非差模糊度固定的高分三号SAR卫星厘米级定轨

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

利用高分三号(GF3A)卫星星载全球定位系统(global positioning system,GPS)观测值,研究了星载接收机天线相位中心改正以及整周模糊度固定对GF3A精密定轨的影响。数据质量分析结果表明,单历元可用GPS卫星的平均数量稳定在7个左右,C1和P2码观测值多路径分别为0.89 m和0.34 m,且变化稳定。精密定轨结果表明,通过在轨校正星载GPS天线相位中心,可将径向、切向和法向重叠轨道差异分别从7.9 mm、12.8 mm和15.5 mm提升至4.3 mm、6.6 mm和8.6 mm。通过非差模糊度固定,可进一步将定轨精度提升至3.3 mm、3.5 mm和3.3 mm,实现了优于1 cm的精密定轨。相关定轨结果与重处理的Sentinel-1相当,为GF3A科学任务实施提供了有力保障。

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.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.