Guidance, navigation and control of asteroid mobile imager and geologic observer (AMIGO)

The science and origins of asteroids is deemed high priority in the Planetary Science Decadal Survey. Major scientific goals for the study of planetesimals are to decipher geological processes in SSSBs not determinable from investigation via in situ experimentation, and to understand how planetesimals contribute to the formation of planets. Ground based observations are not sufficient to examine SSSBs, as they are only able to measure what is on the surface of the body; however, in situ analysis allows for further, close up investigation as to the surface characteristics and the inner composure of the body. To this end, the Asteroid Mobile Imager and Geologic Observer (AMIGO) an autonomous semi-inflatable robot will operate in a swarm to efficiently characterize the surface of an asteroid. The stowed package is 10×10×10 cm (equivalent to a 1U CubeSat) that deploys an inflatable sphere of ~1m in diameter. Three mobility modes are identified and designed: Ballistic hopping, rotation during hops, and up-righting maneuvers. Ballistic hops provide the AMIGO robot the ability to explore a larger portion of the asteroid’s surface to sample a larger area than a stationary lander. Rotation during the hop entails attitude control of the robot, utilizing propulsion and reaction wheel actuation. In the event of the robot tipping or not landing upright, a combination of thrusters and reaction wheels will correct the robot’s attitude. The AMIGO propulsion system utilizes sublimate-based microelectromechanical systems (MEMS) technology as a means of lightweight, lowthrust ballistic hopping and coarse attitude control. Each deployed AMIGO will hop across the surface of the asteroid multiple times. Individual actuation of each microvalve on the MEMS chip provides control torque for rough attitude control with only slight alteration to the hop path en-route to its destination. For optimal use of instrumentation, namely the top mounted stereo cameras utilized in local surface mapping and navigation planning, the robot must remain as upright as possible during data acquisition. Should AMIGO land in an improper orientation, thrusters and reaction wheels will attempt to correct the positioning. Several inflatable structures will be evaluated including a soft inflatable and an inflatable that rigidizes under UV light. The inflatable will be compared under operational scenarios to determine if it produces disturbances torque and an un-steady view for the stereo cameras. Future work is focused on raising the TRL by real world testing system performance and utilizing hardware-in-the-loop simulation models. The thruster assembly can be evaluated on a test stand mounted inside a vacuum chamber. To simulate milligravity, the entire robot will be analyzed in either parabolic flight tests or in buoyancy chambers. A combination of experimentation will validate simulations and provide insight in areas to improve on the design and control algorithms for milligravity asteroid surface environments.