A simulation experiment on the GM estimation for Comet 133P/Elst-Pizarro

Abstract

In China’s asteroid mission to be launched around 2025, (7968) 133P/Elst-Pizarro (hereafter 133P) will be the second target, after a visit to asteroid (469219) Kamo’oalewa. This paper describes a simulation of precise orbit determination for the spacecraft around comet 133P, as well as estimation of its gravitational parameter (GM) value and the solar radiation pressure coefficient Cr for the spacecraft. Different cometocentric distances of 200, 150 and 100 km orbits are considered, as well as two tracking modes: exclusive two-way range-rate mode (Earth station to spacecraft) and combinations of two-way range-rate and local spacecraft onboard ranging to the comet. Compared to exclusive two-way range-rate, the introduction of local ranging observables improves the final GM uncertainties by up to one order of magnitude. An ephemeris error in the orbit of 133P is also considered, and we show that, to obtain a reliable estimate of the GM for 133P, this error cannot exceed a one km range.

Simulated Gravity Field Estimation for the Main Belt Comet 133P/Elst-Pizarro Based on a Satellite-to-satellite Tracking Mode

“…The orbital altitude needs to be adjusted appropriately for future exploration mission. Gao et al (2021a) analyzed the uncertainties of GM and C r for three orbit altitudes of 100, 150, and 200 km altitudes, treating 133P as point-mass. Observation data from ground station combined with onboard range data can significantly reduce the uncertainties in GM and C r .…”