GLAST Large Area Telescope:

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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
• Cost Schedule Summary
• Requirements, Traceability Interfaces
• System FMEA/PRA/Reliability T. Thurston
• System Verification T Leisgang

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LAT System Engineering Overview
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Design Maturity Summary
PDR Delta Baseline Review
Subsystem CDR Peer Reviews
LAT Ready For S/C IT
Mature Stable Requirements Since SRR Interfaces
With Spacecraft Established and Reflected in CDR
Design
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PDR dPDR, Peer Review RFA Closure

• PDR RFAs Submitted, xx of 57 Closed
• Working with GSFC on residual issues
• Calorimeter to grid attachment
• EMI/EMC box level acceptance test
• dPDR RFAs Submitted, xx of 20 Closed
• No design drivers identified
• LAT Initial responses under review by GSFC
• Subsystem CDR Peer Review RFAs

Subsystem Number Of RFAs Status
ACD 19
Calorimeter 30
Electronics/FSW 26
Tracker 39
Mechanical 48
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LAT Mass Status
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LAT Power Status
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FSW Resource Usage Current Estimates
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 EPU 20 MB/sec 5 MB/sec 4
Bandwidth EPU or SIU to SSR 5 MB/sec 40 kB/sec 112
Bandwidth CPU to CPU 2.5 MB/sec 20 kB/sec 125
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Key Science Performance Metrics
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Configuration Management

• 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

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Management Plans
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Change Control Process
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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 Risks
ID Risk Rank Risk Description Risk Mitigation Mitigation Status
Moderate On track
Moderate On track
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System Requirements , Traceability Interfaces
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Specification Tree
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Requirements Development
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)
CCB changes, document updates and test planning
Critical Design Review (May 12-16, 2003)
Reqts. docs imported and linked in DOORS
Reqts. in DOORS linked to planned tests and
analyses.
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.
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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
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Requirements Traceability and Verification
Effective Area Requirement Flowdown
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Requirements Traceability and Verification
Effective Area Requirement Flowdown
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Requirements Traceability and Verification
Example of Flowdown from Mission System
Specification
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Requirements Traceability and Verification
Example of Flowdown from Interface Requirements
Document

• Verification of this requirement includes
  hardware and software components.

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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
  6/13/2003)
• Bring DOORS database up-to-date with recently
  released test plans (ECD 6/30/2003)
• Release reports for all requirements verified by
  analysis (ECD 7/31/2003)
• Long term
• Prepare requirements verification table for level
  2 and 3 requirements
• Link requirements to test procedures (ECD June
  2004)
• Link requirements to test data packages (On-going
  as tests are completed. ECD June 2005)

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Interface Development
Update coming from Rich B.
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Structural/Thermal Interface Overview
Update coming from Rich B.
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Electrical Interface Overview
Update coming from Rich B.
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Interface Documentation Status
Update coming from Rich B.
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LAT Internal Interfaces
Update coming from Rich B.
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LAT External Interfaces
Update coming from Rich B.
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Key Open Interface Issues
Update coming from Rich B.
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Summary

• Weekly Telecons and Frequent Splinter Meetings
  have resulted in
• LAT-SC ICD released
• TKR, CAL and ACD ICDs released and contain 0
  TBXs
• Electronics-LAT Mechanical/Thermal ICD near
  completion and soon to be released
• All Interface Definition Drawings released
• Key open interface issues to be resolved by June
  2003

Update coming from Rich B.
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GLAST Large Area Telescope LAT
FMEA/PRA/Reliability Tim Thurston
SLAC thurston_at_slac.stanford.edu
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System FMEA/PRA/Reliability
Update To LAT Level From Tim Thurston
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GLAST Large Area Telescope System Engineering
Subsystem WBS 4.1.2 Tom Leisgang LAT Systems
Engineering Test Verification toml_at_slac.stanfor
d.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 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 Dynamics
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Performance Verification Electronics
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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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Systems Engineering

• DRAFT
• Cost/Schedule Summary

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CCB Actions Affecting 4.1.2
Change Request Description Status
LAT-XR-01395-01 Systems Engineering Manpower Approved 2.2M
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Budget, Cost, Performance
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Cost/Schedule Status

• Status as of February 28, 2003

Item In k
Budget at Complete 4,647
Budgeted Cost for Work Scheduled (a) 2,583
Budgeted Cost for Work Performed (b) 2,577
Actual Cost for Work Performed 2,880
Cost Variance -302 -11.7 of (b)
Schedule Variance -6 -.2 of (a)
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Manpower Plan
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Procurements

• Long-Lead Procurements
• Major Upcoming Procurements Near-Term (lt 4
  months)
• Orbital Network Engineering
• Stellar Solutions
• Major Upcoming Procurements Long-Term (gt4 months)
• Minor Upcoming Procurements

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Summary

• To be provided