NASA is changing one of the key scientific instruments on Europa Clipper, its next major mission to the outer planets of the solar system, and has brought in a scientific luminary to lead it, project leaders announced today. Clipper is set to orbit Jupiter and study Europa, the icy Jovian moon, across multiple flybys. Earlier this month, NASA headquarters terminated the mission’s ICEMAG magnetometer instrument, citing overruns in its estimated budget. The move left the spacecraft without an essential tool to study Europa’s interior ocean, where astrobiologists hope extraterrestrial organisms might be found.

NASA has chosen Margaret Kivelson, a professor emerita at the University of California, Los Angeles, to lead the effort to develop the science for a simplified magnetometer to replace ICEMAG. The instrument will measure Europa’s magnetic field and gather data on the ocean’s depth and salinity. Kivelson previously led the magnetometer team on the spacecraft Galileo, which orbited Jupiter in the 1990s. She is credited with discovering the ocean beneath Europa’s ice shell.

ICEMAG’s estimated cost had grown to $45 million—nearly three times its proposed price—according to NASA headquarters. Sophisticated internal sensors had vexed the ICEMAG science team and led to much of the extra expense. The new magnetometer will do away with those sensors, using simplified components instead. The downside is that the new sensors will likely lose calibration over time and drift in response to temperature variations. The team is now devising strategies to compensate for these effects.

Robert Pappalardo, the project scientist of the Europa Clipper mission, made the announcement earlier today at the spring meeting of the Committee on Astrobiology and Planetary Science in Washington, D.C. “I recommended to NASA that we immediately stand up a team leader from within the team, and with established magnetometry expertise,” Pappalardo said. “I have the pleasure of announcing that Dr. Margaret Kivelson has accepted that role.”


NASA headquarters officially signed on to the Clipper mission in 2015. The spacecraft is due to launch in 2023, and upon entering Jupiter’s orbit, will collect data on Europa by making multiple close encounters with the icy moon. Today, Clipper is in the middle of perhaps the most critical part of its development. By the end of the year, decades of dreams by hundreds of people should finally begin manifesting as physical realities, in the form of instrument and spacecraft components. Next year, NASA’s Jet Propulsion Laboratory (JPL) in Pasadena, Calif., which is leading the spacecraft’s design and construction, will begin putting the pieces together.

Everyone who has ever held a science textbook is familiar with some of the results of famous space missions—big, beautiful images of Saturn from the Cassini orbiter, for instance, or the famous Pale Blue Dot portrait of Earth by the Voyager 1 probe. But the long road to launch is less understood. Todd May, the former director of Marshall Space Flight Center, noted in a talk several years ago that journalists tend to describe the “real work” as beginning once the spacecraft has left Earth. But, he asserted, getting through development—bringing a spacecraft from PowerPoint to the launchpad—is the real challenge. “The first inch off the ground is the hardest part,” he said. The Clipper science and engineering teams have for years honed and tested every aspect of design, implementation and operation of the spacecraft. The only thing they have not done is build the thing.

Europa presents unique challenges and potential rewards. The moon is located in Jupiter’s radiation belts, a punishing environment similar to the aftermath of a nuclear bomb detonation. Moreover, the spacecraft’s energy source—its solar panels—requires scientists to carefully map its trajectory to collect every available photon so far from the sun. When it reaches the far side of Jupiter, the spacecraft must be able to survive sunless, cryogenic temperatures. The prize for overcoming these challenges is a global saltwater ocean beneath its ice shell hypothesized to have the chemistry and energy necessary to sustain life. If there is non-Earth life anywhere in the solar system, it is there, experts say.

“We are gearing up for one last review needed for confirmation of the mission by NASA,” Pappalardo says. “That is where NASA says that you are ready and cleared to go build the instruments and spacecraft.” In April, the project will go through its “delta preliminary design review” (PDR)—a reevaluation of certain elements of the spacecraft that had given NASA pause. An independent board will assess whether the spacecraft’s designs match up with the mission’s requirements, and that cost, risk and schedule correspond to reality. Once completed successfully, the project will go through another review at NASA headquarters called “key decision point C.” The agency will commit to the calendar and cost determined during the PDR, and the process of finalizing design and fabricating the hardware can begin. “It’s a really fascinating part of the process seeing how everything fits together,” says Zibi Turtle, principal investigator of the Europa Imaging System investigation. “Everybody builds their own instrument, and when they stick them all on the spacecraft, you have to make sure there aren’t any unexpected interactions.”

One of the issues troubling NASA has been the marriage of Clipper’s solar panels with its ice-penetrating radar, called REASON. Originally, the massive radar antennas—used to study the structure of the ice shell, locate lakes within it and find interfaces between the ice and the ocean—was to be mounted on the spacecraft like any instrument. But the radar team and JPL engineers determined that building the radar into the solar array would prevent interference between the two components, while taking up less physical space. This was a fairly radical design in a business where “heritage”—the use of proven technologies—customarily carries the day. In January, REASON passed its “integrated wing review”—an evaluation of its integration with the solar arrays, following separate preliminary design reviews of each. “They showed me off the steps of the scaffolding,” says Don Blankenship, REASON principal investigator, joking that he avoided execution.

But perhaps the greatest unknown for the mission is its ride to space. According to the law funding the spacecraft, Europa Clipper must launch in 2023 on NASA’s Space Launch System rocket currently under development. It is becoming increasingly apparent, however, that this rocket will not be ready in time, which means Clipper might have to ride on a smaller commercial rocket. Such a change would require altering the law—something easier said than done—and would also add a delay, as the heavy-lift SLS would be able to send the spacecraft on a direct, 28-month flight to Jupiter. SpaceX’s Falcon Heavy rocket, a backup commercial option, is not powerful enough for such a trajectory and would require a six-year tour of the solar system to deliver Clipper to its target.


Another challenge for Clipper is the recent loss of its benefactor in Congress. As chair of the Commerce, Justice, and Science appropriations subcommittee of the House of Representatives, John Culberson, the former Texas Republican representative, proved to be Europa’s protector. Unlike every other mission in NASA’s portfolio, he put Clipper not in “report language” that accompanies an appropriations bill (but is not legally binding), but rather, for several years now, into the actual bill. Accordingly, he has been known to boast, by federal law Clipper and Europa Lander (a follow-on mission that would use Clipper data to touch down on the surface and dig around for evidence of life) are the only two missions that it is illegal for NASA not to fly.

When Culberson was defeated for reelection last year, things looked grim. He still had a few tricks up his sleeve, however. “Before I left,” he says, “I won the support of a number of my House colleagues to be sure that they would protect those missions.” And tying Clipper to SLS should help. The rocket is being built in Alabama, home of the powerful chair of the Senate Appropriations Committee, as well as the ranking member of the House appropriations subcommittee responsible for NASA. Those representatives have a vested interest in keeping SLS alive and giving it something to do. Clipper will be ready to launch long before any other payloads for the rocket, such as major missions to the moon or Mars.

In the fiscal year 2019 budget that passed Congress, Culberson directed $545 million to Clipper—enough to get the project over its peak funding year, keeping the team on track for an on-time launch. Moreover, because Congress in recent years has passed continuing resolutions in lieu of full budgets, the record $2.8 billion planetary science allocation will likely remain in force beyond 2019.

After the April design review, Clipper will likely enter the final design and fabrication phase in August. If all goes well, it will lift its first inch from the launchpad in 2023.