JWST’s optical telescope simulator for verification of the Integrated Science Instrument Module

OSIM is a full field, cryogenic, optical simulator of the James Webb Space Telescope (JWST) Optical Telescope Element (OTE). It is the “Master Tool” for verifying the cryogenic alignment and optical performance of the JWST Integrated Science Instrument Module (ISIM) by providing simulated point source/star images individually or simultaneously to each of the four Science Instruments in ISIM. Additionally, each star image can be scanned in focus to support the evaluation of both image quality and best focus for each Science Instrument. OSIM has recently completed supporting the ISIM performance verification test campaign which spanned three separate cryogenic test campaigns over 3 years. In this paper, we describe the alignment to the JWST coordinate system at cryogenic temperatures, OSIM optical performance, repeatability, and its role in testing the cryogenic optical performance of the individual Science Instruments in addition to providing calibration data needed for flight operations.