WFIRST will survey large areas of the sky measuring the effects of dark matter on the distribution of galaxies in the universe. It will also observe distant Type Ia supernovae to use them as tracers of dark matter and dark energy. It will provide a huge step forward in our understanding of dark matter and dark energy.
WFIRST is currently in Phase A.The purpose of Phase A is to develop the mission requirements and architecture necessary to meet the programmatic requirements and constraints on the Project and to develop the plans for the Preliminary Design phase.
Yes, the preparations are on track for a mid-2020s launch.
WFIRST uses a 2.4 m telescope provided by another government agency as the front-end to two instruments, the Wide Field Instrument and the Coronagraph Instrument. The Wide Field instrument provides Wide Field imaging and spectroscopy in support of the dark energy and microlensing surveys and integral field spectroscopy in support of the supernova survey. The Coronagraph provides high contrast imaging and integral field spectroscopy in support of exoplanet direct imaging/characterization and debris disk science. The details of the WFIRST payload can be found here.
Briefly, the spacecraft will study dark matter and dark energy with several techniques. It will perform large surveys of galaxies and galaxy clusters to see the effects of dark matter and energy on their shapes and distributions in the universe. All told, more than a billion galaxies will be observed by WFIRST. It will observe Type Ia supernovae to determine their distance and properties. More than 2000 supernovae will be observed. The details on how WFIRST will study dark energy can be found here.
Briefly, WFIRST will study exoplanets with two very different techniques: microlensing and coronagraph. The mission will stare at the a dense star region toward the direction of the center of our Milky Way galaxy to observe microlensing events. These brightenings caused when two stars exactly align and also provide a tally of the exoplanets around the stars. Over 2000 exoplanets will be detected this way.
The coronagraph instrument will perform direct imaging of exoplanets around nearby stars. It will be able to detect more than 50 exoplanets and observe their properties. It will be a huge leap forward compared to current instruments. Most exciting will be spectral observations of the light from the planets to see what the properties are of the atmospheres and possibly surfaces. Searches will be made for signatures of life on the planets. The details about how WFIRST will study exoplanets can be found here.
Major discoveries coming from WFIRST will be in the areas of dark matter and energy, exoplanets and general astrophysics. We hope to learn the nature of dark matter and energy to determine what they are. We will take a census of exoplonets that are beyond on astronomical unit from their stars, a region that Kepler is not able to survey. We will make the first sensitive direct observation of nearby exoplanets and find what their nature is and if there are signatures of life. We will survey the sky to find the most exotic and interesting galaxies, black holes, and stars.
The WFIRST project is currently studying launch vehicle options. launch vehicles are not typically selected until several years before launch.