Rev 49 - Aug 9-Sep 14, 2007 - Iapetus I1, The only close flyby of Iapetus Options

[volcanopele]

Usually, we get the images several hours after the end of the downlink. That's how I calculated the 7:15-8:15am PDT arrival times for the images on the JPL raw images page. During the Iapetus encounter, however, we get the images in a "real-time" feed, meaning we see the images shortly after (within 15-30 minutes) they hit the ground, during the downlink. However, I expected the JPL raw images page to load the images several hours after the downlink, on the "Non-real-time" feed. But the fact that people were already looking at the images at 4:20am PDT tells me that you guys are getting them as soon as we are seeing them.

[Rob Pinnegar]

Well, we're past C/A now. Hope we get some images soon!

BTW, I assume that the scale of the "bellyband flexure" probably tells us something about the rigidity of the Iapetan lithosphere (and perhaps its thickness, at least thickness-at-the-time)?

[ugordan]

@VP: Well, if it's any consolation to you, the last downlink (yesterday, starting 14:15 UTC) certainly didn't feal "real time" to us. Unless the imaging data was downlinked at the very end of the pass, there was an obvious delay because no new images were posted on the raw page as of 21:30 UTC. I'm inclined to think the raw posting mechanism isn't totally automated, rather it is triggered by someone after the DL is complete. Who knows...

Rob, the way I see in Emily's table, we might not see any new images until tomorrow's huge 14 hour, partly redundant downlink. The next downlink (2 hrs duration) might only contain RADAR SAR data. That huge downlink is scheduled to begin something like 07:00 UTC September 11th.

[Mariner9]

I know there are a couple downloads scheduled during the flyby. Anyone know approximately how often and when the Raw Images site is going to updated today?

And may I add along with everyone else, Oh my f***ing g**d!!!


(no, no, that was "feeling good". You people think I would really swear like that on a public forum?)

[Mariner9]

Oops. Sorry. I didn't refresh my browser for a few minutes, and the "how often are we getting downloads" discussion has already happened.

But I'm still feeling good. This is great stuff. Flyby of a lifetime.

[Stu]

VP: thanks for the info on the parallel ridges, there was a bell ringing at the back of my mind about that but I'd forgotten the details.

Seriously guys, how amazing is this? Front row seats for almost real-time exploration of one of the solar system's most fascinating bodies?! I've managed to see Iapetus in my humble 4.5" telescope a few times... on very clear, still nights, through the light pollution above Kendal... and now I'm looking at images of a dinosaur spine crater-pocked mountain ridge on its surface, almost as soon as they reach Earth! What a fantastic example of what Doug was talking about in his recent presentation - the sheer joy and genuine excitement of "joining in" with a mission and feeling part of it. Many, many thanks to whoever (deliberately or accidentally!) is allowing us to drool over these pictures so quickly.

A true "THIS is how it should be done!" lesson to other space agencies, mentioning no names of course, haha...

[JRehling]

[...]

[Ant103]

Hi

Impressive flyby now And some images to produce .

These are my tries :
Narrow angle camera, today.


RVB wide angle cam

And an oversaturate pic to view more clearly color differences


I'm waiting for narrow RVB images...

[volcanopele]

Here is what I could glean from the playback schedule. Please take time values with a grain of salt. They can be off by a few hours (usually on the plus side). So if ORSHIRES001 doesn't show up at 1:06am PDT, don't come here screaming that something has gone wrong. BTW, all times are in Pacific Daylight Time (this is just copied from my personal notes):

FP1NITMAP001_CIRS - Monday, September 10 - between 2:43 and 3:49 pm
CASSREG001_PRIME - Tuesday, September 11 - between 12:13 and 12:16 am
ICYMAP003_UVIS - Tuesday, September 11 - between 12:16 and 12:31 am
ICYEXO009_UVIS - Tuesday, September 11 - between 12:31 and 12:45 am
ORSHIRES001_VIMS - Tuesday, September 11 - between 12:49 and 1:06 am
FP1DAYMAP001_CIRS - Tuesday, September 11 - between 7:19 and 8:00 am
IAPETUS013_VIMS - Tuesday, September 11 - between 12:51 and 1:00 pm
REGMAPTRL001_PRIME - Tuesday, September 11 - between 2:59 and 4:07 am
REGCOLTRL001_PRIME - Tuesday, September 11 - between 4:22 and 4:42 am
IAPETUS010_VIMS - Wednesday, September 12 - between 8:05 and 9:05 pm
LIMBTOPOI001_PRIME - Wednesday, September 12 - between 8:05 and 9:05 pm
IAPETUS004_CIRS - Thursday, September 13 - between 7:50 and 8:50 pm

[belleraphon1]

Thanks indeed to all those who have made this possible!!!!

Any one else out there old enough to remember the JPL "Blue Room" broadcasts during the Voyager mission? Our local PBS station aired those, and I will never forget watching the commentary of Hal Masursky and, I believe it was Larry Soderblom, as the first Voyager close encounter Io images were being downlinked. The sheer JOY of major discovery happening before our eyes!!!!!

Now here we are 28 years later watching Iapetus reveal itself to us all with data we can save and play with.
Another world develping before our eyes... are there really words that can express the emotions here????

Yes, indeed Stu.... this is how it should be done.

Craig

[elakdawalla]

Since Iapetus is tidally-locked and Cassini has spent most of the mission much closer to Saturn than to Iapetus, the saturnshine imagery is always the same hemisphere -- the one we've already seen over and over. This time around, we get a daylit look at the other side.

Of course, Saturnshine imagery will always only show one hemisphere, the sub-Saturnian hemisphere, regardless of where Cassini is, because that's the only hemisphere that'll get sunlight from Saturn. I think you know this, it just wasn't clear from your post, and in fact I always forget this fact -- you'll never get any Saturnshine images of the anti-Saturnian hemisphere, because that hemisphere never sees Saturn! The point you're making about getting a daylit view primarily of the anti-Saturnian hemisphere is a good one and one I keep forgetting to make.

I was struck by how lumpy this body is as seen in this overexposed image. Another thing is the 3 stars visible aren't streaks at all despite longer exposure. Cassini was obviously tracking Iapetus and the stillness of the stars suggests Iapetus wasn't moving in Cassini's windshield much at the time - more or less just growing bigger and bigger.

When I was talking with Tilmann at the satellites conference about this, he expressed concerns about the quality of the Saturnshine images because of this very geometry; that Cassini would not be able to use its vaunted tracking capabilities to keep long-exposure images from getting blurry. If it's flying by, from a distance, excellent tracking can keep the same points on the surface precisely in the same pixels on the detector. But if the moon is simply growing in the field of view as you approach it directly, the points on the surface are spreading out, and there's no way to prevent some of them from moving from one pixel to the next, introducing a spreading sort of blur. So they had to keep exposures short enough that this radial smear would be less than one pixel, meaning for the LIMTOPOG001 observation, the exposure was forced to be shorter than 56 seconds. I notice that on Tilmann's website, the detailed information for each observation includes a "Radial Smear Table" for the saturnshine observations.

I noticed several 'black' images. I hope these are Saturnshine shots that the automatic contrast stretch didn't handle well and not images where Iapetus got missed. The fact that they are all CL1/CL2 suggests the former may be the case.

Tilmann said something to me about this, which I don't remember perfectly, but it had something to do with avoiding every-other-line-truncation issues with these images by forcing them to occupy a smaller part of the histogram than they otherwise might, so he predicted that many of them would show up on the raw page as black images, annoying people.

--Emily

[ugordan]

Here's my stab at the mosaic, click for full-res:


I took care of varying distances between footprints and they match pretty nicely. The dynamic range on this thing is so big I had to overexpose the northern section a bit even while reducing contrast to make Cassini Regio better visible. I'll try a color one next, but the UV frames are smeared pretty badly.

[elakdawalla]

Nice work!

The UV images are really blurry. Just putting them together in an RGB doesn't work very well (first image). However I found that you can get rid of a lot of the blur and still preserve a little bit of the color information by stacking it with the clear-filter image first. Not ideal, but much better looking.


--Emily

[Stu]

Excellent work on the images sent back so far, well done everyone! Anyone else just want to go to bed right now and wake up when the close-ups are in?

Speaking of which, based on what we've seen today, and the detail we've seen on this part of the Great Wall (HATE "Belly Band", sorry!) has anyone out there an idea just what the images of the Voyager Mountains will actually show? Will we see peaks glinting in the sunlight? More avalanche features? Just curious because I'm giving a talk to an astro society in Carlisle on Thursday night, and although it was meant to be just about Titan I'm making space to feature Iapetus fly-by images too...



Even if no-one has any actual predictions, what would you like to see on those images of the mountains?

[ugordan]

Here's the best I could do to get some color out of the lower resolution filters. The UV filter proved most problematic (particularly in the right half of the mosaic), with its high noise and blur. I'm not too keen on the blue ice to the north, but its for keeping with the spirit of previous composites.