A lander radio science experiment for the estimation of the gravity field and rotation of comet 133P/Elst-Pizarro

The main belt comet 133P/Elst-Pizarro is one of the targets of the proposed Chinese small body exploration mission. The rotation and gravity of this comet will be modelled at the end of the mission phase. To prepare this mission, we performed a radio science simulation based on the current knowledge of the characteristics of 133P/Elst-Pizarro. Simulated two-way Earth–orbiter and orbiter–lander range rate tracking data with a lander positioned at the comet equator were used to determine the gravity field coefficients and the rotational parameters. Our simulation results show that the introduction of the orbiter–lander range rate data can significantly decrease the uncertainty in the initial state vector of the orbiter as well as the uncertainty in the rotation and gravity parameters.