The application of inverse VLBI measurement in Mars orientation parameter solutions

Abstract

High-precision Mars orientation and rotation parameters (MOP) can constrain the internal structure of the planet and the modeling of processes such as polar dry ice waning and waxing. Currently, these orientation parameters are obtained by using traditional range and Doppler measurements between Earth stations and a Mars lander, but these estimations are limited by the propagation delays caused by interplanetary plasma and neutral atmospheres. Unlike the existing approaches, the inverse Very Long Baseline Interferometry (VLBI) involves more than one lander on the planet allowing to cancel these effects by differentiation, providing measurements with a higher-precision. In this study, we perform numerical simulations to assess the precision with which one could determine the MOP using inverse VLBI. Our results are compared with classical two-way range and Doppler. We show that the precession rate can be estimated with inverse VLBI with only 0.05 mas/year uncertainty, which is one order of magnitude better than with two-way range and Doppler. The accuracy of the nutation parameters reaches 1–5 mas, and the accuracy of the Chandler wobble component is down to 0.01 mas, which meets the requirements for investigations on the internal structure of Mars. The accuracy of the Length-of-Day (LOD) variations however, do not show significant improvement with the inverse VLBI technique. We also considered the impact of the lander baseline orientation on the results. Two landers at the same longitude has no additional benefits for the estimation of MOP. But the estimated LOD amplitudes are better than 1 mas when the two landers were at the same latitude.