<title>Telescope simulator for the Nexus wavefront control testbed</title>

Abstract

A telescope simulator was built as part of the Nexus wavefront control testbed, an NGST technology experiment at NASA's Goddard Space Flight Center. This testbed was designed to demonstrate complete control of a segmented telescope, from initial capture of light, through coarse alignment and phasing, to fine phasing and wavefront control. The existing telescope simulator allows testing of the fine phasing and wavefront control steps. A small deformable mirror in the simulator allows generation of an unobscured aberrated wavefront, for use in exploring the range of measurement and correction using the testbed's image-based wavefront sensor and larger deformable mirror. An alternate path under development for the simulator will create a segmented wavefront using three spherical mirrors; three-degree-of-freedom mounts under each mirror enable alignment and phasing experiments that will cover most of the operation sequence. Details of the hardware design and performance will be presented.