Real-Time On-Orbit Estimation Method for Microthruster Thrust Based on High-Precision Orbit Determination

In order to enable the micro-nanosatellites equipped with microthrusters to better complete various space applications, it is necessary to estimate the thrust performance of the microthrusters in real-time on orbit. This paper proposes a real-time on-orbit estimation method for microthrust based on high-precision orbit determination. By establishing a high-precision orbit dynamic model, the microthrust generated by a microthruster is modeled as a first-order Markov model, combined with a high-precision GNSS measuring device, and the satellite position is obtained through the cubature Kalman filter algorithm, velocity, and thrust real-time on-orbit estimates. For a thrust of 100 μN, the error accuracy of the on-orbit estimation is 3.98%; for a thrust of 500 μN, the error accuracy is 1.79%; for a thrust of 5 mN, the error accuracy can be reduced to 1.43%; and when the thrust is 500 μN, the accuracy of orbit determination is 16 cm. This method solves the problem that the traditional on-orbit thrust estimation method cannot perform real-time on-orbit estimation of microthrust on the order of hundreds of μN. The real-time on-orbit estimation of microthrust of micro-nanosatellites equipped with microthrusters of the order of hundreds of micronewtons or even several mN to tens of mN has certain reference value.

COSMIC-2 Precise Orbit Determination Results

<p>We present results for GNSS orbit estimation strategies implemented for the FORMOSAT-7/COSMIC-2 (Constellation Observing System for Meteorology, Ionosphere, and Climate) constellation. The six COSMIC-2 satellites launched on June 25, 2019 into a 24 deg inclination, ~725 km circular orbit. Over time, all satellites will be lowered to an operational altitude of ~520 km. The primary COSMIC-2 science payload is the JPL designed Tri-GNSS Radio-occultation Receiver System (TGRS), which tracks GPS and GLONASS signals on two upward looking choke-ring precise orbit determination antennas facing the forward- and anti-velocity directions. We evaluate recently implemented post-processed orbit determination strategies. These include single antenna GPS-only and GPS+GLONASS solutions, as well as experimental dual-antenna GPS-only processing applying different approaches for the handling of receiver clock parameters (e.g. dual clocks, single clock plus bias). Evaluation metrics include data volume and tracking arc coverage, postfit residuals, internal orbit overlaps, and stability of the receiver clock estimates. We furthermore compare the performance of the six orbiters, and look for differences in quality metrics at the higher and lower orbit altitudes.</p>