MarCO Radio Occultation: How the First Interplanetary Cubesat Can Help Improve Future Missions

Smallsats and cubesats have been suggested as low-cost alternative means to achieve scientific goals for interplanetary missions. On May 5, 2018, NASA launched the first interplanetary cubesat: Mars Cube One (MarCO). MarCO-A and MarCO-B are twin communications-relay cubesats designed to monitor InSight during its Entry, Descent and Landing (EDL) on November 26, 2018. After InSight's EDL, MarCO continued to flyby Mars and conduct a radio occultation of the planet. This is the first-ever radio occultation of a planet other than Earth performed, and also the first planetary science measurement taken by an interplanetary cubesat. This research presents a performance assessment of the MarCO radio science measurements, results of MarCO radio occultation task, and the expected radio science capability of MarCO-like cubesat. Future interplanetary radio science missions can investigate planetary atmospheres, ionospheres, and rings using radio occultation measurements; probe the interior of a planetary body with gravity measurements; and surface characteristics with bistatic scattering. Observations made by tracking MarCO from NASA's Deep Space Network using an open-loop recordings of the X-band radio signal collected during cruise, InSight EDL, and the MarCO radio occultation are presented. Although the noise level of the MarCO radio occultation was too high for precise remote sensing of the atmosphere, the noise patterns are presented and analyzed against simulations. We compared observations with the spacecraft dynamics, Earth atmospheric and ionospheric calibrations, Martian atmospheric and ionospheric model simulations to evaluate the performance of the MarCO radio occultation. This investigation will improve our understanding of engineering and science constraints for future interplanetary cubesats.