NASA Advances New $1.2 Billion Infrared Telescope Toward 2033 Launch

NASA has cleared its next astrophysics observatory to begin detailed design, advancing a far-infrared space telescope called PRIMA into what the agency terms Phase B of development. The decision, announced Wednesday in a release from NASA headquarters, makes PRIMA the first mission in a new category of astrophysics spacecraft, called Probe Explorers, that sits between the agency's flagship observatories, such as the James Webb Space Telescope, and its smaller, cheaper Explorer-class satellites.

PRIMA, short for the PRobe far-Infrared Mission for Astrophysics, is built to observe a stretch of the infrared spectrum that neither Webb nor ground-based radio telescopes can reach well. If the mission clears a confirmation review expected over the next year or two, the observatory will launch in 2033 for a planned five-year mission at the Sun-Earth L2 point, the same gravitationally stable perch roughly a million miles from Earth where Webb currently operates.

The numbers

PRIMA's telescope is modest by space-observatory standards, a 1.8-meter (5.9-foot) mirror, compared with Webb's 6.5 meters. What distinguishes it is temperature and detector technology. The telescope and its instruments will be chilled with liquid helium-3 to 4.5 kelvin, or roughly minus 450 degrees Fahrenheit, cold enough that the observatory's own heat does not overwhelm the faint infrared glow it is meant to detect. NASA has capped PRIMA's project cost at $1.2 billion, not including launch and other non-project expenses.

Two instruments will do the observing. FIRESS, a spectrometer, covers wavelengths from 24 to 235 microns; PRIMAger, an imaging polarimeter, extends coverage out to 261 microns. According to University of Maryland astronomers on the PRIMA science team, the instruments are expected to survey hundreds of galaxies and their central black holes across roughly 10 billion years of cosmic history, measuring how quickly they consumed gas and formed stars. Caltech physicist Jonas Zmuidzinas, whose detector research underlies the mission's sensors, has said the resulting sensitivity gain over earlier far-infrared observatories amounts to a factor of about a thousand.

A decade-long gap in the sky

Far-infrared astronomy has been without a dedicated space telescope since the Herschel Space Observatory, a European Space Agency mission that NASA helped instrument and operate, ran out of coolant in April 2013 after roughly four years of observations. NASA's airborne infrared telescope SOFIA, a modified Boeing 747SP that carried instruments above most of the atmosphere's infrared-blocking water vapor, covered part of that gap until it was retired in 2022. Since then, astronomers have had no dedicated way to study far-infrared light, the wavelength range in which much of the radiant energy released by stars and galaxies over cosmic history shows up after being absorbed by dust and re-emitted at longer wavelengths.

The push to fill that gap traces to the National Academies' 2020 Decadal Survey of astronomy and astrophysics, which recommended NASA create a new, mid-sized "Probe" mission class. NASA funded two competing concept studies in 2024, PRIMA and an X-ray observatory called AXIS, each receiving roughly $5 million for a year-long Phase A study. AXIS was later found not to meet the schedule and budget terms of the original competition and dropped out of contention, leaving PRIMA to advance alone toward this week's decision.

The detectors that make PRIMA possible trace back nearly three decades, to superconducting sensor research Zmuidzinas began with JPL engineer Rick LeDuc in 1999 and later tested at the Caltech Submillimeter Observatory. That technology has since been refined through NASA missions including Spitzer, Herschel and this year's SPHEREx all-sky survey, according to Caltech's account of the mission. A peer-reviewed description of the observatory's design and science case was published this summer in the Journal of Astronomical Telescopes, Instruments, and Systems.

Who is involved

NASA's Jet Propulsion Laboratory in Southern California will manage the mission and build the spacecraft, with Caltech's Infrared Processing and Analysis Center, known as IPAC, running mission science and processing the data. IPAC deputy director Rachel Akeson has noted the center's involvement in NASA infrared missions stretches back four decades, to the Infrared Astronomical Satellite launched in 1983. NASA's Goddard Space Flight Center in Maryland and Marshall Space Flight Center in Alabama round out the agency side, alongside space agencies in France, Italy, Germany, Canada, South Korea, Japan and the United Kingdom, which are contributing instrument hardware and funding.

University researchers make up much of the science team. At the University of Maryland, astronomy professors Alberto Bolatto and Sylvain Veilleux will lead working groups on galaxy evolution and active galactic nuclei, respectively. Once operating, PRIMA is expected to serve as a shared resource for the broader astronomy community through competed observing time, in the manner of Webb and Hubble, rather than a single team's private instrument.

'Humanity's next window'

"The PRIMA mission is humanity's next window into the deep universe. It will unveil the obscure across cosmic time to better understand the formation of planets, stars, black holes, and even how water on Earth came to be," said Nicky Fox, associate administrator for NASA's Science Mission Directorate.

Shawn Domagal-Goldman, director of NASA's Astrophysics Division, said a single mission "can't probe all the universe's mysteries" on its own, but that extending NASA's survey capabilities into far-infrared wavelengths would allow "an incredibly comprehensive look at the cosmos." He described PRIMA as the start of a new decade of missions following the established cadence of Webb and the Roman Space Telescope.

At Caltech, which developed the detector technology at the heart of both of PRIMA's instruments, president Ray Jayawardhana called the mission "a giant leap for far-infrared astronomy, born from decades of daring ingenuity at Caltech and JPL." IPAC scientist Lee Armus, a PRIMA co-investigator, said the observatory would help researchers "discover and understand the role of powerful molecular outflows in galaxies over cosmic time," a reference to the streams of gas that can shut down star formation in a galaxy.

What happens next

Phase B is a roughly year-long stage in which the PRIMA team will refine the spacecraft's design, mature its technology and prepare for a confirmation review that weighs the mission's technical readiness, cost and schedule. Only after that review passes does NASA formally commit to Phase C, full-scale implementation, and to building flight hardware. A miss on cost or schedule at that stage is the kind of setback that sank AXIS, PRIMA's former rival, though NASA officials have not signaled similar concerns about PRIMA's current plan.

If the observatory is confirmed and stays on schedule, PRIMA would launch in 2033 as the debut of a mission class NASA has said it intends to repeat through the next decade, part of what Domagal-Goldman described as a pipeline meant to keep mid-sized astrophysics missions moving behind the far costlier flagship telescopes. The astronomy community's most immediate opportunity to shape that path will come through the mission's general-observer program, which will open telescope time to researchers outside the core PRIMA team once the spacecraft begins science operations.