The launch date for the Europa Clipper mission, which is to study the fascinating moon around Jupiter and, along with the Cassini spacecraft to Saturn, is NASA's most expensive and ambitious planetary science mission, is now in doubt.
The $4.25 billion spacecraft was scheduled to launch in October aboard a Falcon Heavy rocket from the Kennedy Space Center in Florida. However, NASA revealed that the transistors aboard the spacecraft may not be as resistant to radiation as previously thought.
“The transistor issue came to light in May when the mission team was notified that similar components were failing at lower than expected radiation doses,” the space agency wrote in a blog post Thursday afternoon. “An industry alert was issued in June 2024 to notify users of this issue. The manufacturer is working with the mission team to support ongoing radiation testing and analysis efforts to better understand the risk of using these components on the Europa Clipper spacecraft.”
The moons orbiting Jupiter, a massive gas giant, are in some of the harshest radiation environments in the solar system. NASA's initial tests indicate that some transistors, which control the flow of energy through the spacecraft, could fail in this environment. NASA is currently evaluating ways to maximize the life of the transistor on Jupiter and expects to complete a preliminary analysis by the end of July.
To postpone or not to postpone
NASA's update did not indicate whether the spacecraft could still make the roughly three-week launch this year, which would bring Clipper to Jupiter in 2030.
Ars reached out to several experts familiar with the Clipper mission to gauge the likelihood of an October launch, and opinions were divided. The consensus was that there was a 40 to 60 percent chance that people would feel comfortable enough with the problem to launch this fall. If NASA engineers can’t be confident with the existing setup, the transistors would have to be replaced.
The Clipper mission has launch opportunities in 2025 and 2026, but these could result in additional delays due to the need for multiple gravitational assists. The 2024 launch would follow a “MEGA” trajectory, including a Mars flyby in 2025 and a Mars-Earth Gravitational Assist flyby in late 2026. If Clipper were to launch a year later, this would require a second Earth flyby. A 2026 launch would return to a MEGA trajectory. Ars has reached out to NASA for timelines for 2025 and 2026 launches and will provide an update if they provide this information.
Another negative consequence of delays would be the cost. If the mission were to remain on the ground for another year, it would likely result in hundreds of millions of dollars in additional expenses for NASA. This would blow a hole in the planetary science budget.
NASA’s blog post this week isn’t the first time the space agency has publicly addressed these issues with the metal-oxide-semiconductor field-effect transistor, or MOSFET. At a Space Studies Board meeting in early June, Jordan Evans, project manager for the Europa Clipper mission, said it was his biggest concern ahead of launch.
“What keeps me awake at night”
“The most challenging thing we're dealing with right now is a problem with these transistors, MOSFETs, that are used as switches in the spacecraft,” he said. “Five weeks ago, I got an email that a non-NASA customer had done some testing on these radically hard parts and found that they were going ahead (of spec), at radiation levels that were significantly lower than what we qualified them for when we were sourcing our parts, and others in the industry as well.”
Evans said at the time that things were “moving in the right direction” regarding the agency's analysis of the problem. It seems unlikely that NASA would have posted a blog post five weeks later if the problem was still steadily moving toward resolution.
“What keeps me up at night right now is the uncertainty around MOSFETs and the residual risk we're taking on,” Evans said in June. “It's hard to do the kind of low-dose testing in the time frames we have before launch. So we're collecting as much data as we can, including from missions like Juno, to better understand what residual risk we can launch with.”
These are exactly the kinds of problems scientists and engineers don’t want to encounter in the final months before the launch of such a critical mission. The stakes are incredibly high: Imagine making the decision to launch Clipper, only to have the spacecraft fail upon arrival at Jupiter six years later.
