NASA opens its Probe Explorer class with a far-infrared telescope capped at $1.2 billion

The $1.2 billion is a ceiling on project cost. Launch and other non-project costs sit outside it, NASA said, and the announcement does not state a launch vehicle or a launch cost ^[5][20]. Anyone setting that number beside a past astrophysics mission has to add the rocket back in first.

Phase B pays for preliminary design and technology development ^[3]. The cap applies if the mission is confirmed, and confirmation comes at a review of technical, programmatic and cost performance that decides readiness to begin implementation in Phase C ^[4][5].

PRIMA's telescope is 5.9 feet across ^[7], about 1.8 metres ^[17]. It will run deep, sensitive surveys in far-infrared light, a band NASA describes as bridging the gap between existing infrared observatories such as the James Webb Space Telescope and radio telescopes ^[7]. The stated science targets are the origins of planets outside the solar system, how galaxies and their black holes have grown over cosmic history, and how dust and heavy elements built up ^[8]. Launch is targeted for 2033 with a planned five-year mission ^[6], so planned operations run to about 2038 ^[18].

A 2020 decadal survey from the National Academies recommended NASA establish the Probe Explorers class ^[11]. NASA said it chose PRIMA after evaluating concept studies on scientific merit against the decadal recommendations, on the feasibility of their development plans on cost and schedule, and on use of technologies that could support the development of future large missions ^[12]. Part of a probe's job, by NASA's own selection logic, is maturing hardware a later flagship can use.

"A single mission alone can't probe all the universe's mysteries. But by extending the survey capabilities of our fleet into far-infrared wavelengths with PRIMA, we're enabling an incredibly comprehensive look at the cosmos," said Shawn Domagal-Goldman, director of NASA's Astrophysics Division ^[9]. On the pipeline, he said: "With our Webb and Roman space telescopes, we set a cadence of launching premiere-class missions in both halves of the decade. We're going to keep that up and kick off the next decade with PRIMA, as part of a pipeline that will consistently have missions of this caliber ready to go" ^[10].

The Explorers Program is NASA's oldest continuous program, built to give frequent, low-cost access to space through investigations led by principal investigators ^[15]. It has launched more than 100 missions since Explorer 1 in 1958, which discovered Earth's radiation belts, among them Uhuru and the Cosmic Background Explorer, whose investigators won Nobel prizes ^[16].

Now NASA has to hold that number. Far-infrared detectors need cold optics, and thermal and cryogenic engineering tends to run over schedule. Phase B is when that gets priced, and the confirmation review is when NASA says whether the price fits.