Coronagraph Design Survey for Future Exoplanet Direct Imaging Space Missions: Interim Update

NASA is about to embark on an ambitious program to develop a Habitable Worlds Observatory (HWO) flagship mission to directly image ~25 potentially Earth-like planets and spectroscopically characterize them for signs of life, as recommended by the Astro2020 decadal survey. In addition, Astro2020 recommended a new approach for flagship formulation, which involves increasing the scope and depth of early, pre-phase A trades and technology maturation, as part of the new Great Observatories Maturation Program (GOMAP). A critical capability of the HWO mission is starlight suppression. To inform future architecture trades, it is necessary to survey a wide range of technologies, from the relatively mature ones such as the ones described in the LUVOIR and HabEx reports, to the relatively new and emerging ones, which may lead to breakthrough performance. In this paper, we present an interim update on an on-going effort to survey coronagraph architectures for HWO (and, more generally, any future exoplanet direct imaging space mission). The survey uses the Kepner-Tregoe matrix (KT) formalism to capture and organize its findings. We present a preliminary version of the table, as well as: (1) a current list of different coronagraph designs which are being surveyed; (2) proposed evaluation criteria, such as expected mission yields and feasibility of maturing to TRL5 by 2029; and (3) tools and methods which will be used to quantify evaluations of different designs.