A tiny pin stuck in place on ESA's Juice spacecraft may be preventing engineers from unfurling its 16-metre-long antenna as it zooms toward Jupiter.

Launched two weeks ago, the probe just started its eight-year voyage to the largest planet in our Solar System to take a closer look at the Jovian moons first spotted by Galileo Galilei: Europa, Callisto, Ganymede, and Io. 

Juice won't begin its scientific observations until it gets much closer to its target, the Jupiter system, in around 2031, and is right now unpacking hardware previously stowed away for launch. But controllers are having trouble extending its Radar for Icy Moon Exploration (RIME) antenna, an instrument designed to analyze the Jovian moons' surfaces and examine what might lie beneath it.

Astronomers are particularly interested in finding any hidden liquid oceans flowing beneath the icy crusts of Europa, Callisto, and Ganymede. RIME was designed to probe up to nine kilometers below the surface and see if the theories of vast undersea resources are accurate and how useful they could be.

"Juice's ice-penetrating RIME antenna has not yet been deployed as planned," ESA said in a statement. "During the first week of commissioning, an issue arose with the 16-metre-long RIME antenna, which is preventing it from being released from its mounting bracket."

Engineers believe the issue might be due to a small pin that's got stuck and is hindering the antenna from expanding fully. It's estimated that this pin needs to be shifted just a few millimetres to fix the issue.

The RIME antenna is currently only extended a third of its full length, according to an image snapped by a camera onboard the spacecraft.

RIME still trying to deploy ... Source: ESA

Mission control is planning to execute an engine burn and rotate Juice in a bid to jostle its components around and warm up RIME to encourage the pin to shake loose. 

"Juice is otherwise performing excellently after the successful deployment and operation of its mission-critical solar arrays and medium gain antenna, as well as its 10.6-m magnetometer boom," ESA confirmed.

The Euro space agency said it has a lot of time to fix the antenna's issue since the spacecraft still has two months of planned commissioning left. Juice is set to arrive at Jupiter in the next decade, and begin exploring its moons over the following four years; the mission is expected to last until 2035. ®