Active Gravity Gradient Torque Control for Earth-Orbiting Astronomical Telescopes

The controlled pointing of an Earth-orbiting astronomical telescope in the presence of time-dependent gravity-gradient torques is studied using recent techniques for the analysis and synthesis of time-varying linear scalar dynamical systems. We present results which show that effective adaptive control of unstable motions due to gravity gradient torques can be accomplished, resulting in high pointing accuracy and stability for astronomical telescopes in both circular and elliptical orbits.