GLAST Large Area Telescope:

1
GLAST Large Area Telescope LAT System
Engineering WBS 4.1.2 Dick Horn SLAC System
Engineering Manager Dhorn_at_slac.stanford.edu 650
926-8578
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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
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 ICDs
• 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
Design Maturity Summary
PDR Delta Baseline Review
Subsystem CDR Peer Reviews
LAT Ready For S/C IT
Mature Stable Requirements Since SRR Key
Interfaces With Spacecraft Established and
Reflected in CDR Design
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PDR DPDR, Peer Review RFA Closure

• PDR RFAs 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 RFAs Submitted, 17 of 20 Closed
• No design drivers identified
• LAT Initial responses under review by GSFC
• Subsystem CDR Peer Review RFAs

Current Status of all RFAs Available at LAT
System Engineering Website
Subsystem Closed/Total
ACD 17/19
Calorimeter 12/30
Electronics/FSW 23/26
Tracker 17/39
Mechanical 19/48
I T 17/21
Subsystem talks will address key open RFAs
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LAT Mass Status
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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
Resource Total Available Anticipated Usage Margin Factor
EPU Boot PROM 256 kB 128 kB 2
SIU Boot PROM 256 kB 128 kB 2
EPU EEPROM 4 MB 1.5 MB 2.7
SIU EEPROM 8 MB 1.5-2.5 MB 3-5
EPU CPU cycles 200 in 2 EPUs 30 gt 6
SIU CPU cycles 100 in 1 SIU 25 4
EPU memory 128 MB 16-32 MB 4-8
SIU memory 128 MB lt 16 MB 8
Bandwidth instrument to EBM 45 MB/sec 10 MB/sec 4.5
Bandwidth EBM to CPU 20 MB/sec 5 MB/sec 4
Bandwidth CPU to EBM 2.5 MB/sec 20 kB/sec 125
Bandwidth EBM to SSR 5 MB/sec 40 kB/sec 125
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Key Science Performance Metrics
11
Management Plans
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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

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Change Control Thresholds
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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)
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Top System Risks
ID Risk Rank Risk Description Risk Mitigation Status
CAL-004 High Delay in deliveries of flight CDEs Our French collaborators are in the middle of a competitive procurement for the industrial partner that will fabricate all flight CDEs. The procurement process must follow French law and is potentially subject to the delay of administrative reviews The selected industrial partner must design and fabricate appropriate tooling, develop controlled manufacturing process, fabricate and qualify CDE prototypes, and then fabricate 108 CDE for the CAL Qual model by mid Sept, 2003 A higher CDE manufacturing rate is an option to the French contract but may present financial and technical risks. The higher rate would deliver the later modules on schedule. Current top program issue
Proj Mgt - 001 Moderate Inadvertent use of non-flight qualified processes, parts or materials results in cost/schedule impact. EEE Parts Plan In-place. Material Review Board. Preproduction readiness reviews Processes in place
Proj Mgt - 002 Moderate ASICs fail to meet requirements results in schedule impact Focused review test. Margin for re-runs protected where possible Individual risks Identified by subsystem Processes in place
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Top System Risks (continued)
ID Risk Rank Risk Description Risk Mitigation Status
SE--0010 Moderate Inadequate End to End LAT test simulation leads to undetected H/W or S/W problem until at observatory test or on orbit Key early performance integration interface testing through engineering model test bed Early integration of Spacecraft Simulator into development and IT Audit test opportunities and value (Airplane test, T/C Tests) Evaluation of planned functional performance tests to identify residual risks (6/17/03) Finalizing details of S/C Simulator (TBD)
SE--0007 Moderate Critical component failure post LAT integration requiring de-integration impacting cost schedule Extensive use of EM test bed to support flight H/W S/W development Thorough qualification and acceptance tests Pre planned IT actions for de-integration Completed evaluation for improving access (9/02) Qual acceptance planning in-place IT developing contingency plans
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System Requirements, Traceability
Interfaces Section 7-2
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Specification Tree
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Requirements Development
Resulting Level 3 traceability to verification
plans is documented in LAT-TD-02084-01
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Key Requirements Flow
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Key Level 2 Requirements
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Requirements Traceability and Verification
Example of Flowdown from Science Requirements
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Requirements Traceability and Verification
Effective Area Requirement Flowdown
Example from LAT-TD-02084-01, LAT Requirements
Tracking Report
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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)

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Key LAT Interface Overview
Tracker (TKR) Tracker (TKR)
Structural Grid Ti flexure mount
Thermal Conductive Cu strap
Electrical 1.5V, 2.5V, 2.5VDig, 150V Bias Data, Temp sensors, S/W
IT Lift fixture, Electrical test stand
Anticoincidence Detector (ACD) Anticoincidence Detector (ACD)
Structural Grid bolted joint, shear pins
Thermal Conductive bolted joint Radiative coupling w/ TKR
Electrical 3.3V, 28V Data, Temp sensors, S/W
IT Lift fixture, Electrical test stand
Electronics Electronics
Structural Stand-off to CAL Bolted stack Cabling
Thermal Thermal joint to X-LAT Plate
Electrical 27-29V Regulated, Data, S/W
IT Test bed
Calorimeter (CAL) Calorimeter (CAL)
Structural Grid pinned/bolted joint
Thermal Conductive bolted joint
Electrical 3.3V, 3.3VDig,100V Bias Data, Temp sensors, S/W
IT Alignment Tool, Lift fixture, Electrical test stand
GBM GBM
Structural Cabling
Thermal None
Electrical LVDS, 1553 Telecommands
IT None
Spacecraft Spacecraft
Structural Four-point mount to SC flexures, Two-point pinned struts for each radiator
Thermal Isolated (SC Mount, Radiator struts) Radiative (S/A)
Electrical 27-29V Regulated, 25-35V Unregulated, MIL-STD-1553B, Analog and digital sensors, LVDS, EMI/EMC, High speed serial science data
IT Grid perimeter ring, Radiator handling fixture, Radiator lift fixture, Purge, LAT test point
TCS/X-LAT Plate/Radiators TCS/X-LAT Plate/Radiators
Structural Bolted/pinned joints
Thermal Heat pipes, Heaters
Electrical 27-29V Regulated, 25-35V Unregulated Temp sensors, S/W
IT Radiator handling fixture, Radiator lift fixture, X LAT Plate lift fixture, Electrical test stand
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Structural/Thermal Interface Overview
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Spacecraft-LAT Electrical Interface
4 Voltages
SC CDH
4 Temperatures, 8 Voltages
Grid and Antifreeze Survival Heaters
4 Voltages
32 Temperatures
Y
LAT
Science Data
Command Telemetry
SIU
LPDU
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
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Internal LAT Electrical Interfaces
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Key TKR-LAT Interface Requirements
AAnalysis, DDemonstration, IInspection,
TTest TKR-LAT Mechanical and Thermal ICD,
LAT-SS-00138 and TKR-LAT Electrical ICD,
LAT-SS-00176
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Key CAL-LAT Interface Requirements
AAnalysis, DDemonstration, IInspection,
TTest CAL-LAT Mechanical, Thermal and
Electrical ICD, LAT-SS-00238
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Key ACD-LAT Interface Requirements
AAnalysis, DDemonstration, IInspection,
TTest ACD-LAT Mechanical, Thermal and
Electrical ICD, LAT-SS-00363
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Key Electronics-LAT Interface Requirements
AAnalysis, DDemonstration, IInspection,
TTest Electronics-LAT Mechanical and Thermal
ICD, LAT-SS-01794
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Key Open Internal LAT Interface Issues
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Internal LAT Interface Compliance Issues
AAnalysis, DDemonstration, IInspection, TTest
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Key LAT-SC Interface Requirements 1/3
Requirement is being developed
AAnalysis, DDemonstration, IInspection, TTest
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Key LAT-SC Interface Requirements 2/3
AAnalysis, DDemonstration, IInspection, TTest
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Key LAT-SC Interface Requirements 3/3
AAnalysis, DDemonstration, IInspection, TTest
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Key Open External LAT Interface Issues
Face-to-face technical interchange meeting is
scheduled for May 21 22 to discuss remaining
interface issues.
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Interface Documentation Status
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Summary

• Weekly Telecons and Frequent Splinter Meetings
  have resulted in
• LAT-SC ICD released
• LAT-SC 1553 ICD released
• TKR, CAL and ACD ICDs released and contain 0
  TBXs
• Electronics ICD w/ 5 TBXs 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

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System Engineering LAT FMEA/PRA/Reliability Secti
on 7-3 Tim Thurston SLAC thurston_at_slac.stanford
.edu
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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 RTDF
? .96 RTML/STRU ? .99
RTKR
RCAL
RACD
RTDF
RTML/STRU
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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
AEM
BEA
TDA
GASU
SIU
PDU


MMS/MLI
EPU
AEM


GASU
SIU
PDU
2 of 2
Standby
Standby
Standby
Standby
EPU
11 of 12
94 of 96
RACD .9568
RTDF .9884
Standby
2 of 3
STRU
TML
RTKR .989
RLAT .882
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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.

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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
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System FMEA/PRA/Reliability
Fault Tree Analysis LAT-TD-01757-01

• FTAs completed on EPUs, ACD, CAL, TKR, STR,
  TML, GASUs, PDUs, SIUs, TEMs, TEM/PSs
• 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

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System FMEA/PRA/Reliability

• Probabilistic Risk Assessment Component Watch
  List (1 of 2)

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System FMEA/PRA/Reliability

• Probabilistic Risk Assessment Component Watch
  List (2 of 2)

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System Engineering Test Verification Planning
Section 7-4 Tom Leisgang LAT Systems
Engineering Test Verification toml_at_slac.stanford
.edu
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Requirements Verification Process
A tested and certified instrument
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LAT Test Plan Organization
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LAT Performance Verification
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LAT End to End System Verification

• LAT System Verification
• Front End _at_ Subsystem
• TDF In Test Bed
• Integrated LAT _at_ IT
• System Throughput in Test Bed
• Uses event simulators
• Man-made events
• Science Verifications
• Engineering Models
• Qualification Units
• Calibration Units
• Integrated LAT
• Final Verification
• By correlated analysis
• Risk
• Event Processing _at_ orbital rates/distributionnot
  checked

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LAT Science Verification
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Subsystem Qualification Programs
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Subsystem Acceptance Test Program
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Performance Verification Thermal
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Performance Verification Mechanical
62
Performance Verification Electronics
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Performance Verification Flight Software
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LAT Verification Summary

• All LAT subsystems and LAT Instrument have
  complete requirements verification
• All MAR test requirements are performed and
  verified
• All Science Requirements are verified
• Systems Engineering has a closed loop
  requirements verification process in place

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Cost/Schedule Summary Section 7-5
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CCB Actions Affecting 4.1.2
Change Request Description Status
LAT-XR-01395-01 Systems Engineering Manpower Approved 1.8M
LAT-XR-01752-02 SLAC/HEPL Labor Escalation Rates Approved -16K
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Budget, Cost, Performance
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Cost/Schedule Status

• Status as of March 31, 2003

Item In k
Budget at Complete 6,453
Budgeted Cost for Work Scheduled (a) 3,049 (a)
Budgeted Cost for Work Performed (b) 3,049 (b)
Actual Cost for Work Performed 3,029
Cost Variance 20 0.7 of (b)
Schedule Variance 0 0 of (a)
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Summary

• Independent Technical Peer Reviews have been
  completed
• Open issues identified
• Closure plans in work (see Subsystem detailed
  talks)
• Configuration Management Processes in place
• Key metrics established
• Continuous Risk Management process in place
• LAT System Interfaces are established and under
  CCB Control
• LAT FMEA and Fault Tree Analyses baselined
• Verification planning and oversight in place