Hubble Space Telescope pointing control system design improvement study results

Abstract

Unexpected thermally induced disturbances originating in the solar arrays imposed deleterious effects on the pointing performance of the Hubble Space Telescope (HST). A NASA redesign of the onboard pointing control system (PCS) brought the performance back into specification during a majority of the orbit time. As a result of this controller redesign effort, a wealth of flight data was collected and control design simulation models enhanced. Under sponsorship of the NASA Controls/Structures Interaction Program at the Marshall Space Flight Center, a study was conducted to determine if performance improvements could be obtained when advanced modern control techniques under study in the program were applied to the HST PCS. Five modern control techniques were applied to the problem. Flight data and simulation models were provided to the research teams. The methods considered were reduced-order model-based control, linear-quadratic-Gaussian-based control, analytically and numerically derived H^ control, covariance control, and dual-mode disturbance-accommodating control design. The performance of these designs was tested in a government-furnished nonlinear simulation of the HST. In general, some performance improvements over the NASA redesigned controller were seen in the simulation studies.