Spherical Primary Optical Telescope Testbed (SPOT)

This IRAD proposes to continue operation of the Spherical Primary Optical Telescope (SPOT) testbed as an image-based wavefront sensing demonstrator.  In addition to completing phasing experiments of the SPOT segments, advanced wavefront sensing techniques such as geometrical optics phase retrieval and transverse-translation diversity will be applied to the testbed.  A thorough modeling and simulation study of phase retrieval on the as-built SPOT system will also be completed.

The SPOT test bed consists of three one-meter-class segments on tip/tilt and piston actuators.  The purpose of the test bed is to demonstrate wavefront sensing and control technologies for large segmented telescope architectures, without requiring separate dispersive elements or periodic rephasing.  The SPOT architecture utilizes a point source at the radius of curvature of the mirrors and performs image-based wavefront sensing (WFS), also known as phase retrieval.