Juno has arrived!
Posted by Emily Lakdawalla
05-07-2016 1:14 CDT
For a second time, NASA has placed a spacecraft into orbit at Jupiter. The spacecraft operated exactly according to plan, and Juno successfully entered orbit at 02:50 today, July 5, 2016, UTC; a further 15 minutes of engine firing beyond that placed Juno into its desired orbit. The actual burn time of 2102 seconds was only 1 second off of the predicted value.
As of the moment I'm writing this, they hadn't yet downlinked telemetry (or if they did, they haven't told the media); they only received tones from the spacecraft's low- and medium-gain antennae that give the most basic information on spacecraft health. But so far, so good, for everything, and it was a pretty euphoric team at the post-orbit-insertion briefing.
Below is the JunoCam approach movie, 17 days and about 1500 images covering an entire Callisto orbit. There is a soundtrack (by Vangelis), so mute your computer if you're at work before you play it! I'm told there will be a version without all the extra produced padding posted at some point this evening, but it's getting late and I have to drive home...
There are several things to notice in this video. You can see Io, Europa, and Ganymede turning off and back on again as they pass into Jupiter's shadow. You can see belts and zones begin to come into focus as Juno approaches. Sometimes, if you squint, you can spot the red spot. You can see Jupiter's belts fall to a steeper angle as Juno begins to rise in latitude. Some of the moons, especially Callisto, look kind of blinky -- this has to do with the way that the JunoCam instrument works. It's designed for extended targets (things that fill many pixels), not point targets. Scott Bolton said on the press panel this evening that at this phase angle, Callisto was dimmer than predicted. Its dim light, combined with the sharpness of the JunoCam optics, meant that its light was focused into a very small area on the detector. On the JunoCam detector, not all of the area is active, meaning that photons can fall in between pixels, or at least in between areas where they would be detected. When Callisto's light fell into those areas, it seemed to dim in the movie.
Juno principal investigator Scott Bolton was repeatedly asked about plans to release the raw images. During the morning press briefing he said that their release "depends on what we see [in them] and how interesting it is," but by the evening he was saying that the mission intends to release them within a few weeks, though he wasn't specific as to the timeline, citing "technical issues." You can bet I'll keep asking!