Spaceborne accelerometry and temporal gravity analysis from the CHAMP satellite mission.

摘要

The research presented in this thesis was conducted with two central objectives: (1) the development of techniques for the incorporation of satellite accelerometry in geodetic applications, and (2) the recovery of short-period temporal variations in Earth's gravity field from the tracking data of a single, low-orbiting satellite. The data used in this research consisted of double-differenced GPS carrier phase data (approximately 65,000 observations per 30-hour arc), and satellite laser ranging (SLR) data (approximately 100 observations per 30-hour arc) from the CHAMP satellite for the year 2002. The average 30-hour GPS residual RMS of reduced-dynamic orbit determination was 0.80 cm. The average residual RMS of the SLR data was 3.96 cm. The ephemeris (trajectory) estimated from reduced-dynamic processing served as pseudo-observation data for accelerometer calibration and temporal gravity recovery, eliminating the thousands of nuisance parameters associated with the GPS data. Low-rate (0.1 Hz) accelerometer data were calibrated using conventional non-conservative force models, then integrated into the equations of motion in lieu of all non-conservative forces. Attitude quaternions based on in situ star camera data were used to model spacecraft attitude. Thruster perturbations were constrained together by thruster pair and modeled as impulsive velocity increments.; The annual signals of the gravity field up to degree and order three (3 x 3) were recovered, at least partially, from the CHAMP tracking data. Estimating temporal coefficients higher than degree three resulted in strong correlation between coefficients. Analysis of the resulting CHAMP annual gravity signals showed a favorable comparison with the existing results of SLR data gathered over multiple years (1979--2004) from multiple satellites in various orbits. The CHAMP results also compared favorably with the preliminary results of the Gravity Recovery and Climate Experiment (GRACE) satellite mission, and with contemporary geophysical models of ocean mass and continental hydrology.; The research was supported by the Space Geodesy Laboratory of the NASA Goddard Space Flight Center (GSFC). The majority of the data processing and analysis was done with the aid of GSFC computing resources, most notably the computer programs Geodyn II and Solve. The research was funded by a Graduate Student Research Program (GSRP) fellowship from NASA.