NASA announced on September 23 that PRIMA (PRobe far-Infrared Mission for Astrophysics) is advancing to Phase B — preliminary design and technology development. It is the first mission in a brand-new class called Probe Explorers, with project costs capped at $1.2 billion, targeting launch in 2033 for a planned five-year mission.
The mission is managed by NASA's Jet Propulsion Laboratory, with contributions from the Goddard Space Flight Center and the Marshall Space Flight Center. The $1.2 billion figure is a cap on project costs, excluding launch. PRIMA is targeted to launch in 2033 and operate from the Sun-Earth L2 point for five years — picking up the cadence right after the Nancy Grace Roman Space Telescope lifts off in 2026.
Probe Explorers sits between the $10-billion-plus flagship tier (Webb, Roman) and smaller Explorer missions. As Ars Technica put it, NASA is trying to build a billion-dollar space telescope in record time.
"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 of NASA's Science Mission Directorate.
The science goals are concrete: the origins of planets outside our solar system, how galaxies and their black holes have grown and evolved together over cosmic history, and how dust and heavy elements have built up in the universe — ultimately, why the universe looks the way it does today.
PRIMA's 1.8-meter (5.9-foot) primary mirror is tuned to far-infrared wavelengths, 24 to 261 microns — a slice of the spectrum that the James Webb Space Telescope largely skips and that ground-based radio telescopes can't reach. Far-infrared light comes from the coldest, dustiest places in the cosmos: the dust clouds where stars are born, hidden black holes deep inside galaxies.
The last space observatory able to see this band was ESA's Herschel, retired in 2013 after its liquid helium ran out. For more than a decade, the far infrared has been a blind spot in space astronomy. PRIMA will fill it, complementing Webb and Chile's ALMA radio array.
The enemy of far-infrared astronomy is heat — a telescope's own thermal glow drowns out the signal. PRIMA's all-aluminum mirror will be actively cooled to 4.5 Kelvin (about –269°C) by a closed-cycle helium-3 cryocooler, with no stored liquid helium aboard. Herschel's lifespan was dictated by its helium supply — about four years. PRIMA has no such countdown; its five-year design life isn't limited by coolant.
The detectors are another key advance: kinetic inductance detectors (KIDs) developed by Dutch engineers, whose sensitivity is limited only by the natural quantum background. Per JPL, they can complete spectral surveys 3 to 5 times faster than any previous far-infrared instrument.
This is an international effort, with seven partner space agencies: France's CNES, Italy's ASI, Germany's DLR, Canada's CSA, South Korea's KASI/KASA, Japan's JAXA, and the UK's UKSA. Caltech and its IPAC center, Johns Hopkins University (three team members), and Imperial College London are also deeply involved.
Phase B is no guarantee. PRIMA must still pass a confirmation review, where NASA will assess technical, programmatic, and cost performance before green-lighting Phase C, the implementation stage. Only then do the $1.2 billion cap and the 2033 launch target truly lock in. For a telescope meant to serve until 2038, this is just the first step of a long journey.