Planning for Sun-Synchronous Lunar Polar Roving

Abstract

Lunar polar resources can accelerate deep space exploration by resupplying missions with oxygen, water, and propellant. Before lunar resupply can be established, the distribution and concentration of water ice and other volatiles abundant at the poles of the Moon must be verified and mapped. The need for affordable, scalable exploration of the lunar poles motivates the deployment of solar-powered rovers and planning strategies that sustain robotic missions beyond a single two-week period of lunar daylight.

Reliance on solar power at the lunar poles gives rise to significant challenges---and opportunities---for individual rovers to achieve multi-lunar-day longevity. Solar-powered rovers require persistent sunlight for power and heat, lest they succumb to the cryogenic temperatures of lunar night. Although constrained by thermal conditions and available power, opportunistic polar rovers can maintain warmth and ample solar power for several months by following sun-synchronous routes. Strategic, informed route planning that exploits polar lighting enables sustained lunar polar roving and resource prospecting not possible by other means.

This research develops polar roving strategies and applies global path planning methods to generate spatiotemporal routes that provide multiple lunar days of uninterrupted sunlight while satisfying constraints on rover speed, terrain slope, and direct-to-Earth communication. The existence of feasible sun-synchronous routes on the South Pole of the Moon is demonstrated by proof-of-concept examples that last multiple lunar days. These are generated using spatiotemporal predictive models of dynamic surface illumination and Earth view based on ephemeris data and global topographic maps derived from Lunar Orbiter Laser Altimeter data.

In addition, this research addresses issues of route robustness. Predictive model uncertainty stemming from topographic measurement error presents substantial risk to rovers dwelling at predicted local peaks of persistent sunlight. This thesis presents a strategy to selectively deploy limited rover autonomy to reduce risk during unavoidable communication blackouts. Finally, this thesis presents a method of identifying viable landing sites amenable to sustained lunar polar roving. Together, these contributions advance capabilities to plan safe, reliable routes that extend lunar missions by an order of magnitude and enable a future of sustainable exploration.