Analysis of Time-Variable Gravity Field Exploring Performance with LEO Cluster

We studied a so-called crossover point approach for low-cost LEO cluster precise orbit data to recover the global time-variable information without accelerometer systems (ACC) or k-band ranging system (KBR) measurements.This approach can reduce the non-gravitational force effects on LEO,obviously.We analyzed the 20 d data coverage and the orbit radial error effects on this approach.With 20 d precise orbital data,the crossover points have well global coverage.On the other hand,the radial orbit accuracy of COSMIC data is about 15 cm at 800 km orbital altitude.It is not sufficient for the time-variable gravity field recovery with crossover point approach.If the orbital radial component error is reduced to about 1 cm,the time-variable gravity field can be recovery with acceptable accuracy.