FiSI: Fiberscope sample imaging system for robotic comet surface sample return missions

This paper discusses the Fiberscope Sample Imaging (FiSI) system currently being developed for a potential robotic comet surface sample return mission. In this mission concept, the spacecraft would perform touch-and-go maneuver at a small body to collect a comet surface sample. Immediately after the sample is captured the FiSI would perform in situ verification of the comet sample. Sample volume would be estimated and images of the collected sample acquired and evaluated. If the captured sample volume were deemed insufficient, the sample collection maneuver would be re-attempted, multiple times if necessary, until a baseline sample volume was positively confirmed. This repeatability would improve the potential science outcome of the sample return mission. Our proof-of-concept FiSI hardware consists of nine imaging fiberscopes integrated into a single bundle. The nine fiberscopes are designed to provide wide swath coverage of overlapping fields of view within a sample measurement station. The achieved image resolution is in excess of 4 linepair/mm at 20 mm working distance. Surface color and texture of a comet sample simulant would clearly be discernible at this fidelity. The distal end of these fiberscopes are designed to tolerate harsh temperature and radiation environments near a comet while sensitive electronics and optical components at the proximal end can be placed in a more benign electronics bay of the notional spacecraft. An early FiSI prototype was tested in a -50°C chamber and showed no image degradation. To study the FiSI proof-of-concept system response in a microgravity-like environment, a preliminary experiment was attempted using a neutral buoyancy sample. The test result was consistent with Monte Carlo simulation.