CHAMP and GRACE accelerometer calibration by GPS-based orbit determination |
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Authors: | Tom Van Helleputte Eelco Doornbos Pieter Visser |
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Institution: | aDelft Institute of Earth Observation and Space Systems (DEOS), Delft University of Technology, 2629 HS Delft, The Netherlands |
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Abstract: | Current and planned Earth observation missions are equipped with highly sensitive accelerometers. Before using the data, the instrument has to be calibrated by determining scale and bias parameters for each axis. Here, the accelerometer measurements are used in a GPS-based reduced-dynamic orbit determination approach, replacing the non-gravitational force models, and nominally daily calibration parameters are estimated. Additional empirical accelerations are estimated to account for deficiencies in the applied force models. This method is applied to 5 years of CHAMP and GRACE data, resulting in an orbit precision at the level of a few centimeters. In along-track direction the calibration parameters can be estimated freely, scale factors of 0.96 ± 0.014 and 0.95 ± 0.015 are obtained for GRACE A and B, and 0.85 ± 0.024 for CHAMP. A constant scale factor results in the smoothest bias series, with clear trends and occasional jumps. In radial and cross-track direction tight constraints to a priori biases have to be applied. Furthermore, the determined orbits are analyzed with respect to reference trajectories, and SLR, phase and KBR residuals are presented. |
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Keywords: | Orbit determination Accelerometer Calibration GPS GRACE CHAMP |
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