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Gamma-ray Large Area Space Telescope. GLAST Large Area Telescope LAT Pre-Shipment Review Systems Engineering Pat Hascall Systems Engineering Stanford Linear Accelerator Center. LAT System Engineering Overview. Requirements Baseline Maintenance Specifications Updated
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Gamma-beam Large Area Space Telescope GLAST Large Area Telescope LAT Pre-Shipment Review Systems Engineering Pat Hascall Systems Engineering Stanford Linear Accelerator Center SE Overview

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LAT System Engineering Overview Requirements Baseline Maintenance Specifications Updated Interface Control Documentation Waiver Requests (See Section 7) Design Baseline Maintenance Design Documentation Configuration Management Design Changes Since CDR Requirements Verification Plan (See Section 4) Traceability to tests, examination, investigation Running Sell Process with GSFC Project OFfice LAT System Test Plan (See Section 4) Defines Required Tests to Support Verification LAT Environmental Test Plan (See Section 4) Defines Environmental Test Flow & Requirements Based on GLAST MAR SE Overview

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Documentation Status The SE related documentation: see next diagram (s) No Liens on prerequisites and flowdown LAT Specification Current Traceability to confirmation finish Verification Cross Reference Matrix Released LAT Test Plan Released Three pending changes to LAT-S/C ICD: See later outline Several Waivers in Process: See Later Talk I&T documentation status: See I&T presentation QA documentation status: See QA presentation No huge documentation liens SE Overview

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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-00010 : LAT Performance Specification LAT-SS-00778 : LAT Environmental Specification LAT-SS-00115 : Mechanical Subsystem Specification (in definite discharge cycle) LAT-SS-00715 : TCS Performance Specification LAT-SS-00019 : Trigger & Dataflow Subsystem Specification LAT-TD-00399    Software Requirements Specification LAT-SS-00016 : ACD Subsystem Specification LAT-SS-00017 : Tracker Subsystem Specification LAT-SS-00136 : Power Subsystem Specification LAT-SS-00018 : CAL Subsystem Specification LAT-MD-00446 : LAT SVAC Plan LAT-MD-00408 : LAT Performance Verification Plan LAT-MD-02730 : LAT Performance and Operations Test Plan LAT-MD-07658 : LAT Verification Cross Reference Matrix SE Overview

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SC-LAT ICD Pending Changes SC-LAT ICD EIY46311-000C is discharged The accompanying table records pending changes Issues Well In Hand – No Risks Anticipated SE Overview

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Overview of Subsystem Changes Since CDR Design Changes Flowed From LAT MRB Process & CDR Liens Changes joined in conclusive outline documentation Validated through subsystem test programs LAT benchmark plan now executed Resulting changes to coordinated LAT plan have been actualized All progressions predictable with LAT-SC ICD Residual Design Liens Against Flight Software FSW Qualification Test Baselined at 0-6-6 (149/183 rqmts) Delta FQT Planned Pre-TVAC Added Science related channels/diagnostics GRB Detection Final information pressure FSW Standards SE Overview

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Calorimeter Changes Since CDR FM CAL: GRID interface altered to consolidate shear pins 4 shear pins included, mounting tabs balanced EMI/EMC upgrades Exterior metal surface treatment changed to electroless nickel plating EMI gaskets and O-rings seal splits Extra power separating added to AFEE cards PIN photodiodes: somewhat littler, distinctive optical window material Flight outline has been completely qualified ASICs: GCFE and GCRC have extra correction for flight from that utilized on EM CAL Flight screening complete; capability program finishes on 10/15 AFEE load up Improved PIN diode associations; extra sifting Removed Novacap; new QML top substitution Voltage ref diode ebb and flow restricting resistor adjusted FM composite structures utilize an enhanced (autoclaved) curing process Each structure checked for quality in vibration test program SE Overview

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ACD Design Changes Since CDR Mechanical The side layers of Kevlar in the Micrometeoroid Shield were expanded from 6 layers to 8 layers because of an overhaul to NASA\'s orbital flotsam and jetsam show. Adjusted the mechanical mounting of the Photomultiplier Tubes (PMTs). Transformed from a Silicone pruned mounting technique to warm remunerated mechanical mounted. This plan change required a change to the attractive protecting of the PMTs too. Outline change required to avoid splitting of the PMT glass tubes. Minor outline changes on the PMT Housings and fiber bushing tops were made to enhance the light-snugness Composite board aluminum honeycomb grounded The whole Tile Shell Assembly (with Tile Detector Assemblies) was raised 1mm regarding the Base Electronics Assembly and the Large Area Telescope interface. Tile Detector Assemblies and Clear Fiber Cables Redesigned the wave moving and clear fiber connectors to advance gathering and light fixing the identifiers and fiber links. SE Overview

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ACD Design Changes Since CDR (II) Electrical Changed from a 3 autonomous Printed Circuit Board (PCB) stack for the resistor system to a flex board plan. Change set aside a few minutes and enhance unwavering quality. GARC Parity Bit. The way the GARC executes the GAFE summon equality estimation was not reliably dependable so a work around in programming was required (e.g., we ascertain the charge equality in programming and sidestep the equipment count) to determine the issue. GARC Look-at-Me circuitry.  There are two Look-at-Me circuits, an essential and an optional, and every requirements a clock amid power-on reset to introduce properly.  On the FREE load up it was important to cross-strap the approaching differential clock to give these underlying heartbeats to both sides  of the hardware. HVBS establishing change. Amid interface testing between the HVBS and FREE sheets a typical mode commotion issue was found. A capacitor was added to the HVBS and the issue was determined. An aluminized Kapton shield was set between the two FREE sheets on the four twofold column Electronic Chassis. The was done to avoid self prompted obstruction between the two FREE Boards, particularly the GAFE\'s (simple ASIC). SE Overview

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Tracker Changes Since CDR Front-End Electronics: Added a resistor to the tri-state transport for the GTFE control enlist readback, to keep it from drifting when in the high impedance state. Changed the MCM clock transport end from 100 ohms to 75 ohms. Changed the flex-circuit link end resistors from 100 ohms to 75 ohms. Expanded VDD from 2.5V to 2.65V to enhance correspondence edges. Added a Kapton layer to the back of the MCM to enhance electrical disengagement furthermore enhanced the MCM design to diminish the danger of an inclination voltage short. Altered a rationale bug in the GTRC TOT calculation and in the GTRC-to-GTRC correspondence timing. Diminished inside deferrals and expanded drive energy to enhance GTFE-to-GTFE and GTFE-to-GTRC correspondence edges. Disposed of the cover layer from the MCM pitch connector, all together oblige gathering resistances. Changed from Nanonics connectors to Omnetics connectors. Changed the ground-shield plane of the predisposition circuit from incubated ½-oz copper to strong ¼-oz copper. The whole point by point geometric design of the flex-circuit links was revamped post-CDR. The greatest change was to bring 4 of the links up over the edge of the top plate, with 180-degree twists. Added tape and froth to the flex-circuit links, to guarantee that they can\'t move and won\'t be harmed once the sidewalls are put on. SE Overview

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Tracker Changes Since CDR (II) Interface of the MCMs to the Trays Eliminated the mounting screws and exchange cement and built up a totally new method to bond the MCM to the plate with epoxy, including little aluminum arrangement sticks that included washers for setting the bondline thickness. Wiped out the exemplification of wire bonds from the MCMs to the SSDs and inclination circuits (except for two mid plate, which were embodied before this change was made). Stepping stools: Eliminated epitome of wire bonds between SSDs in stepping stools for overwhelming plate and base plate (aside from in Towers An and B). Plate and Converter Foils Added a space to (nearly) cut the substantial thwarts down the middle. Included a carving and preparing venture for all foils. Executed a plan to electrically associate the aluminum center and carbon structure to the MCM ground. SE Overview

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Tracker Changes Since CDR (III) Sidewalls: Put aluminum thwarts on both sides, not simply all things considered. Changed latches from 100 countersink to 120 countersink to appropriate the heap better and anticipate crazing of the carbon-fiber material. Included a locking component for the latches (Solithane on the strings) Eliminated gaps for assessment and rolled out point by point improvements to design of arrangement gaps. Tower-Grid Interface: Complete latch overhaul, in light of the settled unusual cones and studs. Adding locking components to the latches. Flexures changed to have funnel shaped openings. New plan of the clasp on the Grid side of the interface. Totally new CMM and arrangement strategy, in light of the new interface. Best Tray: Added machined corner sections to bolster arrangement homes and the flex-circuit link terminations. Included aluminum protecting over the whole top of the plate, in addition to dark paint on the top. SE Overview

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TEM and TEM Power-Supply Changes Since CDR TEM FPGA code concluded Flow-control changed somewhat to streamline dataflow all through framework Some resistor/capacitor values have changed to improve checking ranges Details of observing circuit have changed and a sub-set of current checking capacities wer

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