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COSMIC GPS Data Processing

COSMIC GPS Data Processing. Yoke Yoon Yago Andres Christian Marquardt. Introduction. Overview of Precise Orbit Determination (POD) activities COSMIC GPS data processing Status of GPS-based POD for COSMIC Preliminary results Future activities/goals

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COSMIC GPS Data Processing

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  1. COSMIC GPS Data Processing Yoke Yoon Yago Andres Christian Marquardt

  2. Introduction • Overview of Precise Orbit Determination (POD) activities • COSMIC GPS data processing • Status of GPS-based POD for COSMIC • Preliminary results • Future activities/goals • Reprocessing of COSMIC data (2006-current) for whole constellation (POD and RO) • Data reprocessing of other RO missions (CHAMP, GRACE, OceanSat-2) • NRT operational POD for future Metop-B (2012), Metop-C (2016/2017) • NRT offline POD for Jason-3

  3. Overview of GPS data processing activities (1/2) • MetOp-A operational NRT • Utilize NRT GPS orbit & clock products from GRAS Ground Support Network (operated by ESOC/ESA) • Based on (batch) sequential estimation • RO data processing • MetOp-A offline POD • Utilize Rapid GPS orbit & clock products from CODE • Based on batch estimation

  4. Overview of GPS data processing activities (2/2) • Jason-2 offline NRT POD • Utilize NRT GRAS GSN products • Batch estimation • COSMIC GPS data processing • Final (Precise) GPS products from CODE/AIUB • (POD) Batch estimation • RO data processing

  5. COSMIC GPS Data Processing • GPS-based POD status • Raw data assessment • Investigate various processing options • Orbit (internal & external) assessment • Planned POD-related activities/analysis • GPS RO (not yet started) • Processing of GPS data from the ROantennas • Derive bending angles and refractivity profiles • Timeline of reprocessing activities • COSMIC POD (from Level-0) commences after summer 2011 • POD and RO product delivery to ECMWF by end of 2012 (GRAS, COSMIC, CHAMP, GRACE)

  6. COSMIC GPS Data Processing Nominal flight direction

  7. COSMIC GPS Data Processing • Assessment of raw data • GPS receiver tracking performance over time • Easy identification of POD problems that arise from s/c tracking or data outages • Planned to be included in theoperational processing facility as part of the monitoring system for future missions COSMIC FM 6

  8. COSMIC GPS Data Processing • Assessment of raw data COSMIC FM 6 (IGOR) MetOp-A (GRAS)

  9. COSMIC GPS Data Processing • POD processing strategy • Use of quaternion for s/c orientation knowledge • GPS phase and pseudorange observations sampled at 1 min (no smoothing) • Precise GPS orbit and (30s) clock product from CODE/AUIB • Parameter settings in NAPEOS gear more toward s/c modelled dynamics • weight on phase data,  = 3 cm • weight on pseudorange,  = 6 m • 30-hr arc (6-hr overlap between consecutive arcs) • 7 consecutive days of COSMIC FM#6 GPS observation data ( 26 Nov – 2 Dec 2008 )

  10. COSMIC GPS Data Processing • Parameter estimates • COSMIC state vector (position & velocity) and clock offset • Step-wise constant drag coefficient (12/arc) • SRP coefficient (1/arc) • 1/rev sine and cosine along- and cross-track empirical accelerations (1/arc) • Carrier phase bias (per pass)

  11. COSMIC GPS Data Processing

  12. COSMIC GPS Data Processing • External orbit product for comparison • UCAR (website) • 27-hr arc (Day 1 00:00:00 – Day 2 03:00:00) • JPL (special request) • 30-hr arc (Day 0 21:00:00 – Day 2 03:00:00) • Orbit overlap assessment • Shows the median of 6 sets of overlap (RMS) statistics

  13. COSMIC GPS Data Processing • External orbit product for comparison • UCAR (website) • 27-hr arc (Day 1 00:00:00 – Day 2 03:00:00) • JPL (special request) • 30-hr arc (Day 0 21:00:00 – Day 2 03:00:00) • Orbit overlap assessment • Shows the median of 6 sets of overlap (RMS) statistics

  14. COSMIC GPS Data Processing • Inter-comparison time period • EUM vs JPL (24-hrs) 00:00:00 - 24:00:00 • EUM vs UCAR (23-hrs) 01:00:00 – 24:00:00 • UCAR vs JPL (23-hrs) • Shows the median of 7 sets of daily RMS statistics

  15. COSMIC GPS Data Processing • Planned activities • Smoothing of the quaternion Quaternion derived frommagnetometer, Earth (highest weight) & Sun sensors

  16. COSMIC GPS Data Processing • s/c orientation (Euler angles) COSMIC s/c tumbles constantlyas it does not maintain a 3-axis stable attitude

  17. COSMIC GPS Data Processing • Planned activities • Smoothing of the quaternion • Simultaneous processing of GPS data from two antennas (same s/c)(JPL COSMIC POD is based on this) POD antenna #1 from COSMIC FM 6 flight direction POD antenna #2 from COSMIC FM 6

  18. COSMIC GPS Data Processing • Preliminary assessment (overlap of DOY 332-333 of 2008) of FM2

  19. COSMIC GPS Data Processing • External assessment (average of DOY 332 & 333 of 2008) of FM2

  20. COSMIC GPS Data Processing • External assessment (average of DOY 332 & 333 of 2008) of FM2

  21. COSMIC GPS Data Processing • External assessment (average of DOY 332 & 333 of 2008) of FM2

  22. COSMIC GPS Data Processing • Planned activities • Smoothing of the quaternion • Simultaneous processing of GPS data from two antennas • Analyze the existence of an along-track bias in inter-agency orbit comparison • POD parameter tuning (i.e. drag coefficient)

  23. COSMIC GPS Data Processing • Planned activities • Smoothing of the quaternion • Simultaneous processing of GPS data from two antennas (from same s/c) • Analyze the existence of an along-track bias in inter-agency orbit comparison • Automate reprocessing of 5-6 years of data for 6 s/c

  24. COSMIC GPS Data Processing • Planned activities • Smoothing of the quaternion • Simultaneous processing of GPS data from two antennas (from same s/c) • Analyze the existence of an along-track bias in inter-agency orbit comparison • Automate reprocessing of 5-6 years of data for 6 s/c • Processing of COSMIC RO data to derive bending angle & refractivity profiles

  25. COSMIC GPS Data Processing • Planned activities • Smoothing of the quaternion • Simultaneous processing of GPS data from two antennas (from same s/c) • Analyze the existence of an along-track bias in inter-agency orbit comparison • Automate reprocessing of 5-6 years of data for 6 s/c • Processing of COSMIC RO data to derive bending angle & refractivity profiles • Challenges in automating COSMIC POD • Handling of large data gaps (especially at the beginning of the mission) • Handling of maneuvers • FM2 and FM5 had attitude control & receiver anomalies in 2007

  26. End of PresentationQuestions?

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