ESA works to free jammed radar boom on Jupiter-bound Juice probe

An artist’s impression of the JUICE spacecraft flying through the Jupiter system, with repeated flybys of Europa, Callisto and Ganymede, frozen worlds that may host habitable seas beneath their icy crusts. Image: ESA

Engineers at the European Space Agency’s mission control centre in Darmstadt, Germany, are struggling to coax a 16-metre-long (52-foot-long) boom to unfold that’s critical to the probe’s ice-penetrating radar instrument. A camera on the spacecraft shows the folded boom trying to unfurl, but something, possibly a small pin, is preventing its full deployment.

The Jupiter Icy Moons mission, or Juice, was launched on 14 April atop an Ariane 5 rocket. On its way to the first of several gravity assist flybys, the spacecraft has successfully deployed its over-size solar arrays and a 10.6-metre (35-foot) magnetometer boom.

But the Radar for Icy Moons Exploration, or RIME, instrument, designed to peer beneath the frozen crusts of Ganymede, Callisto and Europa, requires a fully deployed antenna boom to conduct its observations once in orbit around Jupiter. But the boom remains partially folded.

“Every day the RIME antenna shows more signs of movement, visible in images from the Juice Monitoring Camera on board the spacecraft with a partial view of the radar and its mount,” ESA said in a statement. “Now partially extended but still stowed away, the radar is roughly a third of its full intended length.”

Engineers suspect a tiny stuck pin is stopping the boom’s unfolding, possibly by just a few millimetres.

“Various options are still available to nudge the important instrument out of its current position,” ESA said. “The next steps to fully deploy the antenna include an engine burn to shake the spacecraft a little followed by a series of rotations that will turn Juice, warming up the mount and radar, which are currently in the cold shadows.”

It will take Juice the rest of the decade to reach Jupiter, but engineers would like to wrap up the spacecraft’s commissioning in the next two months or so.

“There is plenty of time for teams to get to the bottom of the RIME deployment issue and continue work on the rest of the powerful suite of instruments on their way to investigate the outer solar system,” ESA said.

NASA’s Galileo probe suffered a somewhat similar problem on its way to Jupiter in the 1990s when its main data relay antenna failed to fully open. But in that case, NASA was still able to accomplish the mission’s primary goals using a smaller antenna to send data back at a slower pace than desired.

RINE is critical to Juice’s mission, capable of peering up to 9 kilometres (5.6 miles) below the icy crusts of the jovian moons Ganymede, Callisto and Europa, data needed to help determine their inner structure and to shed light on presumed sub-surface oceans that may provide habitable environments.