Density prediction in Mars' aerobraking region

Aerobraking at Mars is significantly impacted by the density variability at altitudes between about 100 and 140 km. Density changes can be quite substantial from orbit to orbit and from day to day. Much of this variability arises from tides propagating upward from the lower atmosphere. In this paper we present first results from a method developed to predict density variability in Mars aerobraking region due to this source. It consists of employing physics-based tidal functions to fit tidal temperatures between 60 and 80 km inferred from Mars Climate Sounder measurements on Mars Reconnaissance Orbiter and using these functions to predict the density variations at aerobraking altitudes due to vertical propagation of the fitted tidal components. Validation against densities measured by the Mars Global Surveyor accelerometer suggest that these initial results capture salient features sufficiently well that users may want to incorporate them into operational models.