Simulation analysis of short-period time-varying gravity field in recovery of very-low orbit satellite constellation

Objectives: In comparison to the Bender constellation in the next generation of gravity missions, the Very Low Earth Orbit (VLEO) constellation with the main objective of conducting communication, navigation, and remote sensing has the capability to achieve extensive ground coverage in a short time, increase the spatio-temporal sampling of time-varying gravity field, and is expected to reduce the aliasing effect and improve the detection capability of time-varying signals in gravity field. Methods: We simulated observation data obtained from a VLEO constellation, comprising 300 satellites orbiting at an altitude of 250 km, along with the Bender constellation. Through closed-loop simulation experiments using the short-arc integral method, we compared and analyzed the performance of short-period (7-day) time-varying gravity field recovery of different constellations under varying error conditions. We also studied the impact of varying noise levels, orbit configuration, and aliasing effects on the results. Results: When not accounting for observed noise, the VLEO constellation, as compared to the Bender constellation, is able to effectively mitigate the impact of aliasing effects on the modeling of the time-varying gravity field. For the 7-day time-varying gravity field solution, if the orbital accuracy of the VLEO constellation is 1 cm, and the inter-satellite velocity measurement accuracy of the Bender constellation is 10 nm/s, taking into account the aliasing error, the VLEO constellation has the capability to effectively recover signals up to degree 15, and slightly outperforms the Bender constellation up to degree 8. With the orbit determination accuracy of VLEO satellites ranging from 1 to 10 cm, the addition of the VLEO constellation to the Bender constellation can effectively minimize the aliasing effect and the northsouth striping characteristics in the solution results, thereby improving the recovery performance of the shortperiod time-varying gravity field. Conclusions: The comparative test results show that VLEO constellation can reduce aliasing effect by increasing spatiotemporal sampling, and its introduction can make Bender constellation recover better time-varying gravity field results.