WFIRST low order wavefront sensing and control (LOWFS/C) performance on line-of-sight disturbances from multiple reaction wheels

Abstract

WFIRST Coronagraph Instrument (CGI) uses its Low Order Wavefront Sensing and Control (LOWFS/C) subsystem to maintain the coronagraph contrast in presence of wavefront disturbances from the WFIRST observatory. The Occulting Mask Coronagraph (OMC) dynamic testbed is used to demonstrate LOWFS/C performance together with the coronagraphs. We have demonstrated that LOWFS/C can maintain coronagraph contrast to better than 10-8 in presence of WFIRST-like LoS and low order WFE disturbances for both Hybrid Lyot Coronagraph (HLC) and Shaped Pupil Coronagraph (SPC) modes. However, in our previous tests the LoS disturbances simulated on the testbed were from the modeling of a single reaction wheel with a quasi-static wheel speed. In this paper we will describe the LOWFS/C LoS performance test in which the injected LoS disturbances are derived from all six reaction wheels on WFIRST, each with an independent varying wheel speed profile modeled for a typical coronagraph observational scenario. We will describe the LoS disturbances profile and testbed implementation approach. We will present the LOWFS/C LoS feedback and feed forward loops testbed performance under these realistic LoS disturbances in which we have demonstrated the LoS control that meets the CGI requirement.