NASA Picks a Far-Infrared Telescope to Open a New Class of Missions

NASA has chosen a telescope designed to see the cold, dusty universe in far-infrared light as the first mission in a new category of space science projects, a selection that astronomers had awaited for years and that comes as the agency’s science budget remains under strain.

The mission, called the Probe far-Infrared Mission for Astrophysics, or PRIMA, was announced on September 23. It now moves into its preliminary design phase. The project still has to pass a formal confirmation review before it is fully approved, and NASA has set a cost cap of about $1.2 billion, not counting the launch and some other expenses. If development stays on track, the telescope would launch in 2033 for a planned five-year mission.

PRIMA is the first of what NASA calls Probe Explorers, a class of missions meant to fill the gap between small, inexpensive Explorer satellites and flagship observatories such as the James Webb Space Telescope, which cost many times more. The National Academies recommended creating the category in their 2020 decadal survey of astronomy and astrophysics, the report that sets the field’s priorities for a decade.

The telescope would carry a mirror about 1.8 meters, or 5.9 feet, across. Far-infrared light is emitted by cool gas and dust, much of which is invisible to optical telescopes and only partly reachable by Webb, which works at shorter infrared wavelengths. Because Earth’s atmosphere blocks most of this light, the observations have to be made from space.

NASA says the mission has three main scientific goals: to trace how galaxies and the black holes at their centers grew over cosmic time, to follow how dust and heavy elements built up in the universe, and to learn more about the origins of planets around other stars, including the role of water and other ingredients in the disks where planets form. Sky & Telescope reported that the mirror would be chilled to about 4.5 degrees above absolute zero so that the telescope’s own heat does not drown out the faint signals it is trying to detect, and that the observatory would operate from a point in space about 1.5 million kilometers from Earth.

PRIMA would pick up where the European Space Agency’s Herschel observatory left off when it stopped operating in 2013. Researchers involved in the project say its detectors would let it survey the sky faster and pick up fainter sources than earlier far-infrared instruments, bridging the gap between Webb’s shorter wavelengths and the longer ones studied by radio telescopes.

NASA’s Jet Propulsion Laboratory in Southern California will manage the project, working with the Goddard and Marshall space flight centers. Several international space agencies are partners, including those of France, Germany, Canada, South Korea, Japan, Italy and the United Kingdom.

Sky & Telescope reported that a competing proposal, an X-ray observatory known as AXIS, lost out in part because of federal budget turmoil. The case for the probe class is that it can deliver major science at a fraction of flagship prices; the risk, as the AXIS outcome shows, is that even capped missions depend on budgets that can shift long before a 2033 launch.