FIRST FLIGHT RESULTS ON TIME-OPTIMAL SPACECRAFT SLEWS

This paper describes the design and flight implementation of off-eigenaxis time-optimal reorientation maneuvers for the NASA Transition Region and Coronal Explorer (TRACE) spacecraft. Time-optimal reorientation maneuvers have obvious application for improving the maneuver performance of spacecraft systems. Yet, this type of maneuvering capability has never before been demonstrated in flight. Constrained time-optimal maneuvering of a rigid body is studied first in order to demonstrate the potential for enhancing the performance of the TRACE spacecraft. Issues related to the experimental flight implementation of time-optimal maneuvers on board TRACE are discussed. A description of an optimal control problem formulation found to be suitable for reaction wheel spacecraft maneuver design is given. The optimization model is solved using the pseudospectral optimal control method and includes practical constraints such as the nonlinear reaction wheel torque-momentum envelope and rate gyro saturation limits. Flight results, presented for a typical large angle time-optimal reorientation maneuver, show that time-optimal maneuvers can be implemented without any modification of the existing spacecraft attitude control system and demonstrate a clear improvement in spacecraft maneuver performance as compared to conventional eigenaxis maneuvering.