GLAST LAT Project September 15, 2006: Pre-Shipment Review Presentation 3 of 12 SE Overview 1 GLAST Large Area Telescope LAT Pre-Shipment Review Systems Engineering Pat Hascall Systems Engineering Stanford Linear Accelerator Center Gamma-ray Large Area Space Telescope

GLAST LAT Project September 15, 2006: Pre-Shipment Review Presentation 3 of 12 SE Overview 2 LAT System Engineering Overview Requirements Baseline Maintenance –Specifications –Interface Control Documentation –Waiver Requests (See Section 10) Design Baseline Maintenance –Design Documentation Configuration Management –Design Changes Since PER Requirements Verification Plan (See Section 5) –Traceability to tests, analysis, inspection –Running Sell Process with GSFC Project Office

GLAST LAT Project September 15, 2006: Pre-Shipment Review Presentation 3 of 12 SE Overview 3 Documentation Status The SE related documentation: see next chart (s) –LAT Specification Current –Traceability to verification complete –Verification Cross Reference Matrix Released –LAT Test Plan Released –Three pending changes to LAT-S/C ICD: See later chart –Several Waivers in Process: See NCRs and Waivers –One pending requirement update in 433-IRD-0001 I&T documentation status: See I&T presentation QA documentation status: See QA presentation No significant documentation liens

GLAST LAT Project September 15, 2006: Pre-Shipment Review Presentation 3 of 12 SE Overview 4 Documentation Status (continued) RFAs from previous reviews –See Systems Engineering Web site for dPDR, PDR, and CDR RFA closures glast.slac.stanford.edu/systemengineering/RFAS/RFAS.htmhttp://www- glast.slac.stanford.edu/systemengineering/RFAS/RFAS.htm –Two PER RFA’s open #1: Alignment Verification –Response: Updated response provided #8: NCR/Waiver Review for Unidentified Current and Residual Risks –Response: LAT project/NASA review and update included in this package

GLAST LAT Project September 15, 2006: Pre-Shipment Review Presentation 3 of 12 SE Overview 5 Key Documentation Mission Level Documents 433-SRD-0001: GLAST Science Requirements Document 433-IRD-0001: GLAST Science Instrument – Spacecraft Interface Requirements Document 433-SPEC-0001: GLAST Mission System Specification 433-OPS-0001: GLAST Operations Concept 433-MAR-0001: Mission Assurance Requirements (MAR) for GLAST LAT 433-RQMT-0005: GLAST EMI Requirements 433-ICD-0001: GLAST LAT-GBM Burst Interface Control Document 1196 EI-Y46311: SC-LAT Interface Control Document 1196 EI-S46310: 1553 Interface Control Document LAT Level Documents LAT-SS-00010LAT-SS-00010: LAT Performance Specification LAT-SS-00778LAT-SS-00778: LAT Environmental Specification LAT-SS-00115LAT-SS-00115: Mechanical Subsystem Specification (in final release cycle) LAT-SS-00715LAT-SS-00715: TCS Performance Specification LAT-SS-00019LAT-SS-00019: Trigger & Dataflow Subsystem Specification LAT-TD-00399LAT-TD Software Requirements Specification LAT-SS-00016LAT-SS-00016: ACD Subsystem Specification LAT-SS-00017LAT-SS-00017: Tracker Subsystem Specification LAT-SS-00136LAT-SS-00136: Power Subsystem Specification LAT-SS-00018LAT-SS-00018: CAL Subsystem Specification LAT-MD-00446LAT-MD-00446: LAT SVAC Plan LAT-MD-00408LAT-MD-00408: LAT Performance Verification Plan LAT-MD-02730LAT-MD-02730: LAT Performance and Operations Test Plan LAT-MD-07658LAT-MD-07658: LAT Verification Cross Reference Matrix

GLAST LAT Project September 15, 2006: Pre-Shipment Review Presentation 3 of 12 SE Overview 6 SC-LAT ICD Pending Changes ICN #TitleDescriptionStatus -096 Unregulated Power Voltage For shorts periods of time, the SC will be unable to provide the minimum 25V for the unregulated feeds. The voltage may get as low as 23V.GSFC review -099LAT Integration This is an appendix to the ICD that is meant to capture agreements for Observatory I&T activities.Approved -100LAT Impedance Incorporate into ICD the as-measured LAT differential impedance. Pending SC PRU Measurement -109LAT VCHP Overvoltage The SC limits the voltage on the SIU and DAQ feeds but not on the VCHP feeds.In review -111MLI InterfaceMinor changes to the MLI interface, i.e. velcro sizeIn sign off – SC-LAT ICD EIY C is released –The table below lists pending changes

GLAST LAT Project September 15, 2006: Pre-Shipment Review Presentation 3 of 12 SE Overview 7 Overview of Subsystem Changes Since PER Design Changes Flowed From LAT MRB Process –Changes incorporated in final design documentation –All changes consistent with LAT-SC ICD Residual Design Liens Against Flight Software discussed in FSW presentation Mechanical –Minor blanket modifications Flight Software –Boot code updated

GLAST LAT Project September 15, 2006: Pre-Shipment Review Presentation 3 of 12 SE Overview 8 LAT End Item Data Package The LAT Project provides an EIDP consisting of the following documents, data, and other materials –LAT-level subsystem-level requirements specifications Acceptance test data packages for subsystems –Requirements verification plans and test plans –LAT-level test procedures and reports, and links to test execution logs and records –Open nonconformance reports and waivers –Integration and test records Assembly and Inspection Data Sheets Integration records: mate/demate, installation logs, material mix records –EGSE and MGSE documentation All LAT project documentation is maintained in hardcopy and electronic form at SLAC –The EIDP is a subset EIDP posted on the Pre-Shipment Review Agenda Page: – tmlhttp:// tml EIDP is currently being populated

GLAST LAT Project September 15, 2006: Pre-Shipment Review Presentation 3 of 12 SE Overview 9 Residual Risks ID # Risk Rank Risk Description Risk MitigationStatus SE Low If individual tracker towers do not meet performance requirements due to manufacturing issues (e.g. wire bond breaks) then the LAT may not meet science requirements Reduced On Orbit temperature excursions Optimized placement of towers A/B based on individual tower performance Trending tracker efficiency/dead channels throughout integration testing No current concern for mission performance over life expected Proj Mgt Low If Tracker Noise Flares (NCR684), increase an order of magnitude and spread then some risk to overall tracker noise performance Monitor for occurrence Verified no significant change during TVAC Continue trend in Observatory Test Observed noise is an order of magnitude lower than a concern level and isolated No increased trend during system test to date Elect Low If spare GASU (AEM) FPGA failure (NCR897) is inherent in the design then mitigation on flight unit could impact schedule Complete part failure analysis Survey of part failure records Complete assessment of root cause Part failure analysis & survey complete Root cause identified, no known flight issue

GLAST LAT Project September 15, 2006: Pre-Shipment Review Presentation 3 of 12 SE Overview 10 Residual Risks (Cont) ID # Risk Rank Risk Description Risk MitigationStatus Elect Low If SIU reboot (NCR 880) is an inherent design flaw then loss of data until reboot completed Completed existing data analysis Additional diagnostics/data gathering plan in place Data gathering plan in place should another reboot occur SE- 014 Low If ACD PMTs become noisy again (NCR626), then ACD ability to perform background rejection may be reduced More stringent PMT high voltage screening All noisy tubes were replaced in the flight ACD Flight PMTs are operated at voltages less than voltages that produced noise No new noisy PMTs have appeared after thousands of tube-hours of screening at high voltage Conservative Wiebull prediction shows extremely low chance of potentially noisy PMTs making it through the screening. Elec- 007 Low If the unused QCLK floating pins on PCI FPGA impacts part reliability then mission redundancy may be reduced Completed vendor analysis indicating no known failure mode or impact on reliability Completed LAT analysis indicating no known failure analysis Consider risk of grounding pins should alternative need to open box occurs GSFC Mission Office review and concurrence, no known risk at this time

GLAST LAT Project September 15, 2006: Pre-Shipment Review Presentation 3 of 12 SE Overview 11 Residual Risks (Cont) ID # Risk Rank Risk Description Risk MitigationStatus Elect Low If EPU reboot (NCR 881) is an inherent design flaw then loss of data until reboot completed Completed existing data analysis Additional diagnostics/data gathering plan in place Data gathering plan in place should another reboot occur Elect Low If EPU 0 reboot (NCR 902) is an inherent design flaw then loss of data until reboot complete0 Completed existing data analysis Additional diagnostics/data gathering plan in place Data gathering plan in place should another reboot occur Elect- 012 Low If LATC Verify Errors (NCR855) re- occur on orbit then LAT will not execute science run until corrected Completed existing data analysis Additional diagnostics/data gathering plan in place Consider FSW changes to allow science run with these specific Errors No re occurrence reported since FSW Data gathering plan in place should another LATC verify error occur

GLAST LAT Project September 15, 2006: Pre-Shipment Review Presentation 3 of 12 SE Overview 12 Residual Risks (Cont) ID # Risk Rank Risk Description Risk MitigationStatus Elect Low If EPU reboots (NCR 948) are an inherent design flaw then loss of data until reboot completed Completed existing data analysis Additional diagnostics/data gathering plan in place Data gathering plan in place should another reboot occur Elect Low If EPU reboots (NCR 949) are an inherent design flaw then loss of data until reboot completed Completed existing data analysis Additional diagnostics/data gathering plan in place Data gathering plan in place should another reboot occur

GLAST LAT Project September 15, 2006: Pre-Shipment Review Presentation 3 of 12 SE Overview 13 Residual Risks (Cont) ID # Risk Rank Risk Description Risk MitigationStatus Proj Mgt Low If decision to conduct tracker environmental tests with non flight cable configurations (Waiver ) results in future failure then tracker redundancy may be compromised Tracker cables are redundant Full CPT’s conducted in flight configuration Trackers to be tested at LAT and Observatory Environmental tests No failures to date Continue to monitor thru test program Proj Mgt Low If Tracker flex cables/MCM’s fail that had failed coupons (Waiver ) then Tracker redundancy may be impacted Tracker cables/MCMs are redundant Trackers to be tested at LAT and Observatory Environmental tests No failures to date Continue to monitor thru test program Proj Mgt- 018 Low If finalization of FSW Science Algorithms is delayed or impacts LAT functional performance then Observatory Test Schedule could be impacted FSW build (B1.0) plan in place to add Science requirements New Science Algorithms do not impact established LAT performance Significant CPU/Memory margin to accommodate minor growth Plan to maximize early LAT runtime at SASS Well defined build planning with Proj Office involvement in change control TVAC eval of CPU peak performance indicate small (acceptable) temperature increase with worst case utilization Non interference LAT runtime planning in work

GLAST LAT Project September 15, 2006: Pre-Shipment Review Presentation 3 of 12 SE Overview 14 LAT Mass Properties

GLAST LAT Project September 15, 2006: Pre-Shipment Review Presentation 3 of 12 Page Number 15 LAT Power Status

GLAST LAT Project September 15, 2006: Pre-Shipment Review Presentation 3 of 12 SE Overview 16 LAT Power Status (Continued) Survival Power ComponentCurrentSubsystem Power Estimates (W) Alloc.PARACALCMEASTotalMargin On-Orbit Average Power Total % Regulated VCHP Power Total % Unregulated Passive Survival Power % 1 Power status reflects the LAT steady state orbit average. Numbers do not reflect transition into or out of survival mode, i.e. early orbit operations.

GLAST LAT Project September 15, 2006: Pre-Shipment Review Presentation 3 of 12 SE Overview 17 FSW Resource Usage ResourceTotal AvailableCurrent Usage Margin Factor Source EPU Boot EEPROM (SUROM) 256 kB62 kB*4*B SIU Boot EEPROM (SUROM) 256 kB62 kB*4*B EPU EEPROM6 MB0.59 MB10B SIU EEPROM6 MB0.73 MB8.2B EPU CPU cycles200% in 2 EPUs40%> 5Estimate SIU CPU cycles100% in 1 SIU25%4Estimate EPU memory128 MB16-32 MB4-8Estimate SIU memory128 MB< 16 MB8Estimate * Storing multiple copies (4 currently to use available memory) for risk mitigation

GLAST LAT Project September 15, 2006: Pre-Shipment Review Presentation 3 of 12 SE Overview 18 Instrument Bandwidth Resources ResourceMax Total BW limited by Hardware Max limited by SC- ground transmissi on Ave current BW at 10 KHz max trigger rate* Ave current BW at 2 KHz nominal trigger rate* Margin Factor (for 10 KHz rate) Detector to GASU-EBM45N/A GASU-EBM to EPU-CPU20N/A514 EPU-CPU to GASU-EBM *0.02*2 GASU-EBM to SIU-CPU *0.015*2 SIU-CPU to Spacecraft *0.015*2 EBM: Event-Builder Module EPU: Event-Processing Unit SIU: Spacecraft Interface Unit LAT communication, bandwidth (BW) in Mbyte/sec * Present performance of event filter for EPU- CPU, still being optimized. Eventually the physics filter will be adjusted/loosened to take advantage of the max average bandwidh

GLAST LAT Project September 15, 2006: Pre-Shipment Review Presentation 3 of 12 SE Overview 19 Unit Run Time These unit run times start after the LAT was completely integrated and cover through the completion of the CPT after TV –Does not include integration testing –Does not include unit testing

GLAST LAT Project September 15, 2006: Pre-Shipment Review Presentation 3 of 12 SE Overview 20 LAT System Engineering Summary Process for verification closure with GSFC in place SE Review of LAT Environmental Tests and verification status indicate ready to ship