GLAST Proposal Review

1
LAT Structural Systems
Martin Nordby nordby_at_slac.stanford.edu With
contributions from Youssef Ismail John Ku Mike
Foss Rich Bielawski Michael Lovelette Jim
Haughton Eric Gawehn Larry Wai
15 Apr 2003
2
Agenda

• Design Overview
• LAT design
• Design and interface changes since Delta PDR
• CCB actions, trade studies, and open issues
• Peer Review RFAs 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
Mechanical Design Overview
LAT Structural Design Parameters LAT Structural Design Parameters LAT Structural Design Parameters
Design Spec
Mass 2679.4 kg lt3000 kg
Center of Gravity 149.3 mm lt185 mm
Width 1806 mm lt1820 mm
Height 1081.5 mm 1100 mm
Tracker (TKR) Tracker (TKR)
Mass 504.9 kg (Mar 2003 est)
Size 372 mm sq x 640 h
Interfaces Grid Ti flexure mount and Cu strap
Calorimeter (CAL) Calorimeter (CAL)
Mass 1375.8 kg (Mar 2003 est)
Size 364 mm sq x 224 mm h
Interfaces Grid bolted friction joint
Anticoincidence Detector (ACD) Anticoincidence Detector (ACD)
Mass 270.1 kg (Mar 2003 est)
Size 1806 mm w x 1081.5 mm h
Interfaces Grid bolted joint, shear pins
UPDATE
Grid/X-LAT Plate/Radiators Grid/X-LAT Plate/Radiators
Mass 329.3 kg (Mar 2003 est)
Size 1580 mm sq x 236 mm h
Interfaces Four-point mount to SC flexures
LAT Mass Budget and Current Estimates (kg) LAT Mass Budget and Current Estimates (kg) LAT Mass Budget and Current Estimates (kg)
Estimate Budget
TKR 504.9 510.0
CAL 1375.8 1440.0
ACD 270.1 280.0
Mech 329.3 345.0
Elec 199.3 220.0
LAT Total 2679.4 3000
Source LAT-TD-00564-6 LAT Mass Status Report Mass Estimates for Mar 2003 Source LAT-TD-00564-6 LAT Mass Status Report Mass Estimates for Mar 2003 Source LAT-TD-00564-6 LAT Mass Status Report Mass Estimates for Mar 2003
Electronics Electronics
Mass 199.3 kg (Mar 2003 est)
Size 1417 mm sq x 222 mm h
Interfaces Stand-off to CAL thermal joint to X-LAT Plate
LAT Overview
4
System Block Diagram
TKR Module CFC tray, side walls
ACD Base Elec Assy alum frame
MLI Surrounding ACD
Grid monolithic alum structure
Spacecraft LAT mounting structure
Spacecraft SC bus structure
CAL Modules alum bottom plate
Solar Arrays S.A. mount
Elec. Boxes alum electronics box
Radiator Mnt Bkt Support Radiators at corners of
Grid
EMI Skirt Shields E-Boxes, supports X-LAT Pl
LAT Radiators on /- Y sides of LAT Grid
X-LAT Plate monolithic alum structure
Htr Switch Boxes Operate Radiator heaters
MLI Insulation MLI surrounding underside of LAT
LAT Block Diagram
5
LAT Design Details
Radiator Mount at Grid corners. Note mid-side
Grid Wing
UPDATE
Grid corner detail showing heat pipes, purge
grooves corner chamfer and bottom flange for ACD
Copper thermal straps
Reverse-angle view of VCHP S-bends and DSHP
connection
TKR mid-side and corner flexures
6
LAT Interface Details
UPDATE
Grid Wing with SC mount bracket
EMI Skirt cut-outs around SC stay-clear
SC proposed interface stay-clear on top of
octagonal SC volume
PAF, per Boeing PPG
LAT inside LV fairing static stay-clear
7
LAT Underside Design Details
Empty boxes
GASU box
SIU boxes
UPDATE
Upside-down view of a Grid Y mid-side, showing
DSHPs, Grid Wing, and EMI Skirt
PDU box
TPS (16x)
EPU boxes
TEM (16x)
LAT Underside View of Electronics Boxes
Detail of TEM, TPS, and EPU box stack
8
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

9
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 m2
• 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 Spectrums flexure design
• Agreed to final LAT and SC stay-clear geometry
  around flexure

10
Design Changes Since Delta PDR (cont)
VCHP S-bends
UPDATE
SC-LAT mount region still in work
Radiator panels widened and shortened, reducing
thermal efficiency
Panels cut-out locations fixed
LAT Delta PDR Design July 2002
LAT CDR Design Mar 2003
11
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 Mechanical System Schematic Diagram
LAT Schematic Diagram
13
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
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
Structural RFAs from Peer Review
UPDATE
16
LAT Requirements Flow-Down
17
Key LAT Configuration and Structural Requirements
UPDATEOrigin of Req
18
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 Hytecincluding bottom tray
  and flexure design modifications
• Updated ACD model from GSFCwith new mass
  baseline
• Incorporated reduced CAL model from NRL
• New Radiator model from LMincluding size and
  mount point modifications
• Re-built electronicsnew model based on current
  E-Box and interface designs
• Grid Box model modifiedintegrated wing and X-LAT
  Plate modifications have been included

NEW FEA Model
LAT Finite Element Model
19
Subsystem FEA Model Quality Checks

• Subsystem model evaluation
• Review modelunits, orientation/coordinate
  system, size, mesh resolution
• Review delivery reportdo the report and model
  agree
• FEA model check-runs
• Free-free modal analysischeck model for
  mechanisms
• Translation checkcheck model for inadvertent
  grounding
• Gravity checkcheck that inertial loads are
  reacted only at boundaries
• Temperature checkcheck that structure is free to
  expand/contract
• Analysis comparison runs
• Mass, center of masscompare with subsystem
  estimate
• Modal analysischeck against subsystem detailed
  model and report

UPDATE
20
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 Static-Equivalent Design Accelerations
Source LAT-SS-00778-01 LAT Environmental
Specification, March 2003
UPDATE
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 F.E.A. Model Metrics
21
LAT FEA Model Quality Checks

• FEA model check-runs
• Free-free modal analysischeck model for
  mechanisms
• Translation checkcheck model for inadvertent
  grounding
• Gravity checkcheck that inertial loads are
  reacted only at boundaries
• Temperature checkcheck that structure is free to
  expand/contract
• Analysis comparison runs
• Masscompare model mass with LAT estimate
• Center of masscompare model center of mass with
  LAT estimate
• Modal analysiscompare subsystem modes in LAT
  model against fixed-base results

22
Launch and Thermal Load Case Definitions
UPDATE
LAT Structural Analysis Load Cases
23
Integration and Test Load Case Definitions
UPDATE
24
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

UPDATE
LAT Drumhead Mode
First 10 LAT Modes
25
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

UPDATE
LAT Deflected Shape Plot
26
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
LAT Delta-PDR Structural Analysis Aug, 2002
LAT CDR Structural Analysis May, 2003
Deliver Mech PDR LAT FEA (Sep, 2001)
Deliver Delta- PDR LAT FEA (Sep, 2002)
Deliver CDR LAT FEA(Jun, 2003)
Mission PDR CLA Results Out May, 2003
Mission CDR CLA Results Out Sep, 2003
Prelim CLA Results Out Dec 2001-Mar, 2002
SC Study II Struc Models
Spectrum Proposal Struc Model
Spectrum PDR Struc Model
LAT Env Spec Mar, 2003
LAT Env Spec Jun, 2003
LAT Env Spec Oct, 2003
LAT Structural Analysis Flow-down Schedule
27
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-increasingdirection have
  the same sign. Shear forces sum to zero.
• Design limit loads are the maximaof the TKR
  module loads
• Limit loads identified for peakcompressive,
  tensile, and shear load
• Peak loads all occur in corner bays

UPDATE
Flexure Limit LoadsDelta PDR Analysis Model
Source LAT-SS-00778-01 LAT Environmental
Specification, March 2003
28
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

UPDATE
Tab Limit LoadsDelta PDR Analysis Model
Source LAT-SS-00778-01 LAT Environmental
Specification, March 2003
29
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

UPDATE
ACD Limit LoadsDelta PDR Analysis Model
Source LAT-SS-00778-01 LAT Environmental
Specification, March 2003
30
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

UPDATE
Electronic Box Limit LoadsDelta PDR Analysis
Model
Source LAT-SS-00778-01 LAT Environmental
Specification, March 2003
31
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
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
Integration and Test Flow
UPDATE
LAT Integration and Test Flow
34
Strength Qualification Test Flow
Subsystem Acceptance Tests
Subsystem Qual Tests
35
Vibroacoustic Test Flow

• LAT and GLAST vibroacoustic test plan
• LAT modal surveywithout Radiators, while at SLAC
• LAT sine vibrationwithout Radiators includes
  sine sweep signature
• LAT acousticwithout Radiators
• GLAST Observatory sine vibrationwith Radiators
  but without solar arrays (TBR) includes sine
  sweep signature
• GLAST Observatory acousticwith Radiators but
  without solar arrays (TBR)
• GLAST Observatory shockshock event applied at
  PAF separation plane

Subsystem Acceptance Tests
Subsystem Qual Tests
36
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 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

ACD Accelerometer Placement
CAL Bottom and E-Box Accelerometer Placement
TKR, CAL, and Grid Accelerometer Placement
Source LAT-MD-01196-01, LAT Dynamics Test
Plan, March 2003
38
LAT Sine Vibration Test

• Test goals
• Verify the LATs 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 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 sensitivitypre-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

TKR, CAL, and Grid Accelerometer Placement
Radiators Accelerometer Placement
LAT Sine Vibration Minimum Test Levels
Source LAT-MD-01196-01, LAT Dynamics Test
Plan, March 2003
40
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 Acoustic Test

• Test goals
• Verify the LATs 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 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 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 Surveying (cont 1)
LAT Optical and Muon Surveys During Integration
and Test
Source LAT-MD-00895 LAT Instrument Survey Plan
45
LAT Surveying (cont 2)

• Instrumentation
• Laser trackermeasurement precision of instrument
  is less than 10 microns, but actual precision is
  more a function of room temperature stability,
  reflector ball location precision
• Trackermeasurement precision and instrument
  calibration will be verified with Calibration
  Unit beam tests at SLAC
• Specialized test equipment requirements
• Room temperature controlled to within 5 oC (TBR)
• LAT and GSE/STE temperature stable to within 2 oC
  (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 donethis is
  needed to establish precision and stability
  requirements for STE

46
Summary of Structural Test Issues and Closure
Plans
47
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