Centimeter Level Orbit Determination for GF3A SAR Satellite with Zero-Difference Ambiguity Resolution

Methods The reduced-dynamic precise orbit determination for GF3A was carried out using onboard global positioning system (GPS) observation from December 2016 to February 2017, and the orbit accuracy was evaluated by orbit overlap comparison.

Results The data quality analysis shows that the average of available GPS satellites per epoch remains around 7.The multipath errors for C1 and P2 code observations are 0.89 m and 0.34 m. POD results indicate that the radial, along-track, and cross-track overlapping orbit differences have been reduced from 7.9 mm, 12.8 mm, and 15.5 mm to 4.3 mm, 6.6 mm, and 8.6 mm by modeling onboard GPS antenna phase center correction. Furthermore, the orbit accuracy can be further improved to 3.3 mm, 3.5 mm, and 3.3 mm by fixing the zero-difference ambiguities.

Conclusions Generally, the orbit accuracy of GF3A is comparable to that of the reprocessed Sentinel-1 satellite, achieving a precision better than 1 cm. The high level of accuracy provides a reliable guarantee for the successful implementation of the GF3A scientific mission.

Objectivse This study investigates the impact of onboard receiver antenna phase center correction and zero-difference ambiguity resolution on the precise orbit determination (POD) of the Gaofen-3 (GF3A) satellite.