ESA's Juice Has a Problem

I'm a bit surprised I didn't seem to post anything about the European Space Agency's launch of the JUICE (JUpiter's ICy moon Explorer) probe when it actually launched, just a mention it was going to happen a couple days before the scheduled launch.  I guess the bigger story seemed to be the Starship launch - which ended up being a week later.  

I started hearing rumors this week that the probe has a problem and confirmed it via the mission's website in this post dated April 28th.  They have been unable to deploy the radar antenna on the probe.  During the first week of commissioning the satellite, an issue arose with the 16 meter long antenna for the radar, called the RIME or Radar for Icy Moons Exploration (RIME). Based on information at that link it appears that RIME is a high frequency radar, as in the HF (shortwave) spectrum.  They don't say specifically, but it appears to be around 9.4 MHz, or just slightly lower (longer) than the 30 meter ham band.

Work continues to free the radar and teams at ESA’s mission control centre in Darmstadt, Germany, along with partners in science and industry, have lots of ideas up their sleeves.

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. Now partially extended but still stowed away, the radar is roughly a third of its full intended length.

The current leading hypothesis is that a tiny stuck pin has not yet made way for the antenna’s release. In this case, it is thought that just a matter of millimetres could make the difference to set the rest of the radar free.

If you follow space missions for a while, you encounter things like this. Some (often) tiny thing somewhere doesn't behave exactly as expected.  A similar thing happened to the solar power arrays on the US probe called Lucy to Jupiter's Trojan asteroids, and was successfully resolved.  The other possibility has happened as well, though, such as the Galileo mission to Jupiter being compromised by an antenna that wouldn't deploy properly. 

The idea that the stiction a little pin produces in space isn't exactly what was calculated or expected isn't very surprising to me.  It's also possible the calculations were correct but something was assembled physically different than it was supposed to be.

With a couple of months of commissioning still to come, there's time to try more tricks.  The next steps 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.  Juice is otherwise performing excellently after the successful deployment and operation of its solar arrays and medium gain antenna, as well as its 10.6-m magnetometer boom.

The RIME antenna viewed from a camera onboard JUICE.  If that doesn't look like any antenna you've ever seen, don't feel bad.  I've been around a lot of radar antennas and haven't seen one that looks like that, either.  It may help to see what it looks like in an image from testing of a scale model of the antenna scaled to smaller physical size (and higher frequency) on the bottom left side of that linked page.  This is an ESA image, of course.

Let's wish them well with this.  It could be an interesting mission.