Healing Junocam from 500 million miles away
The Juno spacecraft has had an amazing mission orbiting Jupiter since 2016. One of the biggest problems in exploring the Jupiter is the intense radiation. Jupiter has extremely powerful magnetic fields that trap charged particles. Those particles generate massive amounts of radiation in various bands around the planet – in the range of 500-3600rem/day. Many times a fatal dose for a human. The combined effect can even destroy electronics and instruments onboard any spacecraft sent there.
To combat this, much of Juno’s critical electronic hardware was encased in a special radiation resistant titanium vault. Sadly, not all devices could be put in the shielding. One of those devices was the camera – Junocam. On the 47th orbit, scientists noticed the camera started showing signs of radiation damage in the form of grainy, horizontal streaks. By orbit 56, almost all images showed signs of corruption.
Junocam, like most modern digital cameras, is based on CCD technology. Unfortunately, radiation shows up as streaks, bright spots, and noise. Prolonged exposure damages the silicon-crystal structure of the CCD itself.
By examining the kind of image degradation in the images, mission staff determined a voltage regular on the camera’s power supply was malfunctioning. But how to fix it?
“We knew annealing can sometimes alter a material like silicon at a microscopic level but didn’t know if this would fix the damage. We commanded JunoCam’s one heater to raise the camera’s temperature to 77 degrees Fahrenheit — much warmer than typical for JunoCam — and waited with bated breath to see the results.”
It worked. JunoCam’s imaging was restored and delivered clear images for the next few orbits. Unfortunately, as the mission took Juno closer and closer to Jupiter and Io, image damage returned. Image processing alone couldn’t fix the issue.
There was a deadline. Juno was going to come within 1500km of Io. In a last attempt to fix the camera and get amazing pictures of Io, they cranked the heather all the way up and tried one more time. It worked, and they got crisp images of Io.
They used this same annealing method for several other components in Juno with success. NASA now even thinks they might specifically design components that will be damaged by radiation to be annealed.
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