Nasa has shortlisted four proposals for its next astrophysics missions, due for launch in 2025. The agency has funding to fly two of them, and the four will now each receive funds for a nine-month period of technical study. The two missions will be chosen next year.
The competing proposals are: the extreme-ultraviolet stellar characterization for atmospheric physics and evolution (Escape) mission, which would study nearby stars to determine the severity of their flaring activity; the Compton spectrometer and imager (Cosi), which would look for the results of recent stellar explosions in the Milky Way; the gravitational-wave ultraviolet counterpart imager mission, which would look for the explosions associated with gravitational wave detections; and Leap – a large area burst polarimeter, which would look for jets of particles ejected from exploding stars.
These missions will form part of Nasa’s explorers programme, which is the longest continuously running programme at the agency. The scheme began almost at the start of the space age, in 1958, when Explorer 1 was launched and discovered the Van Allen radiation belts around Earth. The programme has now been responsible for more than 90 missions.