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.

Margaret Kivelson, a professor emerita at the University of California, Los Angeles, will lead the effort to develop 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 ledthe 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.