The Nancy Grace Roman Space Telescope (formerly the Wide-Field Infrared Survey Telescope [WFIRST]; and dubbed WFIRST-AFTA even earlier) is a NASA space observatory currently under development, that is designed to perform wide-field imaging and grism spectroscopic surveys of the near-infrared sky, as well as high-resolution coronagraphic observations of exoplanets and circumstellar disks. The current design of the mission makes use of an existing 2.4 m (7.9 ft) telescope, the same size as the Hubble Space Telescope (HST), that was donated to NASA by the National Reconnaissance Office. The Roman Space Telescope (then WFIRST) is the top-ranked large space mission in the New Worlds, New Horizons Decadal Survey of Astronomy and Astrophysics, aimed to settle essential questions in the areas of dark energy, exoplanets, cosmic reionization, and general near-infrared astrophysics.

The Roman Space Telescope has two main science instruments. The Wide Field Instrument (WFI) will provide a field of view of the sky that is 100× larger than images provided by the HST, and will allow both multi-band ~1–2μm imaging and ~1.3–1.9μm slitless grism spectroscopy. It will measure light from a billion galaxies over the course of the mission lifetime, and perform a microlensing survey of the inner Milky Way to find ~2600 exoplanets. The Coronagraph Instrument (technically a technology demonstrator) will perform high contrast imaging and spectroscopy, enabling astronomers to detect and measure properties of dozens of nearby exoplanets in other solar systems.

Instantaneous field of view of WFIRST/WFI (red contour) compared with that of HST/ACS WFC (cyan). The background image is one of the largest images ever constructed with HST, covering almost half of the nearby Andromeda galaxy (M 31). Image courtesy: STScI, R. van der Marel.

The Roman Space Telescope is designed for a 6 year mission in a quasi-halo orbit at the second Sun–Earth Lagrange point (L2), to which it will launch on a EELV rocket out of Cape Canaveral in the mid-2020s.