High-bandwidth tip-tilt vibration compensation in telescope systems

Abstract

Mechanical vibrations resulting from wind, ground vibrations and actuator imperfections lower the performance of optical telescope systems used for astronomical applications, as well as free-space optical communication. This paper proposes a high-bandwidth tip-tilt compensation system for optical telescopes, in order to reduce the influence of these vibrations. A typical, high precision, motorized telescope system is used as a base for this evaluation. By utilization of a tip-tilt sensor, the resulting tip-tilt errors are measured and analyzed in the frequency domain. A fast steering mirror integrated into the optical path allows to compensate for the measured tip-tilt errors. The performance of the fast steering mirror based system is compared to the original, uncompensated system, as well as to a compensation loop, which uses the telescope mount to counteract measured errors. Experiments demonstrate a significant reduction of the tip-tilt errors due to vibrations by a factor of 5 (altitude axis) and by a factor of 4.6 (azimuth axis) utilizing a compensation bandwidth of up to 810 Hz.