Rev 126 - Feb 4-22, 2010 - Mimas (main target), Tethys, Iapetus, Calypso and mutual events too Options

[belleraphon1]

All

closest look at Mimas ... 30 minutes after periapsis on 02/13/10 at 17:25 UTC

http://ciclops.org/view/6188/Rev126

"Thirty minutes after periapse, ISS will perform a targeted encounter with Saturn's innermost large icy satellite, Mimas. The altitude for this encounter is 9,510 kilometers (5,910 miles) the closest Cassini has ever gotten to this cratered moon. For this encounter, ISS will acquire three mosaics along with another observation where ISS will be riding along with the Composite Infrared Spectrometer (CIRS). ISS' first mosaic of Mimas, GEOLOG001, will start 30 minutes after closest approach when Cassini is 14,800 kilometers (9,200 miles) away from Mimas. GEOLOG001 is a seven-frame, multi-spectral mosaic of the region surrounding the crater Herschel. Herschel, at 130 kilometers (80 miles) across, is the largest impact basin on Mimas, so large that it caused significant amounts of stress on the lithosphere of the small moon and so distinctive that it helped give the satellite the nickname, "The Death Star Moon." These high-resolution observations of the basin will be used to estimate the age of the crater. Scientists will count the number of smaller craters on the basin floor, compared to other regions on Mimas, to set limits on how old the basin can be. The second mosaic, GEOLOG002, will also be a seven-frame, multi-spectral mosaic, this time covering most of the visible surface of Mimas, shown above left. The best resolutions for these two observations will be 87 meters (285 feet) per pixel for GEOLOG001 and 191 meters (626 feet) per pixel GEOLOG002. Next, Cassini will ride-along with a CIRS FP3 temperature map of Mimas' day side, acquiring six narrow-angle-camera images during the scan. Finally, ISS will acquire a full-frame, multispectral observation (GLOCOL001) of Mimas' anti-Saturn hemisphere from a distance of 70,000 kilometers (44,000 miles). Saturn will provide a backdrop for this observation."

Glorious

Craig

[volcanopele]

Don't forget poor little Calypso.

[jasedm]

Yes, I'm glad that Calypso is getting a closer inspection on this rev - it'll be interesting to see how subdued the craters are compared to it's sibling Lagrange moon Telesto

This will mean that everything bigger than a kilometre or so within Hyperion's orbit will have been imaged by Cassini from less than 75,000km, except for Pan, Daphnis, Anthe and Methone - quite an achievement in itself.

Really looking forward to Mimas - I wonder if there'll be more visible faulting around Herschel at the higher resolution?

[DrShank]

waiting in a snowstorm in DC to see if my train will depart on schedule . . .

Just posted some background info, data, and mosaics related to the upcoming Mimas encounter, including a rotating Mimas movie with the latest global mosaic, on my blog. (the movie is too large to upload here)

http://stereomoons.blogspot.com/
http://www.youtube.com/watch?v=CwWBZFIBkr0

enjoy!

Attached thumbnail(s)

 

[belleraphon1]

Very Cool Dr. Shank!!

I cannot wait!

Thanks.

Craig

[scalbers]

Nice to see Dr. Shank's color map update. Here is my latest (in B&W) for comparison:

[scalbers]

"Live" shot via Celestia:

[scalbers]

Here's a little movie...

 mimas9.avi ( 835.5K ) Number of downloads: 520


Near closest approach (WAC FOV) at 1713UTC



View around 1750UTC - looks more elliptical again



"Live" Herschel NAC field of view at 1814UTC

[peter59]

Latest "live" shot at 1713UTC

Thanks

[Hungry4info]

Very much looking forward to images!

[peter59]

Calypso !
http://saturn.jpl.nasa.gov/multimedia/imag...7/N00151487.jpg
http://saturn.jpl.nasa.gov/multimedia/imag...7/N00151500.jpg

[volcanopele]

Just an FYI: the play back earlier was a short one, only running 2 hrs 20 mins. So we only managed to play back some of the data acquired during the periapse period, like the Calypso images and some images acquired of Saturn's haze layers while Cassini was in the planet's shadow. There is another playback period tonight and that one is the normal, 9 hours long. The Mimas data were carried over to that one.

[ugordan]

Eclipse view from Feb 13, WAC RGB:


Hmm, the more I look at this, the more it seems I've got it upside down. The rings look as if it's their unlit side, but their shadow should definitely not fall onto Saturn's northern hemisphere. Perhaps it's just the low illumination making this high phase view look unlit. Hence Cassini being above the ring plane and looking "down" onto the rings.

Edit #2: Yep, it's upside down. The parallax motion is only consistent with Cassini orbiting prograde if the image is rotated. Here's the correct orientation and some brightness/saturation enhancement.

[Astro0]

Wow, Calypso looks like a neat little place
Quick animation.

[Adam Hurcewicz]

I stack to color image from this:

N00151479 ( R )
N00151479 ( G )
N00151478 ( B )

Attached thumbnail(s)

 

[Ian R]

Here's my version of the Calypso flyby:

http://www.flickr.com/photos/10795027@N08/...548039/sizes/o/

[ugordan]

Nice work, Ian!

Reminds me of Telesto, but the surface doesn't appear to be as smooth.

[jasedm]

Some pretty smooth areas at this resolution - it reminds me of Tempel 1 - infilled small craters, and large areas of very smooth terrain.

[Floyd]

Adam--Welcome to UMSF! Nice color image--very crisp. I look forward to seeing your work on more images in the future.

[nprev]

Seems like almost every 'rock' in the Saturn system is pretty much covered with external 'snow'. (Sorry for all the 'quotes'! ) I assume most if not all of this is coming from Enceladus & not the rings; wonder if this tells us anything about the duration of Enceladus' eruptive activity.

[Floyd]

This look at Calypso was from 21,257 km at closest approach--we get 5 more looks from under 50,000 km:
Aug 13 2010 22,867 km phase 87 deg inbound
Sep 23 2010 39,359 km phase 87 deg outbound
Mar 10 2012 43,307 km phase 62 deg outbound
Apr 14 2012 49,523 km phase 61 deg inbound
Sep 30 2015 36,251 km phase 72 deg inbound

volcanopele or anyone who can answer:
For non targeted flybys listed on SM-7_all.txt, what percent will actually be used for imaging? I know sometimes other activities have higher priorities. My question is not for every (nt) on the list, but in general and for the 5 encounters listed above.

Edit: Wow these images get out fast. Wikipedia entry on Calypso is updated with yesterday's image.

[scalbers]

While we're waiting for Mimas images here are some improved movies made using Celestia. The wider angle one is almost the WAC field of view and the other one is about the NAC FOV. In the NAC one we can see Saturn and some other moons go by as Mimas recedes.

http://www.flickr.com/photos/47608252@N08/

[Ian R]

Nice work, Ian!

Thanks Gordan - I've uploaded a more 'viewer-friendly' version to YouTube:

http://www.youtube.com/watch?v=OGbx7_GHXfw

[scalbers]

Nice 3D effect with Calypso, almost looks like we're holding one of those cardboard models and spinning it around

[ElkGroveDan]

I guess I didn't get up early enough. Here's my belated version of calypso

Attached thumbnail(s)

 

[Greg Hullender]

I've uploaded a more 'viewer-friendly' version to YouTube:

Why does it wobble back and forth repeatedly? Is it just showing the same sequence three or four times?

--Greg

[Ian R]

Yes, it's the same sequence of images bouncing forwards and backwards; repeated four times. I prefer this sort of presentation as it allows (in my opinion, anyway) for a better appreciation of the three-dimensional shape of the moon, and is less jarring than a standard 'forward-only' animation.

[Explorer1]

Is it just my imagination, or are there thin parallel lines near the right side limb? What could be causing them?

[volcanopele]

Nope, you're not crazy. I was starting to wonder when someone bring up the neatest thing about Calypso...

[Explorer1]

Nope, you're not crazy. I was starting to wonder when someone bring up the neatest thing about Calypso...

I guess over half a decade of lurking on this forum has honed my observation skills.

[elakdawalla]

Coolness! And good eyes, Explorer1. I noticed those too Given that there's evidence for landsliding-type motion on other small worlds like Itokawa and Eros, I'd speculate wildly that's what we're looking at -- some kind of flow of the surface fluff toward local gravity lows, possibly induced by the vibration from small impacts.

Neat neat neat!

Emily

[Explorer1]

So when is the Mimas image down-link? This is the best view we'll get of Mimas for a long time to come, right? The suspense is just.... ugh!

[imipak]

I know; isn't it brilliant? Anticipation's half the fun! Every encounter is like a mini launch, orbit insertion or EDL

[Stu]

The suspense is just.... ugh!

(Obi Wan Kenobi voice on) Patience, young Explorer... impatience leads to anger, anger leads to hate, hate leads to... well, not a very nice place at all... (voice off)

Seriously, just enjoy it. We're spoiled rotten nowadays, and checking again and again to see if new images are up is all part of the excitement.

[volcanopele]

Tomorrow 5:30am MST/12:30pm UTC, +/- 2 hours

[vikingmars]

I just like very much this oval moon (Cassini pic from Sept 2009). Enjoy !

[tedstryk]

Here we are!!!


http://saturn.jpl.nasa.gov/photos/raw/rawi...?imageID=213591
http://saturn.jpl.nasa.gov/photos/raw/rawi...?imageID=213654
http://saturn.jpl.nasa.gov/photos/raw/rawi...?imageID=213598

[Astro0]

Mimas...quick stitch

[ugordan]

http://saturn.jpl.nasa.gov/photos/raw/rawi...?imageID=213598

Check out that darkening creeping up the crater walls! It's looks like sediment left over from liquid evaporation.

[peter59]

Damn, the best picture is a bit overexposed.
http://saturn.jpl.nasa.gov/multimedia/imag...7/N00151520.jpg

[Stu]

Wow...

http://saturn.jpl.nasa.gov/multimedia/imag...7/N00151591.jpg

[ugordan]

Damn, the best picture is a bit overexposed.

I don't think it's overexposed. More looks like the effect of very low phase on brightness and contrast. Also, who knows what the raw contrast stretch did here.

[Bjorn Jonsson]

Here we are!!!


http://saturn.jpl.nasa.gov/photos/raw/rawi...?imageID=213591
http://saturn.jpl.nasa.gov/photos/raw/rawi...?imageID=213654
http://saturn.jpl.nasa.gov/photos/raw/rawi...?imageID=213598

The last one is obviously Herschel. Very few craters on Herschel's floor and all of them are small. I expected to see some landslides on the crater rim's inside but there are none (or at least no big ones). One thing to keep in mind: The images are heavily contrast stretched because Mimas more than fills the field of view - no black space is visible. So I suspect that what's black in this image really isn't in black (in shadow).

There are some WA context images, for example this one:
http://saturn.jpl.nasa.gov/photos/raw/rawi...?imageID=213720

A nice NA global image:
http://saturn.jpl.nasa.gov/photos/raw/rawi...?imageID=213675

A closeup of Herschel with some black space visible - the contrast stretch doesn't mess things up completely in that case:
http://saturn.jpl.nasa.gov/photos/raw/rawi...?imageID=213654

Mimas' rough and uneven limb:
http://saturn.jpl.nasa.gov/photos/raw/rawi...?imageID=213606

Should be plenty of images for a nice stereo-derived DEM of Herschel . The fact that the subsolar point is close to Herschel might be a problem though.

[volcanopele]

Wow...

http://saturn.jpl.nasa.gov/multimedia/imag...7/N00151591.jpg

Here is an even better version

http://saturn.jpl.nasa.gov/photos/raw/rawi...?imageID=213678

[Bjorn Jonsson]

Check out that darkening creeping up the crater walls! It's looks like sediment left over from liquid evaporation.

The image is heavily contrast stretched since no black space is visible so I think the darkening is only slightly darker than the stuff above it. Still very interesting.

EDIT: From the image someone said was overexposed I now see the contrast is higher than I expected (I'm looking at the images as I type ).

[Stu]

Damn, the best picture is a bit overexposed.

... or, to put it another way...

WOOHOO!!!! New pictures of Mimas! And we can drool over them just a day or so after they were taken!!! How lucky are we?!?!?!?



Stunning pics, Cassini just keeps delivering, doesn't she?

[Floyd]

Wow, what a great set of images, including Epimetheus and Janus playing rocks. Very exciting to be on the Cassini site as the boxes with red X's turn to impossibly great images.

[ugordan]

EDIT: From the image someone said was overexposed I now see the contrast is higher than I expected (I'm looking at the images as I type ).

I'm guessing low albedo variations show up so clearly because of the low phase angle here.

[charborob]

Damn, the best picture is a bit overexposed.
http://saturn.jpl.nasa.gov/multimedia/imag...7/N00151520.jpg

Modifying levels and curves on this image in Pshop, I get this:

There seems to be ridges (outcrops?) on the central peak of Herschel.

[volcanopele]

Four of the images from the encounter are highlighted on the CICLOPS website:

http://ciclops.org/view_event/128/Mimas_Re...yby_Raw_Preview

[angel1801]

There is also a set of Tethys images from about 177,000km available too.

[Juramike]

Tethys images up: http://saturn.jpl.nasa.gov/multimedia/imag...7/N00151608.jpg

[EDIT: see below]

[Poolio]

Nice one, charborob. The darkening in the crater walls is really pronounced in that image. Gordon's interpretation is enticing; I look forward to hearing other possibilities.

Kudos once again to the Cassini team for the spectacular views of another world. What amazing times we live in.

[ugordan]

Gordon's interpretation is enticing;

I made no interpretation, just said what it looks like

[dilo]

Merging N00151591+93+95 (green+IR2+UV2 filters respectively in place of G,R,B channels) with Saturn in background:

This is a enhanced version:

[volcanopele]

Bah! Just when I though I got my color version done before you guys. Curses!

[dilo]

Bah! Just when I though I got my color version done before you guys. Curses!

I would like to see your version, for sure is different (at least in terms of alignment technique, which was difficult for me...)

[belleraphon1]

Wonderful as always.

Yeah, Stu, the fact we get access to these images so quickly still boggles this old space hound.

What is really amazing to me is that we have this old, battered moon (on the surface) riding right next to the most active mid-sized moon Enceladus.
Location in a system does not necessarily tell the whole story?!

Craig

[Adam Hurcewicz]

Janus and Epimetheus eclipses (animation)

[ElkGroveDan]

Well since Adam beat me by a few seconds, here's a MOV file instead

Attached File(s)

 Epimethus.mov ( 690.32K ) Number of downloads: 201

 

[dilo]

Feb, 14 sequence animation:

Note the curious sudden illumination change on Epimtheus from a body on the right, perhaps from Janus itself (strange geometry, however)

Attached thumbnail(s)

 

[ugordan]

Note the curious sudden illumination change on Epimtheus from a body on the right

Looks like "sunset" to me.

[volcanopele]

Nice catch about the change in illumination on Epimetheus. I doubt it is from Janus since that moon is clearly on the OTHER side of Epimetheus from those craters. I think we are just seeing a slight bit of rotation on Epimetheus, and the Sun is setting on the far rims of three impact craters just beyond the evening terminator.

I have to admit that I started to doubt that explanation since I suddenly thought that north might be up, so the terminator we are seeing would be the dawn one... But nope, south is up in your animation, so my explanation holds...

[belleraphon1]

I do not usually throw in attachments so bare with me...

But in this Mimas image I am not convinced all the low albedo stuff is due to shadow.



It is from NAC image N00151508. Also if you look at dilo's colorized global image you can see a few darkish spots in the high phase region. Kinda like the Rhea ring impactors but more dispersed (not in a line)?

Interesting.

Craig

[Explorer1]

Wow this stuff is truly great. Honestly if it wasn't for the central peak Herschel almost looks like it formed some other way. It's just so irregular and different from other big craters, like on the moon or Callisto.
Mysteries abound!

[Juramike]

Compare it to Rhea. Many of the larger craters on that moon are also irregular.

Mass wasting and slumping the crater walls of Herschel seem evident.

EDIT: Looking at the picture that Craig posted it seems that there is a tendency for the walls to form and slump along parallel lines going from lower left to top right.

[Ian R]

Here are my two 'bouncy' animations of this mutual event:

Epimetheus-centric:



Janus-centric:

[Adam Hurcewicz]

- Full quote deleted. Use the "add reply" button at the bottom of the page. -

Nice work !

Your animations show rotations of this monns

[dilo]

Grat animations, Ian! (original quality is clearly better than mine...)
Gordan, you were right!

[Adam Hurcewicz]

TETHYS in (IR1, G UV3)

ir1 N00151608
g N00151607
uv3 N00151606

Attached thumbnail(s)

 

[Poolio]

What we're seeing here is these two co-orbitals exchanging orbits, correct? It seems natural to think that the switching of orbits would need to cause temporary redirections of the moons from their normal elliptical orbits, and therefore the observed rotations and exposure of hidden surfaces to the sun.

[Floyd]

I'm not exactly sure where they are in the process of exchanging orbits, but I think the relative movement we see here is mainly the changing perspective of Cassini as it rushes by.

[Phil Stooke]

This is not the orbital switch. There are several factors - the moving spacecraft, the moons moving relative to the sun and to each other.

Phil

[Poolio]

But changing the observer's perspective couldn't account for the change in illumination of the subject. We must be seeing physical rotation of the moons themselves relative to the sun.

[Phil Stooke]

"in this Mimas image I am not convinced all the low albedo stuff is due to shadow."

These patches don't look unusually dark in images with more overhead lighting, which you can see further up the thread. - but there are real dark spots in places further east.

Phil

[volcanopele]

Yes, exactly. These movies are taken over a non-insignificant fraction of the day for these moons. But it doesn't have to do with any interaction between the two moons.

[Poolio]

Okay, I get it. Thanks. So the rotation we're seeing is just the normal rotation of these moons. "Sunset", like Gordon said about 10 posts ago.

(I should know better than to post before doing my homework. The switching of orbits happened on January 21, more than three weeks ago.)

[Adam Hurcewicz]

I finish colorize MIMAS. This dark areas are more visible.

ir2 N00151593
BL1 N00151591 (like chanel G)
uv2 N00151595

Attached thumbnail(s)

 

[tedstryk]

Adam, it says "Limax 7" in the corner of your images. What does that mean?

[Adam Hurcewicz]

Adam, it says "Limax 7" in the corner of your images. What does that mean?

It's my nick in polish forums: astro4u and astro-forum.org (the largest polish astro forums)
but also I use this nick in other groups: comet-ml

[Juramike]

Final adjusted color composite RGB [IR1, GRN, UV3], with enhancement in the overexposed region:



The ridge at the limb to the upper right of Odysseus is likely a remnant of another large impact basin.

Full res here: http://www.flickr.com/photos/31678681@N07/4361319512/

[peter59]

My mosaic is not of good quality, I hope that someone will do it better, but the view is impressive.

[ElkGroveDan]

My mosaic is not good quality,

It's underexposed.

[remcook]

Nice 'little' storm:
http://saturn.jpl.nasa.gov/photos/raw/rawi...?imageID=213757

[ugordan]

Too contrast-stretched would be a better description.

[Adam Hurcewicz]

And my Mimas mosaic from 4 images:

N00151557.jpg
N00151553.jpg
N00151577.jpg
N00151578.jpg

Attached thumbnail(s)

 

[Adam Hurcewicz]

Color Titan image from 16 Feb. 2010

I use images:

RED and CL2 filters: http://saturn.jpl.nasa.gov/multimedia/imag...7/N00151632.jpg
CL1 and GRN filters: http://saturn.jpl.nasa.gov/multimedia/imag...7/N00151634.jpg
BL1 and CL2 filters: http://saturn.jpl.nasa.gov/multimedia/imag...7/N00151633.jpg
CL1 and CB3 filters: http://saturn.jpl.nasa.gov/multimedia/imag...7/N00151636.jpg


FINAL image:

Attached thumbnail(s)

 

[scalbers]

And my Mimas mosaic from 4 images:

N00151557.jpg
N00151553.jpg
N00151577.jpg
N00151578.jpg

Nice to see this moderately high resolution mosaic. Maybe advantageous for mapping.

[CAP-Team]

I had already checked your site for a map update

[volcanopele]

I already tried updating my copy of Steve's map Steve, what size did you use for Mimas? Did you assume a spherical Mimas? I converted my mosaic to a simple cylindrical map and I can't get things to line up.

[scalbers]

CAP-Team - my first step in updating the map is using a more full disk low-phase image as can be seen here:



VP - I'm using these three triaxial dimensions: 414.8 394.4 381.4. Good question about the fit as Mimas is a great test of our handling of triaxial ellipsoids. Here is a look at the degree of fit (and size relative to the limb) with the image I'm using:



How nice to have Saturn backlighting & highlighting the dark limb, right where this is needed

Steve

[volcanopele]

Well, the issue that I have is that my Herschel comes out looking oblong in the north-south direction, which I think it should..., but it pushes some of the craters north and south of Herschel closer to the poles than what is shown in the map on your website.

[Phil Stooke]

Sounds like the dreaded Peters Projection! Seriously, is it a map projection mismatch?

Phil

[scalbers]

Perhaps VP is working with a planetographic map as I think that corresponds with an oblong appearance for Herschel. The official maps on the CICLOPS site also appear to be planetographic. Conversely I am working with planetocentric coordinates (still on the triaxial ellipsoid), where Hershel should probably look more round.

It appears possible to convert between planetocentric and planetographic. One way (at least for the latitude part) might be the reverse of what is discussed below:

https://isis.astrogeology.usgs.gov/IsisSupp...hp?topic=1550.0

Here BTW is a map using three images from the new flyby.



Steve

P.S. I recall running into the Peters projection on another project, thankfully not this one!

[Bjorn Jonsson]

Looks great even though the contrast stretch is a bit extreme for my taste (completely black shadows in craters etc.). Is the automatic contrast stretch applied to the source images one of the reasons for this?

[scalbers]

Bjorn - yes it's true this looks quite a bit more contrasty and darker compared with say my Enceladus map. For Mimas many of the first images on the map were at higher phase angles. That coupled with such a battered surface tended to give a preponderance of shadowed craters. This kind of became the norm for contrast when newer images are added. New images at low phase thus have to be contrast stretched quite a bit to look consistent. Nonetheless it appears to be a good suggestion and I will try to soften the shadows (and avoid losing details) with some of the imagery.

Here's a slightly less contrasty 4K version:



Steve

[Adam Hurcewicz]

Steve, what software you use to making maps? I searched Google and nothing..

[scalbers]

Adam - I'm using IDL. Using this software I wrote various procedures that help me navigate images, handle the map projections, and do the mapping.

Steve

[Adam Hurcewicz]

Iapetus color image (19 Feb. 2010)

N00151720.jpg ®
N00151716.jpg (G)
N00151719.jpg (

Attached thumbnail(s)

 

[elakdawalla]

Nice! Here's my version Used all the images, stacked to attempt to reduce JPEG artifacts, enlarged 200%.

Attached thumbnail(s)