The impact of accelerometry on CHAMP orbit determination |
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| Authors: | S Bruinsma S Loyer J M Lemoine F Perosanz D Tamagnan |
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| Institution: | (1) Centre National d'Etudes Spatiales, Department of Terrestrial and Planetary Geodesy, 18 Avenue E. Belin, 31401 Toulouse cedex 4, France; e-mail: sean.bruinsma@cnes.fr; Tel.: +33-561332920; Fax : +33-561253098, FR;(2) NOVELTIS, 2 Avenue de l'Europe, 31520 Ramonville-Saint-Agne, France, FR |
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| Abstract: | The contribution of the STAR accelerometer to the CHAMP orbit precision is evaluated and quantified by means of the following
results: orbital fit to the satellite laser ranging (SLR) observations, GPS reduced-dynamic vs SLR dynamic orbit comparisons,
and comparison of the measured to the modeled non-gravitational accelerations (atmospheric drag in particular). In each of
the four test periods in 2001, five CHAMP arcs of 2 days' length were analyzed. The mean RMS-of-fit of the SLR observations
of the orbits computed with STAR data or the non-gravitational force model were 11 and 24 cm, respectively. If the accelerometer
calibration parameters are not known at least at the few percent level, the SLR orbit fit deteriorates. This was tested by
applying a 10% error to the along-track scale factor of the accelerometer, which increased the SLR RMS-of-fit on average to
17 cm. Reference orbits were computed employing the reduced-dynamic technique with GPS tracking data. This technique yields
the most accurate orbit positions thanks to the estimation of a large number of empirical accelerations, which compensate
for dynamic modeling errors. Comparison of the SLR orbits, computed with STAR data or the non-gravitational force model, to
the GPS-based orbits showed that the SLR orbits employing accelerometer observations are twice as accurate. Finally, comparison
of measured to modeled accelerations showed that the level of geomagnetic activity is highly correlated with the atmospheric
drag model error, and that the largest errors occur around the geomagnetic poles.
Received: 7 May 2002 / Accepted: 18 November 2002
Correspondence to: S. Bruinsma
Acknowledgments. The TIGCM results were obtained from the CEDAR database. This study was supported by the Centre National d'Etudes Spatiales
(CNES). The referees are thanked for their helpful remarks and suggestions. |
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| Keywords: | : Orbit determination – Accelerometer – Non-gravitational force model |
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