Six moons with one shot
Posted by Emily Lakdawalla
09-10-2010 17:46 CDT
There are six, count them, six moons in this photo. Plus the outer edge of Saturn's rings. Awesome.This kind of coincidence of moons passing through Cassini's extremely narrow Narrow-Angle Camera field of view is a really, really unlikely event. But if you spend long enough at Saturn, it can happen. Cassini doesn't catch six moons at once by accident, though; someone on the imaging or planning teams had to figure out that this coincidence was going to happen, and that it would happen at a time that Cassini could take a photo, and then get the photograph into Cassini's long list of instructions; so well done and thanks to whoever it was on the Cassini team who was responsible for grabbing this incredible shot!
In fact, they took four shots at this opportunity, two each with different exposure settings. (Here's the originals: 1 - 2 - 3 - 4) Here's a little animation of the two longer-exposure shots, with the six moons called out.It was tough to figure out which moons were which, and in the end, I needed help. Usually I go to the PDS Rings Node Saturn viewer, put in the date of the image (October 6, 2010) and start at 12:00 and then just push forward and backward in time until I can get the view to match the photo, but I was sure that the big moon was Mimas and so I couldn't get it to work out right. So thanks to Luke Dones for helping me match the time (17:10 is pretty close) and name the moons in the Saturn Viewer. Disconcertingly, the Saturn Viewer does not name Daphnis as being in the view, but I think I have had that happen to me with Daphnis before; I don't think it's where the Saturn Viewer thinks it is.
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