Numerical control matrix rotation for the LINC-NIRVANA multiconjugate adaptive optics system

Abstract

LINC-NIRVANA will realize the interferometric imaging focal station of the Large Binocular Telescope. A double Layer Oriented multi-conjugate adaptive optics system assists the two arms of the interferometer, supplying high order wave-front correction. In order to counterbalance the field rotation, mechanical derotation for the two ground wave-front sensors, and optical derotators for the mid-high layers sensors fix the positions of the focal planes with respect to the pyramids aboard the wave-front sensors. The derotation introduces pupil images rotation on the wavefront sensors: the projection of the deformable mirrors on the sensor consequently change. The proper adjustment of the control matrix will be applied in real-time through numerical computation of the new matrix. In this paper we investigate the temporal and computational aspects related to the pupils rotation, explicitly computing the wave-front errors that may be generated.

Operation of a layer-oriented multiconjugate adaptive optics system in the partial illumination regime

“…For our system, θ°¼ 1 deg of sky rotation. 43,44 This arrangement has the advantage that the position of the stars does not change in the focal plane of the WFS. Therefore, the illumination region also remains unchanged.…”

“…These six angles are chosen knowing the actuator spacing so that the smoothing effect inaccuracy is minimal. 43 Each of the calibrated measurements are then numerically rotated to each integral degree. The average of the six numerically rotated measurements forms the final mother-IM for each angle.…”