Flight Implementation of Shortest-Time Maneuvers for Imaging Satellites

Shortest-time maneuvers are constrained time-optimal slews that enable spacecraft to be maneuvered more quickly than conventional rotations. Shortest-time maneuvers can increase a spacecraft's imaging capability without any changes to the hardware. Previous studies have shown that, depending upon the spacecraft design, the increased capability can be over 50%. Motivated by such high increases in efficiencies, the first flight demonstration of a shortest-time maneuver was performed on 10 August 2010 onboard NASA's TRACE Space Telescope. To transition this new technology from flight demonstration to standard operational procedures, several qualification thresholds need to be met. This paper demonstrates two of these qualification thresholds: 1) the ability to consistently and reliably generate flight-implementable shortest-time maneuvers on demand, and 2) flight demonstrations over multiple operational scenarios involving minimum-time slewing, attitude hold for point data collection, and transition maneuvers for scanning operations. The key technology for meeting both thresholds is flight-implementable pseudospectral controls. Flight and operational considerations quickly narrow down the plethora of pseudospectral options to the Legendre and Chebyshev techniques. All flight implementations were performed using the spectral algorithm of the Legendre pseudospectral method.