Small Spacecraft Technologies for the Next Decade of Radio Science Planetary Investigations

Scientists have applied precision measurements of the properties of spacecraft radio signals to make significant discoveries about planetary atmospheres, ionospheres, rings, surfaces, shapes, and internal structure. Generally, these studies have involved radio links between large spacecraft and giant Earth-based antennas. GRACE and GRAIL pioneered spacecraft-to-spacecraft links to measure the gravity fields of Earth and the Moon, respectively. Many additional interesting studies throughout the solar system are possible if small spacecraft are utilized. For example, deployment of groups of small spacecraft in orbit about another planet could enable dramatic temporal and spatial resolution improvements for atmospheric and gravitational investigations. To carry out such missions, the highest technology priority for the radio science community in the next decade is the maturation of multi-band crosslinks between robust small spacecraft in suitable planetary orbits. This requires advances in miniaturized radios, stable oscillators, and orbit insertion.

A critical need is the development of key technologies for software-defined radios (SDR) to meet the size, power, and mass constraints of small spacecraft. The Iris SDR used for the MarCO CubeSat mission to Mars provided experience for further advances towards science-quality radiometric measurements, including new functional capabilities for simultaneous open-loop recordings at multiple wavelengths and agility to swap the transmit/receive frequencies. Ultra-Stable Oscillators (USOs) have been critical instruments for radio occultation experiments since the Voyager mission. Small spacecraft cannot accommodate the mass and power of the current top-of-the-line USO (Allan deviation ~2´ 10-13 at ~100 s). The goal is to mature smaller units with comparable stability based on newer technologies. Orbit insertion technology is currently not matured for small spacecraft, but new research is currently underway aimed at achieving smallsat planetary orbits using aerobraking.

This paper will establish the potential science benefit from small spacecraft radio science investigations, survey current technology efforts, and identify additional areas of needed developments.