Enhanced orbit and baseline determination for formation-flying LEO satellites with spaceborne accelerometer measurements.

The ultra-sensitive accelerometer onboard low Earth orbit (LEO) satellite can measure the non-gravitational accelerations acting on the satellite in an adequate range and frequency bandwidth with high precision. By replacing the non-gravitational force models, accelerometer measurements are introduced in GNSS-based precise orbit and baseline determination (POD and PBD) to improve the quality of the derived orbit and baseline solutions. A modified accelerometer measurement processing strategy is employed, and 1 month of flight data collected by the GRACE and GRACE-FO missions are processed. For single-satellite POD, the obtained orbit solutions are evaluated through comparisons to the Jet Propulsion Laboratory reduced-dynamic orbits, independent satellite laser ranging (SLR) and K-Band ranging (KBR) measurements. Orbit comparison and SLR validation results show comparable accuracy of the orbit solutions derived with non-gravitational force models and accelerometer measurements. However, the KBR validation reports that the relative position precision is considerably improved by 22 and 27% for GRACE and GRACE-FO, respectively. For dual-satellite PBD, the obtained baseline solutions are also evaluated by the KBR measurements. The validation results reveal that the baselines are improved significantly with the high-precision accelerometer measurements. The KBR residuals are reduced from 0.59 to 0.43 mm for GRACE, and from 0.62 to 0.48 mm for GRACE-FO, with the precision being notably improved by 27 and 23%, respectively. Furthermore, in addition to the analysis in the time domain, we find that the performances of the accelerometer measurements are more remarkable in the frequency domain for both POD and PBD, where more than 67% of the KBR residuals are reduced within the frequency interval of 1.5 to 5 cycles per revolution. These results, therefore, demonstrate the great potential of high-precision accelerometer measurements in dynamic POD and PBD, which can offer more precise relative orbits for formation-flying LEO satellites, particularly in the frequency domain. [ABSTRACT FROM AUTHOR]