Telescopes of 8 meter class, like Large Binocular Telescope (LBT), are based on the concept of Deformable Secondary Mirror (DSM); in order to calculate the best DSM shape that correct the measured aberrations we need to calibrate the AO system, so we need a correlation between the DSM and the wave front sensor (WFS), i.e. we need the Interaction Matrix (IM). Usually we obtain the IM in laboratory or at the telescope using as source a reference fiber that illuminates both the deformable mirror and wave front sensor. But in case of LBT and all large telescopes, this technique can be very difficult or sometimes impossible, and calibration may be required to be performed on sky. So we need new calibration techniques, and we investigate about sinusoidal modulation one for LBT case. In the Arcetri solar tower (inside Arcetri Observatory) we recreated a set up environment similar to the telescope, and thanks to that we can test the calibration system in the same condition of the LBT. In preparation for the test some simulations of this sinusoidal modulation technique were needed, in order to choose the best parameters that increased SNR and reduced integration time. The paper will detail the simulation results of the calibration LBT system made with this new technique, and these results will be used to drive our tests in the tower.

Date Published: 11 July 2008
PDF: 11 pages
Proc. SPIE 7015, Adaptive Optics Systems, 70153A (11 July 2008); doi: 10.1117/12.789273

Published in SPIE Proceedings Vol. 7015:
Adaptive Optics Systems
Norbert Hubin; Claire E. Max; Peter L. Wizinowich, Editor(s)