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Precision Orbits Analysis for CHAMP Gravity Field: Insights from UCPH and EGM96 Data

This paper discusses the utilization of precise orbits for gravity field models based on 10 s data from August 2001, presented during the CHAMP Science Meeting in Potsdam (Sept. 2, 2003). The research applies energy conservation methods and various friction calculations to enhance results. It presents coefficients for gravity disturbances from EGM96 and assesses errors, comparing findings with EGM96 and Greenland's anomalies. Conclusions highlight the influence of solar activity on data precision and propose future improvements in attitude processing and gridding techniques to enhance data accuracy.

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Precision Orbits Analysis for CHAMP Gravity Field: Insights from UCPH and EGM96 Data

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  1. CHAMP Gravity Field Models using Precise Orbits by C.C.Tscherning & E.Howe Department of Geophysics University of Copenhagen, Denmark 2. CHAMP Science Meeting, Potsdam, Sept. 2, 2003.

  2. Introduction • 10 s data from August 2001 • TUDelft precise orbits and revised attitudes • Same method as in earlier studies 2. CHAMP Science Meeting, Potsdam, Sept. 2, 2003.

  3. Method Energy conservation 2. CHAMP Science Meeting, Potsdam, Sept. 2, 2003.

  4. Friction Calculated • (1) From velocity and y-accelerometer • (2) Scalar product of velocity and acceleration vector • (3) Bias parameter determined for each half day • (1)+(3) Gives best results 2. CHAMP Science Meeting, Potsdam, Sept. 2, 2003.

  5. Estimation of coefficients • T up/downward continued to fixed altitude or radial distance using EGM96 gravity disturbances. • Values gridded 0.5o using LSC (geogrid) • Coefficients and errors from Fast Spherical Collocation 2. CHAMP Science Meeting, Potsdam, Sept. 2, 2003.

  6. UCPH2003_03 Geoid 2. CHAMP Science Meeting, Potsdam, Sept. 2, 2003.

  7. Error-estimates x 10-11 2. CHAMP Science Meeting, Potsdam, Sept. 2, 2003.

  8. Degree-variances 2. CHAMP Science Meeting, Potsdam, Sept. 2, 2003.

  9. Error-degree variances • UCPH: solid, EGM96 ---, EIGEN-2 …. 2. CHAMP Science Meeting, Potsdam, Sept. 2, 2003.

  10. Cumulative geoid error 2. CHAMP Science Meeting, Potsdam, Sept. 2, 2003.

  11. Comparison with EGM96 0.5o gravity 212675 mean gravity anomalies with error below 5 mgal NMAX=60. 2. CHAMP Science Meeting, Potsdam, Sept. 2, 2003.

  12. Comparison Greenland 2150 5’x10’ mean gravity anomalies in North-West Greenland. 2. CHAMP Science Meeting, Potsdam, Sept. 2, 2003.

  13. Differences UCPH2003_2 - _3 2. CHAMP Science Meeting, Potsdam, Sept. 2, 2003.

  14. EIGEN-2 - UCPH2003_03 2. CHAMP Science Meeting, Potsdam, Sept. 2, 2003.

  15. CONCLUSION (I) • Data are still contaminated with considerable noise due to the still large solar activity in the selected period. • The uncertainty of scale-factors of the accelerometers and the noise in the attitude measurements reduced the precision of the calculation of the external forces. 2. CHAMP Science Meeting, Potsdam, Sept. 2, 2003.

  16. CONCLUSION (II) • Data from later periods with lower solar activity may give better results. • Attitude processing must be repeated • Gridding could be improved using general LSC and taking into account the along-track error-correlations. • Kinematic orbits may give better results 2. CHAMP Science Meeting, Potsdam, Sept. 2, 2003.

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