Enabling Mars Radio Occultation by Smallsats

Abstract

We introduce a Mars Radio Occultation (RO) mission concept leveraging on small satellite (smallsat) technologies that will enable measurements that address both Mars science and exploration priorities. The RO technique measures the Doppler shift of radio signals of a spacecraft occulting behind a planet's limb, providing information about the planet's atmospheric density, temperature, and pressure profiles. We design a smallsat constellation and simulate “crosslink” RO observations between the smallsats to determine the expected accuracy and spatiotemporal coverage of Mars RO atmospheric profiles. Such measurements are key to spacecraft Entry, Descent and Landing (EDL), and Ascent from the Surface (AST) of Mars. Today, the number of Mars atmospheric profiles measurements with high vertical resolution is limited, especially near the surface where satellite-based passive measurements are inhibited by atmospheric absorption. We find that crosslink ROs between a constellation of six smallsats provide global and diurnal cycle coverage with dozens of occultations per day, providing temperature information from near-surface up to ~45 km with altitude-dependent accuracy that ranges between <0.5 K at lower altitude to <5 K in the middle-to-upper atmosphere. Ionospheric ROs measure the electron density with accuracy of ~5 - 10% at the peak ionospheric height between 100 and 140 km. We conclude that measurement by a smallsat constellation can augment existing observing platforms by reducing observational gaps and yield high resolution measurements required for safe spacecraft operations during EDL and AST.