acoustic oscillations, observations of distant supernovae, weak gravitational lensing. Completing a census of exoplanets to help answer new questions about the potential for life in the universe: How common are solar systems like our own? What kinds of planets exist in the cold, outer regions of planetary systems? – What determines the habitability of Earth-like worlds? This census makes use of a technique that can find exoplanets down to a mass only a few times that of the Moon: gravitational microlensing. The census would include also a sample of free-floating planets with masses likely down to the mass of Mars. Establishing a guest investigator mode, enabling survey investigations to answer diverse questions about our galaxy and the universe. Providing a coronagraph for exoplanet direct imaging that will provide the first direct images and spectra of planets around our nearest neighbors similar to our own giant planets. Instruments The telescope is to carry two instruments. WFI The Wide-Field Instrument (WFI) is a 300.8-megapixel camera providing multi-band visible to near-infrared (0.48 to 2.30 µm) imaging using one wideband and six narrowband filters. A HgCdTe-based focal-plane array captures a 0.28 square degree field of view with a pixel scale of 110 milliarcseconds. The detector array is composed of 18 H4RG-10 detectors provided by Teledyne. It also carries both high-dispersion grism and low-dispersion prism assemblies for wide-field slitless spectroscopy. CGI The Coronagraphic Instrument (CGI) is a high contrast coronagraph covering shorter wavelengths (575 nm to 825 nm) using dual deformable mirror starlight-suppression technology. It is intended to achieve a part-per-billion suppression of starlight to enable the detection and spectroscopy of planets with a visual separation of as little as 0.15 arcseconds from their host stars. History The design of the Roman Space Telescope has heritage to various proposed designs for the Joint Dark Energy Mission (JDEM) between NASA and the Department of Energy (DOE). Roman adds some extra capabilities to the original JDEM proposals, including a search for extra-solar planets using gravitational microlensing. In its present incarnation (2015), a large fraction of its primary mission will be focused on probing the expansion history of the Universe and the growth of cosmic structure with multiple methods in overlapping redshift ranges, with the goal of precisely measuring the effects of dark energy, the consistency of general relativity, and the curvature of spacetime. On 2 March 2020, NASA announced that it had approved WFIRST to proceed to