The White House’s fiscal year 2027 budget request for NASA, released on 3 April, proposes cutting the agency’s total funding from $24.4 billion to $18.8 billion, a reduction of roughly 23 percent. Within that, the Science Mission Directorate would be cut by 46 percent, from $7.25 billion to $3.89 billion. Adjusted for inflation, the proposed NASA top-line would be the lowest since 1961, according to analysis by The Planetary Society.
The proposal does not reduce spending evenly across the agency. The Exploration directorate, which covers the Artemis Moon programme and human spaceflight, would receive a 9 percent increase, to $8.51 billion. Everything else shrinks. Space Technology would fall 32 percent. Aeronautics, 35 percent. The Office of STEM Engagement would be eliminated entirely.
What the request actually terminates
The White House described the science cuts as targeting “over 40 low-priority” missions. In a notable departure from previous budget practice, the request does not explicitly zero out those missions by name. Instead, as Casey Dreier, Chief of Space Policy at The Planetary Society, noted in his 23 April analysis, the missions simply disappear from the budget document. The only way to identify what is proposed for termination is to compare the FY 2027 request line by line against the FY 2026 and FY 2025 documents and note the absences.
After that comparison, The Planetary Society counted 53 missions likely facing termination, spanning all four major science divisions. The Planetary Society noted that The Planetary Society and multiple media organisations have submitted repeated requests to NASA for confirmation of the proposed terminations since early April. NASA had not responded as of the date of publication of that analysis.
The breakdown, by division: 17 heliophysics missions, 16 Earth science missions, 10 astrophysics missions, and 10 planetary science missions. The estimated lifecycle cost of the operational assets proposed for cancellation totals approximately $13.2 billion, according to The Planetary Society’s figures.
The missions involved
Among the proposed terminations are both operating spacecraft and missions in development. On the operating side: the Juno spacecraft, currently in extended operations orbiting Jupiter; New Horizons, now in the outer solar system well past Pluto; the Chandra X-ray Observatory, which has been returning high-resolution X-ray observations for nearly 25 years; the Fermi Gamma-ray Space Telescope; and the Solar and Heliospheric Observatory, a 30-year joint mission with the European Space Agency. The OSIRIS-APEX spacecraft, repurposed after delivering asteroid Bennu samples to Earth in 2023 and now on course to study asteroid Apophis following its 2029 Earth flyby, is also proposed for termination.
On the development side, the entire NASA Venus portfolio would be eliminated. This includes DAVINCI and VERITAS, both Discovery-class missions selected in 2021, and the US contribution to ESA’s EnVision mission. No comparable full-target elimination appears for any other destination in the solar system under this proposal.
Fourteen additional proposed terminations would break active international partnerships. According to The Planetary Society’s analysis, these include the Rosalind Franklin Mars rover, a joint ESA mission that NASA agreed to launch after Russia’s participation collapsed following the 2022 invasion of Ukraine; LISA, the space-based gravitational wave observatory; Athena, the planned ESA X-ray observatory; XRISM, a joint mission with JAXA; and Euclid, the ESA dark matter and dark energy telescope already in operation. Several of these missions depend substantially on US hardware or launch contributions.
In Earth science, the proposed cuts fall notably on missions monitoring atmospheric carbon dioxide and climate. OCO-2 and OCO-3, which track atmospheric CO₂, are both proposed for termination, as is the Aura satellite, which has monitored the ozone layer for two decades. The Atmosphere Observing System and CYGNSS, which provides surface wind speed data used in tropical storm forecasting, are also named in The Planetary Society’s list.
What is preserved, and why that matters
Not everything is cut. Missions with a clear relationship to the Artemis lunar programme, including the Lunar Reconnaissance Orbiter and VIPER, are retained. Mars surface assets tied to future human exploration, including the Perseverance rover and the Mars Reconnaissance Orbiter, remain in the budget, though Perseverance’s operating funds would be halved. Three missions currently in peak development and nearing launch, NEO Surveyor, Dragonfly, and the Nancy Grace Roman Space Telescope, are all funded.
The pattern that emerges from the preserved missions is not primarily about scientific priority. The 2023 Planetary Science Decadal Survey ranked missions by scientific merit, independent of their relationship to human exploration goals. The proposed budget does not track those rankings closely. What it does track, in Dreier’s reading, is proximity to the Artemis architecture.
Dreier also noted a structural problem with the budget document itself. Unlike previous requests, the FY 2027 submission does not include actual spending figures from the prior completed fiscal year, preventing the standard line-by-line comparison that congressional staff and advocacy organisations use to assess budget changes. The document also assumes, incorrectly, that Congress had enacted last year’s budget proposal, which it had not.
The congressional response
The proposal has faced early and bipartisan resistance on Capitol Hill. House Science Committee Chairman Brian Babin (R-TX), in his opening remarks at a 21 April hearing on the request, stated that many of the proposed cuts had been rejected by Congress previously and expressed confidence they would be rejected again. The hearing drew similar responses from both Republican and Democrat members.
Senator Jerry Moran (R-KS), who chairs the Senate Commerce-Justice-Science Appropriations Subcommittee, the body that funds NASA, said publicly at the annual Space Symposium on 12 April that he would work toward a balanced appropriations bill covering exploration, science, aeronautics, and workforce. A group of 22 senators, led by former astronaut Senator Mark Kelly (D-AZ), submitted a letter requesting NASA Science be funded at $9 billion in FY 2027. A bipartisan group of 103 House members signed a complementary letter, led by Planetary Science Caucus co-chairs Don Bacon (R-NE) and Judy Chu (D-CA).
On 29 April, the House Commerce-Justice-Science Subcommittee advanced a budget bill that holds NASA’s overall topline flat at the currently enacted $24.4 billion, though it includes a 17 percent cut to the Science Mission Directorate. That bill advanced to the full Appropriations Committee in a party-line vote. The Planetary Society noted that the House bill represents the likely lower bound of credible FY 2027 outcomes, making it considerably harder for the Office of Management and Budget to implement its more drastic request during any continuing resolution period.
On 1 May, The Planetary Society and more than 20 partner organisations, including professional societies, labour unions, industry associations, and academic institutions, sent a joint letter to House and Senate appropriations leadership warning that if the OMB request were enacted, it would end US leadership in space science and damage the nation’s scientific workforce in ways not easily reversed.
The open question
This is the second consecutive year the White House has submitted a proposal of this scope for NASA science. Last year, Congress walked back similar cuts and appropriated $24.4 billion for the current fiscal year; only one mission, Mars Sample Return, was ultimately cancelled. Whether that precedent holds again will depend on how quickly the Senate releases its own bill and whether the two chambers can move through the appropriations process before any continuing resolution takes effect.
The Planetary Society’s analysis notes one practical constraint that distinguishes this proposal from a normal budget disagreement: the missions proposed for termination cannot easily be restarted once shut down. Extended-mission spacecraft are not paused, they are decommissioned. International partnerships that are broken require years to renegotiate, if they can be rebuilt at all. The data that would have been collected between shutdown and any hypothetical restoration is simply gone.
The full list of 53 missions identified by The Planetary Society as likely targets for termination is available on their website. The Senate’s own CJS appropriations bill is expected in May or June.
