Exploring Exoplanets with a Starshade Mission

"Exo-S" is NASA's first community-directed study of a starshade (or “external occulter”) plus telescope system for a space-based direct imaging mission to discover and spectrally characterize exoplanets. The Exo-S final report was released in early 2015, and it includes two options: (1) a
standalone mission using a modest aperture (1.1-m) space telescope launched together with a 30-m starshade, and (2) a 34-m starshade launched independently to rendezvous with an existing larger space telescope (in this case we specifically consider WFIRST/AFTA).  Both options can image nearby
exo-Earths, sub-Neptunes, and previously known and newly discovered Jupiters.  Both missions can characterize the atmospheres of giant planets with low-resolution spectroscopy, while the larger mission can also characterize exo-Earths and mini-Neptunes.  We also explored the full range
of planet sizes and temperatures that might be accessible to such a mission, for each of the nearest stellar systems.  For the coming year, the Exo-S team has set its sight on WFIRST, and an enhanced mission scenario where the telescope ends up at L2 instead of geosynchonous orbit — and what it could do with a starshade.