1. GLAST Large Area Telescope:
Gamma-ray Large Area Space Telescope
GLAST Large Area Telescope:
Instrument System Engineering
Tim Thurston
Stanford Linear Accelerator Center
Stanford University
LAT Instrument System Engineer

2. Instrument System Engineering
Outline
Requirements &Subsystem Reviews
Design Integration
Systems Analysis
Configuration Management & Control
Next Quarter Plan

3. Requirements Reviews – Level III
Subsystem Requirements Reviews.
ACD Completed March 20
Tracker Completed March 22
Calorimeter Completed March 28
Science Analysis Software Completed April 20
Electronics & DAQ Completed April 25
Mechanical Completed May 2
IOC Completed May 3

4. Subsystem PDR’s (Peer Reviews)
Subsystem Preliminary Design Reviews (SS-PDR)
Tracker Complete - June 19
ACD Complete - July 26
Performance and Simul. Complete - July 26
Calorimeter Complete – July 27
Mechanical August 15
Electronics, DAQ, & Flt S/W August 16
IOC& Science Analysis S/W August 17
Instrument Preliminary Design Review ( I-PDR)
Draft Submittal Mid September
PDR Submittal Week of October 8
I-PDR/Baseline Review Week of October 29

5. LAT SPECIFICATION TREE
Level I
Project Specifications
Program Plan Requirements
Level II System Specifications
Level II(a) System
Operations Concept Document
433-OPS-0001
Science Req’ts Document
433-SRD-0001
Mission Assurance Requirements
433-MAR-0001
Mission System Specification
433-SPEC-0001
Level II(b) Element
Spacecraft Performance Spec.
LV Interface Specification
LAT-SC IRD
433-IRD-0001
GBM Instrument Performance Spec.
Science Support Center Spec.
SGL Comm Interface Spec.
Mission Operations Center Spec.
GBM IOC Specification *
LAT Instrument Performance Spec. LAT-SS-00010
LAT IOC Performance Spec.
LAT-SS-00015 * *
Level III
Subsystem Specifications * *
LAT - ACD Spec. LAT-SS-00016
LAT - TKR Spec. LAT-SS-00017
LAT - CAL Spec. LAT-SS-00018 *
LAT Subsys. ICD
LAT-SS-00137
LAT SAS Spec. LAT-SS-00020 * * * * * *
LAT - T&DF Spec.
LAT-SS-00019
LAT Mech. Spec.
LAT-SS-00115 *
LAT IOC Spec. LAT-SS-00021
* SS-PDR
Complete
Level IV
Design Specifications
LAT Design Spec.
LAT-SS-00???
LAT Design Spec.
LAT-SS-00???
LAT Design Spec.
LAT-SS-00???
* LIII Spec.
Review
Complete
LAT Design Spec.
LAT-SS-00???
LAT Design Spec.
LAT-SS-00???
LAT Design Spec.
LAT-SS-00???
LAT Design Spec.
LAT-SS-00???
LAT Design Spec.
LAT-SS-00???

6. Integration Issues IDT issues addressed over past quarter:
SAA protection Scenario
Subsystem Interface – Module pitch adjustment, ACD envelope change
Performance simulation parameters identified
Interface definitions matrix drafted
Concept, system & design documentation
Operational scenarios and concepts

7. Integration Issues

8. System Analysis
Efforts continue to identify the necessary system analyses for validation and verification. Areas under review are:
Instrument degradation and performance impact
Command, control and data interfaces
Autonomy functions and processes
Operating modes and transition
Data triggering, filtering, collection, archiving and dissemination
Health monitoring and command processing
Non-standard operating modes – primarily those associated with component(s) or partial system failure.
Operation anomalies – Ground and Onboard

9. System Analysis Risk and Reliability FEMA working group was formed.
Subsystem reliability and operability targets were established.
Reliability block diagrams for subsystems have been drafted. Critical elements are being addressed.
No single point failure exist for the LAT instrument.
The performance degradation associated with component failures is being analyzed. This is expected to continue beyond PDR. With the conservative margin of the LAT design, the LAT reliability targets should be easily achieved.

10. Configuration Management and Control
Document, Requirements, and Change Control
LAT Document Management System (LDMS) is up and operational. LDMS provides WEB capture and distribution for all LAT document.
Change Procedures are being utilized. SE is the control point for controlled documents.
DOORS requirements tracking tool is operational. Requirements are yet to be loaded in to the tool.
Data capture & control
No progress since last quarterly review.