Oh, I'm most emphatically not saying that such very low-altitude flybys aren't very much worth doing for Cassini -- probably several times. Besides mass spectrometric analysis of the denser plume cloud and better gravity data, the CIRS could probably nail down with great accuracy both how wide the tiger-stripe vents really are and how warm the fluid coming out of them really is -- and, if it was warm enough, the NIMS could also provide more data on the composition of the erupting fluid when it first emerges. It's just a pity that we couldn't also get really high-res photos of the vent sites as well -- especially since, according to Scalbers in the "Stardust Mission to Saturn" thread below, the region will soon be in seasonal shadow until 2030.

In that connection, I was puzzled by the failure of Porco's "Science" article to mention at all one thing that positively jumps out at the viewer even in Cassini's first Enceladus close-ups: the moon's "freckles". Quoting Helfenstein ( http://www.aas.org/publications/baas/v37n3/dps2005/450.htm ): "Among the most mysterious newly-discovered features are small, sub-kilometer-sized dark spots and circular pits that sometimes cluster in a honeycomb like patterns near faults and scarps. Their origin is unknown, but perhaps the pits and dark spots identify sites of explosive venting of subsurface volatiles through fractures or volcanic conduits." But there's not a peep about these in Porco's otherwise very detailed "Science" article. The fact that they're dark makes it likely that we're looking at the dark products of methane and the other organics expelled from the vents and then radiation-processed by solar UV and Saturn's own radiation belts -- although it's possible that they might also contain some bits of rocky debris from Enceladus' interior, or salts dissolved from that rock into the water and then redrying on the surface after expulsion. Maybe they're mentioned in some of the other "Science" articles, since I only have Porco's and Spencer's?

No, they are not mentioned. The dark leopard spots are found in Samarkand Sulci in the equatorial sub-Saturnian hemisphere. to keep the Science article manageable, it was limited to South Polar geology and plume analysis.

Are you referring to features seen in this and also this raw image?
If so, the statement that the features seen are indeed dark isn't backed up by strong evidence, IMHO. They really look like topographic shading effects on small dome-like or spike-like features in the grooves. Several of the larger ones, specifically in the second image I linked, at the top center clearly give the impression that we're looking at their shadowed regions. They otherwise don't look any darker than the surrounding ice to me.

Well, the Enceladus-3 flyby C/A distance is official in one sense: Wikipedia is now reporting it

The planetary society Cassini tour page now has the new value. Emily says she got he new trajectory from Dave Seal on the navigation team, so this is about as official as it gets.

Yeah, it's been "official" for several weeks now; I got it from Seal's MP presentations, I believe, in late December 2005. In fact, the 25 km figure is popping up everywhere except on the Cassini public website

I just read the materials in the 060323 Reference Trajectory Update package that Cassini Mission Planning (MP) released today and the 25 km C/A altitude for the 61En targeted flyby does not appear to be set in stone (viz., "not finalized yet" according to MP).

Having said that, the new tour tables do show 25-31 km C/A figures but it looks as if MP may revisit this issue before 2008.

Can you tell us anything more about just what they plan to accomplish with such a low-altitude flyby?

The precise science observing schedule is still TBD, which is not surprising due to fact that 61En has brand new flyby geometry. As EccentricAnomaly pointed out earlier in this thread, one of the working assumptions is that INMS will be pointed to RAM near or during C/A, so I presume INMS plume data is going to be a high-level goal, assuming, of course, the 25 km figure holds up.

I'll only note in passing that the Rev-28 Enceladus RSS plume occultation is shaping up to be a very important observation.