Will budget cuts force NASA to withdraw from Europe's next Venus mission?

The European Space Agency (ESA) is still in the dark about NASA's participation in its Venus exploration mission Envision despite the project's tight deadline, ESA representatives said in a recent media briefing.

Envision, which began construction in 2025, will map the atmosphere and geology of Earth's closest neighbor, the fiery Venus. The spacecraft will rely on a NASA-made instrument called VenSar — a novel synthetic aperture radar — to map the planet's surface in three dimensions and with a resolution of up to 3 feet (10 meters).

Funding for the instrument, currently being built by engineers at NASA's Jet Propulsion Laboratory (JPL), is, however, uncertain. The Trump administration included VenSar in the sweeping cuts to NASA's science funding, which are part of the president's 2026 budget proposal. Although the U.S. Congress is taking steps to restore the funding, insiders told Space.com that ESA shouldn't wait too long and might be better served to cut its ties with NASA and build the instrument in Europe if it wants to avoid years of delays.

Envision must lift off for its 15-month journey to Venus in 2033 at the latest, or the distance between the two planets will be such that the trip would be unfeasible, ESA's Director of Science Carol Mundel said at the media briefing, which was held on Jan. 8. Mundel said that missing the 2033 deadline would mean having to wait for at least three years to launch during the next planetary alignment.

"We are in constant contact with NASA on Envision," Mundel said in the online briefing. "We remain in normal collaboration with NASA, but we also appreciate that NASA do continue to have some financial challenges."

Technology exists in Europe to develop VenSar domestically. In fact, the instrument was initially supposed to be built by Airbus in the United Kingdom. But sources say that whoever would be chosen to replace the instrument needs to begin moving fast to make the deadline.

"We continue to discuss with our member states how we can continue to deliver this mission," Mundel said. "We are very well aware of those deadlines."

Mundel added that NASA JPL teams continue "business as usual" with their work on VenSar and have recently passed the preliminary design review, a key early-stage milestone before production begins.

Overall, 19 ESA missions will face funding shortfalls if the Trump administration gets its way. Many of those collaborations, however, are expected to be rescued by Congress, including the gravity-wave detector LISA (the Laser Interferometer Space Antenna), a planned constellation of three satellites orbiting in a triangular formation 2.5 million kilometers (1.6 million miles) apart.

On Jan. 6, the U.S. Congress published its budget proposal, which would restore most of the funding cut by Trump and provide NASA with $7.25 billion for science in 2026. The overall NASA budget for 2026 would be $24.4 billion in 2026, only about one billion less than the 2025 spending. (Trump's budget request allocated just $18.8 billion to the agency.)

The confirmation of Jared Isaacman as NASA's next administrator, however, raised concerns among some experts due to Isaacman's known preference for exploration and commercial space technology.

During the media briefing, ESA Director General Joseph Aschbacher said he had not yet met with Isaacman to discuss priorities.

ESA is expecting a busy year overall, Aschbacher said during the briefing, with 65 new satellites built with ESA's participation to be launched. In addition, the BepiColombo spacecraft, launched in 2018, is set to arrive at Mercury, its destination, in December. The probe will commence scientific exploration of the least understood planet of the inner solar system in early 2027.

The delayed HERA mission, launched in October 2024, is also going to meet its study object this year — the double asteroid Didymos/Dimorphos. The smaller of the two space rocks, Dimorphos, was the target of NASA's DART asteroid deflection experiment in 2022. HERA will enable scientists to study the effects of DART's impact in great detail.

In addition to the ongoing uncertainties around NASA's future direction, ESA has some choices to make in its own Human and Robotic Exploration program due to the decisions of its member states, which were made at the agency's latest high-level council. Although the summit, held in Bremen, Germany, in November of last year, passed a record-breaking budget of 22.1 billion Euros ($25.63 billion) for the next three years (an increase of 5 billion Euros, $5.8 billion, compared to ESA's 2022-2025 budget), the member states assigned much less money to human and robotic exploration than the agency had hoped for.

"Based on the level of subscriptions we received in Bremen, we will have to set a number of priorities in [the exploration] program for the years 2026 to 2028," Daniel Neuenschwander, ESA's director for human and robotic exploration, said at the Jan. 8 briefing. "By the end of February, we will have the main priorities set."

Most of ESA's space exploration programs are conducted in cooperation with NASA, including missions to the International Space Station and exploration of the moon and Mars. The NASA budget chaos might possibly impact Europe's delayed ExoMars Rosalind Franklin rover. The Mars Sample Return mission, for which ESA was developing a return vehicle, is not expected to go ahead, and the agency is looking to repurpose the technology for an entirely new mission.