Rev 165 Apr 23-May 11 2012, Enceladus E19 and close Dione flyby Options

[jasedm]

The latest looking ahead article is available.

This revolution includes another 74km Enceladus flyby with infrared studies on approach and recession, and RSS as prime instrument at C/A for gravity readings over the south pole. We don't get this close to Enceladus again now until October 2015.

Also a close Dione flyby at around 8000km with some great hi-res imaging and mosaics to look forward to, and some distant Titan cloud hunting.

[jasedm]

Initial far-encounter images have landed - Enceladus from distance, and some nice plume shots.

Can anyone explain this image? The top half is fairly 'clean' but the bottom half is speckled with cosmic-ray hits and sundry noise - I've not seen this before, how does it occur in the same image??

Looking forward to what should be some splendid close Dione pics....

[ugordan]

Can anyone explain this image? The top half is fairly 'clean' but the bottom half is speckled with cosmic-ray hits and sundry noise - I've not seen this before, how does it occur in the same image??

I forget the exact technical reason, but in essence the CCD readout speed overwhelmed the speed the downstream components can handle (say if the spacecraft recorder configured telemetry rate was set lower) so the lower part of the image was forced to sit on the CCD for a while longer. This increases dark current background (brightening seen visible) as well as chances of cosmic ray hits. BTW, this complicates dark current calculations for calibration quite a lot.

Chances of this happening depend on whether both cameras are active simultaneously, binning and compression mode, spacecraft telemetry pickup rates (the speed at which ISS sends packets to the spacecraft recorders, which also depends on whether other instruments are actively collecting as well).

[brellis]

ugordan, you understand that from an armchair? In Croatia? Why haven't they hired you yet?

[ugordan]

It's explained in the extensive Porco, et. al. paper from 2004 about Cassini's ISS. Since I had to reverse-engineer most of the official calibration code for my purposes, I kind of needed to know things like this about the cameras...

[jasedm]

Wow! comprehensive answer ugordan, makes a lot of sense - thanks!

Jase

[stevesliva]

Sounds like an interesting tradeoff between adding the additional complication of a dedicated buffer, or not. Since the buffer would be just another thing that could break.

[ugordan]

There is a buffer, it's just not large enough to hold an entire unbinned frame. More on this in section 3.9.4. of the ISS paper I mentioned.

Now back to your regular science program schedule...

[Phil Stooke]

http://saturn.jpl.nasa.gov/photos/raw/?start=1

Beautiful new pictures of Enceladus and Dione. I love the set with the big impact basin right at the top of the disk of Dione and Saturn behind it.

Phil

[elakdawalla]

I put together just a few of the goodies from this flyby: http://www.planetary.org/blogs/emily-lakda...2/05041544.html

But I can't believe I'm the first one to post any of these, with the first images having been on the ground for more than 24 hours now. Hellooooo! This is a forum about image processing! There are so many more awesome pictures from this flyby to play with! Is anybody else out there interested in playing and sharing?

[Ian R]

This one's for Phil and Emily ...

[Phil Stooke]

Thanks! Very nice.

Phil

[Ian R]

This is an enhanced IR-GREEN-UV view of a crater at 132 degrees W, 53 degrees N, which lies between the two principle arms of Arpi Fossae:

[brellis]

Ian, I feel like I'm looking at a seashell - wow! thanks

[Ian R]

You're welcome! I've added two more frames, turning it into a mosaic:

http://www.flickr.com/photos/10795027@N08/...57624830467026/