Single-Axis pointing of an underactuated spacecraft equipped with two reaction wheels

The study proposes a novel approach for single-axis pointing of an underactuated spacecraft using only two reaction wheels (RWs), which is based on a simple yet effective wheel rate command. The control law can be used for aiming the line of sight of a sensor, a nozzle, or an antenna toward a target direction, or solar panels toward the sun, after failure of one wheel for a nonredundant control system hardware or, in the case of multiple failures, for redundant systems.