PSR Section 21

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Section 21 Enhanced Formation Flying (EFF)
. . . Dave Folta EO-1 Enhanced Formation Flying
Lead
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EFF Design
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Performance Required

• Mission Orbit Requirements
• Paired Scene Comparison Requires EO-1 to Fly in
  Formation With Landsat-7.
• Maintain EO-1 Orbit With Tolerances Of
• One Minute Separation Between Spacecraft
• Maintain Separation So That EO-1 Follows Current
  Landsat-7 Ground Track to /- 3 Km
• Derived Orbit Requirements
• 6 Seconds Along-track Separation Tolerance
  (Maps To /- 3km Wrt Earth Rotation)
• Plan Maneuver in 12 Hours
• Derived Software Constraints
• Code Size approximately lt650Kbytes
• CPU Utilization approx. lt50 Average
• over 5 Hours
• Less than 12 Hours Per Maneuver Plan

EO-1 Formation Maneuver Frequency Is
Ballistic Dependent
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EFF Verification Approach

• Level-1 Autocon-gUsing a PC and Workstation
  Environment to Develop, Test, Provide High
  Fidelity Simulations, Script Development, and
  Proof of Concept Fuzzy Logic Rules
• Level-2 Software Test FacilityUsing Mongoose
  Breadboard With Flight Software, Test All
  Interfaces to the ACS and CDH for Telemetry and
  Commanding. Utilized Simulated Tensor Data and
  Noise
• Level-3 SpacecraftUsing Spacecraft Mongoose
  Etc., Test Against Realistic CPU Loading, GPS
  Constellation Simulator and Tensor, Etc.

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Subsystem Level

• Verify
• EFF
• AutoCon-F
• GSFC
• JPL
• GPS Data Smoother
• SCP
• Algorithm Flight
• Code Uploads
• for JPL

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EFF Verification Matrix
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EFF Test Results

• AutoCon-F Numerical Benchmark Testing
• AutoCon-F Was Benchmarked Against AutoCon-G for
  Each Build
• EFF/AutoCon-F MG5 Testing
• Will It Fit and Execute on the EO-1 MGV Processor
  
• EFF/AutoCon-F Interface and Numerical Accuracy
  Testing Performed on the Test String From October
  1998 to August 1999
• EFF/AutoCon-F Testing on EO-1 (gt20 Hours of
  Testing Onboard)
• EFF/AutoCon-F Successfully Executed on EO-1 in
  April 1999
• Round 1 of CPT in July Found Increasing Time
  Required for Maneuver Planning and Unacceptable
  CPU Utilization
• Round 2 of CPT on September 1 Passed All Test
  Criteria
• EFF/AutoCon-F Successfully Executed During
  Thermal Vac in October 1999
• GPS Smoother Testing
• Conducted on the Test String Using Simulated
  Tensor Data
• Scheduled for Spacecraft Testing on December 7,
  1999 Using Real Tensor Data From Simulated GPS
  Constellation

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EFF CPT Test Results

• Criteria Passed
• GSFC Targeter Produces Maneuver Plan
• GSFC Targeter Maneuver Consistently Reproduced
• JPL Targeter Code Uploaded
• JPL Targeter Produces Maneuver Plan
• CPU Utilization Within Limits

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CPT Test Timeline

• 2353L EFF_cpt.prc started.
• 0004L Table upload complete
• 0016L GSFC targeter produced first maneuver plan
• 0025L GSFC targeter produced identical maneuver
  replan
• 0025L JPL targeter code uploaded started
• 0115L JPL targeter code upload completed and JPL
  maneuver planning started
• 0200L JPL targeter produced maneuver
• 0201L GSFC targeter tables started being reloaded
• 0208L GSFC targeter table upload completed and
  GSFC targeting restarted
• 0217L GSFC targeter produced identical maneuver
  replan
• 0220L Test complete. EFF left running on
  spacecraft to simulate a heavy load on the
  spacecraft for the remaining CPT testing.

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Configuration Changes

• EFF Tested During S/C CPT
• Parsing of Execution to Minimize CPU Utilization
  - Logic Error
• Code Changes for Step Size Control of Propagator
  - Code Error
• Storing of Spacecraft State Table
  - Initialization Error
• GPS Leap Second Sign Change - Logic Error
• EFF Tested in Thermal Vac
• No Changes
• Positive Independent Verification
• Of EFF Made Using Test Bed and
• Ground Software, AutoCon-G

Sample EO-1 / L7 Formation
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Action Item Status

• Action
• Additional S/C Level Functional Testing to
  Eliminate Risk Due to GPS Smoother (scheduled Dec
  7)
• High Degree of Confidence That EFF Flight
  Software Functions Correctly and Will Be Able to
  Successfully Autonomously Control EO -1 /
  Landsat7 Formation
• On-orbit Check Out Procedure Will Allow for
  Software Adjustment Via Scripts,Table Loads, and
  Patches

Readiness Residual Risk