The Clipper

The first thing I learned about the Europa Clipper is that the spacecraft's name is more than a mere nod to the romantic sailing ships of yesteryear—it's an apt description of how the mission works.

The radiation environment around Jupiter is hard on spacecraft, due to the planet's large magnetic field, which traps charged particles from the sun. Rather than orbiting Europa in the heart of that radiation, the Clipper will fly around Jupiter in large, egg-shaped orbits that are mostly outside the harmful radiation belts. Over the course of two to three years, the Clipper will dive into the radiation 45 times, whizzing past Europa to gather data before the spacecraft then, as Dipak Srinivasan puts it, "gets out of Dodge."

Srinivasan is the RF telecommunications lead for Clipper at the Johns Hopkins University Applied Physics Laboratory. He told me the spacecraft will behave like an ancient sailing ship speeding between trade stops. After a Europa flyby, the Clipper will spend about three weeks in safe harbor beyond Jupiter's radiation, transmitting science data back to Earth. Srinivasan said these signals serve double duty: Not only do they carry mission data, ground controllers measure their Doppler shifts to pinpoint the spacecraft's location.

The Clipper mission's goal is to assess whether Europa is habitable.

"We really want to understand the composition of Europa's interior and exterior, and see whether that composition is commensurate with what we think is required for life," Srinivasan said.

Europa is slightly smaller than Earth's Moon. Its surface is an icy shell 25 kilometers thick, sitting atop an ocean about 100 kilometers deep that contains twice as much water as our own. Scientists suspect the ocean is salty, and stays liquefied because of the immense tidal forces exerted by mighty Jupiter.

"Wherever there's water on Earth, there's life," said Srinivasan. "Given the fact that there is liquid water on Europa, and the fact that it's been there for billions of years, makes it one of the likeliest places for life in our solar system."

During each flyby, the Clipper will scan Europa with an array of science instruments. There's an ice-penetrating radar, a magnetometer to measure the ocean's salinity, and a thermal camera to look for warm spots near the surface. Other instruments will examine plumes of saltwater that may periodically spray into space. Cameras aboard the Clipper will deliver views of the surface in resolutions down to a meter per pixel; our best views of Europa so far come from the Galileo mission, and have a maximum resolution of 6 meters per pixel.

The mission is being jointly developed between the JHU Applied Physics Laboratory and NASA's Jet Propulsion Laboratory.

"It's kind of neat," Srinivasan said. "You have an all-star cast of people across both institutions, both of which have significant deep space experience. You're kind of pulling from a really, large bench and you're coming up with really clever solutions on how to make this work."