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Posted by: volcanopele Sep 20 2007, 03:58 PM

The Looking Ahead article for Rev50 was posted on Tuesday:

http://ciclops.org/view.php?id=3800

There are three, non-targeted icy satellite encounters coming up at the end of the month: Dione, Enceladus, and Tethys. The Tethys encounter has a very similar geometry to those we've seen over the last few months, showing the region west of Ithaca Chasma at moderate phase angles. The Dione and Enceladus encounters are much more interesting, IMHO.

The Dione encounter will cover the sub-Saturnian hemisphere. A large mosaic is planned over that hemisphere at 270-300 m/pixel (around 20 footprints IIRC). This would allow coverage of the wispy terrain terrain there at phase angles which should make the view pretty dramatic. Also, the impact basins of the leading hemisphere should be quite visible.

The Enceladus encounter will provide the best view to date of Enceladus' leading hemisphere.

Posted by: Phil Stooke Sep 20 2007, 04:15 PM

Thanks, VP - and may I say, doesn't this show what an incredible mission Cassini is? One amazing encounter after another. Three years in, and we are still getting wonderful new vistas in quick succession. And a teaser for the next orbit with more untargeted encounters. Galileo would have been like this... too bad! - but Uranus and Neptune await.

Phil

Posted by: Juramike Sep 20 2007, 04:26 PM

Wow!!!

SAR Radar over Tseghi
Radiometry over FQA supra-basin and W Shangri-La Adiri
Altimetry over Adiri
HiSAR over Shiwanni Virgae
ISS and VIMS over Adiri

This will give some really cool-o information!

-Mike

Posted by: Decepticon Sep 30 2007, 02:01 PM

When do these encounters get uploaded to earth? Boy I can't wait!

Posted by: volcanopele Sep 30 2007, 05:40 PM

Images are downlinked today and tomorrow (hopefully...). Some should show up tonight, say around 9 or 10 pm PDT, and more will show up around noon PDT. Times VERY approximate.

Posted by: CAP-Team Oct 1 2007, 06:17 AM

NAC and WAC images from Dione are in, together with some images of Enceladus, but not the leading hemisphere images.

Posted by: ugordan Oct 1 2007, 07:50 AM

Yes, some nice shots of Enceladus' plumes, albeit with lossy compression used on longer exposures. Those Dione shots are nice and contrasty, they should make for a nice mosaic.

Posted by: volcanopele Oct 1 2007, 07:51 AM

Dione stuff looks very nice so far! Hope the rest comes down tomorrow. I of course, want to see the Enceladus leading hemisphere images. Hopefully, you are all crossing your fingers and toes.

Posted by: ugordan Oct 1 2007, 07:55 AM

Why? I mean, what are the odds of another cosmic ray trip right when you really don't want it?

*grins*

Posted by: volcanopele Oct 1 2007, 07:59 AM

That's not what I was worried about, but thanks....

Posted by: ugordan Oct 1 2007, 08:21 AM

Oh, you mean mistargeting the moon? I forgot all about that one.

Here's the rough two-frame Dione mosaic, this is the first time I used GIMP (yikes, only thing available at work...) and managed to actually do something with it so be gentle:

Posted by: Stu Oct 1 2007, 09:06 AM

V nice gordan

My rather arty attempt... just having a bit of fun on a day off work, when I really should be learning my Best Man's speech for my brother's wedding on Friday...

Posted by: MarcF Oct 1 2007, 11:51 AM

Really Nice. Good to have some news about one of my favourite moons (I mean Dione).
Some Enceladus pictures are also available:
http://saturn.jpl.nasa.gov/multimedia/images/raw/raw-images-details.cfm?feiImageID=129239
Thin crescent with south polar geysers.
Marc.

Posted by: volcanopele Oct 1 2007, 07:20 PM

The rest of the Dione images that will be downlinked are now on the JPL raw images page.

Posted by: Decepticon Oct 1 2007, 07:31 PM

So no Enceladus?

Why do I get a odd feeling like something is wrong?


EDIT : Awww crap I just noticed this.. ^^^

Posted by: CAP-Team Oct 1 2007, 08:08 PM

No Tethys either...

Posted by: volcanopele Oct 1 2007, 08:10 PM

Quite frankly, I saw the Tethys stuff as much lower priority since it covered the same area we've seen multiple times before, at better resolution. But the Enceladus images...

Posted by: ugordan Oct 1 2007, 08:16 PM

OK, I know I'll be sorry for asking this, but... what was it this time?

Posted by: volcanopele Oct 1 2007, 08:25 PM

Can't say... but the spacecraft is perfectly fine. Everything is working.

Posted by: JRehling Oct 1 2007, 09:03 PM

Check out the difference between Enceladus's nightside and the background! Is that how bright the E-ring is when backlit, or are we seeing Saturn's night side in ringshine?

Posted by: n1ckdrake Oct 1 2007, 09:19 PM

A mosaic of Dione from the recent flyby.

Posted by: Sunspot Oct 1 2007, 10:13 PM

Someone needs to read the spacecraft operating instructions more carefully.

Posted by: Bjorn Jonsson Oct 1 2007, 10:43 PM

Could also be a DSN problem...

Posted by: ugordan Oct 2 2007, 09:11 AM

That's a very nice mosaic, n1ckdrake. What did you use to geometrically reproject the footprints?
One final touch would be to equalize the brightness of all the footprints. As was the case in the big Iapetus mosaic, I believe clear filter frames are linear here so you can use the brightest footprint that shows empty space off-limb and linearly scale the others. Most footprints here have blackness somewhere so it's basically dimming or brightening the brightest point in each of them until it matches their neighbors.
I've done it in my rough version of this mosaic and it looks good, but the perspective change necessitates geometric reprojection - without it the whole thing looks apalling.

Posted by: Floyd Oct 2 2007, 03:56 PM

By now somone must know what happened to the missing images from Enceladus and Tethys. Could you fill us in?

Posted by: MarcF Oct 2 2007, 04:12 PM

Are some Dione pictures also missing ? The last Dione mosaic (featuring the "Voyager 1 hemisphere" between Amata and Aeneas) does not seem to be complete.
Marc.

Posted by: Decepticon Oct 2 2007, 06:31 PM

Does mistargeting get a official report?

Curious maybe we get some more view on the next Rev.

Posted by: n1ckdrake Oct 2 2007, 09:14 PM

Thanks for the comments ugordan. The program I used for the mosaic is Photoshop CS2's Photomerge. And thanks for the advise on how to equalize the image brightness.

Posted by: alan Oct 3 2007, 03:32 AM

Hey, how about looking on the bright side, we have 84 images of Dione we didn't have before. Plus some beautiful mosaics put together less than a day after the images were posted.

Posted by: nprev Oct 3 2007, 04:31 AM

True...but the mystery of the missing images deserves an answer. Personally, hoping that it's just a website thing...

Posted by: djellison Oct 3 2007, 07:16 AM

And at some point I'm sure the Cassini significant events report will explain what, if anything, has happened. We already get all the images that come down as quickly as they can get them online - and you want verbose flight ops reports in real time on top of that. Be realistic.

Floyd, nprev, Decepticon, Sunspot, Ugordan - you're all acting a bit like spoilt children. How about a little more patience.

Posted by: volcanopele Oct 3 2007, 07:31 AM

I want to apologize for getting everyone all riled up over this. Sometimes I wear more of my frustration on my sleeve than I wear my excitement of the images we DO get. The Enceladus images that I was most anticipating will not show up, and as Doug said, I'm sure an explanation will show up in the significant events report. However, we did get plenty of great Dione images, and we should be greatful we have that.

Posted by: ugordan Oct 3 2007, 08:41 AM

I can say that the way I reacted personally was not an gesture of impatience. It was a reaction based on VPs negative hint and I was merely curious on what the issue was. Slightly annoyed there obviously was an issue, but that's it. Nothing more, nothing less, I don't see how it was a crybaby reponse. Lessons learned since the Iapetus flyby.

I will refrain from further comments like this. However, in the future it would be nice if anyone who has some knowledge on these and similar things either let us know or keep us totally in the dark, instead of just dropping vague hints.

As VP said, we should be grateful we got some nice Dione images and as Alex so succintly put it in another thread "there is no such thing as routine in this business". Sorry for further increase of noise in this thread.

Posted by: angel1801 Oct 3 2007, 09:32 AM

I have checked the solar system simulator and we will get another chance to see the leading hemisplere of Enceladus on November 17, 2007.

At 6 Hours (UT), Enceladus will we about 115,000km away at closest approach.

Saturnshine imaging will be needed to see the portions from 90W to 0W longitude.

Posted by: rlorenz Oct 3 2007, 12:11 PM

Exactly, Doug. It is exactly because people get upset when their expectations are not met that I am
disinclined to discuss future observation plans in any detail.

Posted by: nprev Oct 3 2007, 12:23 PM

You're right, Doug, and apologies to you also, Ralph; didn't mean to come off that way, and what I wrote sounded pretty bad in retrospect. (We ARE spoiled in many ways here.)

Certainly no critique of the Cassini team was intended, and we're always grateful for any information that they have the time & inclination to post; never meant to act as if this is an entitlement, it's an exceedingly generous gift!

Posted by: The Messenger Oct 3 2007, 02:16 PM

Space is hard. I don't think there is anything comparible to the years of success we have enjoyed from the Cassini mission; and even with complete failure at any time in the future, this mission should go into the books as the most successful space voyage period.

If you have followed the event log closely, Cassini has experience a much-higher-than-expected rate of two bit errors. (Was it Rosetta or V Express that recently posted a similar worry?). Cosmic ray switching is unavoidable; the sluggishness in the reaction wheels is hamstringing. The ability of the spacecraft to recover from these incidents is a remarkable citation of the adaptive skills and forsight of the Cassini team. (All of whom should be wearing well-deserved insult-proof skin by now.) For more than ten years they have kept an intricate game of tetras going from the end of a time-delayed joy stick.

Even more important, there may be unexpected gems of science found in the unexpected clam shelling of Cassini during closest approach. Unplanned safe modes during Galileo's closest approaches were the hallmark of the mission. Likewise Voyager (I?) clamshelled during a close ring pass. With all the unexpected visual candy we are witnessing, no one should be surprised if unanticipated electromagnetic/gravitational/particle/plasma/magnitotails/gremlins are influencing the spacecraft in unanticipated and yet to be characterized ways.

Posted by: ustrax Oct 3 2007, 02:41 PM

Relax a bit muchachos!
I'm sure http://www.unmannedspaceflight.com/index.php?s=&showtopic=3967&view=findpost&p=97472 has still plenty of tresor arcs to open before our eager eyes...

Posted by: tedstryk Oct 3 2007, 03:23 PM

In addition to the inherent difficulties of operating a mission like Cassini, I think our perspective is clouded by the fact that earlier missions, such as Voyager, Viking, and the Mariners had plenty of missed shots, shots that were lost in transmission, and smeared shots. In fact, of one looks at the old Voyager raw images on the PDS (and I don't mean when the scan platform was stuck at Saturn), one will see that not every imaging attempt worked out.
However because we didn't have lists in advance for these missions of all the frames that would be taken and only saw selected, processed images in print publications (as opposed to the RAW jpegs), the encounters came off looking flawless. Frames that were not transmitted, targeted, or received, so long as there was no major outage, such as with Voyager's scan platform at Saturn, were not missed by anyone except a handful of scientists. Now, with targeting lists and the jpegs appearing right away, every little problem is noticed, creating a distorted perspective.

Posted by: elakdawalla Oct 3 2007, 04:00 PM

Also, I think that current missions' excellent performance is raising our expectations. Based on past performance it's not unreasonable to expect that the rovers and Cassini will return more than 90% of the data we expect to see from any science plan -- but remember that the MER team originally planned for fully one in three entire sols to be lost to anomalies of various kinds, whether in space-based or ground-based systems, and I'm sure the Cassini team's planning includes similar expectations. It's reasonable to be regretful when opportunities are missed; but opportunities will be missed as a part of normal spacecraft operations, there's no avoiding that, and there's typically nothing wrong with the spacecraft when it happens.

Of course it's also reasonable for us to be a bit worried when there are hints of something being wrong. Thank goodness for the candor of the Significant Event Reports!

--Emily

Posted by: JRehling Oct 3 2007, 04:29 PM

Given that seven Enceladus flybys will take place in the extended mission, I assume that this is largely a matter of science deferred instead of science lost. (Unless all seven put the longitudes from this go-around into night.) Sure, earlier observations can help target later ones, but the Enceladus map is going to end up extremely complete and detailed in the next couple of years. I'm already contemplating an Enceladus globe on my desk.

Posted by: Bjorn Jonsson Oct 3 2007, 04:37 PM

Excellent points. For example, there are lots of Voyager images that are smeared because the scan platform was moving while the shutter was open, only a part of the target is within the frame, there are DSN dropouts with complete images missing or with partially missing images etc. Some of this is true of Galileo images as well. With no JPGs available in real time back in the Voyager/Galileo days you don't discover things like this until you look at the PDS data. I have noticed similar things in the Mariner 10 data. A mission like Cassini isn't easy to fly and never becomes a routine task that always works 100% flawlessly.

Posted by: tedstryk Oct 3 2007, 04:38 PM

It should hang from the ceiling, and spray mist from the south polar region

Posted by: ugordan Oct 3 2007, 05:31 PM

I'm personally a Iapetus or Hyperion ummm.. globe man, myself. They've got interesting shapes at least!

Excellent points on the expectations. Missions like Cassini and MER set the standards high and it's only natural to feel sorry for opportunities lost. It's also true giving the public detailed knowledge of what was planned can stimulate greater disappointment after a glitch. For example, taking a look at the latest PDS release I notice there's at least one observation (Rhea and possibly Enceladus as well) that were entirely missed by the cameras for one reason or another. Looking back at that and not knowing what was expected you merely say to yourself Okay, that's curious. Moving on... With prior knowledge of what potentially great imagery was planned and lost, one would probably feel much worse.

Browsing the Voyager PDS dataset is indeed a sobering experience. There's just so many things that can go wrong and spoil a great shot, it's almost a miracle things work out fine most of the time. Of course, it's times when it doesn't work out that people tend to notice...

Now, what's with the delay on those Dione color mosaics?

Posted by: angel1801 Oct 3 2007, 05:33 PM

I downloaded the extended mission flyby .txt file some while ago and for Enceladus, the leading hemisphere will get 5 good looks at the leading hemisphere.

March 12, 2008 (high southern latitudes)

August 11, 2008 (C/A at 27S, 98W)

October 9, 2008 (C/A at 28S, 98W)

October 31, 2008 (C/A at 28S, 110W)

November 8, 2008 (C/A at 31S, 106W)

So we will get the leading hemisphere imaged at good resolution somehow within the next 13 months.

Posted by: Mariner9 Oct 3 2007, 05:39 PM

As everyone has pointed out, occasional problems will result in lost encounters.

On the bright side, off the top of my head I can think of a number of "once in a lifetime" encounters that Cassini succeded:

- Huygens landing (data relay)
- Hyperion targeted flyby 2005
- Iapetus targeted flyby 2007
- Phoebe targeted flyby 2004

And I may be spacing, but I can't think of any "once in a lifetime" encounters that Cassini failed.

I think the record so far is pretty damn impressive.

Posted by: tedstryk Oct 3 2007, 08:19 PM

Hyperion - just use a piece of cheese.

Iapetus - get a dark globe and leave it outside under a tree with a lot of birds in it...splat.

Posted by: nprev Oct 5 2007, 12:34 AM

Ah. Ted is clearly a "white on black" advocate!

Posted by: volcanopele Oct 5 2007, 11:30 PM

From the Significant Events Report:

Posted by: nprev Oct 5 2007, 11:47 PM

Thanks, VP. A little bird told me it was a DSN problem...

(sigh)...aging infrastructure strikes yet again...

Posted by: alan Oct 6 2007, 02:59 AM

Mimas and Epimetheus?

http://saturn.jpl.nasa.gov/multimedia/images/raw/raw-images-details.cfm?feiImageID=129516

Posted by: n1ckdrake Oct 6 2007, 08:18 AM

Yes, I'm 99.9% certain that is Epimetheus alongside Mimas. The distance between Mimas and Epimetheus at the time this image was taken was approximately 300,000 kilometers.

Very nice image!

Posted by: dvanavery Oct 7 2007, 04:49 AM

It's somehow a relief to know the problem was caused by Earthbound equipment failure....... the Enceladus data is just as lost, but at least it cannot be attributed to the Cassini program in any way. (I had the same initial impulse as everyone else here upon hearing the news......overwhelming urge to slam forehead into keyboard.....especially coming on the heels of last month's Iapetus cosmic ray safing event)

but as others have pointed out, we've been very lucky so far......

It almost seems justified to have some sort of redundant storage onboard the spacecraft to guard against things going wrong on the ground during busy mission phases. Something that could function somewhat like an external backup drive on a PC.......so that if one encounter's data downlink was missed immediately prior to another encounter, the main memory could be dumped to backup and overwritten with new data, and the backup memory could be read at leisure once the DSN problems get resolved on Earth (theoretically you would have at least the entire apoapsis of each orbit to resolve issues and downlink the backed up data).

Of course if redundant storage were included, the pressure would be enormous to just fill said extra storage with more non-redundant observations instead. There are probably a lot of arguments and tradeoffs to be made either way..........but it's heartbreaking to think that there was data that was captured successfully, then erased without ever being seen.

Cassini's SSR-A and SSR-B are already designed to operate sort of like this during mission-critical events (Huygens relay and playback, for example), but for most other flybys, there is nowhere for the data on one of the SSR partitions to go if Earth cannot downlink it promptly. Seems like a glaring lack of redundancy that future missions should address. Since any future outer planet missions well be built around solid state memory that is 10-20 years further advanced then the 1994 era tech which stores Cassini's data, this should not be hard to implement.

WRT the servo heater issue at DSS-63 which caused the problem, it sounds much less severe than the disintegrating main bearing from last fall. The tone of the signifigant events report suggested that the problem came up all of a sudden, but will be (or has been) repaired quickly. Is the a DSN status site that could give more details?

-dave V.

Posted by: angel1801 Oct 8 2007, 05:00 PM

I was looking through the raw image gallery just under a hour ago, and suddenly the Enceladus, Tethys and a lot more of the Dione images have appeared.

The images were not lost after all.

Posted by: ugordan Oct 8 2007, 05:18 PM

Now THIS is a nice surprise. Is this the "lost" data or only bits that weren't lost?

False color, enhanced view of Dione, cca. 200 000 km:


Looks like something got splattered across the surface at about 2 o'clock. It's almost got a ray system look to it.
A funky processing to bring out the rays:

Seems to originate from the relatively fresh and deep crater there.

Posted by: scalbers Oct 8 2007, 07:44 PM

Some Enceladus images are up on the raw images page. Perhaps the data were still there on the spacecraft when they got another DSN downlink opportunity. Pretty neat.

Above are the clear filter raw images at and just after closest approach. They are centered on the leading hemisphere near 107W longitude, so I think the bright limb is somewhere near 0 degrees.

Posted by: ugordan Oct 8 2007, 07:54 PM

Enceladus IR3/GRN/UV3 composite, it looks close to what calibrated colors through these filters look (see http://i108.photobucket.com/albums/n15/ugordan/EnceladusIR3GRNUV3.png):
http://i108.photobucket.com/albums/n15/ugordan/enc_raw_false.jpg

Enhanced IR3/GRN/UV3 view of Tethys:
http://i108.photobucket.com/albums/n15/ugordan/tethys_raw_enhanced.jpg

Posted by: CAP-Team Oct 8 2007, 07:58 PM

Simulated views of Dione and Enceladus to illustrate the "new" terrain.

Posted by: n1ckdrake Oct 9 2007, 03:01 AM

A mosaic of Dione from the recent flyby.

Posted by: Decepticon Oct 9 2007, 05:27 AM

Very nice work everyone!

Curious, why is part of Dione so dark?

Posted by: n1ckdrake Oct 9 2007, 07:41 AM

You're right Decepticon, it was a little too dark. I think the updated version looks a little better.

Posted by: volcanopele Oct 9 2007, 11:28 AM

Wow, I am in complete shock! This [of Enceladus] is amazing! Can't wait till I get back home from DPS to work on these.

Maybe, not in complete shock. The apparent age is about what I expected [age: South Polar Region <= Leading Hemisphere Planitia < Diyar and Sarandib Plantitia]

*clink* My contribution to the swear jar.

Posted by: JRehling Oct 9 2007, 02:34 PM

I would scratch the "almost". I think this is a ray system. Dione has about 15% the gravity of the Moon. A modest sized crater should be able to create rays that span a hemisphere.

Great processing on the "lost" data! This is like a mini-Christmas having this all appear so suddenly.

Posted by: MarcF Oct 9 2007, 05:16 PM

Isn't it the ray system of the crater Creusa, which was discovered on a relatively distant picture taken by Voyager 2 ?
I think it was the only crater ray system discovered by the Voyagers in the Saturnian System, with the exception of Cassandra (also on Dione), which was later shown not to correspond to a crater ray system.
Anyway, I'm happy to see that finally the pictures were not lost.
Marc.

Posted by: MarcF Oct 9 2007, 05:35 PM

I found the Voyager 2 picture on the Raw Image Data from the Voyager Mission to Saturn provided by Emily at the TPS site:

http://planetary.org/data/voyager/dione/C4399616_GEOMED.png

The ray system is visible if you increase the contrast. Unfortunately, I do not have the tools to do it.
Marc.

Posted by: Decepticon Oct 9 2007, 06:29 PM

This was my atempt at stacking. I'm not sure what I did wrong. (Still learning)

Not much craters on this side of Enceladus.

Posted by: Phil Stooke Oct 9 2007, 08:41 PM

Here's that Voyager 2 image, not quite so dark.

Phil

Posted by: MarcF Oct 9 2007, 08:49 PM

Great !! Thanks Phil.
Marc.

Posted by: tedstryk Oct 10 2007, 12:42 AM

Here is a more natural version of the Voyager view.

Posted by: Phil Stooke Oct 10 2007, 01:11 AM

Good one, Ted. When I make a view with a more flattened lighting gradient (high pass filtered) it's because I want uniform tones for mapping. Ted's is much more realistic as a depiction of the surface as seen by the spacecraft.

Phil

Posted by: tedstryk Oct 10 2007, 02:06 AM

I actually do the high pass filtering too, but then combine it with other techniques to preserve low frequency features. As you indicate, it is a difference in purpose. I am simply trying to make pretty pictures.

Posted by: David Oct 10 2007, 02:25 AM

They're pretty clear in the first false-color vision. In that coloring, they look like yellowish streaks emanating from a deeper yellow patch in the upper right. There is a crater there, but it's not absolutely clear that that's not an accident -- i.e., the crater that can be seen might have impacted by chance about in the middle of whatever earlier event caused the streaking. (To my eye, tracing the rays to a common center actually leads to a point a little to the side of that crater, though of course that could be an illusion.)

One thing about Enceladus that sprang to mind on looking at the latest images is how smooth its limb is. Mimas, and other satellites even larger than Enceladus, show obvious surface features on the limb -- but Enceladus appears to be absolutely flat at any scale where the curvature of the limb is apparent. Enceladus doesn't have a lot of surface gravity, and obviously there is some cratering and other processes going on on its surface -- how does it stay so flat? Even with the resurfacing caused by the plumes, why doesn't something stick up high enough to be noticed on the limb?

Posted by: alan Oct 14 2007, 06:24 PM

I haven't seen any new images on the raw image page since these were posted. Did the webmaster go on vacation?

Posted by: ugordan Oct 14 2007, 07:15 PM

I'll hazard a guess that all the instruments are powered off during checkout of the new flight software.

Posted by: scalbers Oct 27 2007, 05:13 PM

I added a couple of Enceladus images from this encounter to my map to help complete the leading hemisphere.

http://laps.noaa.gov/albers/sos/sos.html#ENCELADUS

We now can get a better global idea of the cratering distribution. Smoothest equatorial areas would be near the center of the leading and trailing hemispheres. Are there preferred longitudes of the "precipitation" of snow?

Posted by: Exploitcorporations Dec 3 2007, 08:20 AM

This is a portion of the massive 20-footprint Dione mosaic, work in progress...there seem to be a few frames missing at the eastern limb.

Posted by: OWW Dec 3 2007, 03:04 PM

That's really great! Can't wait to see final result.