Cryogenic performance of a high precision photogrammetry system for verification of the James Webb Space Telescope Integrated Science Instrument Module and associated ground support equipment structural alignment requirements

The James Webb Space Telescope (JWST) is a general astrophysics mission which consists of a 6.6m diameter, segmented, deployable telescope for cryogenic IR space astronomy (~35K). The JWST Observatory architecture includes the Optical Telescope Element and the Integrated Science Instrument Module (ISIM) element that contains four science instruments (SI) including a Guider. The alignment philosophy of ISIM is such that the cryogenic changes in the alignment of the SI interfaces are captured in the ISIM alignment error budget. The SIs are aligned to the structure's coordinate system under ambient, clean room conditions using laser tracker and theodolite metrology. The ISIM structure is thermally cycled and temperature-induced structural changes are concurrently measured with a photogrammetry metrology system to ensure they are within requirements. We compare the ISIM photogrammetry system performance to the ISIM metrology requirements and describe the cryogenic data acquired to verify photogrammetry system level requirements, including measurement uncertainty. The ISIM photogrammetry system is the baseline concept for future tests involving the Optical Telescope Element (OTE) and Observatory level testing at Johnson Space Flight Center.