The Exo-S probe class starshade mission

Abstract

Exo-S is a direct imaging space-based mission to discover and characterize exoplanets.With its modest size, Exo-S bridges the gap between census missions like Kepler and a future space-based flagship direct imaging exoplanet mission.With the ability to reach down to Earth-size planets in the habitable zones of nearly two dozen nearby stars, Exo-S is a powerful first step in the search for and identification of Earth-like planets.Compelling science can be returned at the same time as the technological and scientific framework is developed for a larger flagship mission.The Exo-S Science and Technology Definition Team studied two viable starshade-telescope missions for exoplanet direct imaging, targeted to the $1B cost guideline.The first Exo-S mission concept is a starshade and telescope system dedicated to each other for the sole purpose of direct imaging for exoplanets (The "Starshade Dedicated Mission").The starshade and commercial, 1.1-m diameter telescope co-launch, sharing the same low-cost launch vehicle, conserving cost.The Dedicated mission orbits in a heliocentric, Earth leading, Earth-drift away orbit.The telescope has a conventional instrument package that includes the planet camera, a basic spectrometer, and a guide camera.The second Exo-S mission concept is a starshade that launches separately to rendezvous with an existing on-orbit space telescope (the "Starshade Rendezvous Mission").The existing telescope adopted for the study is the WFIRST-AFTA (Wide-Field Infrared Survey Telescope Astrophysics Focused Telescope Asset).The WFIRST-AFTA 2.4-m telescope is assumed to have previously launched to a Halo orbit about the Earth-Sun L2 point, away from the gravity gradient of Earth orbit which is unsuitable for formation flying of the starshade and telescope.The impact on WFIRST-AFTA for starshade readiness is minimized; the existing coronagraph instrument performs as the starshade science instrument, while formation guidance is handled by the existing coronagraph focal planes with minimal modification and an added transceiver.