<title>Mirror Segment Alignment Using A Multiple-Order Radial-Grating Shearing Interferometer</title>

A method has been developed for comparing the tilt and phase of segments of a collimated wavefront using a multiple-order radial-grating shearing interferometer. Here the extension of this technique to segmented primary mirror tilt and phase alignment is considered. A configuration for the interferometer and a method of unambiguously measuring a two-dimensional array of segments is presented.