Strategies for disturbance compensation at large telescopes

Nowadays, large ground-based astronomy is entering into a new level of size, technology and astronomical questions. This requires an integrated, interdisciplinary team to create the fascinating observing instruments that we have today and expect for the future. In this context, the field of control engineering can and has to deliver ideas and solutions that help increasing the optical performance of these telescopes. Precisely because ground based telescopes have grown in size, the requirements for the optical alignment and the detector quality have tightened and difraction limited observations are more and more enabled only by active and adaptive optics, which have to be integrated well into the optical system as a whole. Correction of wavefront errors due to atmospheric aberrations by adaptive optics featuring deformable mirrors is a standard technology available now. The classic adaptive optics control loop is a pure feedback system designed to eliminate the effects of atmospheric wavefront distortion on the detector output. For these systems, reducing the load on the feedback part and increasing the disturbance rejection properties can be achieved by a disturbance feedforward. This book mainly focuses on the design and study of accelerometer-based disturbance feedforward for the Large Binocular Telescope and its results when applied to observations with LBTI. This includes a mechanical model of the telescope's main mirrors, an optical model of the relevant low order effects on the focal plane, and a comparison of different estimation techniques to estimate the mirror's position from its accelerometer readings.