GLAST Large Area Telescope: LAT System Engineering WBS 4.1.2 Dick Horn SLAC System Engineering Manager Dhorn@slac.stanfo

1. Gamma-ray Large Area Space Telescope GLAST Large Area Telescope: LAT System Engineering WBS 4.1.2 Dick Horn SLAC System Engineering Manager Dhorn@slac.stanford.edu 650 926-8578

2. Topics • LAT System Engineering Overview D. Horn • Design Review Summary • Key System Performance Metrics • Configuration Management And Technical Baseline • Risk Management • Requirements, Traceability & Interfaces • System FMEA/PRA/Reliability T. Thurston • System Verification T. Leisgang • Cost & Schedule Summary D. Horn

3. Gamma-ray Large Area Space Telescope LAT System Engineering Overview Section 7-1

4. WBS 4.1.2 System Engineering 4.1.2 LAT System Engineering D. Horn System Integration & Audits D. Lung/T. Thurston Interface Develop. & Verif. R. Bielawski Test Planning & Verif. T. Leisgang/S. Sawyer • FMEA/FTA/PRA • Risk Management • Ground System Interfaces • System Reviews • Internal ICD’s • Spacecraft ICD • Interface Verification • LAT System Verification Plan • Performance Test Planning • Test Procedure Audits • Test Discrepancy Resolution Configuration Mgmt N. Cramar Requirements Mgmt W. Davis • Document Control & Release • Requirements Management • Configuration Item Data List • System Metrics

5. Fiscal Years 2000 2001 2002 2003 2004 2005 2006 2011 SRR PDR PER CriticalDesign Review BeginLAT I&T PreShipReview Ops. Prelim. & Sys. Design Final Design Engr’g Models Build & Test Flight Units LAT I&T Observatory I&T FABRICATION PHASE COMMISSIONING PHASE Design Maturity Summary PDR Delta Baseline Review Subsystem CDR Peer Reviews LAT Ready For S/C I&T Mature & Stable Requirements Since SRR Key Interfaces With Spacecraft Established and Reflected in CDR Design

6. PDR & DPDR, Peer Review RFA Closure • PDR RFA’s Submitted, 43 of 57 Closed • Key residual issues: • Calorimeter to grid attachment • Closure of Tracker Engineering Model Results • EMI/EMC box level acceptance test • dPDR RFA’s Submitted, 17 of 20 Closed • No design drivers identified • LAT Initial responses under review by GSFC • Subsystem CDR Peer Review RFA’s Current Status of all RFA’s Available at LAT System Engineering Website Subsystem talks will address key open RFA’s

7. LAT Mass Status

8. LAT Power Status LAT-TD-00125-04 Subsystem allocations have been reduced to CDR estimates to ensure LAT system CCB action for future power growth

9. FSW Resource Usage Current Estimates LAT-TD-1121-02

10. Key Science Performance Metrics

11. Management Plans

12. Configuration Management LAT CM Change Control Process LAT CM Elements • LAT CM Defined By LAT MD-00068-01 • Major Supplier CM defined internally • Key Subsystem Doc CM Transferred to LAT CM upon Subsystem Delivery to LAT • Change Control Process In Place

13. Change Control Thresholds

14. Risk Management • LAT Risk Management Defined By • LAT-MD-00067-03 • Parallel Process To GSFC …. • Continuous Process Across LAT • Risk Ranked By Probability and Impact to Technical, Cost & Schedule Risk Ranking Impact Low Risk (Selected Mitigation) Moderate Risk (Selected Mitigation) High Risk (Mitigation Required)

15. Top System Risks

16. Top System Risks (continued)

17. Gamma-ray Large Area Space Telescope System Requirements, Traceability & Interfaces Section 7-2

18. Specification Tree

19. Level 2 Reqts Peer Reviews (Aug. 2000) Level 2 Reqts placed under LAT CM LAT System Requirements Review (Sep. 2000) Level 3 Reqts Peer Reviews (Mar.-Apr. 2001) Level 3 Reqts placed under LAT CM Line-by-line reviews of LAT and IOC Performance Specs by Subsystem Mgrs, Engineering and Science Leads Updates require approval of LAT change control board Top-level subsystem performance requirements were reviewed by Subsystem Mgrs and LAT Engineering and Science Leads Updates require approval of LAT change control board Preliminary Design Reviews (Jan. & Jul. 2002) Reqts. docs imported and linked in DOORS CCB changes, document updates and test planning Reqts. in DOORS linked to planned tests and analyses. Critical Design Review (May 12-16, 2003) Impacts from changes are flowed up or down as they are identified. Level 4 Reqts developed by subsystems Level 4 Reqts placed under subsystem CM Subsystem design specifications are controlled at the subsystem level. Level 4 requirements are managed and tracked at subsystem level. Requirements Development Resulting Level 3 traceability to verification plans is documented in LAT-TD-02084-01

20. Key Requirements Flow

21. Key Level 2 Requirements

22. Requirements Traceability and Verification Example of Flowdown from Science Requirements

23. Requirements Traceability and Verification Effective Area Requirement Flowdown Example from LAT-TD-02084-01, LAT Requirements Tracking Report

24. Requirements Traceability and Verification • Future Work • Near term • Incorporate all CCB-approved Level 2 and 3 changes in requirements document revisions (ECD 6/30/2003) • Long term • Complete compliance verification table for level 2 and 3 requirements • Link requirements to test procedures (ECD June 2004) • Link compliance to test data packages & analysis reports (On-going as tests & analyses are completed. ECD June 2005)

25. Key LAT Interface Overview

26. Structural/Thermal Interface Overview

27. LVDS 1553 Power Signal Spacecraft-LAT Electrical Interface 4 Voltages SC C&DH 4 Temperatures, 8 Voltages Grid and Antifreeze Survival Heaters 4 Voltages 32 Temperatures +Y LAT Science Data Command & Telemetry LPDU SIU SIU Timing SC PRU 28V ± 1V SC PDU 25V – 35V 8 Discrete Controls DAQ +X 4 Discrete Monitors VCHP 6 Temperatures, 12 Voltages EGSE 22 Temperatures Burst Trigger 4 Voltages GBM Note: Redundancy not shown

28. Internal LAT Electrical Interfaces

29. Key TKR-LAT Interface Requirements* A=Analysis, D=Demonstration, I=Inspection, T=Test * TKR-LAT Mechanical and Thermal ICD, LAT-SS-00138 and TKR-LAT Electrical ICD, LAT-SS-00176

30. Key CAL-LAT Interface Requirements* A=Analysis, D=Demonstration, I=Inspection, T=Test * CAL-LAT Mechanical, Thermal and Electrical ICD, LAT-SS-00238

31. Key ACD-LAT Interface Requirements* A=Analysis, D=Demonstration, I=Inspection, T=Test * ACD-LAT Mechanical, Thermal and Electrical ICD, LAT-SS-00363

32. Key Electronics-LAT Interface Requirements* A=Analysis, D=Demonstration, I=Inspection, T=Test * Electronics-LAT Mechanical and Thermal ICD, LAT-SS-01794

33. Key Open Internal LAT Interface Issues

34. Internal LAT Interface Compliance Issues A=Analysis, D=Demonstration, I=Inspection, T=Test

35. Key LAT-SC Interface Requirements 1/3 Requirement is being developed A=Analysis, D=Demonstration, I=Inspection, T=Test

36. Key LAT-SC Interface Requirements 2/3 A=Analysis, D=Demonstration, I=Inspection, T=Test

37. Key LAT-SC Interface Requirements 3/3 A=Analysis, D=Demonstration, I=Inspection, T=Test

38. Key Open External LAT Interface Issues* *Face-to-face technical interchange meeting is scheduled for May 21 & 22 to discuss remaining interface issues.

39. Interface Documentation Status

40. Summary • Weekly Telecons and Frequent Splinter Meetings have resulted in: • LAT-SC ICD released • LAT-SC 1553 ICD released • TKR, CAL and ACD ICD’s released and contain 0 TBX’s • Electronics ICD w/ 5 TBX’s in review • Interface Definition Drawings released or near release • Complete Implementation of LAT-GBM ICD • All key open interface issues to be resolved by August 2003

41. Gamma-ray Large Area Space Telescope System Engineering LAT FMEA/PRA/Reliability Section 7-3 Tim Thurston SLAC thurston@slac.stanford.edu

42. System FMEA/PRA/Reliability Instrument Reliability Target: RLAT .85 for 5 year Mission Life Instrument Element Reliability Targets (Established 05/2001) RCAL .96 RTKR  .96 RACD .96 RT&DF .96 RTML/STRU .99 RCAL RTKR RACD RT&DF RTML/STRU

43. System FMEA/PRA/Reliability LAT Instrument Reliability Block Diagram TEM TEM-PS CAL TEM TEM-PS TKR 15 of 16 15 of 16 RCAL = .9776 RTKR = .9668 EPU BEA TDA AEM GASU SIU PDU MMS/MLI EPU AEM GASU SIU PDU 2 of 2 Standby Standby Standby Standby 11 of 12 94 of 96 EPU RACD = .9568 RT&DF = .9884 Standby 2 of 3 STRU TML RTKR = .989 RLAT = .882

44. System FMEA/PRA/Reliability Reliability Calculations Assumptions/Methodology • Both Mil-HDBK-217F and vendor provided data are being used for the of failure rates estimates. • LAT level reliability analysis extracted some component reliability numbers from element level reliability reports. Because of slightly different view of reliability relationships and partitioning, LAT level results vary slightly from reliability stated in element reliability reports. • All reliability numbers normalized to 30 °C ambient using Mil-HDBK-217F derating factors. The conservative factor is 1.5x improvement per 10 ° C reduction. • Massively redundant detections components, CAL and TKR, allowed to degrade up to 10%, ACD detection components allowed to degrade 2 of 96, Tower modules allowed to degrade to 15 of 16, and ACD BEA allowed to degrade to 11 of 12. All degradations expected to be within science performance margins. • Some passive elements such as resistors and wires are not included in the model. Failure rates for these elements are considered extremely low.

45. System FMEA/PRA/Reliability • CAL Module Reliability Block Diagram CAL Power Feed CAL Signal Feed CAL AFEE CAL Power Feed CAL Signal Feed CAL AFEE CAL Detector Element CAL Power Feed CAL Signal Feed CAL AFEE 43 of 48 CAL Power Feed CAL Signal Feed CAL AFEE CAL Power Feed CAL Signal Feed CAL AFEE CAL Power Feed CAL Signal Feed CAL AFEE CAL Detector Element CAL Power Feed CAL Signal Feed CAL AFEE 43 of 48 CAL Power Feed CAL Signal Feed CAL AFEE RCAL(x) = .99964

46. System FMEA/PRA/Reliability Fault Tree Analysis – LAT-TD-01757-01 • FTA’s completed on EPU’s, ACD, CAL, TKR, STR, TML, GASU’s, PDU’s, SIU’s, TEM’s, & TEM/PS’s • ~160 fault elements/components • MMS & MLI are the only single point failures identified. Probability of failure is not realistic • No other single point failures without ground contingency – (Software) • Most components multiple redundant Failure Mode & Effects Analysis - LAT-TD-00374-01 • ~ 800 failure modes identified • No severity category 1 failure modes • One element to watch w/severity category 2 failure mode • Four elements to watch w/ failure mode severity category of 2R, Two elements to watch w/ severity category of 2MR

47. System FMEA/PRA/Reliability Probablistic Risk Assessment – LAT-TD-02083-01 (Draft) • Likelihood estimates made for all fault sequences with failure mode categorization of 1, 2, 2R, 2MR • PRA watch list provided with fault sequences prioritized from most likely to least likely. • PRA watch graphically summarized in a 5x5 risk matrix. Limited Life Item Analysis - LAT-MD-00551-02 • No limited life items identified within the 5-year design life

48. System FMEA/PRA/Reliability Probabilistic Risk Assessment/FMECA Summary

49. System FMEA/PRA/Reliability Probabilistic Risk Assessment – Element Watch List

50. System FMEA/PRA/Reliability Probabilistic Risk Assessment – Component Watch List (1 of 2)