Development of the GEMS Telescope Optical Boom

A deployable Telescope Optical Boom (TOB), derived from the venerable Coilable boom, has been developed for the Gravity and Extreme Magnetism SMEX (GEMS) X-ray polarimetry mission led by the NASA-Goddard Space Flight Center (GSFC). The driving requirements for the TOB are precision deployment repeatability and thermal stability, as well as deployed stiffness. Achieving these requirements would be challenging with any deployable structure, but GEMS adds the constraint that the boom fit around the optical fields of view while staying within the very limited Pegasus-class launch vehicle shroud volume and mass allocation. Given these challenges, the GEMS project has funded the development of the 0.85 m diameter, 4 m long, carbon fiber Coilable TOB, through several iterations of engineering and test hardware. This development effort has succeeded in validating the performance requirements for GEMS.