequency launch environment –Test for workmanship on hardware such as wiring harnesses, MLI, and cable support and strain-reliefs which will not have been fully verified at the subsystem level –Interface verification test for subsystem structural interfaces to the LAT Grid Configuration –Fully integrated, except the Radiators are not installed –Supported off of its spacecraft (SC) mount brackets, on the Vibration Test Stand –The LAT is tested in all three axes, X, Y, and Z independently, requiring re-configuration between tests –The LAT is powered off during sinusoidal vibration testing, and the E-GSE cable harnesses removed Specialized test equipment requirements –The Vibe Test Stand must support the LAT at the SC interface with flight-like connections –The Stand must allow for reconfiguration to alternate axes, with the LAT attached, to avoid unnecessary handling

39. LAT-PR-01967-01Section 8.2 – Structural Design39 GLAST LAT Project CDR/CD3 Review, May 12-16 2003 LAT Sine Vibration Test (cont) Instrumentation –Accelerometers mounted to the LAT and test stand, to cover the entire dynamic range predicted for the LAT and subsystems Outstanding technical issues –Accelerometer sensitivity—pre-test dynamic analysis will indicate the level of precision and dynamic range needed for this test –Finalize LAT degrees of freedom at STE connection (simulating a “fixed” connection or a flexure) –Establish test levels based on Observatory CLA, without exceeding interface limit loads Source: LAT-MD-01196-01, “LAT Dynamics Test Plan,” March 2003 TKR, CAL, and Grid Accelerometer Placement Radiators Accelerometer Placement LAT Sine Vibration Minimum Test Levels

40. LAT-PR-01967-01Section 8.2 – Structural Design40 GLAST LAT Project CDR/CD3 Review, May 12-16 2003 LAT Sine Burst Test Test goals –Complete qualification of the LAT interface to the SC, and surrounding regions Configuration –Same configuration as the sine vibe test Specialized test equipment requirements –Same requirements as the sine vibe test Instrumentation –Same instrumentation as the sine vibe test Outstanding technical issues –Establish test levels with pre-test analysis, to develop proto-qual level interface loads

41. LAT-PR-01967-01Section 8.2 – Structural Design41 GLAST LAT Project CDR/CD3 Review, May 12-16 2003 LAT Acoustic Test Test goals –Verify the LAT’s ability to survive the acoustic launch environment –Test for workmanship on LAT hardware, especially that hardware which responds to acoustic loading –Validate the acoustic analysis Configuration –LAT is fully integrated, including the Radiators –Mounted to STE using the flight-configuration bolted joint –LAT +Z-axis vertical, and with Radiators integrated to the Grid as well as to the STE at the SC strut mount points –LAT is powered off during acoustic testing, and the E-GSE cable harnesses removed Specialized test equipment requirements –The Vibe Test Stand must support the LAT in the same degrees of freedom as the SC flexures, to avoid over-constraining the Grid and Radiators –The STE fills the volume between the Radiators, so must approximate the acoustic behavior of the SC Instrumentation –Accelerometers mounted to the LAT and test stand –Microphones mounted around the LAT

42. LAT-PR-01967-01Section 8.2 – Structural Design42 GLAST LAT Project CDR/CD3 Review, May 12-16 2003 LAT Acoustic Test (cont) Outstanding technical issues –Establish acoustic fill and response requirements of STE to adequately bound response of SC –Define post-test modal signature test to verify that LAT dynamic response matches baseline –Finalize accelerometer and microphone placement –Perform pre-test acoustic analysis LAT Acoustic Test Levels Source: LAT-SS-0077801, “LAT Environmental Specification,” March 2003

43. LAT-PR-01967-01Section 8.2 – Structural Design43 GLAST LAT Project CDR/CD3 Review, May 12-16 2003 LAT Surveying Survey program goals –Verify as-integrated interface stay-clears –Verify LAT alignment requirements –Verify science performance requirements Validate analytical thermal-mechanical analysis models Develop correlation functions for thermal-mechanical distortion Predict the expected on-orbit precision of the instrument Survey program description –Optical surveying Subsystem inspection measures position of survey retro-reflector balls with respect to physical features and active elements of subsystem module After integration, laser tracker measures bearing and distances to balls on the LAT and in the integration room Data reduction of measurements produces position location information for all balls relative to room coordinate system, and prediction of measurement precision This will establish location of subsystem surfaces and features in their as-integrated positions, providing a verification check during integration –Muon surveying Uses naturally-occurring cosmic-ray muons Muons generate straight-line tracks through TKR modules Mis-alignments between modules will show up as a step in the reconstructed track With muons generating enough cross-tower tracks, the relative locations of tower can be measured This will be used to precisely establish the locations and attitudes (and changes) of TKR modules

44. LAT-PR-01967-01Section 8.2 – Structural Design44 GLAST LAT Project CDR/CD3 Review, May 12-16 2003 LAT Surveying (cont 1) LAT Optical and Muon Surveys During Integration and Test Source: LAT-MD-00895 “LAT Instrument Survey Plan”

45. LAT-PR-01967-01Section 8.2 – Structural Design45 GLAST LAT Project CDR/CD3 Review, May 12-16 2003 LAT Surveying (cont 2) Instrumentation –Laser tracker—measurement precision of instrument is less than 10 microns, but actual precision is more a function of room temperature stability, reflector ball location precision –Tracker—measurement precision and instrument calibration will be verified with Calibration Unit beam tests at SLAC Specialized test equipment requirements –Room temperature controlled to within 5 o C (TBR) –LAT and GSE/STE temperature stable to within 2 o C (TBR) –Support stands allow for leveling the LAT to within 0.2 degrees to ensure proper functioning of heat pipes –Chill plates provide a heat sink for the Grid during in-air testing Outstanding technical issues –Investigating the use of inclinometers during thermal-vacuum testing –Thermal-mechanical model of LAT in test configuration has not yet been done—this is needed to establish precision and stability requirements for STE

46. LAT-PR-01967-01Section 8.2 – Structural Design46 GLAST LAT Project CDR/CD3 Review, May 12-16 2003 Summary of Structural Test Issues and Closure Plans

47. LAT-PR-01967-01Section 8.2 – Structural Design47 GLAST LAT Project CDR/CD3 Review, May 12-16 2003 Summary and Conclusions UPDATE Structural Analysis Summary Verification Test Summary Conclusions Summary –LAT Dynamics Test Plan has been written and is ready for initial release –LAT Thermal Test Plan has been written and is ready for initial release –LAT Survey Plan has been written, with final pieces coming together for release before CDR –Test instrumentation and levels are understood Further work –Perform pre-test analysis to finalize instrumentation and STE requirements –Expand test plans with results of pre-test analysis –Complete test implementation plans