Dither Sensing for Controlling a Segmented-Mirror Telescope

Image-plane multidither sensing has been found to be suitable for adaptive wavefront correction in a large telescope in which the main optic is a precise reflector divided into lightweight, controllably actuated segments. In image-plane multidither sensing, the telescope is aimed at a star or other distant point source and image data are recorded as each segment in turn is dithered slightly about a nominal position and orientation. The image data are processed into actuator-control signals for adjusting the nominal segment positions and orientations to obtain the desired wavefront correction.