**FTS-NASA-VOICE**

**June 28, 2005**

**1:00 p.m. CDT**

Coordinator Good afternoon, and thank you all for standing by. Today's
conference call is now being recorded. If anyone has any objections,
they may disconnect at this time. Now I'll turn the meeting over to your
host, Ms. Trina Ray. Ma'am, you may begin.

L. Spilker I'm going to go ahead and begin. Welcome to this month's
CHARM telecon. Our topic today is Cassini-Huygens first anniversary, and
the spectacular science returns that we have had after orbiting Saturn
for one year. We plan to go from 11:00 am to 1:00 p.m. today. My name is
Linda Spilker, and I'm the Cassini Deputy Project Scientist and a
co-investigator with the composite infrared spectrometer team. I'll be
your moderator for today's telecon.

First, I want to talk about some simple logistics. There are two ways to
view today's presentation. One is to download the PowerPoint file and
the movie files into the same directory. Then open PowerPoint; click on
"View show," and the movie should play for you. The second is to
download the PDF file or PowerPoint file, step through it and then play
the movies as we get to them separately.

Just a couple of things. Through the phone system, please try and use
your mute button that's on your phone. Another option for muting is star
six, but each time you mute and unmute, it will place a beep on the
recording. So if you can use your mute button that would be much
appreciated, and please feel free to ask questions at any time during
the presentation. I'd like to go ahead, then, and introduce our
distinguished panel for today.

Our first panel member is Andy Ingersoll from Cal Tech. He is a Cassini
imaging team member, and he's also a Voyager veteran.

A. Ingersoll Hello there.

L. Spilker Hello, Andy. Andy specializes in planetary atmospheres, and
he is one of our storm masters. He figures out how giant storms form and
merge in Saturn's atmosphere. I've known Andy for a long time, and you
could certainly say that Andy has a deep understanding of giant planet
atmospheres.

A. Ingersoll Kind words.

L. Spilker Our next panel member is Jeff Cuzzi. He's from the NASA Ames
Research Center. Hello, Jeff.

J. Cuzzi Hello, Linda and everybody.

L. Spilker He is the Cassini interdisciplinary scientist for rings and
also a veteran of the Voyager project. Jeff has studied planetary rings
for many, many years, and he is truly a "Lord of the Rings."

Next on the panel is Elizabeth Turtle, known as "Zibi." Hello, Zibi.

E. Turtle Hello.

L. Spilker She's from the University of Arizona and she is an associate
on the Cassini imaging team, and a youthful member of our panel. Zibi is
a satellite whiz. She specializes in understanding the surfaces of Titan
and the icy satellites.

Our next panel member is Michele Dougherty from Imperial College. Hello,
Michele.

M. Dougherty Hello, Linda.

L. Spilker She is the principal investigator for the Cassini
magnetometer instrument, and Michele is indeed a marvel with magnetic
fields - her specialty. The final panel member is Shaun Standley, and
he's now at JPL. Hello, Shaun.

S. Standley Hello there, Linda.

L. Spilker He is our Huygens specialist, and now a senior systems
engineer with the Cassini spacecraft team. Cassini recruited him from
the other side of the ocean, and we are very happy that he has decided
to join our JPL Cassini team.

S. Standley I'm very happy to be here.

L. Spilker Oh, great. Great. I'd also like to thank Trina Ray very much
for working so hard in putting this package together for us today. What
I'd like to do is give a brief overview of the mission and then move on
to our other panelists.

So if you go to slide number three on your package, what you'll see on
the left is a launch photo. Cassini was launched on October 15, 1997
from the Kennedy Space Center. On the left of the photo is a predawn\--
You can see in the photo this was a predawn launch. Cassini lit up the
clouds as we flew through them, and it was a very spectacular event to
witness.

On the panel on your right, Cassini had a seven-year cruise in going
from Earth to Saturn. During that time, we actually had gravity assist
with a number of planets. In fact, we had two Venus flybys in 1998 and
1999, an Earth swing by in 1999. We flew by Jupiter in 2000, arriving at
Saturn on July 1^st^ of 2004. We took this rather complicated and
convoluted path to Saturn because we were basically borrowing energy,
called a gravity assist, in order to get us to Saturn without having to
use quite as much fuel. Those flybys were very successful.

Moving on to slide four, that's a picture of the Cassini spacecraft. The
spacecraft itself is about 22 feet tall. The high-gain antenna has a
diameter of 13 feet, and the mass of the spacecraft, if it's 2.8 tons
without any fuel and what they call a "wet" spacecraft with the fuel on
board in six tons. At Saturn orbit insertion, we had 700 watts of power.

Cassini is powered by three radioisotope thermoelectric generators, and
so as those decay as the mission goes on, we have slightly less power as
time goes by. There are a series of 12 instruments on the orbiter and
also six aboard the Huygens probe, and they're grouped into groups of
instruments on the remote sensing pallet. We have the composite infrared
spectrometer, the imaging subsystem with a narrow and wide-angle camera,
the visible and infrared mapping spectrometer and the ultraviolet
imaging spectrograph.

The high-gain antenna itself is used for Cassini experiments for both
the radar experiment as well as the radio science experiment. Then we
have a suite of fields and particles instruments that include the
Cassini plasma spectrometer, the cosmic dust analyzer, a dual technique
magnetometer, an ion and neutral mass spectrometer and a radio and
plasma wave science. As we said, there's a suite of six instruments
onboard Huygens, and I'll let Shaun talk in a little bit more detail
about those.

We have two engines aboard the spacecraft that we use to power it. Those
are basically the highlights of the Cassini spacecraft, and you can
always go to our Web page for Cassini to find out more details about
each instrument.

On page five, we have an overview of the tour. What we have planned so
far is a four-year prime mission with the possibility of an extended
mission for a year or two with a healthy spacecraft, and in the
four-year prime mission, we have planned 75 orbits around Saturn. As
part of those, we have 45-targeted Titan flybys. Titan is the tour
engine for Cassini. We use gravity assist flybys of Titan in the same
way that we flew by Venus and the Earth and Jupiter in order to save us
a tremendous amount of fuel, and also, we have nine targeted icy
satellite flybys as part of the mission where we go very, very close to
each of these worlds to get close up pictures and fields and particles
data and science data.

The science objectives for the tour are broken down into five basic
categories. They include the world Titan, the only moon in the solar
system with a thick atmosphere, a thick rather opaque atmosphere at most
wavelengths, the planet Saturn itself, the rings of Saturn, the seven
rings that are there and all of the little ring moons that orbit around
Saturn; the icy satellites. There's a whole retinue of icy satellites,
and you'll hear more about those from Zibi. Then the magnetosphere
itself, this giant invisible bubble where the solar wind runs into the
magnetic field of Saturn and the many complex and fascinating
interactions that go on there.

If you click now on the tour movie - in fact, the movie doesn't quite
have the right name to run in PowerPoint. So if you go outside
PowerPoint to run it, or you could rename the movie
"petal_tour.orig.movie.mov" and that would help it run with PowerPoint,
but if you go outside PowerPoint, you can run it from the file in which
you've placed it.

The tour movie just shows each of the 75 orbits that we've planned for
Cassini. You can see the first orbit, first big looping orbit coming in.
Then we dropped of the Huygens probe on the third orbit we called Orbit
C, and then went into a series of orbits that are set up for good radio
occultations of the rings and of the planet. Then we rotate back into
the equatorial plane, rotate back into the magnetotail, have a big orbit
for a good sampling of that region basically in the magnetotail of
Saturn and then go into a series of orbits we call the Titan 180
transfer where we increase the inclination again, decrease it. That's
the third year of the tour.

Then finally in the fourth year of the tour, you'll see a series of very
closely, very tight orbits as we increase the inclination for the fourth
year of the tour. So those are basically the highlights of the tour.

The Cassini mission status. As of July 1^st^, the orbiter has completed
basically one year of its four-year tour about Saturn, and to date, the
orbiter systems are all performing normally. The consumables are running
at predicted, and that's good news - the hydrazine and the fuel we use
on board Cassini.

The instruments are all performing well. Although, we have what we call
liens on the instruments, some things that are not working quite as well
as they did when the mission was first launched. That included the radio
science KA band uplink transmitter. That's not working properly at the
current time. The MIMI, one of their components if the LEMS instrument
and the actuator motor is not working properly on that instrument. The
CAPS instrument also has some articulation problems with its motor that
they're working on.

The CIRS instrument, there's some interference from the reaction wheels
that shows up in the CIRS data and we're working that. Finally, the INMS
instrument has reset problems, and they're putting together some
software to deal with this. So basically, all the instruments are still
working, returning good data. There just are some small glitches in
their performance.

The Huygens atmospheric probe, that entry and descent occurred on
January 14^th^, and that was quite spectacular, really a remarkable
success for Huygens. The probe returned two hours and 27 minutes of
data, including over an hour of data on the surface, and our highest
hopes, we're hoping for a few minutes of data and that extended
basically until the deep space network antennas on the Earth basically
set. So it was a very spectacular success for the mission.

To date, the orbiter's completed 10 of its planned 75 orbits. So we have
a lot of exciting science and orbits to come. We've had 6 of our 45
targeted Titan encounters, and 5 of those have been closer than 2500
kilometers and so bit by bit, we're pealing back and understanding Titan
and its surface. We've had 14 of 79 close flybys of satellites where we
define "close" in this case is less than 100,000 kilometers and in fact,
two of those have been targeted flybys of Enceladus. So we've had two of
those to date.

With that, I'd like to turn the panel discussion over to Zibi and she's
going to talk about Titan. Take it away, Zibi.

E. Turtle Thanks. I'm going to start off by talking about the sensing
observations of Titan, and then turn it over to Shaun who's going to
talk about the more close up observations of the surface from Huygens.

So on slide eight, there's a group of images that have been taken of
Titan's surface. Titan's surface is obviously very exciting because it's
something that we hadn't really seen before. The atmosphere prevents it,
makes it very difficult to observe the surface, very high optical depth
at visible wavelengths, and you can only really see down to the surface
in the near IR and even better out at longer wavelengths.

Our observations of the surface have been acquired over the last ten
years actually by Earth-based observers, and what Cassini is showing us
is a much closer view finally, but everything that we've seen so far
matches up at low-resolution. It all matches with what we've seen from
Earth. So that's a nice consistency over the past decade or so.

So the top panel of slide eight shows our best map at the current time.
This includes data through last December. There are some students
working here very hard to get some of the more recent observations into
this map, but that's going to be something that we'll just kind of build
up as we have more and more data of the surface of Titan.

Almost all of these images were taken by the camera, and what you can
really see is that there are a lot of albedo variations on the surface.
There are bright areas and there are dark areas. There seems to be more
variations in brightness, actually, at the equator, which is intriguing,
than at the mid-latitudes.

The top of this map is actually at about 35 degrees latitude because
it's currently northern winter. It's about the equivalent of late
January on Titan right now. So the northern hemisphere isn't
illuminated, which means that the ISS and VIMS instruments can't observe
there yet.

What we see are these intriguing albedo patterns, and a lot of very
intricate patterns on the surface. It's been thought, because we've been
seeing the surface, as I mentioned, for quite a while. It's been thought
that the dark areas might represent low areas where the hydrocarbon
materials that are falling out of the atmosphere have collected; whereas
the bright areas are higher standing ice that has been washed off, or
cleaned off by some processes.

So the observations that we have to date are certainly consistent with
that. There are areas\-- On the far left, there's a little bright area
surrounded by dark material and you can see what look like little dark
channels actually running through it. That would be consistent with the
dark areas being lower lying than the bright areas.

One of the other things that's very interesting that we see is
suggestive of wind erosion of the surface. On the right, there's a
middle patterned labeled xxx15:52xxxaeolian pattern that shows a bright
feature with bright tendrils almost kind of extending over the dark
areas towards the southeast. All of these images have north up I should
say. So towards the southeast, there are these kind of bright tendrils,
and we see that in a lot of places - bright material kind of diffused,
extending only to the east or the southeast of bright areas over the
dark material.

There are other areas where we see patterns that are suggestive of
tectonics. For example, the bottom image here where you can see these
dark fairly linear patterns intersecting with each other at fairly sharp
angles, and that would be suggestive of\-- That's suggestive of faulting
and processes acting deep in the ice. We see this on a lot of different
icy satellites.

It's something that's certainly different about Titan is that there are
a lot of different processes going on that are probably interacting with
each other. So it's not simply that there are tectonics, but these
tectonic features like on Earth may have been modified after they formed
by aeolian processes, by wind erosion or deposition, and also perhaps by
fluvial erosion, by streams if there's liquid running on the surface as
we have some evidence for.

So that's one of the most exciting things about Titan is actually how
even though it's a totally alien place with a very different surface,
very different temperature, different materials, a lot of the processes
acting seem to be very similar and very familiar.

The central set of images shows a couple of examples of impact craters.
The one in the top panel is actually quite a large structure - 400
kilometers across or so depending on where you measure it, and this is a
fairly low-resolution image that was taken in December. The bottom three
that are labeled ISS, RADAR and VIMS are three different views of a
smaller crater - not small by any means. It's about 80 kilometers in
diameter, but it's certainly smaller than the other one.

I should say that all of the white bars to the right of these images are
200 kilometers. So the images aren't to scale to each other, but that
gives you a kind of feel for the scale of the image.

So these three bottom images show what this crater looks like at
different wavelengths to ISS and the near infrared, to RADAR, and then
to VIMS further out into the infrared. In fact, this is a three-color
composite of three different wavelengths that VIMS observes in. That's
one of the really exciting things about Cassini is that we have so many
different ways to observe things with it and really start to constrain
what the surface processes and the properties of the material ... by
using these different ways of viewing the same area.

So that's kind of the overall view from ISS. The next slide shows the
two radar swaths that have been acquired - the first close flyby in
October and then the second in February. You can see on slide nine in
the upper left that one of the first radar pass is actually further
north above where the surface is illuminated. The radar, obviously,
doesn't care whether it's night or day and can observe the surface
there. So they have a track, a northern track and then a southern track.

I don't know what we did to deserve it, but I showed you that\-- I
referred to that large circular, annular structure that we saw in the
December flyby that it's a crater. The reason we know it's a crater now
is that by some incredible coincidence, the T3 radar swath crossed it.
That swath had been planned well before we had actually made that
observation in December and been able to see that annular. So that was
quite serendipitous.

So one of the images on the lower right, just below where it's labeled
"Impact crater," shows that very large crater, and then the smaller one
beneath that shows the smaller crater. We can start to use these
observations to understand the surface of Titan and the way the crater's
probed deeper into the surface than a lot of the other processes. So
they'll help us constrain the underlying properties of Titan's surface.

There's also, in the radar data, evidence for channels, and you can see
in the upper right, there are two different images that show evidence
for surface flows. One has\-- The left one has these very bright
channels that look like channels flowing up to the upper right. Then the
other one, the one to its right labeled "East of Gannessa" has what look
like little outwash channels or something like that. Again, bright.

Things that are bright in radar are rougher at the wavelength of the
radar. So the wavelength of Cassini's radar is 2.2 centimeters. So these
things are rough\-- The bright areas are probably rough at that scale.
There are some other really intriguing pictures that the radar has
detected. The one labeled in the bottom left where you have the label
"Gannessa Macular," on the left hand side of that image, there's about
100 kilometer diameter what looks like a dome structure. There may be
even flows radiating from that.

This is all interpretation just based on these images, and photo geology
can be risky, especially with a new instrument on a foreign planet. But
what this looks like\--

L. Spilker Zibi, we need to go a little bit faster.

E. Turtle Okay. So what this looks like is perhaps a volcanic feature
the same way we have on Venus with upraised domes and flows moving away
from it. One of the other really intriguing features on slide ten that
the radar detected is these cat scratches; these very narrow, dark,
linear features that tend to go in the east-west direction. Those are
very suggestive of dunes. So perhaps this is indicative of particulates
that have fallen out of the atmosphere being carried by the wind and
forming longitudinal dunes, which is something that we also observe on
Earth and on Mars.

Then on slide 11, some more wavelengths to be represented. This is VIMS
data, and this is some data from October that show a very intriguing
bright feature on the surface, and you can see\-- What they've shown
here is just what this feature looks like at many different wavelengths
and then a color composite.

They've, again, interpreted the morphology of this feature to be
indicative of volcanism. Perhaps, this is a small volcano on Titan. So
I'll turn it over to Shaun there to talk about closer views of the
surface.

S. Standley Okay. Well the first thing we have here is a movie of what
the descent imager and spectro-radiometer saw during its descent. So if
you can start that, you'll see we start off in haze, and we stay in haze
for a very long time - down to about 30 kilometers - and then you can
see flashes of the surface coming up as we're peeping through the
clouds. You can see the dendritic patterns of probably drainage channels
right away. They're a very obvious feature, and something that looks
like a coastline but isn't separating the dark from the light highlands.

Coming in a little bit closer, you can see an ellipse go by that we call
the landing ellipse. Of course, it's not, but it's a very obvious
feature we could track the progress of Huygens by, and we finish up with
a surface shot of a very flat area that we landed in. So we can talk
about those in a little bit more detail now as we go to the next slide.

This show is entitled "Huygens' Landing Site" and I'm going to start on
the bottom right hand side, and move up. The first image on the bottom
right shows an ISS image of Titan with the expected probe landing site
overlaid. It entered the atmosphere at the white dot you can see in the
inset and then streaked across from right to left during entry and then
when the parachute deployed and the wind caught the probe, it was
predicted to move back across, from left to right and landing in the
middle of the ellipse there.

Moving on to the middle image. This is a VIMS space map with the
position of the landing site and the Huygens CISR mosaic overlaid. This
gives you a great idea of how tiny the observations of Huygens are
compared with those taken by the orbiter. We really are landing in a
very small ...it's like landing in Death Valley and inferring the
structure of the rest of the Earth just from those shots. A very tiny
part, but a very detailed part of Titan we're looking at. You can see
the Huygens mosaic, the DISR mosaic up there on the left.

So let's move to the next slide, which shows some of the most
fascinating shots that DISR brought back. This shot on the left, it
looks a lot like the Santa Barbara coastline to us, but of course it's
not. The flat dark area in front was thought to be liquid at first, but
isn't. But behind that, the shoreline definitely, you're definitely
looking at higher ground. This shows very well something that Zibi
referred to earlier.

If you look on the right image, you can see light highlands with dark
channels and dendritic patterns spread across them. This shows what we
think is essentially black snow, dark precipitation falling from the
atmosphere, precipitating out, settling on the highlands at first and
then later on, there's some sort of liquid, probably methane rain,
rising off this dark accumulation of material...

M. Ota ...Question.

S. Standley Yes.

M. Ota This is Matthew over with the Saturn Observation Campaign. You're
talking about this liquid, the sludge. Can you give us laypeople an idea
of the consistency of this sludge?

S. Standley It's hydrocarbons, but I wouldn't want to give you
consistency better than that. I mean I couldn't really tell you. It's
long chain hydrocarbons, basically oil, but I couldn't give you a more
detailed description of the constituency other than that.

M. Ota Okay. Thank you.

S. Standley So although the highlands are shown here to be light, the
DISR team lead told me it was a bit like photographing an oil stain on
an asphalt parking lot. The contrast here isn't really that good for
them but definitely you can see the dark accumulation of material in the
channels. So you're pretty much seeing something that looks like a dry
arroyo here.

Moving on to the next slide, you can see a close up of the\-- On the
left hand side, you can see a dark strip moving diagonally upwards. This
is blown up on the right hand side. You can see a long straight channel
with dendrites coming off it.

J. Kremer I need to ask a question. This is Jennifer Kremer from Ames.
I'm not looking at the PowerPoint with you guys, so I was hoping you
could tell me what slide you're on.

S. Standley At the moment, I'm on number 15.

J. Kremer Thank you.

S. Standley Yes, long, straight dark channels with dendritic patterns
moving off it and these are more suggestive of an upwelling of liquid
from underneath the surface rather than being possibly a drainage
channel as we were looking at on the previous slide. This suggests
probably, once again, liquid methane springs coming up from beneath the
surface.

Also on the right hand image, you can see a long lighter feature, a long
gray feature moving out from the dark channels about two-thirds of the
way up to the west. This is thought to be an upwelling of water ice and
possibly ammonia from under the surface - first evidence here of
cryovulcanism.

L. Spilker If speakers could keep to a minute or two per slide; we're
falling a little bit behind. Thanks.

S. Standley Yes. The final slide is a good shot of the surface phase of
Huygens when it was landed, when it had landed. You can see the horizon
there at 88.5 meters away and the closer rocks are a few centimeters
across. An interesting feature here is that you can see that there's an
erosion feature near the center rock, the one with the four on it. It's
look like some of the debris has been rinsed out from underneath it.
When Huygens landed, it was a lot hotter than the surrounding
environment. Imagine it hissing as it sank into the material of the
surface and the gas chromatic mass spectrometer on Huygens actually saw
higher methane abundances as Huygens settled into that surface.

So there's good evidence of a layer of liquid methane just below the
surface of this sandy material that you see here. With that, I'll hand
on to the next presenter.

A. Ingersoll Hello. This is Andy Ingersoll, and I'm going to switch to
slide 17. A lot of the interest in Titan really stems from the fact that
Titan is a smallish object and it can't hold on to all of the elements
in its atmosphere. So its atmosphere is constantly evolving. In
particular, the lightest element, hydrogen, escapes to space. It
evaporates. In fact, the Earth has lost a lot of hydrogen too, but that
causes changes in the chemistry of the atmosphere.

So what's left behind, if you start out with methane, which is the
simplest compound of carbon and hydrogen - you can imaging. What's left
behind is the heavier element, the carbon. So you're constantly
increasing the carbon to hydrogen ratio, and you're constantly building
up heavier hydrocarbons in the atmosphere and that's the whole basis of
the theory that there should be or might be hydrocarbon lakes on Titan.

This slide shows what Cassini has contributed to that debate, let's call
it, because the INMS instrument actually dips into the atmosphere. As
the spacecraft passes about 1,000 kilometers, the INMS takes a little
scoop of the upper, upper, upper atmosphere and measures the
composition. As you can see, the last bullet there; by measuring the
hydrogen and methane, you can estimate how much of it is escaping and
the escape fluxes are higher than anticipated and that would say, "Well,
we certainly expect these hydrocarbon lakes." It's something of a
mystery that we haven't found them in the same abundance that we
expected them.

Let's move on to slide 18. The INMS did detect a lot of interesting
hydrocarbons and nitriles, which are compounds with nitrogen in them.
You can see the list here. C~6~H~6~ is benzene actually, but it'll go up
from bottom to top. In the upper slide, you see hydrogen, methane,
nitrogen. The atmosphere itself is mostly nitrogen with a lot of methane
in it, but there are, as you can see, these more complicated
hydrocarbons.

If you were to toss in a little oxygen, you'd have the main elements for
life, which is another reason Titan's so interesting, not that we really
expect life to have evolved at these low temperatures, but it's very
interesting to see how far purely physical processes can take you in
forming complicated compounds that are precursors to life and so there's
great interest in that subject as well.

Let's move on. The haze movie isn't working on my.... Another
interesting thing about Titan; I'm a meteorologist and I find it
fascinating how active the atmosphere is because you're ten times
farther from the sun. So you're getting one-percent of the sunlight at
the top of the atmosphere compared with the top of Earth's atmosphere.
Then a lot of that sunlight gets either absorbed or reflected. The
sunlight at the ground is just a few tenths of a percent of what you get
at Earth, and yet, it's a very active atmosphere.

For instance, in the movie, the haze changes with time. In the little
strip labeled "South Polar Convective Clouds," this is slide 19. That's
a four hour sequence, and if you stare at it for a while, you can see
that these convective clouds change with time. They could be somewhat
like, perhaps, slow moving thunderstorms on Earth, or slow moving
convective clouds on Earth and yet, they're being powered by a few
tenths of a percent of the amount of sunlight.

Let's move on to slide 20. Interestingly, the winds on Titan are
somewhat higher than the winds on Earth. The jet streams on Earth are
perhaps 40 meters per second, which is about 100 miles per hour. So
compare that 40 meters per second, the jet streams on Earth, with this
slide lower left, which shows you wind speeds on Titan getting up above
100 meters per second. So that's actually 2.5 stronger than the jet
streams on Earth and yet, all of this is being powered by this feeble
sunlight. It's really quite contradictory and quite a mystery, and quite
a challenge for atmospheric scientists.

All right. I think it's time to turn it over to....

L. Spilker Andy, maybe we can just ask if there are any questions, just
if there are a couple of questions on Titan. Now might be a good time to
take them. Any questions out there on Titan?

M Is there a key for slide 17? The graph on the top left there; I don't
have any context for that.

A. Ingersoll That's too technical a question for me. What do you mean a
"key?"

M Well, it's got the lines there and I don't know how to read that or
what that's telling me.

A. Ingersoll Yes. This is the record\-- Each one of those is a record of
the altitude that the spacecraft was at as it flew past Titan. So the
light blue lines, sky blue lines shows the spacecraft coming in from
2,000 kilometers attitude and at the local time of about 16.5 hours, it
was at its minimum altitude of 1200 kilometers and then it flew back out
of the atmosphere. The spacecraft experiences very little drag during
these passes, but it's enough ... INMS instrument to scoop up some
atmosphere and sample it.

M Then the inverted curve there, the Lat TB, Lat TA, Lat T5?

A. Ingersoll The latitude on the scale\-- The latitude scale is off on
the right side.

M I see. Okay. Then the TA, TB?

A. Ingersoll Those are the different names for the different times, the
different parts in the tour that the spacecraft flew past Titan.

M Okay. Thank you.

L. Spilker Okay. Andy, do you want to hand it over to Zibi?

A. Ingersoll You got it, Zibi.

E. Turtle Okay. So I'm going to go ahead to slide 22. It shows the kind
of latest views of a lot of the icy satellites. We often refer to these
as the naked satellites because Titan is also icy, but it has a thick
atmosphere whereas the other satellites don't have as big atmospheres,
although they're not completely atmosphereless.

The 23^rd^ slide shows one of our views of Iapetus. This is actually
quite a distant flyby that occurred on New Years Eve, and despite the
distance - I think the range was over 60,000 kilometers - it's a
spectacular data set. Iapetus is a very strange place. It was known from
observations before that Iapetus was unusual in that it has one side
that's very dark, and another side that's very bright.

What the Cassini observations have revealed is more of the detailed
structures on the surface. There are a number of huge basins. You can
see a couple of those impact basins here - one off on the right hand
side near the terminator and then another one in the center of the disk.
One of the things that will help to interpret what the source of this
dark material is the interaction, the topographic relationships. You can
see there are some little craters - not little - but relatively little
craters that basically appear as bright circles with bright spots in the
center of them. What this means is that the dark material is a fairly
thin coating on the surface that has slid down in little landslides,
slid down into the bottom of the crater revealing ice along the rims of
the craters.

You can also see some dark streaks moving away from the boundary into
the brighter terrain. So that helps us understand what the origin of the
material is. We don't yet really know what the origin is. A lot of the
models seemed consistent with it coming from outside, from somewhere
other than Iapetus and these observations are also consistent with that.

M. Ota Matthew Ota at the Saturn Observation Campaign. A quick question.
I read somewhere that one theory is that the ridge was formed by A-ring
material and if so, is that ridge on the ring plane?

E. Turtle The ridge is on the equator - the ridge that you can see
running around the center of Iapetus. It's more likely to be a tectonic
structure than due to material falling out. We don't yet know if it goes
all the way around, or if it's only on part of the satellite, but it
does really run around most of the satellite's equator, and so it's
probably an endogenic feature, something that was formed within the
crust of Iapetus rather than material falling in and piling up because
then impacts often don't just pile up on the surface. You actually get a
lot more deformation, destruction of the surface.

M. Ota Another question, Zibi. On slide 23, it shows on the left side
that ... bellyband shows. You've got an arrow pointed to that. On the
previous slide, 22, in about the same region, there's a sharp
discontinuity. Is that just\--

E. Turtle I think that's just a mosaicing artifact.

M. Ota Okay. Thank you.

E. Turtle There's a lot of topography on Iapetus, but that clip is not
real.

M. Ota So 23 looks much more like it should?

E. Turtle Yes. I'm not sure what happened with the image there.

M. Ota Okay.

M I'm sure you guys are aware of some of the "Sedona face on Mars" types
that have been implying that this makes it looks as if it's
manufactured.

E. Turtle It looks kind of like a walnut.

M Richard Hobland ... again.

M They say it looks like two halves that were cemented together at the
center.

E. Turtle Yes. Well it's certainly a challenge to understand its
origins, and we're looking forward to future observations of the other
side so we can see whether it goes all the way around.

L. Spilker We should probably move on, Zibi.

E. Turtle Yes. The next slide, number 24, shows some observations of
Phoebe and an animation of Phoebe as Cassini approached it just over a
year ago. We had the Phoebe flyby right before Saturn orbit insertion.

Phoebe's probably a captured object from the outer solar system based on
a lot of the Cassini observations and it's a very intriguing body. It's
clearly been very heavily cratered, and there's even some evidence of
layering in the crater walls. So it's a very interesting object with a
lot of geology in and of itself. Unfortunately, we won't be able to see
it close up again.

The next slide, number 25, has a number of images and other information
about Enceladus. Enceladus has always been intriguing in that it's quite
small. It's only got a diameter of 500 kilometers and yet, it clearly
has evidence for endogenic geologic activity and Cassini has shown that
in even greater detail. The slides on the upper right show fractures all
over the surface and no matter\-- The closer the image has got, the
finer scale of the fractures we saw.

There are impact craters as well, but in a lot of places, those impact
craters have actually been deformed so the ice has been mobile enough
that over the lifetime of that crater on the surface, its actually
deformed under it. So that's very intriguing. Then in the Enceladus
flybys earlier this year, there were some really surprising magnetometer
observations. I was going to turn it over to Michele to address that
aspect of Enceladus.

M. Dougherty Sure. I can do that. If we can focus in on the images to
the top left of the picture, the one in white with the white background
shows you data that we took from the first Enceladus flyby. Both of the
flybys - one was in February, one was in March - were quite far away
from the body, and we didn't expect to see anything in the MAG data.

What we expected to see was if we're looking down on the equatorial
plane essentially and what I've got in there, upstream of the moon
itself, are vectors of the magnetic field. You can see far away from the
moon. We came in from the bottom and we then moved up towards the top
left. You can see that the magnetic field vectors are pointing towards
Saturn and so essentially what we have there is the field due to Saturn
itself. We expected the data to remain the same during the entire flyby,
but you can see as we got close to the moon, the field lines seem to
bend around the actual moon. So it was almost as if there was an
obstacle to the flow.

We were expecting the plasma flow coming in from the left to carry
Saturn's field essentially on to the surface of Enceladus and then
beyond and behind it. That didn't happen, with the implication being
that something was acting as an obstacle to the flow of the plasma from
Saturn.

One of the ideas that we came up with to describe that was that there is
an atmosphere at Enceladus, which hasn't been observed before. The upper
regions of that atmosphere are being ionized, and it's the ionized
region that has been essentially behavior, or acting as an obstacle to
the flow of plasma.

So what we did is we put together that little schematic at the top of
the page there, which shows you Saturn to the left. It shows you the
magnetic field lines of Saturn, the dipole type field lines, and they're
co-rotating around Saturn and they carry with them not only the plasma,
but the field ions as well. You can see the hot plasma flowing towards
Enceladus and it's not able to essentially go down onto the surface. So
we have this obstacle which we think is an atmosphere.

In addition to that, there are a couple of minutes worth of data on the
second flyby, which shows some signatures in the field which don't match
with the interaction that comes from an atmosphere. It's almost as if
there's some type of internal signature that we don't quite understand.
So when we saw that, we got very excited and we described the
observations to the project. We've now persuaded them to move the next
flyby, which is on the 14 of July, from a distance of 1,000 kilometers
down to 175 kilometers. So that will allow us to get very close to the
surface and to be able measure not only the atmosphere, but to be able
to see whether there are some internal signatures as well.

Then the last thing I wanted to talk about was essentially the figure on
the bottom right. That's data from the dust instrument on board Cassini,
and that shows that there was an elevated dust flux, which\
CDA observed as close to the body, and so that implies that Enceladus is
producing dust and it could be the source of the E-ring. That's what
people have postulated in the past. So the coming up flyby on the 14^th^
of July is going to be extremely interesting to us.

W If I may ask a question actually.

M. Dougherty Sure.

W How do the dust flux that was observed near Enceladus compare to the
dust flux in the rest of the E-ring?

M. Dougherty I'm not sure of the exact amount. It's elevated by a small
amount. One is the follow-on slide when I talk about the observations
from the magnetosphere itself show that there is essentially a diffuse
E-ring going all the way out to the orbit of Titan, and that's one of
the great surprises too.

W Great. Thanks.

E. Turtle Moving on to slide 26, one of Cassini's other discoveries has
been the nature of the wisps that Voyager saw on Dione. You can see on
the upper left there's an image of Dione at lower resolution and on the
right, what's been referred to as wispy train running across the
surface, and Cassini had, again, a relatively distant flyby, but close
enough to get a really good view of the surface, and the imagine in the
upper right and the lower left; those two images show what's causing
this brightness, and it's actually series of fractures on the surface
that are exposing bright cliffs and that's what's causing it to look
bright. So you can just see all of these detailed fractures.

Of course, as I mentioned, we have fractures on Enceladus and Tethys, in
fact, has a different set of tectonic structures with just one huge
chasm running across one side of it. So inter-comparison of these
satellites is going to be really important to understanding their
different histories.

The next slide, number 27, shows impact craters on the wide variety of
satellites we have. The upper ones on the left show some huge basins on
Rhea and on Tethys. You can see.... Tethys kind of looks like an eyeball
from the right illumination, and then there's another large basin 300
kilometers across on Tethys. Mimas too has a single, very large crater.
That has a different morphology, and using, as I mentioned with respect
to Titan, you can use the morphology of craters to infer information
about the deeper structure of a planet.

Then the two center ones are much smaller targets and so have smaller
craters. Although, you can see in the upper right of this image of
Phoebe that there's also quite a large crater there and some small
craters on Epimetheus. Again, this helps us to understand the properties
of those bodies.

The lower left image shows part of a basin on Iapetus, with another
smaller basin and a huge landslide that's covered about half of the
floor of that. Then on Enceladus, as I mentioned, the craters are
actually deforming from viscous relaxation within. So by comparing this
wide suite of crater morphologies, we can really start to understand the
differences between these satellites.

Then on slide 28, there's another way we can get at the deeper structure
of these satellites is to measure the gravity, and the radio science
experiment has done that for a number of the satellites. We'll continue
to do that. This, combined with the imaging observations, helps us get
the density of the body. So for example, Phoebe is relatively dense at
1.6 grams per centimeter cubed, as is Enceladus. Some of the other
bodies; you can see Iapetus here has a density of about one. Obviously,
the density water ice is one. There are some complications. Because the
size of these bodies, you wouldn't expect just one for pure water ice.
But the difference is in the densities of these bodies is also helping
us to understand their internal structure, and will put constraints on
their histories. So those data will continue to come in and be very
exciting.

M. Ota Quick question. Matthew Ota with the Saturn Observation Campaign
again. Why does Hyperion tumble?

E. Turtle Why does it? I guess its history is such that it hasn't, that
its been impacted and its doesn't have a constant pull. I'm not
answering this question very well because I'm not a dynamics expert.

M I think, actually, there's a resonance between Hyperion's orbit period
and Titan, which causes its rotation vector to actually be chaotic. It
tumbles for that reason. It is dynamics.

L. Spilker Okay. Any other quick questions on icy satellites? Okay.
Zibi, do you want to turn it over to Andy?

E. Turtle Yes. The next set of slides is about Saturn, and Andy's going
to talk about those observations.

A. Ingersoll Well, nice to be talking, but actually, the first two
slides are about the magnetic field and radio emissions from the planet,
and Michele's going to talk about those.

M. Dougherty Sure. I can do that. On slide 30, this shows observations
from the radio wave instrument on board Cassini. The color plot shows
you the radio emissions that Cassini observes every planetary rotation.
What the instrument is able to do is essentially observe them quite a
long distance from Saturn as well, and so the bottom left hand figure
shows observations which were taken as Cassini was approaching Saturn,
and it compares them to observations which the Voyager I and II
spacecraft took of the rotation rate of Saturn. So essentially what the
instrument does is it uses the radio wave observations to work out what
the rotation rate of the planet is.

As you can see, the rotation rate, which Voyager I and II observed is
rather different to that which Cassini observed as it was approaching
Saturn. The third peak there shows you that since Cassini has gone into
orbit around Saturn, the rotation rate seems to have changed yet again.
We really don't understand this. We want to try and understand why it
seems to be changing because that will then give us a better idea about
the deep interior of the planet.

This links onto the next slide, which shows magnetic field observations,
which the magnetometer instrument took during Saturn orbit insertion.
That's the bottom left hand plot there. The magnetic field of Saturn is
quite strange. If you compare it to that of the Earth and that of
Jupiter, the dipole axis is aligned with the rotation axis of the
planet, whereas with Jupiter and the Earth, there is a large tilt
between the two, and usually, Planetary Dynamo Theory predicts that
there needs to be that tilt.

At Saturn, we haven't been able to measure that to date, and so that's
one of the main things that we want to try and do with the MAG
observations is try and get a better understanding as to whether the
internal field is really axially symmetric as it seems to be, or whether
there's some high order moments that are hidden away at this stage that
we haven't been able to observe. What we really want to do is try and
get to higher latitude to allow us to make observations of the internal
field over the poles.

But until we can do that, what we're able to do is we're able to see a
signature in the magnetic field, in the equatorial plane where we've
been making observations so far, which also seems to be occurring at the
planetary rotation rate. We've been able to predict what the rotation
rate of the planet is from that and it seems to be very close to that
which the radio waves seem to be seeing too.

So one of the things we need to be working on is trying to understand
why this rotation rate is changing, and once we understand that, then
hopefully we'll get a better understanding of where the internal field
is coming from, but also of what the interior of the planet is like as
well. Okay Andy.

A. Ingersoll Well, thanks, Michele. All of this discussion is very
relevant to the winds because Saturn is a fluid planet. We don't have
continents to provide a reference frame from which to measure the motion
of the atmosphere. So we need these hips like, and magnetic fields,
which comes out of the interior of the planet and generated down there,
or the radio emissions, which are, in some way, probably tied to the
magnetic field - we need these proxies of the rotation of the interior
Saturn in order to provide a reference frame from which to measure the
wind.

Now we actually measure the winds by, once you've chosen a reference
frame, we track cloud features in the atmosphere. This slide, which is
32, shows a number of different measurements of those winds using the
Voyager rotation rate as a reference frame. I'll say what happens if you
use the new Cassini rotation rate as a reference frame.

But if you use the Voyager rate, and if you use the Voyager cloud track
winds, you get the solid black line. You can see at the equator that big
bulge off to the right - 450 meters per second, which is about 1,000
mile an hour wind at the equator. That actually makes Saturn, at the
time of Voyager at least, the windiest planet in the solar system.
That's about ten times the speed that your airplane hitches a ride on
the Earth's jet stream. The jet stream is about 40 meters per second on
Earth.

However, the points labeled HST - that stands for Hubble Space
Telescope - in the 1990s, late-1990s and mid-1990s seemed to be getting
by same method - cloud track winds and using the Voyager reference
frame - seemed to be getting much slower speeds - around 70 meters per
second - representing quite a big drop in the wind speed. By the way,
that big of drop with that high a wind speed\-- There's so much kinetic
energy tied up in those winds that if you just turn that kinetic energy
into heat, it would have heated the atmosphere around the equator and it
would have taken several years for that temperature to cool back down
again. So this is a tremendous amount of energy for a very cold planet.

So when Cassini got there, we had the advantage of being able to look in
a lot of different filters. The ones labeled CH~4~, that's a methane
filter. That enables us to look quite high in the atmosphere, and we can
see hazes up above the main cloud deck. Those blue points seem to agree
with the Hubble data, indicating slower winds, whereas the green and red
points labeled "CONT", continuum, they see deeper. Those are about
halfway between Voyager and....

So what we seem to be seeing is a vertical wind sheer where the highest
altitude winds are the slowest and the deeper winds are faster. Although
we have not seen winds\-- At least the imaging experiment did not see
winds as high as the Voyager winds. The VIMS instrument, which is
looking in the infrared, did see winds as fast as the....

So it appears\-- They were able to see the deepest. So it appears that
the deeper you get, the faster the winds are and the high altitude winds
are the slowest. We're still working out the details, and whether it all
quantitatively fits together still has yet to be seen. At the other
latitudes, all the way down to near the South Pole, you can see that
there's been no change between Cassini and Voyager over a 20 year....

Okay. Move on. Another fascinating thing about the giant planet is that
they have lightening. They have lightening storms probably - we don't
really know - but probably due to the same mechanisms that form
lightening storms on Earth, falling raindrops, falling ice particles and
so on. So if you look in the lower right panel, the right panel, the
RPWS is an instrument that detects both radio waves and also plasma
waves. It's an instrument on the orbiter.

One particular kind of waves looks all the world like the radio waves
that you get from a lightening discharge, a sudden sharp, short-lived
burst of radio emissions. The burst lasts for less than a second, sort
of like the static on your AM radio when there's a good thunderstorm off
in the distance. This just shows a history of these bursts over about a
two-hour period. They occur at all radio frequencies, at least....

So Saturn got very active as Cassini was approaching it, and the RPWS
team said, "Well, we think we're seeing lightening bursts from, radio
emissions from lightening. Would you guys," speaking to Caroline Porco
of the imaging team, "Would you guys please look for a storm?" We were
aided in that search by the fact that the radio bursts come periodically
as Saturn rotates. There are a few hours when you get the bursts and
there are a few hours when you don't get them and then ten hours later,
it all repeats. It very much looks like it's tied to Saturn's rotation.

So there's a picture of something we call the dragon storm, which was
always facing us when the bursts were occurring. So that was a very nice
corroboration that we were seeing lightening.

There are some mysteries. We only\-- I didn't quite give you all the
details. We got the radio emissions when the dragon storm was in the
shadow, still facing Cassini, but not in sunlight ... to the left of
this image. Then when the dragon storm, still facing Cassini but in
sunlight, we didn't get the bursts. That is perhaps explained by the
idea that the ionosphere comes on during the day and blocks the radio
emissions from moving out to the spacecraft. But again, as with all
scientific questions, you answer one and you have a couple of new ones.
We're still working out the details of that.

The next slide, 34, shows some of this collapsing ionosphere. This shows
electron density versus altitude. That is the ionosphere basically and
this is nighttime ionosphere. The one labeled "June 8^th^," there was no
ionosphere during the night time. That would have permitted the radio
waves, allowed them to come out and be detected at Cassini. On other
days like May 3^rd^, there was a good, healthy ionosphere even on the
night side. So there is a lot of variability and that needs further work
as well. I think I'm done with Saturn's atmosphere, the windiest planet
in the solar system. I'll turn it over to Jeff Cuzzi, and we'll talk
about rings.

J. Cuzzi Okay. Thank you, Andy. Can everybody hear me?

W Yes.

M Yes.

J. Cuzzi Okay. So the first actual picture in the ring segment is at a
beautiful approach composite taken by the imaging team showing Saturn's
rings with something like a natural color, sort of a salmon color, which
relates to the composition. I'll talk about that a little bit later.

It shows the nomenclature with the brightest ring being the B-ring. The
A-ring is the outer ring separated by the Cassini division, which is
actually full of material with a low abundance or optical depth. Then
inside the B-ring, you have the C-ring. The dark band sort of two-thirds
of the way out to the A-ring is called the Encke Gap. I'll talk about
that later. It's about 300 kilometers wide.

One of the interesting things to keep in mind here is even though we've
learned a lot about ring structure between Voyager and Cassini, most all
of the structure you see in this image is not currently under study. We
really don't understand much about Saturn ring's structure. Another
thing that's kind of interesting about this particular picture is what
it doesn't show, and what it doesn't show is the spokes that we saw with
Voyager on approach and in fact, true of both Voyager encounters, these
shadowy features that came and went, covering the rings, thought to be
related to perhaps impact on the rings.

These features were seen by Hubble as very low elevation angles but then
went away. So does this mean that the rings just aren't getting hit by
material right now, or not? That's one of the questions that another
slide I have is going to address.

Another thing I want to point out from this slide is that the particles
in the B-ring and the A-ring are actually brighter and pinker than the
particles in the C-ring and the Cassini Division, which are darker and
grayer. This is thought to be due to sort of an interplanetary pollution
with small particles constantly coming in, bombarding the rings and
making the ice grayer.

Okay. Let's move on to the next slide. This is a beautiful picture of
Saturn, the north pole of Saturn as shadowed by the rings. The sun is
below to the right shining up to the rings, casting their shadow on the
planet. This really illustrates - well, you see at the bottom of the
frame is sort of the A-ring and the Cassini Division. It's obviously the
A-ring is sort of translucent. You can see right through it to these
fine thread-like dark shadows cast by the denser ringlets in the C-ring.

The very dark band there is the shadow of the B-ring where most of the
material is in the ring. In fact, in the very center of that dark band,
essentially no light is getting through at all. So the very center part
of the B-ring is very, very opaque, never penetrated by any Voyager
experiment, any occultation and we're really interested to know what's
in there. That's where the treasure's buried if there's treasure in the
rings. We're going to be very interested to see what we learn about that
material. The little moon there is actually Mimas.

Okay. So I want to move on from this. Just keep this in mind. This
basically tells you what rings are. They're just regions of different
abundance of ring material. Next slide.

W Yes, you're on 38, Jeff?

J. Cuzzi Yes. I'm on 38 now. We should really remember to thank the
project because just as we were going into orbit, after one of the most
critical maneuvers in the entire mission, the project let us turn the
spacecraft around and conduct some really critical science maneuvers
looking right down at the rings when we were very, very close to the
rings. In doing this, I had to buck numerous review boards, of which I
was on actually one of them, because good sensible engineering practice
would say you should never do anything this crazy, but we did and we got
some absolutely terrific data.

This is one of the highest resolution ever taken images, or ever
possibly will be taken of the rings, taken by the imaging team during
the SOI time period. What this illustrates is several of these spiral
waves that we do see in the rings. These are one of the kinds of
features we do understand because the orbit periods of material varies
with location. There are certain places where the orbit periods of
A-ring particle is an integer faction of the orbit period of some moon.
That's called a resonance.

At those resonances, these moons, even though their gravity is very,
very weak, can actually cause these waves to be kicked up. The same
physics is what causes spiral arms and spiral galaxies. So we've learned
quite a bit about spiral galaxies, even by studying the waves in
Saturn's rings.

So these are spirals. They're very tightly wrapped. It's like a watch
spring. Down and to the left is a density wave. It's a spiral wave of
packing and compression expansion effects. On the upper right is a
bending wave. This is actually kicked up by a moon that's inclined. So
it goes up and down, and it actually causes the ring to flap like a flag
in the breeze, or like a piece of corrugated tin.

So even though the rings locally are very, very thin - only tens of
meters thick vertically - this flap is several kilometers in height. So
it's quite a significant affect. These waves not only are beautiful, but
they're very important because by measuring the wavelength of the waves,
we can determine the mass density, the mass density in the rings, which
is very difficult from the optical thickness, or the area density in the
rings. The mass density is a very crucial parameter for telling us how
quickly the rings get polluted, or how big the particles are and all
kinds of things.

Also, the rate at which these waves damp tells us about the viscosity in
the rings, or the rings, because they have all of these many, many
little particles from centimeters to meters in size constantly colliding
at low velocities, it has the nature of a fluid and the fluid has a
viscosity and the viscosity damps particle motions and is responsible
for a lot of the structure that we see.

So these waves a very, very important, and there are several dozens of
them in the rings - maybe dozens, maybe even a hundred at this point
with Cassini's observations. But again, very important, but a small
fraction of the total structure that we actually observe.

Let's move on to the next slide, which is slide 39. This is another
observation that was taken during the Saturn orbit insertion by the
RPWS, the Radio Plasma Wave Spectrometer team. What this is it's a time
series running horizontally and running vertically, it's a spectrum of
frequencies. These are from zero to 20 kilohertz. So if you could hear
these waves, they would be audio waves - the same frequencies you hear
with your ears - but these are actually radio waves. So as time goes on,
what you see is these little bursts or blotches of color.

There's intensity only at a certain frequency or tone. So it sounds a
little bit like something that beeps on your phone at different
frequencies. What the team believes these things are is the spacecraft
is picking up plasma waves traveling on cones that connect the
spacecraft to a place where some meteor is hitting the ring. The opening
angle of that cone determines the frequency.

So what we're counting here is effectively the impact rate of something
like centimeter size meters hitting the ring, and you can kind of\--
Well, actually, this is one of the interesting things. We infer they're
centimeter size from the rate that we can kind of count here - how many
are there over 30 seconds, and what not. What we do not have now is a
theory that actually relates that to prove that these are really
centimeter size guys and that would be very powerful thing for some
smart grad student to develop some day.

Anyway, it seems that there are really meteorites hitting the rings.
This is a very interesting result, and so the lack of spokes that I
referred to earlier probably has to be explained some other way. Perhaps
there's a charging of the ring plane so that it's positive and it just
electrostatically sucks all of the dust right out of any kind of dust
cloud that gets created. We do expect that something like that is going
on. We expect we'll be seeing spokes later on in the mission as the
elevation angle of the rings gets smaller like it was during Voyager and
with Hubble when we actually saw spokes.

Okay. Let's move on to the next slide. Slide 40; this illustrates just a
tiny sample of data that's coming in from two different instruments -
the CIRS instrument, which is shown on the top color-coded, sort of
overlaying on a Voyager image of the unlit face of the ring.

CIRS is the telescope that measures the heat emission from the rings,
and what you're seeing here is color-coded from cold to hot. The dense
region of the B-ring where not much light is getting through and the
particles are sort of in the shade is the coldest. It's only 70 degrees
Kelvin or less actually in this image here. The images in the optically
thinner regions where the lights getting through are warmer.

> Now why is this really important is that CIRS can actually use this
> kind of observation to tell us how long it takes a typical particle to
> make its way through the ring. Getting through the ring can be
> difficult. It's like a traffic jam. There's a lot of stuff there. You
> don't just orbit away from the lit side to the unlit side. You may
> have to kind of shuffle your way through. This kind of local dynamics
> is something that CIRS can tell us by telling how the temperature
> varies from top to bottom in rings of different optical thickness.
> They'll be measuring the temperatures as the sun angle changes as a
> function of time as well.

Another thing CIRS is measuring and has shown is how the sort of the
emission of A-ring particle changes as you go to the longer wavelengths;
that is that as the grains in the surface start to act as little
billiard balls instead of a continuum, the particles seem to emit less
radiation. They seem to get colder, and this is very interesting because
it's going to tell us more about what the composition of the rings are.

Composition is actually the strong point of the VIMS instrument. That's
shown down on the bottom panel. That's a little expansion of just a tiny
little piece of the VIMS scan just crossing the Cassini Division, which
is that sort of lavender pink looking material, and the inner A-ring,
which is sort of the blue stuff on the right, and the outer B-ring is
the blue stuff on the left. This was actually taken during the SOI
experiment as well, but like CIRS, VIMS has a huge amount of new data
they're getting. Every day, there's more stuff coming in and it's just
going to be great.

But now, instead of having just one spectrum, VIMS has the critical
advantage that it's measuring a full spectrum of the ring brightness
with very high wavelength resolution. So it sees these bumps and dips at
different wavelengths that are characteristic of composition in a way
that no other instrument really can.

So here what we can tell is that even in the Cassini Division, which is
those sort of five lavender looking bands, one of them is sort of a
different color from the others. So even a region that's similar in all
aspects - optical, depth, ring particle, albedo and so on - it seems
like even some of those regions are different from their neighbors.

One interesting thing that VIMS has shown is that the Cassini Division
and the C-ring are dirtier than the B-ring and the A-ring; that is, they
have more silicate material as if, again, this is consistent with
getting polluted by meteoroids coming from interplanetary space. The
C-ring and the Cassini Division get polluted faster because there's less
mass there basically. Another good reason why we have to know the mass
density.

But the interesting thing here is that that change in composition is not
abrupt over the very abrupt optical depth boundary of the A-ring. It
changes very gradually. The color in that sort of green-blue area to the
right changes very gradually as you cross a very abrupt inner A-ring
boundary. So there's a lot going on here that involves dynamics as well
as composition.

Next slide. We have yet another kind of occultation and yet, another
wavelength. The radio signs experiment, which uses the high-gain
antenna, transmits three radio wavelengths, and as the spacecraft goes
behind the, as here indicated by the red line crossing through the ring,
those three radio wavelengths penetrate the rings and gives us
ultra-high resolution measurements of the ring structure, as indicated
by the little traces in the bottom panel, which show a number of little
density waves in the outer A-ring that were never seen by the Voyager
radio science experiment because it was very hard to penetrate the
A-ring at that time. Even the A-ring, not to mention the B-ring.

But not only does the radio science experiment gives us this ultra-high
radio resolution; it gives us particle size information as well. That's
because it has these three radio wavelengths and it's because the radio
wavelengths are on the same order as the size of the particles in the
rings, which vary from, let's say, centimeters to meters. So the fact
that particles interact with wavelengths of their own size in a very
complicated way, which is very sensitive to their size, allows us to
make very sensitive measurements of the particle size distribution and
how it varies across the ring.

That's illustrated in the next slide where here, we have two phony ring
images. Each one of them is created by taking these one-dimension cuts
through the ring and spreading it out to make it look like A-ring. It
just makes it a little bit easier to see. The upper panel shows the
whole ring system, and the color code is something like reddish pink
means bigger particles and green means smaller particles.

The very white bands in the middle show where the rings were so opaque
that effectively, they don't have particle size information because only
one wavelength got through. Optical depth in that very dense region is
something like four or even maybe larger. It's very, very opaque. This
is the very dense region that casts that very dense shadow on the planet
in one of those first slides that I showed. So again, here we are. We're
comparing measurements at different wavelengths, and we're going to
learn a lot more that way.

But you can see how, even across the A-ring, sort of to the right of the
Cassini Division, the typical particle size starts as pretty large, and
then gets smaller as you go out. Then in the bottom panel, as you go
further and further out into the A-ring, the very outer part of the
A-ring gets kind of blue. So here, we're seeing really an increase in
the number of small particles possibly because this region is very
stirred up by lots and lots of density waves from the satellites.

Next slide. The imaging team is focused in on some of these smaller
regions and made some very, very exciting results. This slide shows sort
of three panels. The left hand side and the central panel show the Encke
Gap, which is 320 kilometers across. The left hand side shows a little
satellite Pan, which was actually discovered by Voyager and its
interactions. It's right in the middle of that Encke Gap. Its
gravitation influence basically opens that whole Encke Gap up. It pans
about 20 kilometers across.

> The center panel is an enlargement that shows the structure in the
> Encke Gap and what you notice there on the left-hand edge is sort of a
> wave like pattern. The physics of this is basically very much like a
> stream flowing over a rock. Downstream from the rock, you have a
> ripple in the stream, which is fixed compared to the rock. Meanwhile,
> the water is flowing right through it.

The same kind of physics here. We have the ring material. The Pan is up
to the left, up off the top of the slide, and we have the ring material
to the left of Pan or inside Pan is actually moving downward in this
frame, as is Pan. Its orbit gets tweaked into these eccentric wavy like
structure, and they're just moving right through there. So this was a
very exciting result to see this in such glorious detail.

Actually, the bottom horizontal trait there, that white saw tooth
looking pattern indicates that this perturbation of the edge is not a
simple sign wave. It's very complex, and it looks like a beating or
harmonic interaction of different periods, indicating there may be more
than one moonlet in the Encke Gap.

In fact, if you look closely at that slide, you'll see numerous little
ringlets in the Encke Gap and my belief is each one probably is
associated with a little moonlet of some kind or other. These moonlets
come and go. They vary with time. They vary with longitude. Sometimes,
you'll see material sneaking up on Pan and then it basically just
disappears. So it's a very, very dynamic place.

The little panel on the right shows a brand new Cassini discovery, which
is another moon, which we've dubbed the wave maker. This is in a very
narrow gap called the Keeler Gap at the very outer edge of Saturn's
rings. You can see, again, the same general morphology - the little moon
there causing these little waves in the edges of the gap. So it's very
exciting now that we have two moons embedded in the rings, not just one
and there probably are more as well. Certainly these moods can't form
within the ring. So it helps us believe that the rings actually come
from some broken up moons as predecessors.

Let's move on to the next side. This shows some results from the Cassini
ultraviolet spectrometer. It's forte of this instrument is to take
stellar occultations of the rings. This is just a tiny little piece of
one of their, now they have eight cuts through the rings, and the UVIS
is getting lots of very, very exciting results, of which I'll just
emphasize one or two here because now, they can see waves in the very
low optical depth regions of the rings like the Cassini Division in that
second bullet.

This is our first opportunity now to measure the surface mass density in
some of these regions, which really, really constrains how these
optically thick regions get darkened by meteorite impacts and it really
forces us to consider that these rings are not as old as the solar
system. They would get a lot darker if they were as old as the solar
system.

In the interest of time, I think I want to move on to the next slide,
which got a little bit\-- Let's skip the one you've got, which has got a
red panel at the bottom. Skip right over that one. That's a bogus slide.
Right on to slide 46, which shows a composite of F-ring observations.
The F-ring is a fascinating, narrow stranded ring. First glimpse by
Pioneer 11, studied again by Voyager.

Voyager realized the F-ring was startled by two little ring moons called
Pandora and Prometheus. These are seen as the lower left and lower right
panels. At the time Voyager went by, we believed that these moons
somehow confined the F-ring by their gravitational perturbations in the
same way that Pan keeps the Encke Gap open.

But now we realize that's probably not the case. These moons are
probably close enough, massive enough and eccentric enough that this
whole region between them is chaotic. The orbits are not fixed. Anything
orbiting in that region occasionally has its orbit tweaked. There are
probably a lot of little things in there colliding all of the time. All
of these little strands come and go. The various outrigger strands
around that central F-ring core are not the same strands we saw with
Voyager. So it's a very, very interesting region. In fact, the imaging
team has discovered two, three new little objects in this region. It's
in their science paper. At least one of them has been lost. So a lot of
these things may just be transient.

The central panel of that lower row shows some interactions between
Prometheus and the F-ring - these dark waves. Essentially, Prometheus
enters that whole diffuse band, and as it does that, because it's on an
eccentric orbit - so is the F-ring - it perturbs the particles ... open
up. That same interaction explains most, but not all of those little
kinks you see in the upper foreplex in this slide in the core of the
F-ring. Most of those kinks are caused by Prometheus, but not all. In
fact, in the very upper central panel, you see lots of fine scale
structure that's not caused by Prometheus and are probably again
requires little tiny moons embedded in that same region.

Let's move on to the next slide. This is just a pretty picture. Slide
47, basically showing that we're having a multi-sensory experience here
with all of our different telescopes. The visible labeling cameras, the
radio wave lengths occultations, the infrared thermal wavelengths and
also the near infrared that's not even shown here as well as the
ultraviolet are going to give us this multidimensional picture of the
properties of the rings.

Finally, the last slide on here is just an example. It's just a
beautiful picture, but it does kind of give you a hint of what Saturn
would look like without the rings. I would venture to say not quite as
spectacular, but this just really emphasizes how very flat and thin the
rings are. They are only tens of meters thick and most all of the
brightness you're seeing here in the equator plane is due to the warps
and the wiggles in the F-ring that actually make not is a perfect plane.

So it's a beautiful picture, and I'm just going to close with that and
hand it off to Michele.

M. Dougherty Sure. Okay. I've lost the pictures on my screen, so I've
got hard copies of them. So I won't be able to talk about the color, but
what I'm going to now move on to is talk about some of the observations
of the magnetosphere that we've made in the last year, and this covers a
whole range of different topics. I won't be able to go into any of them
in too much detail, but the first one I want to look at is slide 49,
which shows observations from the UVIS instrument on board Cassini, and
what this shows is observations of oxygen. They're two different
pictures that you can see there. The one in the top left shows the
viewing geometry of this particular observation, which was taken during
or just after Saturn orbit insertion.

What we're looking at there is essentially a schematic of Saturn. We can
see the zero line along the Y-axis is essentially the equatorial plane,
and then we have radial distance above and below the equatorial plane
and the X-axis also shows you something similar. So you can get an idea
about the size of the picture that we're seeing there. The projected
slit of the UVIS instrument is shown centered at about two Saturn radi
widths. So that gives you an idea about where UVIS was taking
observations.

The bottom figure shows you the actual data that they obtained and the
color scale on the right hand side shows you; as the color gets
brighter, it shows you that the actual density of the oxygen increases.
So what you can clearly see from there is that oxygen atoms were
detected by UVIS in this rather large cloud surrounding Saturn.

What the team thinks it was seeing was these atoms were produced as a
result of moonlets in the ring system colliding together, and they
shattered ice particles and these ice grains which resulted from that
were bathed by Saturn's radiation belt and essentially, it's the oxygen
atoms reflecting in the sunlight that UVIS is actually seeing.

Essentially, the implication is is that the magnetosphere is essentially
full of this neutral atomic oxygen and observations, which have been
taken over a period of time now show that the density of this oxygen
varies over time, but also it varies depending upon where you are in the
magnetosphere as well.

Just to give you an idea about how much oxygen there is there; between
the period of Christmas and July of this year, about 500 mega-kilograms
of oxygen was gained and then lost in the system. So it gives you about
how much oxygen there is in the system and how it's changing over time
as well.

If we move on then to the next slide, which is slide 50\--

M I believe slide 51 is next.

L. Spilker Yes. I think you're off just by one, Michele. It's 51.

M. Dougherty Oh, okay. That's the ring ionosphere observed by INMS.
Okay. Sorry. On the view I've got, it's shown as 50. This shows data
which was taken by the Ion Neutral Mass Spectrometer during Saturn orbit
insertion and there are two different figures, again, that you can see
that. The one in the top left shows a view looking down on the north
pole of Saturn during Saturn orbit insertion. We have the different
rings being shown there and overlaying on top of that is the trajectory
of the spacecraft as it approached Saturn for the first time, with that
little circle right at the top showing you the ascending ring plane
crossing.

The color part of the trajectory shows you when the main engine was
burning during Saturn orbit insertion, essentially allowing the
spacecraft to be captured by the gravity of Saturn. Then at the bottom
part of that figure there, you can see where the actual observation was
taken by INMS during this time. What this observation showed is it
showed essentially the discovery of O~2~^+^, well the fact that it's
dominated the composition of the ionosphere of the rings.

The INMS team has speculated that this was formed as a result of
disassociation of water that took place. The oxygen that resulted from
that then reacted possibly with itself as a result of interactions on
the surface of the rings, and the reason that this happened was because
the lighter element hydrogen probably escaped into Saturn's atmosphere;
so it wasn't available to recombine with the oxygen.

So what this process did was essentially form molecular oxygen and this
was then subsequently ionized to form O~2~^+^. So really what these
observations allowed was us to get an understanding of what the ion
chemistry is and the different types of ice surface reactions that took
place within the vicinity of not only the rings themselves, but the
atmosphere of Saturn too.

If we can then move on to the next slide - I won't give you a number
because I'll probably get it wrong. This is observation from the CDA
instrument, the Cosmic Dust Analyzer, which shows a diffuse E-ring, and
I referred briefly to this when Zibi asked me the question about the
dust observations when I talked Enceladus.

These measurements were taken in the E-ring plane by CDA over the first
year's worth of observations. I mentioned to you earlier that scientists
have long speculated that Enceladus is the source of Saturn's E-ring.
Well, in fact, it's a little bit more complicated than that in the sense
that there seems to be a very diffuse E-ring, which is extending well
beyond the region of Enceladus. Enceladus is very close into the planet,
just beyond four planetary radii. You can see that dash line and while
... 4 planetary radii shows where you the orbit of Enceladus is.

You can see the marks which were shown on this plot in the different
colors, which show you what the particular density is, shows you the
observations which have been made by the dust instrument of either dust
or small ice grains in this particular region.

Now, these observations were rather a surprise because optical remote
sensing observations before Cassini got to Saturn showed that the
diffuse E-ring only extended out to about 15 planetary radii. So these
new observations show that it extends much beyond that. It's actually
going out as far as Titan's orbit.

Now something to keep in mind about CDA is it allows us to measure, or
it allows the team to measure not only the small ice grains, but also
the dust in the vicinity of Saturn as well. So it's going to allow the
team to investigate the physical and the chemical properties of both of
these different substances.

Okay. I think the next slide also shows some observations from CDA. This
shows some observations of some very high velocity dust streams, which
are originating in the Saturn system. They're actually detected when
Cassini is out in the solar winds. They were first detected as Cassini
was approaching Saturn. So in early 2004, these observations were seen.
This is the first time that these type of dust streams have been
observed at Saturn, and you can see\-- We've got a view looking down on
the equatorial plane, which shows what these dust streams look like as
you move further away from Saturn. You can see the very great radial
extent that they've observed at as you move away from Saturn. So not
only were they observed as we approach Saturn, but they've also been
observed when the Cassini spacecraft has moved back out into the solar
wind during the first year of the orbital ellipse.

What we think is happening is the dust particulars are essentially being
spewed out of the magnetosphere of Saturn as a result of the
co-rotational electrical field, and the team has been able to make
measurements of the composition of these stream particles and they seem
to be made up primarily of rock forming particles - so essentially
silicates and carbon and oxygen and ion. They think that the likely
source of these is at large distances away from Saturn, probably on the
outskirts of the A-ring. They will continue to take observations of
these during the rest of the tour to see if they can try and better
understand the observations.

Okay. Moving on to the next slide then, this shows or describes rather,
some observations which the magnetometer instrument has made whenever
we've got close to Saturn. The picture that you see there shows a view,
again, down on to the equatorial plane of Saturn with some of the orbits
of the different moons shown. The orbit of Enceladus is shown very
clearly there. The sun is off to the right, and overlaying on that are
trajectory plots from the different orbits of Cassini as it's orbited
around Saturn.

In addition to that, in red, we see regions where ion cyclotron waves
have been observed by the MAG instrument. Now these waves are generated
when neutral particles in the magnetosphere are ionized, and they're
picked up the magnetic field of Saturn. We're able to observe them as
perturbations in the magnetic field. The frequency at which they occur
allow us to work out which molecules or ions actually generated the
waves. So what we're able to do is we're able to observe that within the
close vicinity of Saturn, we see ion cyclotron waves occurring at water
group frequencies - so essentially OH, water itself and H~3~O~2~. These
have been seen, as you can see from the figure, at nearly all radial
distances and local times within the E-ring.

The observations of the waves and the work that we're doing on them is
going to allow us to get an understanding of how much material is being
lost from the E-ring and that's going to allow us to get a better
understanding as to where the plasma and the magnetosphere is coming
from. In fact, what we see in the magnetometer data but also in the
plasma data and some of the density data from the radio wave instrument
is that we see regions of hot plasma; almost bubbles of hot plasma
moving away from Saturn and we have empty flux tubes or cold flux tubes
moving back in. So there's some plasma transport taking place in this
region, which we're hoping we will be able to better understand by
combing all of the different data sections.

Let's move on then to the next slide, which shows some observations
which the magnetospheric imaging instrument onboard Cassini took - the
instrument known as MIMI. This has three different detectors and one of
them called INCA allows the instrument to measure energetic neutral
atoms. The two figures that you see here essentially show observations
which were taken during the Saturn orbit insertion flyby, which allows
the instrument and the data from it to show that there's a new radiation
belt, which we didn't know about before very close to Saturn.

The top figure shows you the ENA image, or the image of the energetic
neutral atoms, which was taken as Cassini passed over the rings. The
rather large bright region that you see just above Saturn's limb - so to
the top right of the image - is essentially caused by the energetic
neutral atoms, which are being produced by charge exchange collisions,
which are occurring between the main radiation belt ions, which you can
see a schematic of in the bottom figure, and the gas distributions in
the near equatorial plane.

But in addition to that, not only would the main radiation belt, which
we knew was there; not only was that observed, but in addition to that,
there was this extra band of emissions seen just above the equator. This
also, the team thinks was produced by the same energetic neutral atoms
from the main belt. But these occurred as a result of being stripped in
Saturn's exosphere. So between the inner edge of the D-ring and the
cloud tops. What they think happened is that they were trapped
temporarily there as energetic ions and then they were reemitted again
as energetic neutral atoms and it was then as they were emitted as
energetic neutral atoms that the INCA sensor was able to observe them.

So what the bottom figure is showing you is essentially a schematics of
what the MIMI team thinks is occurring. You're seeing not only the main
radiation belt, but you're also seeing this new trapping belt much
closer into Saturn, and the view also shows the Cassini spacecraft and
the two viewing geometries of when it was able to first observe the main
radiation belt, and then observe this new trapping belt.

Let's move on now to an observation of Saturn's aura, and this is linked
to some of the magnetic field observations, but also some of the other
fields and particles observations as well. It's a very clear example of
how if we combine all of the different data sets, we're able to get a
much better understanding of what's going on in the magnetosphere of
Saturn.

What we see here are some images which were taken by the Hubble Space
Telescope as Cassini was approaching Saturn. We put together an
observing campaign during this time because at this particular time,
Cassini was in the upstream solar wind and so what the fields and
particles instruments were able to do was to measure observations in the
solar winds. We were then able to propagate them to Saturn, and we're
able to observe how the aura at Saturn changed as a result of that.

We saw that they did change, but one of the surprises was that they
seemed to change more as a result of changes in the dynamic pressure of
the solar wind rather than changes in the BZ component of the
interplanetary field, and this is very different when we compare it to
the Earth. At Earth, the aura seemed to be driven as a result of changes
in sign of the BZ component whereas at Saturn, at least from the
observations as we approach Saturn, it seems to be linked more to a
compression of the magnetosphere as a result of an increase in the solar
wind pressure.

But the observations that I want to talk a little bit about now are
those shown in the bottom right hand figure. These were observations
which were taken by the fields and particles instruments onboard Cassini
during Saturn orbit insertion or on the outbound pass of Saturn orbit
insertion. I realize it's a very busy plot, but let's focus first on the
third panel, which shows the magnetic field magnitude. What I want you
to do is really to focus in on the region in between the final two dash
lines, which essentially shows you that the magnetic field is rather
disturbed there. There's a decrease in the magnetic field.

At the same time, the panel above that, which shows the radio wave
observations shows that there was a very large increase in the SKR, in
the Saturn Kilometric Radio observations during this time. The panel,
the second bottom panel shows an increase in the ion flux observations
from the MIMI instrument, and the bottom panel shows an increase in the
energy flux of the plasma.

So essentially what we think we were seeing there is that there was a
compression of the magnetosphere as a result of an increase in the
upstream solar wind pressure, and as a result of that, we've got
reconnection taking place in the tail. We've got an injection of plasma
as a result of that. There was a burst of radio emissions and there was
also a change in the magnetic field. So we think this is the first
observation of reconnection occurring in the tail of Saturn, and
generating probably observations of the aura, but we weren't taking
observations of the aura at the time. So hopefully, we'll get a chance
later on in the tour to be able to take similar types of observations.

Then the final slide I wanted to talk about was some observations,
again, from the MIMI instrument. These, again, were taken during Saturn
orbit insertion. What these show are counts versus mass per charge. So
essentially what it's showing you is it's the host of different ions,
that one of the sensors, the KIM sensor in the MIMI instrument observed
during this particular time. You can see peaks of different types of
ions. We've got O~2~^+^. We've got O^+^. We've got a very small peak at
N^+^. We've got some helium in there as well.

But as you can clearly see, most of the ions which are being observed
are arising from water. The absence of nitrogen, of N^+^ and N~2~^+^, is
very perplexing because before Cassini got to Saturn, it was assumed
that we would see a lot of the N~2~^+^ because we expected it to be
picked up by Saturn's magnetic field as it draped itself around Titan's
exosphere. We expected Nitrogen to be picked up from the exosphere of
Titan. That clearly isn't taking place in the type of quantities that we
expected it to.

The molecular hydrogen that we see could be as a result of one of the
disassociation products of methane in Titan's atmosphere, but that would
imply that there is pick up taking place, or large pick up taking place
from Titan's atmosphere, which doesn't seem to the be case, at least as
far as the nitrogen is concerned. So it's more likely that the molecular
hydrogen we're seeing is probably originating from the water products,
but this is something that we need to try and better understand and not
only will we be able to do that with the fields and particles
instruments ... magnetosphere, but as we get closer to Titan. On some of
the follow-up Titan flybys, we will be better able to understand that as
well.

L. Spilker Okay. Thank you, Michele. Now, are there any questions on the
Saturn rings or magnetosphere section? Okay. If there are no questions,
what I want to do is in the interest of time, there's a series of slides
starting with slide 59, 60 and 61 that has some Gee Whiz Cool Facts that
we've collected about the mission, such as how many pictures were taken
of various targets, and how many miles has Cassini traveled? I just
wanted to point out so you can look at those and make your guesses and
see how close you get.

One of my favorites is how much propellant was saved by using Titan for
gravity assist? This just shows the power of being able to use a target
like Titan and the fact that in the first year of the tour, using Titan
gravity assist, we've saved six times what would have taken for the
change in velocity for our biggest maneuver, which was a 96-minute main
engine burn at Saturn orbit insertion. So we really have a lot of
usefulness for Titan besides just getting really fascinating data,
really cool data about that particular target.

Then with the final slide of the presentation, 63, just talking about
some of the upcoming events and what can we look forward to in the next
year for Cassini. We're about half way through the series of
occultations and occultation orbits. We have four more sets of
occultations to go, and so we're ending that phase of the mission with
getting good looks at the rings, the high inclination. Then we'll enter
a phase where we go back into the equatorial plane and rotate the petal,
or the direction of the orbit around so that it points back into the
magnetotail, and we get a good sampling of the magnetotail. We also have
frequent Titan flybys as we do that.

One of our big events coming up is the closest approach yet to
Enceladus. That's on July 14^th^ and we'll be coming within 175
kilometers, and that's the closest we've actually come yet to any target
with the Cassini spacecraft, and we'll be flying close to the south
polar region of Enceladus. It should be a fascinating flyby.

Also, we have something we're calling "Six Worlds in 80 Days." In an
80-day period, we have two Titan flybys and also some very good close
flybys of Tethys, Hyperion, Dione and Rhea. So a very satellite
intensive period in the tour as well.

Then finally, the last bullet there lists the nine targeted Titan flybys
that are coming up over the next year, and the dates of those flybys. Of
particular note is the October 28^th^ flyby where we'll actually get the
radar SAR coverage of the Huygens landing site. So that will be very
interesting to now go back and look in detail with radar and with the
other instruments at also at multiple times at the Huygens landing site.
So with that, I'd like to go ahead and conclude.

I'd like to thank the speakers very much for their good presentations
and for keeping on time and then just ask one more are there any
questions on the line? We've got about five minutes?

C. Marble Yes. This is Chuck Marble, NASA Ambassador from California. I
haven't heard a whole lot in the press since the initial situation with
the Huygens' probe where there appeared to be some sort of a difficulty
with Channel A and Channel B where all of the images were unable to be
relayed back. Do we know for sure what went wrong and what can we learn
from that?

L. Spilker Yes. I think we know now that it looked like it was a command
that did not get in to turn on some hardware on board the probe, or on
board the orbiter actually that would have been able to pick up both
channels. So it's just it was a commanding error, and just given the
large volume of commands and things. Probably the lesson learned is
you're going to have human errors. You just have to check the best you
can to try and catch it.

The fortunate thing is that we did have an array of deep space network
stations that were simultaneously tracking the Huygens probe. So the key
experiment, besides losing some images, the experiment we would have
been able to do also with the orbiter is the Doppler wind experiment. By
having all of those stations on the ground, we think that we'll
basically be able to recover the Doppler wind experiment and get a wind
profile as the Huygens probe was floating to the surface. So yes, there
was a commanding error, but it looks like we can recover the science for
that particular part of the mission.

C. Marble The commanding error; was that software embedded at launch
time, or was that a command that was failed to be relayed up through the
Deep Space Network?

L. Spilker I think it was a command that was just inadvertently omitted
from the series of commands that we sent up to the spacecraft.

C. Marble So we did get enough ground measurements for the Doppler wind,
but we lost about what - 300 images?

L. Spilker Right. The two channels had a lot of redundant data, but in
the case of the images, the data were not redundant. They were just
basically sending different pictures back on each channel, but if you
look at some of the mosaics, we do have plenty of overlap and so on with
the various images to really put together a nice view of what Titan
surface looks like.

C. Marble You bet. One more question about Titan. In some of the earlier
images, there appeared to be what almost looked like ground fog, and it
sounds like the elemental composition could be conducive for that. Do
you think that there is fog on the surface of Titan?

L. Spilker Zibi, are you still there? Do you want to take that?

E. Turtle At the resolutions of the ISS experiment, we haven't seen any
changes from orbit-to-orbit, and the first three flybys had about the
same geometry. So we got three views, three similar views of Titan. Were
there things like ground fog? One would expect them to occur in the same
places, but not necessarily to be identical from orbit-to-orbit, and we
haven't seen any evidence of that. We haven't seen any evidence of
changes from orbit-to-orbit.

Also, VIMS would be able to detect\-- At various wavelengths, the clouds
are quite obvious to VIMS and they can tell whether things are clouds.
They can also tell what altitude, to some extent things are at. They
haven't seen strong evidence for ground fog either.

C. Marble Thank you. One last question. On the ground based image on
Titan, you could see, as you mentioned, what appears to be somewhat
erosion on the lower part of the rocks are visible. Do we think that
that was something that happened a long time ago, or do we think that it
goes through seasonal changes and maybe there is some sort of lift that
will be coming back over that area again in the future?

E. Turtle Is Shaun still on the line? Does he want to speak to that?

L. Spilker I think he had to go.

E. Turtle Okay.

W Yes, Shaun had to go.

E. Turtle We don't have good constraints at all really on how\-- on the
ages of Titan's surface at this point. There certainly are seasonal
affects, but the differences that we see, for example, between the
albedo patterns at the equator and at the poles may actually be the
affects of cumulative seasons. So the fact that we saw more clouds at
the south pole up until about six months ago may mean that it rained
there fairly recently, but the features there are going to be not just
due to the most recent rainfall, but due to rainfall that's over
several, several, hundreds of seasons. We just can't constrain ages at
all yet.

C. Marble Got you. Thank you guys very much. After all of these years of
waiting, this is kind of like being Charlie in the Chocolate factory.
Thanks a lot, guys.

L. Spilker Thanks, once again, to the speakers. With that, we'll
conclude the CHARM telecon.