[X] My Assistant

[jsheff]

The January PSG meeting is now in progress and the tour for extended mission is scheduled to be chosen on Thursday (Feb 1). There are 13 tours being considered OF4a, PF-3, PF-4, PF-6, PF-6h9, PF-7, PF-8, PF-9, PF-10, PF-11, PF-12 & PF-13 --plus 'tweaks' on these tours e.g. there is a PF-8a, PF-9a

S-S-So ... has anybody heard anything?

- John Sheff
Cambridge, MA

[john_s]

The winner is (drum roll please) PF6h9. Officially adopted on Thursday. I haven't sifted through all the details yet, but from my parochial point of view, I know it includes seven close Enceladus flybys, so that's good. Most of the science groups (Titan, Rings, Magnetosphere, Saturn, and Icy Satellites) were pretty happy with this choice- it packs in an amazing number of science opportunities.

John.

[tasp]

I am noting the amazing amount of interest in the current Iapetus encounter, and point out we have not had a Titan or Enceledus encounter generate this kind of interest in a long time.


Therefore:

Be it resolved, the primary goal of the extended, extended mission:

Iapetus

[rlorenz]

I am noting the amazing amount of interest in the current Iapetus encounter, and point out we have not had a Titan or Enceledus encounter generate this kind of interest in a long time.
Therefore:

Be it resolved, the primary goal of the extended, extended mission:

Iapetus

Dynamically that would be a challenge - because Iapetus is so far out there
the orbits are long, so you get far fewer flybys total.

A lot of the interest in Iapetus is simply because it has only this close flyby -
if there are X interesting things about a body (argue amongst yourselves about
how much X is for Titan vs Europa vs Callisto vs Iapetus etc.) and you
discover some fraction f of the remaining mysteries on the Nth flyby
then
first flyby gives you fX, second gives you (1-f)fX, third gives you (1-f)^2fX findings
etc. After 35 flybys, the incremental value of each indeed goes down. If f is very
small, the rate of novel findings declines only slowly

If the observation/operations are well-understood (as I'd argue is mostly the case
for optical/spectral study of Iapetus etc) then f is large - say 0.3 or something
So this first Iapetus flyby has tons of excitement

Enceladus and Titan had more total surprises and exploited more novel
instrumentation like Radar and INMS which took a while to figure out, and figuring
out how to best acquire VIMS and ISS data through the atmosphere also took some
trial and error) maybe f is smaller, 0.05 or less? (Recall many instruments are
recording seasonal or local time variability, radar sees only 1% of the surface at
a time, etc.)

Sooooo, I agree another flyby or two of Iapetus (particularly to get gravity to understand
its internal structure) would be nice, but the question is how many Titans and Enceladi
to you sacrifice to get them? (And as I've argued above, the answer depends how many
Titans you have under your belt already..) I bet after two or 3 more Iapetus flybys, it
would get pretty uninteresting, whereas Titan's mysteries will endure..

then of course these idealistic arguments have to be modulated by what a dynamically
feasible orbital tour can do (delta-V, flyby geometries, making sure the flyby doesnt happen
in eclipse, or during solar conjunction or something..), and then there is ring science, and
Saturn science, and magnetospheric science to fold in....

p.s. don't underestimate Dione