Process Noise Identification and Observer Design for the Large Binocular Telescope

Abstract

Estimation and correction of telescope vibration have proven to be crucial for the performance of astronomical interferometers. For this purpose the large binocular telescope (LBT) has been equipped with an optical path difference and vibration monitoring system (OVMS), which will serve to ensure conditions suitable for adaptive optics and interferometry. The vibration data is acquired with accelerometers build into each of the six main mirrors and at significant locations of the measurement equipment. The sensor signals are converted into tip-tilt and optical path difference data, which can be fed into the control loop of the adaptive optics and interferometers in order to permit the correction of structural vibrations at frequencies up to 100 Hz, and possibly beyond. In this paper the real-time estimation of the mirrors movement based on acceleration data is investigated. This includes the identification of a structural model from an operational modal analysis and identification of environmental excitations in terms of process noise needed for the design of a Kalman filter.