Four astrophysics mission proposals to study stars, galaxies and some of the most violent explosions in the universe have been selected for further study by NASA.
The selected missions are competing for funding as part of NASA’s Explorers Program and were announced by the agency on Thursday, Aug. 18. The Explorers Program focuses on small to medium-sized missions that can make a big science impact but also can be built and launched in a much shorter timeframe than large, expensive missions.
Two Astrophysics Medium Explorer missions and two Explorer Missions of Opportunity will now move into the mission concept study phase. NASA will evaluate the concepts before selecting one Mission of Opportunity and one Medium Explorer in 2024. The chosen pair of missions will then prepare for launches in 2027 and 2028.
The two Medium Explorer teams will each receive $3 million for a nine-month mission concept study. These are:
— UltraViolet EXplorer (UVEX). The mission would survey the whole sky in ultraviolet light to provide new insights into galaxy evolution and the lifecycle of stars. The spacecraft would seek to capture light from the explosion that follows a burst of gravitational waves caused by merging neutron stars, as well as study massive stars and stellar explosions. The principal investigator is Fiona Harrison at Caltech in Pasadena, California.
— Survey and Time-domain Astrophysical Research Explorer (STAR-X). The spacecraft would use sensitive wide-field X-ray and ultraviolet telescopes to study supernova explosions and active galaxies. Deep X-ray surveys would map hot gas trapped in distant clusters of galaxies. Combined with infrared observations from NASA’s upcoming Roman Space Telescope, these observations would trace how massive clusters of galaxies built up over cosmic history. The principal investigator is William Zhang at NASA’s Goddard Space Flight Center in Greenbelt, Maryland.
The two Mission of Opportunity teams will each receive $750,000 to conduct their own nine-month concept study. These are:
— Moon Burst Energetics All-sky Monitor (MoonBEAM). The spacecraft would operate in the so-called halo orbit between Earth and the moon, meaning it would be able to see almost the whole sky at any time, watching for bursts of high-energy gamma rays from distant cosmic explosions. MoonBEAM would then rapidly alert other telescopes so they can study the source. The principal investigator is Chiumun Michelle Hui at NASA’s Marshall Space Flight Center in Huntsville, Alabama.
— A LargE Area burst Polarimeter (LEAP). LEAP would be mounted on the International Space Station to study gamma-ray bursts from the energetic jets launched during the formation of black holes after the explosive death of a massive star, or in the merger of objects such as neutron stars, and black holes. The principal investigator is Mark McConnell at the University of New Hampshire in Durham.
The costs for medium explorer missions are capped at $300 million each, excluding the cost of launch. NASA Mission of Opportunity costs are capped at $80 million each.
“NASA’s Explorers Program has a proud tradition of supporting innovative approaches to exceptional science, and these selections hold that same promise,” Thomas Zurbuchen, associate administrator for NASA’s Science Mission Directorate, said in a statement.
“From studying the evolution of galaxies to explosive, high-energy events, these proposals are inspiring in their scope and creativity to explore the unknown in our universe.”
Explorers is NASA's longest-running program and aims to provide regular opportunities for launch of space science missions. The first mission dates back to Explorer 1 in 1958, which discovered the Van Allen radiation belts surrounding Earth. More than 70 U.S. and cooperative international scientific space missions have been part of the program.
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Andrew is a freelance space journalist with a focus on reporting on China's rapidly growing space sector. He began writing for Space.com in 2019 and writes for SpaceNews, IEEE Spectrum, National Geographic, Sky & Telescope, New Scientist and others. Andrew first caught the space bug when, as a youngster, he saw Voyager images of other worlds in our solar system for the first time. Away from space, Andrew enjoys trail running in the forests of Finland. You can follow him on Twitter @AJ_FI.