The WFIRST web page gives a good description: https://www.jpl.nasa.gov/missions/wide-field-infrared-survey-telescope-wfirst/ https://www.jpl.nasa.gov/missions/

The WFIRST web page gives a good description: https://www.jpl.nasa.gov/missions/wide-field-infrared-survey-telescope-wfirst/ https://www.jpl.nasa.gov/missions/wide-field-infrared-survey... There are 2 instruments. The coronagraph instrument (“WFIRST-CGI”) is a high contrast imaging test bed. If we want to have a technology path to image exoplanets, we need to test and improve the tech we have for masking the starlight of a target star, while allowing us to see the reflected light from a nearby exoplanet. For earth like exoplanets, this is a 10^10 brightness difference. WFIRST will hopefully get us to 10^8. To get there, you need deformable mirrors, wavefront sensing, and active control. We will also be able to get coarsely binned spectra from WFIRST. Spectra (in general — I’m not sure if WFIRST will get there) would allow us to detect presence of water absorption features in the reflected light. Eventually, we might be able to sense the oxygen A and B bands, which would indicate non-equilibrium chemistry.