High-order wavefront sensing and control for the Roman Coronagraph Instrument (CGI): architecture and measured performance

The Nancy Grace Roman Space Telescope (``Roman’') is a 2.4m space telescope scheduled for a 2026 launch. The Coronagraph Instrument (CGI) on Roman is a technology-demonstration instrument with a coronagraph and, for the first time in space, deformable mirrors and active wavefront control. This paper walks through the algorithmic and system-level architecture of the HOWFSC implementation for CGI, including the use of ground-in-the-loop (GITL) operations to support computationally-expensive operations, and reports on instrument performance measured during thermal vacuum testing in instrument integration and test. CGI achieved better than $5\times {10}^{-8}$ total raw contrast with two independent coronagraph architectures covering 3-9 and 6-20 $\lambda \mathrm{/}D$ between them and a ${360}^{\circ }$ dark hole on each. The contrast limits appear to be driven by time available for testing, and do not appear to represent a floor in the achievable performance of CGI in flight.