Asteroid Surface Resource Characterization through Distributed Plasma Analysis of Meteoroid Impact Ejecta

The Meteoroid Impact Detection for Exploration of Asteroids (MIDEA) concept leverages the natural space environment in order to provide a measurement of surface composition from a small constellation of orbiting sensors coordinated by a parent spacecraft. This measurement is derived from the plasma produced by meteoroid impacts on the asteroidal surface. The plasma, composed of ions liberated from the surface and from the meteoroid, is formed from the rapid conversion of the meteoroid's kinetic energy into vaporization and ionization. On surfaces facing the sun, the photoemission of electrons results in a net positive surface charge that expels the positive ions away from the asteroid. Orbiting plasma sensors can capture and measure this charge, inferring the ion species through time-of-flight mass spectroscopy. The parent spacecraft synthesizes these impact plasma measurements to construct a map of potential resources on the asteroid surface. Compared to spectroscopic techniques, the detection of impact plasma can be accomplished using extremely low-mass and low-power sensors. Using this concept, a nominal mission to a 100–1000 m asteroid may be achievable with a parent spacecraft in the 10–20 kg range, carrying ten or fewer free-flying sensors that are each less than 100 g in mass. This would be a dramatic reduction in mass (and correspondingly in propulsion requirements) compared to the Hayabusa, NEAR-Shoemaker, and OSIRIS-REx spacecraft, which have dry masses of 380, 487, and 880 kg, respectively. At MIDEA's low mass scale, many individual constellations could be launched in parallel to different asteroids, performing a broad survey of potential targets for in situ resource utilization (ISRU), and bringing the cost of asteroid exploration down to a level where commercial entities could afford to undertake such a mission. Additionally, the processes governing spectroscopic measurements are limited by the optical resolution of the instrument, resulting in an averaged measurement at the spatial resolution on the asteroid surface, which is typically on the order of 1 m. In contrast, the impact plasma measurement provides the ability to determine the surface composition at a micron scale, which would provide a better indication of the heterogeneity of the surface. Our objective for this project was to design an ultralight plasma sensor that would support the MIDEA concept. To this end, we undertook an initial feasibility analysis considering the rate of meteoroid impacts and the geometry of the subsequent expansion of impact plasma. We then designed and prototyped an ultralight plasma sensor that could detect a transient plasma signal consistent with our models.