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

[Bjorn Jonsson]

I tried stacking 6 of the most recent images in RegiStax. They were obtained at a range of ~490,000 km. I omitted the polarized UV images as they looked too noisy and fuzzy.

This version has been sharpened with wavelet processing followed by postprocessing in Photoshop (mainly brightening it slightly). Probably overprocessed, doesn't look as nice as Deception's version above:



The following version has been processed to reveal the nightside. As these are not long-exposure images and the JPG compression destroys dark, low contrast details not even large scale features are visible on the nightside. However, Iapetus' entire limb is apparent and the irregular terminator looks nice:

[Michael Capobian...]

It sure looks like the Belly Band postdates Henri and is superimposed on top of it, which has some interesting implications. I guess we'll be able to tell for sure in the next set of images.

[Rob Pinnegar]

If the degraded basin that is right next to Henri is going to be visible on this flyby, maybe it should get a name too.

[volcanopele]

Which degraded basin? Henri is rather degraded.

Michael Capobianco, that's my sense too, that the equatorial ridge here is built-up on top of Henri's ejecta.

[Stu]

Hey, how's this for a "family portrait"..? Pioneer 11 and Voyager 1 - with New Horizons - all in the same field of view as Iapetus during tomorrow's encounter?



I know we won't actually see them, but kinda cool to think they'll be "in the area"...

[volcanopele]

Just a little update. This evening, we can expect to get three observations down from the spacecraft: ISS_049SA_SATSYSFIA001_PRIME, ISS_049IA_M33HRS001_PRIME, and ISS_049IA_GLOBMAPG001_PRIME . The first two is meant as a family portrait image set. SATSYSFIA001 can be thought of as a Kodak moment-type observation as Cassini images the entire Saturnian system from near-Iapetus using both the WAC and NAC cameras. Expect lots of ring NAC images and distant images of all the major moons of Saturn, plus a Wide-angle camera overview. M33HRS001 is an Iapetus observation immediately following SATSYSFIA001. Iapetus will almost fill the view in this observation. Hopefully, the targeting will be spot-on and I can use this image for controlling the other crescent/Saturn-shine images that come down later tonight and tomorrow. This view will have a pixel scale of 1.7 km/pixel. Finally, ISS_049IA_GLOBMAPG001_PRIME will also come down. This observation is a two-frame mosaic of the crescent at 1.3 km/pixel. CLR and UV3/GRN/IR1, as well as GRN polarized, images are expected for each footprint. These images are expected between 9 and 10pm tonight (though they could show up as early as 8:30pm, depending on how the Raw images page ingests images).

Tomorrow morning images from the ISS_049IA_LIMBTOPOG001_PRIME and ISS_049IA_SATUSHINE001_PRIME observations will come down. LIMBTOPOG001 is a two-frame mosaic of the crescent at 800 m/pixel. CLR and UV3/GRN/IR1, as well as GRN polarized, images are expected for each footprint. Saturn-shine observations over both poles are also expected with this observation. Expect anywhere from 0.82 to 1 pixel of smear in these Saturn-shine images. ISS_049IA_SATUSHINE001_PRIME is also expected. This sequence includes a four frame mosaic over the the crescent, 2 three-frame mosaics in saturn-shine over the polar regions, a frame over the ridge, and a frame over the south-western part of the impact basin in northeastern Cassini Region ("Joan"). These images are expected to be on the raw images page sometime between 7:15 and 8:15 am tomorrow morning.

[volcanopele]

Emily, those features along the ridge are superimposed impact craters:

[mgrodzki]

also made with infrared, GRN and ultraviolet

[elakdawalla]

Ah. Of course. It's obvious, now that you've explained it to me. I didn't recognize them because of the foreshortening. If it were less of a crescent view, there would have been craters along the ridge to compare them to, like in the image you showed; but with just the crescent illuminated it was quite mysterious.

Nice map!

--Emily

[Decepticon]

Here we go again!

http://saturn1.jpl.nasa.gov/multimedia/ima...iImageID=126174

[Rob Pinnegar]

Which degraded basin? Henri is rather degraded.

There's another one just to the southeast of Henri that is about the same size but is even harder to see. There isn't much left of it, but you can see it when it is close to the terminator.

Somebody pointed it out a year or two ago -- I can't remember who noticed it first.

[Edit: If you look at the collage of Iapetus images from the first page of this thread, it's visible in the images from the 7 o'clock and 8 o'clock positions on the "wheel".]

I hope we get the chance to see the Iapetus shots within the next couple of days after the close encounter. Good job this is happening on a Monday morning -- it would've been torture if it had been on a Friday.

[elakdawalla]

The latest set looks like ISS_049IA_M33HRS001_PRIME and appears to be perfectly targeted. Well done team!

EDIT: and here's my composite of that one. It's got stacked IR and Red for red, stacked green and clear for green, and just blue for blue (the UV3 one was a bit JPEGGy and cosmic-ray-hit to do much with)

I was busily erasing cosmic ray hits from the short-wavelength channels when I noticed that there seemed to be a "hit" in the same place on two of the channels. Three light spots, actually, repeated from channel to channel, which means they weren't hits, they were features; they were the pole-facing southern rims of three craters north of the equator. Neat! There was also one longer-exposure clear image in this observation, and you can see the outline of the limb -- with a hint of some interesting topography -- and maybe one mid-sized crater in the north polar area by Saturnshine, but not much else.

Also a few images from ISS_049IA_GLOBMAPG001_PRIME seem to be up, but not all of them.

Bedtime for me; I'll have to wait until tomorrow to see what Santa has brought!

--Emily

[JRehling]

[...]

[Steve G]

This one is about 60,000 km closer, crudely enhanced and rotated for easier interpretation. Looks like a crater chain running parallel to the ridge.

Attached thumbnail(s)

 

[Steve G]

Man must explore. And this is exploration at its greatest - Dave Scott