WASHINGTON — As NASA prepares for a key review of the Europa Clipper mission, a report by the agency’s inspector general warns that the mission’s launch may face delays and significant cost increases.

The report by NASA’s Office of Inspector General (OIG), released May 29, also said that a follow-on lander mission, which Congress has funded over the objections of the agency, is also unlikely to be ready for launch in 2025 as directed and likely will cost significantly more than expected, upsetting the balance of priorities for the agency’s planetary science missions.

The Europa Clipper mission is currently scheduled for launch in 2023 to go into orbit around Jupiter. The spacecraft will make dozens of close approaches to Europa, a large icy moon believed to harbor a subsurface ocean of liquid water. The spacecraft’s instruments will help scientists determine if Europa is potentially habitable.

Europa Clipper has advanced faster than NASA originally intended thanks to the advocacy of now former Rep. John Culberson (R-Texas), a House appropriator who secured far more money for the mission than requested. The OIG report notes that in fiscal years 2013 through 2019, Congress provided $2.04 billion in funding for Europa missions, primarily Europa Clipper, while NASA requested only $785 million in the same period.

That funding, though, may not be sufficient to keep the mission on track for a 2023 launch, a date that has already slipped a year from original plans. “Despite robust early-stage funding, a series of significant developmental and personnel resource challenges place the Clipper’s current mission cost estimates and planned 2023 target launch at risk,” the OIG report states.

Among the issues cited in the OIG report was the selection and development of Europa Clipper’s instruments. The report found that the project selected instrument proposals with cost estimates “later found to be far too optimistic.” This was exacerbated by an instrument selection process intended to avoid conflicts of interest that largely excluded the Europa Clipper management team at the Jet Propulsion Laboratory because some of the instrument proposals came from teams also at JPL. This, the report states, may have led to integration issues, such as with a radar instrument whose design changed when the mission changed from nuclear to solar power.

NASA has since terminated one of the originally selected instruments, a magnetometer called ICEMAG, and plans to replace it with a less complex facility magnetometer. However, several other instruments have also suffered significant cost increases and are at risk of “de-scope reviews” that could alter their designs or remove them entirely.

A second issue is a workforce shortage issue at JPL, where several other missions are competing with Europa Clipper for personnel. The OIG report states that Europa Clipper was understaffed by 42 full-time equivalent positions as of October 2018, a shortfall that grew to 67 by December.

Barry Goldstein, project manager for Europa Clipper at JPL, said at a March meeting of the Space Studies Board’s Committee on Astrobiology and Planetary Science that workforce availability was a key reason the mission’s target launch date recently slipped by a year to 2023. “It was pretty clear to me that we were not going to make it,” he said. “We had just too many shortfalls in our workforce.”

Complicating the mission’s development is continued uncertainty about the choice of launch vehicle. Congress has repeatedly directed NASA to use the Space Launch System for both Europa Clipper and the later lander mission, although NASA has pushed for using a commercial launch vehicle, either United Launch Alliance’s Delta 4 Heavy or SpaceX’s Falcon Heavy, to launch the mission instead. While only SLS can send Europa Clipper on a direct trajectory to Jupiter, saving several years of travel time, NASA argued in its fiscal year 2020 budget request that using a commercial vehicle could save more than $700 million.

The OIG report found a much small cost savings by switching vehicles. NASA estimates that using an SLS will cost $876 million for Europa Clipper, versus $450 million for either Delta 4 Heavy or Falcon Heavy. When savings in mission operations created by the shorter travel time are factored in, using the SLS costs less than $300 million more than either commercial alternative.

However, the report concludes it’s too late to produce an SLS in time for a 2023 launch. NASA estimates it needs 52 months to produce a core stage for the SLS, the long-lead item for the vehicle, and six months for launch integration. “NASA would have had to order the third Core Stage in September 2018 to make a July 2023 launch window,” the report states. “As of March 2019, NASA had not ordered a third Core Stage.”

The report comes ahead of a milestone called Key Decision Point C, expected this summer, when NASA will set a formal cost and schedule estimate for the mission through a process known as joint confidence level (JCL) analysis. A similar analysis performed last October by the mission’s standing review board, according to OIG report, “determined a very low probability for a 2022 launch and provided a 70 percent confidence level for a 2024 launch at a mission cost between $3.5 billion to $4 billion.” That cost, the report noted, is far higher than earlier projections, which pegged the mission at around $2 billion, and approaches the original cost estimate for a Europa mission in the 2011 planetary science decadal that the report considered too expensive for NASA to pursue.

The OIG report was even more critical of the proposed lander mission, which Congress has directed NASA to launch by 2025. “NASA will be unable to meet a 2025 launch date due to workforce and schedule risks with the Lander and SLS development,” the report concluded. It concluded that, based on development times for flagship-class missions like the Mars 2020 rover, “the earliest it could launch would be late 2026,” a date that assumed that the mission started Phase A development at the beginning of 2019, which it has not.

“Both of the planned Europa missions are ambitious endeavors that should be grounded in realistic cost and schedule commitments,” the report concluded.” Given the unresolved technical, workforce, and budgetary challenges, we believe NASA—motivated by congressional mandates—is working towards unattainable Clipper and Lander launch dates.”

Complicating the future of the missions is the fact that Culberson lost reelection in 2018 and is no longer in Congress to advocate for the mission on the House Appropriations Committee. A version of a fiscal year 2020 spending bill approved by that committee May 22 provides $592.6 million for Europa Clipper, the amount requested by NASA, but no funding for the lander mission. The report accompanying the bill directed NASA to use the $195 million in lander funding provided in 2019 to continue technology development for the mission through 2020.

However, the bill retained language directing NASA to use the SLS to launch both missions, and also kept the requirement to launch Europa Clipper in 2023 and the lander in 2025, despite the lack of funding for the lander mission in the 2020 bill.