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CLOCK ALIGNMENT, ORBIT DETERMINATION QUALITY ASSURANCE

CLOCK ALIGNMENT, ORBIT DETERMINATION QUALITY ASSURANCE. od_constellation.pl tdp2clk1b.pl gni1a2gnv1b.pl kbr_prefit.pl. Why. GRACE USO’S Run Free Relative clock needs to be < 0.16 ns for 0.5  m range error. Common Clock Bias < 100 ns => < 0.7 mm orbit error Orbit Determination

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CLOCK ALIGNMENT, ORBIT DETERMINATION QUALITY ASSURANCE

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  1. CLOCK ALIGNMENT, ORBIT DETERMINATIONQUALITY ASSURANCE od_constellation.pl tdp2clk1b.pl gni1a2gnv1b.pl kbr_prefit.pl

  2. Why • GRACE USO’S Run Free • Relative clock needs to be < 0.16 ns for 0.5 m range error • Common Clock Bias < 100 ns => < 0.7 mm orbit error • Orbit Determination • Geometric Corrections to Phase Center • K-Ka Light Time Correction

  3. How, od_constellation.pl, + • GPS fixed to FLINN Solution • Currently 3 cm comparison to IGS • < 3 cm scatter from high elevation SLR with older less accurate FLINN • Latency ~10 days • Solution Strategy • 30 hour data arcs (6 hour overlaps) • Reduced Dynamics • Accelerometer may be incorporated later • White noise clocks • Epoch State, Drag, Solar Scale, Stochastic Accelerations

  4. Functional Tests • Use CHAMP data in place of GRACE • 3 Days Successfully Processed for GRACE A & B • Some parameter tuning will be necessary for GRACE

  5. In Flight Quality Assurance

  6. Preflight Quality Assurance • Look at CHAMP orbit and clock overlaps • CHAMP has a poor oscillator • Look at Ground Station Clock Synchronization with GPS

  7. CHAMP Clock Overlaps

  8. CHAMP Clock Overlaps

  9. Station Clock Tests Expected Improvements: USN1, Currently 10’s ns reference clock changes

  10. CHAMP Orbit Overlaps

  11. Summary • Clock Calibration/Orbit Determination Process is preflight ready • Some Post launch tuning is necessary

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