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Home » Space News » What happened to Juno?

What happened to Juno?

By Dean Little | Ares Astro

Last month we posted an update about the Juno mission. As you would all know by now, the Juno spacecraft is currently in a highly elliptical orbit around Jupiter. This means that once every 53.4 days, it passes by the gas giant at roughly 2,600 miles above its uppermost gases. This is Juno’s current perijove; the closest point of a satellite to Jupiter in its orbit, and it is just close enough to the surface to see under it’s massive cloud cover. Oh, and in case you were wondering, the furthest point in an orbit from Jupiter is known as apojove!

In an otherwise smooth mission so far, right before its second perijove, Juno encountered some unexpected problems and went into safe mode, shutting down its scientific instruments. As mentioned in our previous article, this is a self-preservation manoeuvre that ensures the instruments aren’t damaged in unforeseen circumstances.

Since coming out of safe mode, NASA has now been able to track down what caused the anomaly.

It turned out to be a software issue with one of Juno’s instruments, JIRAM (Jupiter Infra-Red Aurora Mapper). While the instrument itself isn’t damaged, it has been having some problems relaying data back to Juno’s main computer and will require a software patch. While NASA engineers work on a fix, the basic solution implemented for last week’s perijove was to simply turn the instrument off, and in doing so, data collection proceeded nominally as you can see from the photos from perijove 3 below. NASA hopes to have this problem with JIRAM solved and all sensors back online for the early February perijove.


There is however one slightly more troubling issue. During the October perijove, Juno was supposed to fire its main engines to lower its apojove and decrease its orbital period from 53.4 days down to just 14. Unfortunately, two of the valves controlling the helium supply to the engine were operating a little slow, taking minutes to open rather than just seconds.

As they have been unable to improve the performance of these valves, they are yet to conduct the manoeuvre which has led to further delays in data collection. This has proven to be rather problematic because of how orbital mechanics works. To shorten the radius of a certain point in an elliptical orbit, which in this case is Juno’s apojove, the spacecraft must decelerate at the opposing point in its orbit. Unfortunately, in this case, Juno’s perijove where the initial anomaly originally occurred.

Despite the challenges ahead, we are confident in the expertise and ingenuity of the NASA team to solve these problems. We can’t wait to see even more fantastic images and scientific discoveries of the mysteries that lie hidden beneath the clouds of Jupiter, the largest planet in our solar system.

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About Dean Little

Martian colonist, hacker, coder, inventor, maker, polyglot, musician & astronomer. A citizen of Earth, reaching for the stars!

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