Alignment of the elements of a segmented mirror using different combinations of wavefront sensors: numerical simulations

Segments alignment is one of the fundamental factors affecting the shape of the PSF of an optical segmented surface (composed by mirrors or lenses). Tilt and piston of each segment must be very well and uniformly adjusted in relation with the rest of segments. The Shack-Hartmann sensor is very efficient in detecting the local wavefront tilt, and the Curvature sensor is sensitive enough in order to detect local piston errors in the segmented mirrors (1). We show, with numerical simulations, how suches two sensors work in the presence of tilt and piston aberrations. Then, we propose a combine sensor that simultaneously senses the wavefront by Shack-Hartmann and Curvature techniques. An iterative process should improve the measures.