Thruster Attitude Control System Design and Performance for Tactical Satellite 4 Maneuvers

Abstract

During the initial mission operation, the perigee altitude of the Tactical Satellite 4’s highly elliptical orbit was raised from 185 to 700 km through several delta- maneuvers. Tactical Satellite 4 employs two deployable solar arrays that have structural bending modes less than 1 Hz. It was a concern that the interaction between the off modulation of the thruster control system and the structural modes during the delta- maneuvers may cause undesirable high-frequency short pulse firings (thruster chattering), control performance degradation, and even structural damage to the solar arrays, if left unabated. The phase-plane controller for the thruster attitude control system was designed to abate these undesirable effects by employing hysteresis in the switching lines. The hysteresis was proven to be effective in addressing these concerns. This paper describes in detail the thruster pointing control system and its performance achieved on orbit, based on the telemetry data collected during delta- maneuvers, in comparison with analytical predictions.