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.

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

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

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

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.

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

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.

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.

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

*grins*

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

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:
Click to view attachment

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...


Click to view attachment

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/imag...iImageID=129239
Thin crescent with south polar geysers.
Marc.

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

So no Enceladus?

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


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

No Tethys either...

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...

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

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

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?

A mosaic of Dione from the recent flyby.

Click to view attachment

Someone needs to read the spacecraft operating instructions more carefully.

Could also be a DSN problem...

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.

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

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.

Does mistargeting get a official report?

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

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.

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.

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

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.

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.

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.

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.

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.

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!

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.

Relax a bit muchachos!
I'm sure Cousins-O'Higgins has still plenty of tresor arcs to open before our eager eyes...

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.

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

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.

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.

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

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?

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.

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.

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.

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

From the Significant Events Report:

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

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