Just 8 days until the next Enceladus encounter.

CICLOPS Rev 80 Looking Ahead will appear here soon.

Cassini Enceladus 080EN Mission Description is here now.

We get to fly through the south polar jets again.

-Floyd

[edit] Soon = somtime before encounter

Yikes they are really going to be diving trough those ice plumes. Makes me wonder if a post encounter view of Saturn might look something like this:

I just made an animation of the encounter (60MB MPG file, right-click on image below to download):



It's from the point of view if the ISS narrow-angle camera, using pointing & position info from the SPICE kernels--pretty frenetic panning around at times! For a lot of the approach the camera looks to be pointing out into space--maybe towards where the plumes are located?

Let me be the first to say both "OOO!!!" and "AHHH!"....damn cool!!!!

Doug will probably dislike your chosen background music, but he'll get over it... Really beautiful work, man; absolutely inspiring. Thank you for sharing it with us!

Joe that's an inspirational piece of work! - many thanks for sharing it with us.
Am I right in concluding that the sequence planners may have allowed for some saturnshine exposures on the outbound leg?
I think the camera pointing into space is a consequence of other instruments being 'prime' during the very closest approach, in order to get other data on the plumes themselves.
Can't wait for the results on this one.

My pleasure... and thanks to Cassini for timely updating of the SPICE navigation data, allowing such looks into the future.



Don't know about specific plans. The team does publish such info sometimes in their "science plan" SPICE files, but the current plan, S42, ends on August 11 (hours before the Enceladus flyby ) and the next plan, S43, hasn't been posted yet. Usually there's a several day gap between the end of one plan and the posting of the next.

Maybe the links Floyd gave in the first post will tell some more, when updated.

That may well be true, but I suspect it may also be related to the rapid motion of Enceladus across the sky as seen from Cassini during such a low altitude encounter... the spacecraft can't turn quickly enough to track the surface during the entire encounter, so before closest approach, the attitude is set ready to image the south pole, with the remote sensing instruments pointing north. The south pole is then in the field of view as soon as possible, yielding the highest resolution images.

I imagine they also want to avoid exposing the camera to a high-speed encounter with particles in the plumes.

Enceladus is in eclipse from 224-21:42 to 225-00:08 --- T

Note to self: figure out how to model eclipses sometime. Saturn's oblateness makes it even harder than otherwise.

Is there any chance for Saturn Shine imaging during this encounter?

There is some chance. But keep in mind that the sub-solar point is pretty close to the sub-Saturn point during the encounter, so areas illuminated by Saturn would also be illuminated by the Sun.

During the eclipse, well, you'd be seeing the same areas we would be seeing immediately before the eclipse starts, at good resolution, in sunlight.

Link to map of Enceladus encounters on Emily's What's up in the solar system for week of August 4

Looking at the planned ISS pointing during the encounter in more detail, it looks like there is a long dwell time on the Cairo tiger stripe, vent 'E':



Any particular reason to concentrate on that one? One interesting thing is that it's exactly on the day/night terminator at the time of the observation (the green square shows the NAC view):

Might've answered your own question in your post. Bet they're looking for some high-phase optical plume pics.

That would be very cool - this is high speed flyby (compared to most for Cassini) so lots of trade-offs at C/A, but perhaps there will be an attempt to take a number of images over cairo vent 'E', to enable the construction of a crude movie of the plume - similar to that achieved by Voyager 2 at Triton.
It would make sense to concentrate on the day/night terminator, as the plume would show up better against the nightside.

Here's another animation, a much less frenetic, real-time view of the first four minutes or so after closest approach:

Enceladus Aug. 2008 flyby, real-time (60MB mpg file)

It starts just before closest approach with the ISS cameras pointing out into space (almost due north). The cameras fixate on the Cairo tiger stripe (vent E) for quite a while. This is only the first four minutes--looks like there's about a half-hour of ISS time possible before the eclipse.

The Mission Description is up. Link



http://saturn.jpl.nasa.gov/multimedia/prod...description.pdf

My appetite is whetted. Big time.

That was beautiful! Thank you for making those!

Joe, Really great animation!

CICLOPS description is now up (with a really nice detailed explanation of the camera pointing sequences): http://ciclops.org/view/5156/Enceladus_Rev_80_Flyby

Wow!!!! This is going to be some encounter!!!!

Craig

A detailed description indeed. Reminds me of the (still definitive) Iapetus imaging sequence plan by Tilmann Denk.

Wow... fantastic detail in the description!

I like the comment at the end from Carolyn Porco: "Prepare to be amazed!"

Unfortunately, it's too much to hope for a few bugs on the windshield as well...

Not to stray too far OT here, but I really wonder how much material a future Enceladus plume sampling instrument could accumulate doing flybys like this. Perhaps Cassini is testing the water...? (yeah...go ahead & shoot me for that, it's deserved.)

They're blogging the encounter here:
http://blogs.nasa.gov/cm/blog/cassini-aug08/

And there's a pretty sweet encounter video there...

It is a good encounter video, and informative, but I find our own "less frenetic" simulation compliments this new (and official) one pretty well. I like them both.

There has been a lot to look forward to on this mission, but I rate this encounter among my personal big three. First there was the anticipation of the first aerial and surface pictures of Titan from Huygens, and they didn't disappoint. Then there was waiting for the first shots from the Iapetus flyby. Needless to say, well worth the wait.

Now we await the best photos we will see from this mission of the tiger stripe active vents. We will see ...

Wonderful. This has to be the best flyby yet in terms of availability to the public of instrument plans, sequences and computer simulations of the encounter.
It's very obvious the amount of work and close-scrutiny that has gone into the spacecraft attitude, trajectory, and pointing so that every conceivable opportunity for measurements with all of the instruments can be achieved.
It looks like Cassini will be operating at the absolute limits of its capabilities with regard to screwing as much science as possible out of the flyby - I'm particularly interested to see what comes out of what's being referred to as the 'skeet-shoot' images - it seems very experimental seat-of-the-pants stuff.

I'd be surprised if any spacecraft to date has executed a more complicated list of commands during such a short near-encounter timescale.

Can't wait.

Sounds like an impressively complicated and exacting maneuver to get Cassini's rotation to just cancel out Enc's apparent motion during the skeet shoot.

From the description, looks like they're taking just one photo at each of the skeet shoot locations--so no closeup "movies" of plumes? What are the odds the plumes would even be visible, looking down on them?

Hypothetically, anyone know what the typical shutter times are for the ISS cameras in this kind of lighting, also the minimum cycle time in "burst mode"?

As I understood it, Cassini's rotation won't be able to cancel out Enceladus' motion at all. They'll spin the spacecraft as fast as possible and wait for the moon to overtake the camera FOVs. This will at least lower the motion smear somewhat.

I'm very, very skeptical any plume will be visible at roughly a 90deg phase angle, looking down on sunlit (albeit terminator) area. I don't believe that's even the goal.

You can pretty much forget about any "movies" from such a close range. The C/A part of the encounter is practically gone within a minute and the fastest the ISS camera can take frames is IIRC every 20 seconds, and that's using at least 2x2 binning, possibly lossy compression as well and probably the fastest telemetry pickup rate available to the instruments (in other words, it's the only instrument producing significant quantities of data - this probably also excludes "BOTSIM" ISS mode).

Shutter times for the WAC can be a few ms only, I think NAC needs at least 20-ish ms (thin air figure) for good S/N ratio at 90deg phase icy terrain illumination.

I was going by this quote:

"A special spacecraft maneuver implemented for this flyby first points Cassini's ORS platform ahead of Enceladus while the spacecraft is spun at its fastest speed in the direction that Enceladus moves across the sky. When Enceladus' apparent motion eventually overtakes the spacecraft spin and passes in front of the ISS cameras, the relative motion of the camera boresight across the surface of Enceladus will be briefly matched well enough so that the ISS NAC will be able to obtain seven very high resolution snapshots of selected geological features."

So call it "briefly matched well enough."

Thanks for the info on camera specs.

Here's yet another animation, concentrating on the ISS pointing for the half-hour or so after closest approach, ending just before the eclipse:

Enceladus Aug. 11 21:06-21:36 (67MB mpg file)

That one runs at about 10x real-time (compared to 90x for the first animation).

The skeet shooting images will be full-frame images, actually. Exposure times are on the order of 15-35 ms, though I have seen lower for the NAC.

Speculation here: might we see a plume shadow, similar to the martian dust devil shadows we see in pics from mars orbiters?

I don't believe a shadow can/will be visible, the plumes are much more subtle than martian dust devils are and the low exposures will likely add a bit of noise to the images as well. The fact the plumes are only visible at high phase angles means they don't intercept much light in the first place. What is intercepted is mainly scattered, otherwise the plumes would appear dark.

Also, keep in mind the solar illumination will be coming in at a low angle so topography will be very pronounced, it would be much harder to spot shadows on that than a smooth martian surface.

How about plume material that might be up in the sunlight, but silhouetted against the night side?

That would be potentially visible in an ideal situation, but again, there are two problems: the phase angle is still too low and scattered light off the sunlit surface might swamp out any signal from the plumes. I don't think I've ever seen a clear sign of the plumes at a 90 deg phase angle in distant Enceladus imagery.
It'd be nice to be wrong on this, though!

Here's some more good stuff on the WAC part of the closest-approach imaging, from Anne Verbiscer, who wrote the looking ahead feature on the ciclops site:

Neato

--Emily

So there's a wide-angle shot over the limb while no sunlit terrain is visible? If any image shows the plumes, it will be that one! I can't wait!

Sorry, ugordan, it's a WAC over the terminator, not limb. After ring-plane-crossing in 2009, the plumes will still be sunlit while the surface will be in darkness, providing just the opportunity you describe for ideal plume imaging.

Good to see the interest that this flyby has garnered - guess we'll all have to wait and see
My vote for close-up plume shots/movies would be the later (equatorial flybys) - back-scattered light on the outbound leg perhaps.....

For a change this is pretty good timing for us Brits... Anyone wanting to stay up late to follow the fly-by will be able (weather permitting) to catch one of the year's best meteor showers too.

The Perseid meteor shower is due to peak at 06.00BST on the morning of August 12th, so anyone staying up late the previous evening will - again, weather permitting - see more shooting stars than usual, and by the time the sky brightens early a.m. next morning we might be getting some Enceladus images, maybe? So, my timetable looks like it's set... finish work at 10, online by 10.20 to follow the fly-by here, go outside around 11.30 to watch the meteor shower, back inside at around 04.00 and check how the fly-by went, head off to bed 6ish... Hmmm, I like the sound of that plan.

I got 0530 UTC for images to show up on the JPL Raw images page.

Thanks VP, appreciate that tip. Looks like bed at 7 instead of 6 then

For those interested primarily in the close approach imaging (including the Skeet Shoot), that playback won't start until nearly 1800 UTC on 12 August.

Very nicely done animation - I enjoyed listening to the accompanying Gayne Ballet Suite.

YouTube has the clip from 2001: A Space Odyssey:

http://www.youtube.com/watch?v=anjVjj4w5rA

Nice atlas and map of Enceladus posted a few days back, in case you missed the link on the Latest from Saturn Multimedia Images page.

I plan to make a mosaic or 2 from the coming data. In the meantime can anyone please direct me to information concerning the optics of ISS. Particularly on the focal length, etc.

I remember one Cassini image with the NA camera which showed a slightly smeared surface of Enceladus. Many icy blocks were visible along the scarred surface. It was presented as the highest resolution image of that moon. Further I remember that it was 2x2 binned and a WA image was taken along (BOTSIM mode).
Can anyone check which resolution this NA image was ? It should taken in 2005.
It would be interesting to compare it with the best NA images of tomorows flyby.

Robert