[X] My Assistant

[jasedm]

I feel a bit like a caretaker sweeping up in the background, what with all this Messenger Mercury activity, but here goes :
The Ciclops looking-ahead detail has been posted for Cassini's Rev 56, disappointingly, no Methone observations are slated (closest we get from here on in) but I'm sure there's a good reason.
Interestingly, they list two 'calibration sequences' for the NAC just prior to apoapse when there will be a 'stare' into the (relative) blackness of space to determine camera sensitivity, and any damage to the optics. I presume that this is so that any lens anomalies can be subtracted from subsequent images. Strikes me as good housekeeping what with the lull in Titan observations until 22nd Feb.
Ok, as you were, back to my sweeping (GO MESSENGER!!!!)

[edstrick]

If Cassini had retained a simple 1-degree of freedom (fore-and-aft) scan platform, a roll maneuver and platform slew could have permitted imaging while the antenna was on Earth for the RSS occultation. Another victim of NASA and JPL's total failure to contain costs during the "Mariner Mark II" development of a new "low cost" multi-mission outer solar system vehicle.

[rlorenz]

If Cassini had retained a simple 1-degree of freedom (fore-and-aft) scan platform, a roll maneuver and platform slew could have permitted imaging while the antenna was on Earth for the RSS occultation. Another victim of NASA and JPL's total failure to contain costs during the "Mariner Mark II" development of a new "low cost" multi-mission outer solar system vehicle.

RSS occs are pretty power-consuming. Even if there were a scan platform there might not be power
to run it and its instruments as well as all the RF downlinks near the end of the nominal mission as the RTGs
run down

I don't disagree scan platforms add enormously to flexibility during the fleeting geometric opportunities
that present themselves on a mission like Cassini, but
a) 'simple..scan platform' may define the null set
as future outer solar system Flagships are being considered and costed, people are wondering how
Cassini was as cheap as it (apparently) was

MMII would have been a bargain if implemented as originally intended - a platform designed once and
re-used for multiple missions - 2 missions for the price of 1.5, 3 missions for the price of 2 maybe.... but
as so often happens with multiple missions (remember how Pathfinder was Mesur Pathfinder....?)
budget got squeezed, CRAF got killed, and Cassini is what it is.

[ugordan]

RSS occs are pretty power-consuming.

Isn't the HGA transmitter limited to something about 20 watts? Is the TWTA the power hungry part in the equation?

[tallbear]

Isn't the HGA transmitter limited to something about 20 watts? Is the TWTA the power hungry part in the equation?

RSS Occs are preferably done using 3 frequencies S , X , Ka which give Cassini Occs more info than anything
Voyager could do ... If I recall correctly that's something like 80 watts ... and for any occs after Rev 28 we have had
to 'borrow' power to get 3 frequency RSS Occs .....( RTG power decay ) .... that means that other instruments
have to be put to sleep in order to get the power for the RSS Occ.... In the XM we are trying to keep 3 frequencies
for the RSS Occs in the first handful of Revs... but for occs in 2009 and later we have to basically do the occs
Voyager style...

While we all wish for a scan platform ..... besides the budget decision .... It turns out that as launch plans evolved
and Cassini ended up going up off a Titan IV that the S/C would not have fit in the vehicle if the Scan Platform
had been in place.....

and on a final note .... For RSS Occs.... we need the S/C to be absolutely stable.... nothing on the S/C is allowed to
be moving during an RSS Occ ... so the scan platform wish would lose out to practical matters..... the trades are always
to get the best science possible

T

[tedstryk]

Some great images have been posted from February 8. I never remember seeing these in the latest images, but if you do the actual search for the targets, they are there.
Here are a few example shots.

Dione

Great multispectral set (Feb 8)
http://saturn.jpl.nasa.gov/multimedia/imag...iImageID=142851
Another set. (Feb 10)
http://saturn.jpl.nasa.gov/multimedia/imag...iImageID=142860

Rhea

Sequence of Rhea in front of Saturn - excellent quality mulitispectral set. (Jan 17) Also a lot of frames in this set taken when Rhea was no longer in front of Saturn.

http://saturn.jpl.nasa.gov/multimedia/imag...iImageID=140388
http://saturn.jpl.nasa.gov/multimedia/imag...iImageID=141179

Some, such as this one, appear to be part of an opposition surge study (I am guessing by the shear number of frames taken, coupled with the relatively distant view and low to 0 phase angle). (by now Jan 18)

http://saturn.jpl.nasa.gov/multimedia/imag...iImageID=140156

By the end, the terminator is on the other side.

http://saturn.jpl.nasa.gov/multimedia/imag...6/N00099978.jpg

There are two multispectral Tethys sets, although they are rather distant. The first example is from Jan 29, the second from Jan 30.

http://saturn.jpl.nasa.gov/multimedia/imag...iImageID=141794
http://saturn.jpl.nasa.gov/multimedia/imag...iImageID=141910

Sorry if this has already been covered somewhere, but there are also neat multispectral sequences of Saturn and Titan. I know this is the icy moon thread, but since this post is primarily about the icy moons, I figured I would put it here instead of the general forum or Titan forum.

Wide angle, Jan 29

http://saturn.jpl.nasa.gov/multimedia/imag...iImageID=141614

Narrow angle, Jan 29

http://saturn.jpl.nasa.gov/multimedia/imag...iImageID=141622

Wide angle, Jan 30

http://saturn.jpl.nasa.gov/multimedia/imag...iImageID=142121

Narrow angle, Jan 30

http://saturn.jpl.nasa.gov/multimedia/imag...iImageID=142135