Orbit Determination for Gravity-Field Recovery of a Martian Satellite Gravimetry Mission

Observing the temporal variations of a planet’s gravity field provides direct constraints on its internal composition and dynamics. A satellite mission concept called MaQuIS employs the successful mission technology of GRACE-FO and GRAIL and is dedicated to improving our knowledge of the Martian gravity field, thereby enabling studies on planetary dynamics, subsurface water reservoirs, and seasonal changes such as melting cycles.

In preparation for such a mission we are conducting end-to-end simulations. That involves the generation of synthetic tracking, inter‑satellite ranging, and accelerometer data for a range of orbital configurations and sensor designs, including quantum sensors. The synthetic observation data are used to recover simulated gravity field solutions in order to evaluate the mission’s scientific outcome. A key element of the latter is the orbit determination. It yields orbit residuals that express the misalignment of the observed trajectory with the a‑priori model predictions and serve as the observation vector for the gravity‑field inversion.

In this talk I will discuss the main pitfalls that arise when adapting Earth-well‑tested orbit‑fit algorithms to the Martian environment, in particular the difficulty of combining high-precision inter-satellite ranging data with less accurate radio Doppler tracking measurements.