NASA Evaluating Europa Clipper’s Ability to Withstand Radiation as Launch Nears

Three months before the scheduled launch of the $5 billion Europa Clipper mission, NASA has revealed that it is evaluating whether the spacecraft can withstand Europa’s intense radiation environment. At least some of the transistors that control the flow of electricity to operate spacecraft systems are not as radiation resistant as expected. Testing is underway to better understand the implications.

Scheduled for launch on October 10, Europa Clipper will study Jupiter’s moon Europa. Covered in ice, some scientists believe a liquid ocean flows underneath with plumes occasionally erupting through the ice. Life as we know it needs water and where there’s water there may be life prompting intense interest in whether microbial life could have evolved in Europa’s ocean. Clipper will orbit Jupiter and make about 50 passes of Europa, getting as close as 25 kilometers (16 miles) to study any ocean residue that may be on the surface. If lucky, it might even fly through a plume.

The intense radiation environment around Jupiter means the spacecraft’s electronics must be hardened to survive those repeated swingbys. Jupiter’s magnetic field is 20,000 times stronger than Earth’s, creating the most punishing radiation environment in the solar system, second only to the Sun.

Radiation-hardened spacecraft components are not uncommon. They’re needed for Earth-orbiting spacecraft that fly through the Van Allen belts and national security satellites designed to survive nuclear detonations.

Clipper’s electronics are protected by an approximately 1-centimeter (half-inch) thick aluminum “vault” that was closed up tight last October.

In May, about the same time the spacecraft was shipped to Kennedy Space Center in preparation for launch, the Europa Clipper team was “advised that similar parts were failing at lower radiation doses than expected,” NASA said yesterday.

The problem isn’t limited to Clipper. An industry-wide alert went out in June and NASA said “the issue that may be impacting the transistors on Europa Clipper is a phenomenon that the industry wasn’t aware of and represents a newly identified gap in the industry standard radiation qualification of transistor wafer lots.”

Europa Clipper was built at and the program is managed by the Jet Propulsion Laboratory in Pasadena, CA. The Johns Hopkins University Applied Physics Lab (APL) in Laurel, MD designed the spacecraft body in collaboration with JPL and NASA’s Goddard Space Flight Center in Greenbelt, MD. Testing is underway at JPL, APL and Goddard to ascertain how many of the transistors may be susceptible. NASA said data obtained so far “indicates some transistors are likely to fail” and NASA is evaluating options to maximize their longevity. A preliminary analysis is expected at the end of this month.

The spacecraft is already in the final stages of processing for launch on a SpaceX Falcon Heavy during a 21-day window that opens on October 10. That provides some leeway, but if a resolution can’t be found by the end of October, the mission will have to wait until the planets are correctly aligned once again. Clipper needs gravity assists from Mars and Earth to reach Jupiter. After leaving Earth it goes around Mars, then back to Earth, then off to Jupiter, a so-called Mars Earth Gravity Assist or MEGA trajectory.

NASA declined to answer questions today, including how long it’ll be until that next launch opportunity arises, saying all the information they will provide for now is in the blog post.

NASA’s science priorities are guided by Decadal Surveys produced by the National Academies of Sciences, Engineering, and Medicine. A mission to Europa was the second highest priority in the 2011 planetary science Decadal Survey, with Mars Sample Return as the highest.

Budget constraints during the early years of the Obama Administration sharply limited NASA’s plans for Mars Sample Return and the agency had no plans to pursue a Europa mission, but Rep. John Culberson (R-TX), who became chair of the House Appropriations Commerce-Justice-Science subcommittee in 2015, had other ideas. Passionate about the possibility of finding life in Europa’s ocean, for all four years that he chaired the subcommittee he directed NASA to build not only an orbiter, but a lander, by specific dates and launch them on NASA’s Space Launch System rocket. The language was in the bill itself, making it the law of the land not just a recommendation in the accompanying report. Culberson often proudly proclaimed that Europa Clipper was the only NASA mission required by law.

Culberson lost his reelection bid in 2018, but Europa Clipper was far enough along that its future was secure even as costs grew to $5 billion despite replacement of the ICEMAG instrument with a less expensive model. Talk of a subsequent lander has faded, however, and Congress was finally convinced that Falcon Heavy was a better choice for the rocket.