WASHINGTON — Cost overruns on three instruments for NASA’s Europa Clipper spacecraft led NASA to consider dropping them from the mission and ultimately requiring significant changes to some of them.

At a July 9 briefing to the Committee on Astrobiology and Planetary Sciences of the National Academies, NASA officials said they recently conducted “continuation/termination reviews” for the three instruments: a camera, infrared imaging spectrometer and mass spectrometer. Those reviews were prompted by cost overruns on those instruments.

“We’ve been struggling on cost growth on Clipper for some time,” said Curt Niebur, program scientist for the mission at NASA Headquarters. “Overall, we’ve been largely successful in dealing with it, but late last fall, it became clear that there were three instruments that experiencing some continued and worrisome cost growth.”

The outcome of the reviews, he said, could have ranged from making no changes to the instruments to, in a worst-case scenario, terminating the instruments. The leadership of NASA’s Science Mission Directive recently decided to keep all three instruments, at least for now.

“We are flying the entire payload, and every decision in the memo is intended to maximize the chance that we will retain the entire payload through launch,” he said.

However, there will be changes to some instruments, particularly to the Mass Spectrometer for Planetary Exploration/Europa, or MASPEX. That instrument is designed to measure the composition of the Jovian moon’s very tenuous atmosphere and any plumes of material that erupt from its surface.

MASPEX was suffering serious cost and schedule problems, Niebur said, a situation “that deteriorated further” during and after a risk assessment earlier this year. “It was really felt that significant relief was needed to avoid termination of MASPEX,” he said.

“We pulled out all the stops” to keep the instrument on the mission, he said, because of its importance in evaluating the habitability of Europa. The instrument now has a cost cap and its risk classification has changed from Class B, with a low tolerance for risk, to Class D, with a greater acceptance of risk. The mission’s overall “Level 1” science requirements will also be modified to reduce the mission’s reliance on MASPEX and the instrument’s performance requirements.

NASA also decided to replace the principal investigator (PI) of MASPEX, which had been Hunter Waite of the Southwest Research Institute. Niebur said that the institute, which retains responsibility for developing the instrument, has appointed an acting PI, Jim Burch, and will nominate a permanent replacement to be approved by NASA Headquarters.

Niebur praised Waite for an “incredible job” on MASPEX, but that new leadership was needed to keep the instrument on the mission. “To get it the final 10 yards to the end zone, we need somebody with more experience,” he said. “Jim Burch is a good match for that.”

A second instrument, the Europa Imaging System (EIS), will also get a cost cap. The camera system was suffering technical issues he described as not particularly surprising, but those problems, combined with cost growth, posed a greater concern.

One option considered by the agency was to remove a wide-angle camera (WAC) from the instrument “because it has less intrinsic scientific value” than its narrow-angle camera, Niebur said. Instead, NASA decided to keep both cameras and place a cost cap on EIS, with instructions to prioritize development of the narrow-angle camera. The mission’s Level 1 requirements will change to reduce reliance on the wide-angle camera.

“If you have to cut corners on the WAC, that’s OK,” he said. “In the worst-case scenario, if we have to go forward without the WAC, we will.”

The third instrument, the Mapping Imaging Spectrometer for Europa (MISE), did not see significant changes. Niebur said that reviewers found its design had stabilized after past issues which affected its cost and schedule. “The decision for MISE was straightforward, to adjust the cost and the schedule and to simply continue on,” he said.

These reviews are not the first time that instruments for the mission have faced problems. Last year, NASA terminated a magnetometer instrument called ICEMAG because of continued cost growth and technical problems. The agency replaced it with a simpler and less expensive magnetometer with a different PI.

Some members of the committee wondered if the instruments were being singled out for the overall cost growth in the mission, which as an agency cost commitment of $4.25 billion. Jan Chodas, project manager for Europa Clipper at the Jet Propulsion Laboratory, said that the instruments used about the same amount of budget reserves as the spacecraft, or about $70 million each. However, she said that dollar amount was a much larger fraction of the overall cost to build the instruments than for the spacecraft.

Chodas said that Europa Clipper now has a launch readiness date of 2024, a year later than plans announced last year. There are launch opportunities in the summer and fall of 2024 for the mission, including an August launch window using the Space Launch System that would send the spacecraft directly to Europa. An October launch window would require Mars and Earth gravity assists, extending the flight time, but could also be done by commercial launch vehicles such as SpaceX’s Falcon Heavy.

NASA remains engaged in a debate with Congress about how to launch Europa Clipper. Congress has for several years mandated the use of SLS for the mission as well as a follow-on Europa lander mission. NASA has requested the ability to use other vehicles, citing cost savings and the lack of available SLS vehicles, which for the next several years are devoted to the Artemis lunar exploration program.

A House appropriations bill introduced July 7 would give NASA some flexibility, requiring Europa Clipper to launch on SLS only “if available,” a provision not found in previous spending bills. However, some in Congress continue to press NASA to use SLS on the mission. “NASA must increase the pace of SLS production to ensure an SLS is available for the Europa missions,” said Rep. Robert Aderholt (R-Ala.), ranking member of the commerce, justice and science appropriations subcommittee, at a July 8 markup of the bill.

Chodas said that while the Europa Clipper program has been working to support launches both on SLS and alternative vehicles, she needs a decision soon on which vehicle will launch the spacecraft. That uncertainty forced the program to delay its critical design review from August to December of this year.

“We really need a definitive decision on that launch vehicle by the end of this calendar year,” she said.

Jeff Foust writes about space policy, commercial space, and related topics for SpaceNews. He earned a Ph.D. in planetary sciences from the Massachusetts Institute of Technology and a bachelor’s degree with honors in geophysics and planetary science...