Cryogenic optical position encoders for mechanisms in the JWST optical telescope element simulator (OSIM)

Abstract

The JWST Optical Telescope Element Simulator (OSIM) is a configutable, cryogenic, optical stimulus for high fidelity ground characterization and calibration of JWST's flight instruments. OSIM and its associated Beam Image Analyzer (BIA) contain several ultra•precise, cryogenic mechanisms that enable OSIM to project point sources into the instruments according to the same optical prescription as the flight telescope images stars -correct in focal surface position and chief ray angle. OSIM's and BIA's fifteen axes of mechanisms navigate according to redundant, cryogenic, absolute, optical encoders-32 in all operating at or below 100 K. OSIM's encoder subsystem, the engineering challenges met in its development, and the encoders' sub-micron and sub-arcsecond performance are discussed.

Vision algorithm for the Solar Aspect System of the HEROES mission

“…Augmented reality literature is full of fiducial markers that carry information payloads, and there are even patterns of relatively small marks that still carry information without relying on inter-fiducial distance. For example, the fiducial marks used in the 2-axis encoder described in [25] rely on a pattern of small marks which can deliver position knowledge when only part of the pattern is visible.…”