RAW TRANSCRIPT -- NOT YET REVIEWED FOR CORRECTIONS BY CASSINI PERSONNEL

**FTS-NASA-VOICE**

**Moderator: Trina Ray**

**August 26, 2008**

**1:00 pm CT**

Coordinator: Excuse me. I'd like to inform all participants that today's
call is being recorded. If you have any objections, you may disconnect
at this time.

I would now like to turn the meeting over to your leader for today, Ms.
(Jane Jones). Thank you, you may begin.

(Jane Jones): Thank you and welcome everybody to the Fourth Anniversary
Charm Presentation Part Three of Three. This is such an exciting year as
the final year of our prime mission that we had to break our anniversary
CHARM into three pieces.

We have two great speakers today; the first is Dr. Jeff Cuzzi. Jeff's
main interests are in planetary science - planetary system origin and
evolution. He was trained as a radio astronomer, observing Saturn with a
NRAO Interferometer in 1975, which was at the same time of the exciting
discovery of radar backscattering from the rings.

He became drawn to learn all the aspects of Saturn's mysterious rings
and ultimately rings around other planets as well. Jeff was the study
scientist for the first engineering studies of a Titan entry probe done
by Ames back in the 70\'s. And this eventually became the Huygens probe.

He was invited to join the Voyager Imaging Team in 1978 and led the
rings - the team's ring subgroup through planning all of Saturn, Uranus
and Neptune in counter ring observations.

He's received two NASA Exceptional Scientific Achievement Medals, the
AIAA Lawrence Sperry Award and - for his work on planetary rings. In
1989, he was selected as the interdisciplinary scientist for rings on
the NASA ESA Cassini-Huygens Mission. And recently he has collaborated
on several popular books on the Cassini results.

Jeff is also actively studying how fluid dynamics and turbulence might
have played a role in the centuries-old puzzle of the primitive
meteorite record. He served as Chief of the Planetary Systems branch of
Ames Space Science Division from '92 to '96 but is now just a scientist.
I hope that's great.

Okay, so Jeff, take it away.

Jeff Cuzzi: Okay, hello everybody. Can everyone hear me okay? I guess
you're all on mute so I'll never know.

(Jane Jones): I can hear you just fine.

Jeff Cuzzi: Okay, great. Okay, well, so it's a pleasure to talk to you
about rings today. It's getting very hard to give a full Cassini talk in
less than an hour - it's almost impossible. But I\'ve done it. But for
rings I think we can try to summarize most of the main advances that
we've had in Saturn's rings over about the last four years. So that's
what I'm going to try to do.

A lot of what Cassini has done is cumulative. That is, some of these
observations that we're going to talk about were taken in the first year
or the second year. But it's just taken us this long to, you know, tie
them all together and do the theoretical modeling and start to make
sense of it.

And in fact, even to get around to looking closely enough at some of
these observations to find some of these signals that are just buried in
there.

Okay, so this first slide here is maybe unusual. I'm sure all of you are
pretty knowledgeable so this won't surprise you. But it's an unusual way
to look at the rings. This is actually a picture of the rings from the
unlit face. The sun is shining on the other side.

And I think it's nice because it tells you where most of the material is
very, very clearly. The big dark swatch right through the center of the
rings is the B ring which normally looks quite bright. And this gives
you a real good sense of just exactly how much more material there is in
the B ring than there is in any of the other rings.

And you can even see, there are parts of the B ring that are so dark
that almost no light at all is getting through there. So this is one of
the big, big goals of Cassini was to penetrate these dense parts of the
B ring because we were just never able to do that with Voyager. And as I
hope I'll show you, we're really doing that in spades now.

Now the - just the next slide illustrates the classical ring boundaries,
the B ring again, the region that's all full of material sort of in the
center of the ring. The A ring is the outermost ring outside - just
outside the A ring is a little narrow stranded ring called the F ring.
I'll talk about that quite a bit in much more detail. And I'll talk
about the structure in the A ring as well.

The A ring is full of wave patterns that we've been studying and the
little narrow gap sort of toward the outside edge of the A ring is
actually two of them - one very near the edge are little gaps where
there's a moonlet. So we'll talk about that.

CD is a Cassini Division - used to be thought that was empty. People
actually speculated and talked about sending space craft through the
Cassini Division. But you can see it really is another ring in its own
right, pretty much like the C ring which is the ring inside the B ring.
The Cassini Division and the C ring have a lot of properties in common
and what we really don't understand.

Inside the C ring, there's a very faint ring called the D ring that you
can't really even see in this image. And far outside the main rings
there are what we call the diffused the rings - the G ring - which is
relatively confined to a couple of thousand kilometers.

And the E ring which is this very, very broad - goes all the way from
probably Nemus all the way out to, you know, the 20 Saturn radii or
something like that and it's centered on Enceladus and we're going to
talk about that. Of course that was one of the big exciting discoveries
of Cassini.

Okay, so moving on to the slide. Now we're moving away from the dark
side here and here, this is the more traditional ring view here. Let me
just make a note. Okay, where you can actually make out in this one -
this is a true color image and you can actually make out some of the
slightly tawny, warm tan colors of the ring. So they're really not
white.

And this is very, very important to understand. Not only are they not
white but the color varies from place to place. It\'s a little hard to
see that in this picture. But I'll show you some other pictures and make
that a little bit more clear.

Again, all of this beautiful structure in the B ring \-- we call this a
regular structure \-- it's just not at all understood. All the structure
in the C ring, almost none of it is understood. We do understand a lot
of the structure in the A ring and I'll get to that later.

Okay, next slide is sort of an overview of what I'm going to say here.
I'm going to start - this talk is actually derived somewhat from a
presentation that we gave to the people at NASA headquarters a couple of
weeks ago where we reviewed all the major accomplishments of Cassini.
But I've put actually some more in it here.

But basically these break down into the whole area of ring particle
composition; that is what are the rings made of. The (size distribution)
of the particles which is interesting in its own right and also from the
standpoint of well, you know, how do you analyze the data. You have to
know what the particle sizes are.

Then the second general topic, all this ring structure. You know, how do
you explain it? What are the processes that we can point to that account
for that structure? Sort of a sub-set structure but a very important one
is the role of what we call moonlets, which are objects - maybe
asteroid-sized, you might say, comet-sized objects that are much too big
to be a ring particle.

They actually influence the surrounding material. But they're really too
small to count as a full on satellite like Mimas or Tethys or Titan.
These little moonlets are in and around the rings. And we've known that
for a little while. We really want to know exactly where they are, how
many of them are, how big they are and what their role is.

I'm going to talk a little bit about dust in the Saturn system because
there's at least one very important role that dust plays. That is the
role of meteoroid dust from outside the solar system. Then I'll wrap up
with a little bit on the role of electromagnetism.

So even after our four years here, these questions are still somewhat
staring us in the face. They still are a little puzzling. What does give
the rings their reddish color? Okay, we know they're red, we're learning
a lot about that. Still not quite sure exactly what it is, what material
makes them be not pure white.

What is the age of the rings? This is related to how they were formed.
This depends on a couple of things that Cassini has not been able to
measure yet but we do hope to measure in the extended mission that (Dave
Seal) will be telling you about in the next talk.

This whole idea, (the fine) structure of the B ring, the regular
structure of the C ring - these are outstanding questions. So I'm going
to hit on these as we go through the talk.

Okay, next slide. Okay, starting out on the idea of composition, two
things shown here. The picture is a Cassini image, the color in it has
been stretched a little bit. But you can tell, even with that stretch,
that Enceladus which is the moon up there is just white. I mean
Enceladus - the surface of Enceladus is pretty near pure water ice. And
as we all know, pure water ice is pretty white.

And yet the rings are simply not white - they're red. So why is that?
The spectra that you see in the plot at the left are from the VIMS
instrument on Cassini - wonderful instrument, observes the brightness of
the rings. It's converted into a reflectant by taking out solar
spectrum.

As a function of wavelength, way over on the left is the visual part of
the spectrum between about three tenths of a micron and six tenths of a
micron or seven tenths of a micron. You can see in that region of the
spectrum the brightness increases very fast from the short wavelengths
and the long wavelengths. And that's what makes the rings look red.

Then as you go further to the right in that spectrum, you see these deep
dips. Those are absorption features of water ice, very characteristic
spectral signatures proves to us there's water ice there. And there's
not much else as far as we can tell. There's some little arrows there
that points to where we would expect to see carbon dioxide of CH which
is the signature of organic material.

Organic material tends to have a lot of carbon in it with hydrogens
attached to those carbons. And every time you have one of those bonds,
it absorbs at about three and a half microns and we just don't see that.

So that's very interesting that we don't see this organic signature and
we don't see CO2. But we see plenty of ice and it's a little bit red.

Okay, so now next slide indicates that before Cassini got there, the
best we could do from the ground, we had sort of one spectrum like this
that was the average spectrum for all the rings together. Now we have
thousands of these spectra because Cassini can map each one of these
little ringlets in a scan across the rings. We have thousands of these
spectras. How can we start to put together all this information?

The way we've done it is, we start by pulling out some kind of coarse
metrics of the information. Like for instance, over here the blue bar
represents what is the slope of the spectrum in the short visible
wavelengths. The green bar represents what is the slope of the spectrum
at the longer visible wavelengths. And the orange and red bars represent
what are the depths of the water ice bands.

So now we can just extract those four properties and look at how they
vary as a function of distance as we go through the ring. And that's
shown in - not quite on the next slide. Okay next time step around that
one. So now we get this plot that shows on the top, there's just the
brightness of the rings. The C ring is faint, the Cassini Division is
faint, the B ring and the A ring are brighter.

And what we see in the bottom plot is these various metrics. So you can
see the red line and the sort of orange-gold line which represents the
depth of the water ice bands. Those properties vary sort of smoothly
through the rings. That is as you go across the inner edge of the B ring
where you see from the top panel, the brightness drops very sharply
which is same thing that happens at the inner edge of the A ring.
Between the A ring and the Cassini Division the brightness drops off
like a rock.

But in the bottom panel you can see the color does not change that
abruptly as you go across these edges. But it does change in a global
sort of a way as you go through the rings. So we have generally speaking
the Cassini Division and as you go into the C ring, these ice band
depths are smaller which means you have less ice or smaller grains or
some dirty material that's, you know, preventing the ice from absorbing
in those regions.

And then you see as you go through the B ring, sort of in the middle of
the B ring there's a region of fluctuations in the water ice abundance.
This is associated with - at least some of this is associated with the
very, very optically thick regions in the B ring. But as I pointed out
in my first slide, it was blocking all the light, okay.

So there's some very interesting correlations here between the
absorption by water ice and the region in the ring or the optical duct
in the ring. Now look at the blue line and the green line. The blue line
shows the visible flow, the redness if you like - the visible
wavelengths.

And it kind of tracks along with the water ice band depths pretty well.
There are some differences, like in the C ring, for instance, there's
some features that show visible wavelengths that are weaker in the band
depths.

But it's tracking pretty well. This indicates to us that whatever is
doing the absorbing at the short visible wavelengths, that is whatever
is making the rings red is in the water ice and correlated with where
the water ice is. Where the water grains are, that\'s where this red
stuff is.

Where the water grains are bigger, there's more of the red stuff.
However, the green which represents some other spectral property of the
rings at longer wavelengths doesn't - it looks totally different,
varying hardly at all through the A ring, B ring and Cassini Division.

And then as you get into the C ring, there's this very interesting hump
right in the middle of the C ring. It just doesn't correlate at all with
anything else. So this tells you there's maybe a third or fourth
material there that - and the rate of distribution of that is
decorrelated and different from whatever's causing the water absorption,
whatever's causing the red. So this is very, very interesting.

We just start to take a look at this and that's all we're really doing
is just starting to take a look at this. Okay, next slide indicates what
we can do even more with the cameras now. Cassini\'s cameras have a much
higher resolution, looking at much finer detail than the VIMS experiment
does, but their spectral resolution is very coarse.

So instead of having 300 channels across all those wavelength bands that
the VIMS covers - actually the individual range VIMS has about 100 but
the imaging only has about 15. But you can see we can look at much, much
finer detail. And in the bottom panel on the left, actually you can see
that, you know, this is the very outer part of the A ring - that very,
very outer part of the A ring actually looks kind of different in its
color from the whole rest of the A ring.

So that's very interesting to track that kind of thing. The dot plot
over on the right indicates how we're going to start to do this by
correlating the colors - one kind of color that is the slope - maybe
that green line slope I showed you before along the vertical axis and
the blue line slope I showed you before, along the horizontal axis\...

Man: Trying to figure out\...

Jeff Cuzzi: Is there a question here?

Man: Oh, I'm sorry - go ahead.

Jeff Cuzzi: Okay, so what this shows is with enormously higher spatial
resolution now we can really watch how these slopes and color ratios
change as you go in and out of different ring regions. So again, just to
give you a sense, we have barely seen the tip of the iceberg from the
standpoint of measuring this composition from Cassini. But we've got an
enormous amount of evidence and data that we're just getting started to
analyze right now.

Okay, next slide. Okay, now we'll talk a little bit about science
distribution here. These two graphics are actually not pictures of the
rings. They're sort of phony. They're created from taking a one-line
scan through the ring by the radio telescope on Cassini. As Cassini goes
behind the rings as we watch from the Earth, it broadcasts the radio
signal right through the rings.

So we get just a line of transmission through the rings as space graph
goes behind. But we get it at three different wavelengths in the
microwave region, 2 centimeters, 4 centimeters and 13 centimeters. And
the way the transparency of the rings varies from one of these
wavelengths to the other tells us about the sizes of the particles in
the rings because if you're a 2 centimeters particle, you're going to
block those 2 centimeter waves but you're not going to block the 13
centimeter waves.

So we can learn an enormous amount by watching how these different
wavelengths vary. Okay, so basically this plot - the lower ones - the
upper ones shows the whole ring system where pink tends to mean larger
particles and green is smaller particles. And white just means it's just
opaque to at least one of the wavelengths.

The lower plot shows just the outer part of the A ring. You can see this
dark band is the Encke Gap, which I'm going to talk about later. You saw
it as a very narrow gap in the first image that I showed you. The very
narrow gap at the very outer age is called a Keeler Gap. And you can see
as you go outwards in the A ring, the color changes from green to blue
which tells you that you're seeing more and more small particles as you
move out in the A ring.

This is emphasized a little bit more on the next plot which is a little
bit busier but it's got a little bit more quantitative information.
Let's look at the left hand panels here. The top panel and the third
panel just show the transparency, if you like, the opacity of the ring
at a couple different wavelengths.

The top one is through the B ring, the third panel is through the
Cassini Division and the A ring. And you can see these different color
curves are diverging from each other. These are the optical depth or the
opacity at different wavelengths.

So by differencing these wavelengths, we end up with results like in the
second panel and the fourth panel which actually shows us the abundance
of particles of different sizes as we go through the rings.

So in the second panel, you can see that, you know, the abundance is a
four to ten centimeter size particle takes a big jump in the inner part
of the B ring compared to the very small particles. Whereas in the outer
part of the B ring they're all about the same.

And then similarly in the bottom panel you can see that the very small
particles are about constant all the way up to the very outer part of
the A ring where they start to increase. But the sort of intermediate
sized particles are gradually increasing all the way through the A ring.

This is probably because the A ring gets more and more stirred up by
(resonance)s with the moons as you go further out and it just sort of
shatters and breaks up the particles more. I'm going to talk more about
(resonance)s in just a few more minutes.

So let\'s just skip over that right panel and move on to the next slide.
Another thing we can do to measure the size of the particles is actually
use the cameras in different geometries. So this is a beautiful picture
the Cassini took when the sun was actually hidden behind the planet.

And as we're, you know, we're in Saturn's shadow here. And what you see
at the bottom left is sort of a faint little part of the sun sort of
refracting through the atmosphere of the planet. Basically the sun
itself is behind the planet.

And so now we're looking at light that's been basically scattered
forward by every little particle. It turns out that particles that are
very small, like the wavelength size of the light or somewhat smaller
than the earth - a little bit larger than that. They seem to scatter
quite a lot alike in the forward directions, what people call the
windshield effect. When you're driving into the sun, you see every
little piece of dirt and grit on your windshield because all those
little pieces of dirt and grit are scattering light into your eye, okay.

Well it's the same thing here. And the - probably - you can see, of
course, the main rings are lit up by all of the little tiny amount of
dust that is in the main rings but you really now see these diffuse
rings. The big, broad, bright ring that pretty much crosses the slide is
the E ring. And the sort of faint or smaller diffused fuzzy ring between
the E ring and the main ring is the G ring.

So you can really pick these things out in this geometry and learn quite
a lot about the particle sizes.

So next slide sort of tells a few things we've learned - the, you know,
we can learn a lot about the size and even the shape of these grains and
even whether they're solid or kind of clustered aggregate particles from
this geometry.

We discovered a couple of new rings associated with two of these little
moons that orbit just outside the main rings - Janus and Pallene. And
also, there's also a couple of other little moons that are in between
the G ring and the E ring that are - actually have little arcs of debris
trailing along them in which they kind of move around with respect to
these arcs.

So there's this mixture of moons and rubble and small particles all
through this system.

Next concept indicates that actually we - the spacecraft spent quite a
bit of time in the E ring, okay. The Cassini dust analyzer was going in
and out through the E ring through quite a bit of the mission and it has
detected not only water - kind of obvious - but also some sodium which
might be coming from salt. And also silicon which is probably coming
from rocky material silicates in the E ring grains and even some grains
that are almost entirely metal, which are in some funny orbits.

So some of this is a little bit of a mystery still but it's all
connected because the E ring, as I'll tell you in a little while, is
actually caused by jets coming off the surface of Enceladus. I may not
even show that.

But this is pretty well known by now that Enceladus has got these big
jets pumping out, fine particles that are mostly water and that's
supplying the E ring. But the fact that we're seeing this salt and these
silicates is also telling us something very interesting about Enceladus.

Okay, next concept. I just want to point here something - most of you
probably know this but this very same picture that captured this
beautiful shot of the rings actually captured - this little dot here is
the Earth and Moon. And in the enlargements, you can actually see both
the Earth and the Moon. It's pretty amazing from a billion miles away to
be looking back and seeing ourselves.

Okay, next slide just indicates that we, or course, don't have just the
cameras, we have the VIMS. And this really illustrates how much cruder
the spatial resolution is of the VIMS. But you're getting a huge payback
with VIMS in all the different wavelengths that vary over a factor of
six or seven or eight, you know.

So you're really getting a huge handle on the size of the particles from
VIMS as well. And this is just getting started right now - to learn
about this.

Okay, so I think that's somewhat wrapping up the - at least the first
part of this, the composition, the size, distribution. Major results are
as far as we can tell, the A and the B rings have the purest water ice
in the solar system. And they're purer than anything on any of the
moons. But they're much redder at the same time than any of Saturn's
moons.

So this is a bit of a puzzle. And we've tried matching this with outer
solar system objects which a lot of people know to be red, like Pluto is
kind of pink, Triton is kind of pink - a lot of these Centaurs and
Kuiper Belt objects are red. And we've tried that. They don't really set
all that well.

We've also looked at more radical possibilities, like maybe this reddish
color is an oxidized iron compound, like what makes Mars red. And that
has some appeal to it. It's just that it's hard to imagine how you would
get that oxidized iron in there without getting all the silicates it
usually hangs around with. So it's a bit of puzzle.

Certainly the evolution of the rings by meteorite bombardment, which
I'll talk about later, and the ring atmosphere is going to affect
things. The composition of the rings varies with time. So we've
understood the particle size distribution. We're seeing through the
thick rings for the first time and so on.

Okay, so I said all this. Let's move on to a little bit on the
structure. So this is a global picture on the left. It shows the - all
four of the gas giant planets - Jupiter, Saturn, Uranus, Neptune - along
with their retinues of what we call ring moons. And we can see that all
four of the gas giants has its own retinue of ring moons and has its own
rings.

Now the idea is that where you have - the graphic on the right, it shows
where you have a satellite, who's orbit period is an integer multiple of
the orbit period of some ring particles, shown as the red dash line here
or where the orbit period of the particle - of course as you get closer
to the planet, the orbit periods get shorter, just like Mercury goes
around faster than Saturn.

Okay, so these are short periods, the rings - if a ring particle goes
around some fraction of the orbit of the satellite, then you have
(resonance). And when you have (resonance), it's like every time that
ring particle comes back to the same longitude, it kind of sees the same
satellite there. So it's like strobe light effect. You can over time
amplify the very weak gravity of these moons and create significant
disturbances to the orbits of the ring particles.

Okay, and what does this do? Well because of this disturbance which is
shown at the red circle, combined with the very weak sub-gravity of the
rings combines to create these spiral patterns which actually propagate
away from the (resonance). See, this is indicated - the density wave
crest in this - his is a two-arm spiral. We have patterns like this in
the rings that are 40 arms and 50 and 60 arms spirals - it just depends
on the (resonance).

Now the physics of all this is almost identical to the physics of the
arms in spiral galaxies. And we're learning an enormous amount about
these physics by studying the rings.

Let me show you some examples of this. Next slide shows sort of an
overview of what I'm - a couple of different things I'm going to be
talking about. This is the outer part of the A ring, the Encke Gap is in
the middle with a little ringlet in there. The Keeler Gap is towards the
outside. The F ring is about 1,000 or 1,500 kilometers outside the edge
of the A ring.

And it's got - you can see its little shepherding moon there. The
various bright bands to the left of the slide are these spiral density
waves. So I'm going to go through this sort of in succession.

So let's just hop to the next slide which is a close up. It's actually a
movie of some of these spiral density waves taken by Cassini. Some of
these things - they're spirals and they're like watch springs, they're
that tightly wrapped up, okay.

So you can see that the wavelengths decreases away from the (resonance).
Some of these things propagate outward. Some of them propagate inwards.
Now we're - at least on mine, we're starting to approach the Encke Gap
with its various ringlets in the middle of it and a particular kind of a
wake pattern on the inside edge which is caused by the moon in the Encke
Gap, not by a spiral density wave.

Okay, you can see the A rings is full of these things. Let's go to the
next slide. Next slide shows sort of a shot showing many, many spiral
density waves. The really beautiful thing about these waves is once
you've identified one, you can use it to measure the mass density of the
ring that it's moving through.

So you can know how many grams per square centimeter are there. That's
very, very important to know and it's really the only way to measure. So
now because these waves are everywhere in the A ring, you know, we can
really nail the surface mass density in the A ring.

Not only that, it tells us about the mass of the moon that causing the
wave. So now we can measure the mass of the moon. We take a picture of
the moon, we know how large it is, we can actually infer the density of
the moon. So we can see that all these little moons around the rings are
relatively low density. And all around half a gram per cubic centimeter,
only about half the density you saw in water ice. So they're probably
all rubble pile which is very interesting thing to know.

Okay, next slide. I guess, I think in the interest of time here, I want
to skip over this a little bit. It's a very recent result. It just
indicates on an even finer scale how we can use these density wave
results to measure how the size of the particles varies even from one
side of the Cassini Division to the other.

So if we have time, if anyone wants to ask me about that later, I'll be
happy to talk about it.

Okay, next slide gets to some structure that's really not well
understood. These are osciltations taken by the Radio Science Team and I
talked a little about earlier. And these are parts of the ring that are
penetrating the densest part of the B ring which is shown by the figure
at the bottom right where that red bar indicates the radial extent of
these osciltations.

And you can see that even in the densest regions of the rings. Let's
look, say, at around the top right hand panel, right around 106,000 -
105,000, 106,000 kilometers. You can see two little peaks going up.
Here, the way this goes is that more material goes down. That is, this
is a plot of brightness coming through.

So the transparency of the ring increases upwards. You can really see,
there's a lot of very, very fine scaled structure here, even in these
dense parts of the rings. And it's a little bit of a puzzle as to how
these channels, if you like, can be preserved even in such dense parts
of the rings.

But it's a major victory and discovery for Cassini to penetrate this
dense part of the ring at all, it's the first time it's ever been done.
And we've got like 17 of these osciltations and we're just starting to
look at that now.

Okay, next slide. Here's a very big question that has emerged and it
relates to the age of the ring. So what is the mass of the rings. I told
about the spiral density waves. So now what the mass of the A ring is.
Well there aren't too many of those in the B ring and so because it's
obvious that's where most of the mass is we do have an uncertainty as to
what the total mass of the rings really is.

Some models have suggested that where light does get through the B ring,
it's really only coming through a very, very small fracture - nearly
empty gaps. And the most of the B ring is just absolutely opaque.

When I want something absolutely opaque, you just don't know how much
stuff is there, okay. So there is a bit of an uncertainty there as to
what the mass of the B ring is. It's been suggested that it might be
much more massive than we sort of have traditionally thought.

Third paragraph indicates that if the masses of the B ring, at least -
and maybe the mass of the rings as a whole - is much more that the
current estimates, then one of our reasons for thinking that the rings
are young may be misleading.

And this reason is that the rings are being bombarded by meteoroids all
the time. These meteoroids are very dark material. They're rich in
carbon and silicates. They\'re like, you know, a comet. You know, a
comet, it's not a snowball. It's really a dirt ball with ice in it. So
this stuff is very dark - full of carbon, full of silicon.

And we have estimates of what the mass of that material is hitting the
rings today and over the age of the solar system. And it just is
impossible for the rings to absorb that much mass and avoid getting
polluted to the point where their particles would get much darker than
they are today.

If the rings are as old as the solar system and if their ring mass is
what we think it is. So the idea is that some people have said, well,
but maybe the rings could be as old as the solar system. If they're
really much more massive than we think or if the flux of meteoroid
material is much less than we think.

So it's these two very key things to measure mass of the rings and the
flux of the meteorites.

Okay, we haven't done that yet - the last paragraph indicates that we're
going to get a good measurement of the flux of the meteorites in the
extended mission. (Dave) will tell you how we're going to do that. We do
it basically by flying by a moon and looking at it, a little amplifier
of what this meteoroid flux is.

So that's a very, very important measurement - has been measured by
Jupiter the same way be Galileo. The numbers are kind of close to what
we're assuming so we don't think there's a big surprise but it just has
to be measured. The ring mass is a whole different issue and I'll get
back to that probably at the end of the talk.

Okay, so I want to talk a little bit more about structure. The F ring
has been a puzzle for quite a long time. It shows all kinds of structure
and all kinds of time scales. Those multiple strands in the rings, well
Voyager saw strands like that. But by the time we got there with
Cassini, we realized, well these are different strands, they're in
different places, different spacings. Everything's different.

Not only that, we noticed all these streamer structures. And like the
top panel shows these dark sort of fan-shaped gores going all downstream
from the ring - little bright blur at the bottom of that top right-hand
panel is actually the moon, Prometheus.

And you can see in the bottom left-hand panel, there\'s Prometheus kind
of pulling out a gore material from the F ring. And you can see its dark
channel. But then you look at a different place - the center panel on
the bottom - you don't see gores through these streamer-looking
features.

Well a lot of this is actually explained by dynamical models. That is -
actually my movie has now ceased so if I back step one and then step
back into the slides I can restart the movie. And what you can see is
the - you notice there's a little piece of the F ring and there's
Prometheus. You notice they're moving from left to right. That means
that both of them are eccentric and that they're not great circles,
they're eccentric, they're distance where the (unintelligible) to each
other varies.

And as that distance varies, you can see when the moon gets very close
to the F ring, it actually sets up a perturbation in there. But the
appearance of that perturbation changes as the moon comes and goes. You
know, those gaps open and close. Depending on when you take that
picture, that structure is going to look different. So we finally
understand this part of it for the first time.

Okay, next slide. There is other aspects of the F ring I'm going to
return to later. Now I'm going to talk a little bit about ring vertical
structure. This was sort of a traditional picture of the ring, that is
the particles were many - spaced by many times their own size. It was
very puffed up. They're moving at fairly low velocities - maybe
centimeters per second - but fairly puffed up.

However, collisions between these particles probably damp these roads of
velocities. Next slide shows a more realistic model of the rings where
the particles are at a much more flattened layer.

Okay, so how do you tell the differences? You notice this whole layer is
only 30 meters think. So the bigger ring particles in there is maybe 10
meters in size but the layers may be 30 meters thick. You can see it's a
much denser, less open layer. How do you tell the difference between
these?

Next slide indicates something that Cassini actually did. It's been
known for decades that the brightness of the rings reaches a sharp cusp
just like the full moon effect. When the moon gets to full, it gets
much, much brighter just within the last few hours, you know, of its
brightness because essentially every little shadow from every little
rock is getting covered up. That is, the sun is right behind our back
and everything we see is fully illuminated. We're not seeing any shadows
at all.

(Matthew Otto): Question.

Jeff Cuzzi: Yeah.

(Matthew Otto): Yeah, this is (Matthew Otto) with the Saturn Observation
Campaign.

Jeff Cuzzi: Yeah.

(Matthew Otto): The slide shows that the thickness of the rings is 30
meters.

Jeff Cuzzi: Yeah.

(Matthew Otto): Is that thickness averaged across the entire structure
of the ring system?

Jeff Cuzzi: Yeah, that would be sort of a typical thickness here, just
as an order of magnitude.

(Matthew Otto): Okay, being that the entire ring system is the width of
basically the - roughly the distance from the Earth to the Moon\...

Jeff Cuzzi: Yeah.

(Matthew Otto): That is amazingly thin.

Jeff Cuzzi: Yeah. People talked about as thin as a razor blade. It's
much thinner than a razor blade. It's like a piece of paper the size of
Golden Gate Park.

(Matthew Otto): Wow. Okay, thank you.

Jeff Cuzzi: Okay, so the rings are amazingly thin. And when people have
been struggling for generations to look at them (edge-on) and try to
figure out what their thickness was, we've just been fooling ourselves.

What we've been seeing is maybe vertical ripples and flapping in some of
these waves or vertical waves or maybe some of these little ringlets are
inclined. That's what we've been seeing, not the actual thickness - not
the local thickness.

Okay, so basically this measurement by Cassini of the opposition effect
has indicated -because VIMS can do this at different wavelengths. It can
measure sort of the sharpness of this peak. The upper right panel shows
the sharpness of the peak.

And you can do this in re- the bottom right panel shows you can do in
regions where the particles are dark and regions where they're bright.
And you find that the sharpness of the peak is much more narrow in
regions where the particles are bright than where they're dark.

And this is a give-away that this is not a shadowing effect due to, you
know, particles hiding in their own shadow. But it's just like a photon
scattering around the (regolith) or the surface of these particles.

So this really does support the idea that the rings are much more
densely packed than we thought they were before.

Okay, next slide shows something that we are learning an enormous amount
about - a really enormous amount about in the rings and it's a structure
that's too small to be seen even with the best images. So we have to
infer it.

So now this movie that's playing is what we call self-gravity wakes.
These are structures that formed because the rings are so flattened down
and so compact, even the tiny self-gravity of the ring particles wants
to make them clump up into dense regions.

But they're still orbiting around Saturn. And the ones closer to Saturn
on the left-hand side of this movie are moving faster than the ones
further from Saturn on the right-hand side of the movie. So this creates
a sheer. And just like on a freeway, you know, the left-hand lane is
usually moving faster than the right-hand lane - same deal here.

So as these clumps try to form the sheer just pulls them apart. So we
have this great dynamic process where these things we call self-gravity
wakes are always forming and always dispersing. But they always have
this characteristic slanted nature.

And this is exactly what we see with Cassini. The left two panels
indicate what we're doing here. The dashed red one and the dashed red
two indicate how we watch stars go behind the rings and they can go
behind the rings in a variety of different angles. They don't have to go
from right to left like is shown in this yellow line in the picture.
They can go at any angle across the ring.

Well down at the bottom you see sort of snapshots of these wakes. And
what you see is that depending on if you go through a geometry like
number one where you're looking at these wakes kind of long direction
on, you're going to see a lot to holes. If you look through them in a
direction where, you know, they're sort of face on to you, you're not
going to see as many holes.

So we can really start to put together a three-dimensional CAT scan of
this very, very fine-scaled structure which is only hundreds of meters
in size - can't see it with the cameras.

But over time, with dozens and dozens of these osciltations by Cassini
at a range of different angles, we can start to learn all about these
wakes. And the bottom chart shows the kind of thing we're learning. This
blue plot just shows you that's the optical depth in the A ring, from
the inner A ring to the outer ring.

The green plot shows the optical depth in these gaps between the wakes.
And you can see it varies from place to place in sort of a systematic
way. And the red stars show you the - sort of the height to width ratio.
So we're really getting a three-dimensional look at these things.

These wakes are getting maybe higher and fatter and thicker right around
the Encke Gap, you know. So it's a very, very interesting structure.
This is really not that well understood, why there should be this very
global variation. It might have to do with the fact that there's more
(resonances) as you move out through the rings.

But you can see from all the spiky blue lines on the outer part of the A
ring, that's even more (resonances) out there. And yet the height to
width ratio is starting to go down there. So this is a bit strange.
It\'s a very interesting result though. We're really learning a lot
about wakes this way.

Next slide shows a beautiful color picture that actually illustrates
this. You can see the - this is again from the (unlit space) and the -
from the foreground to the rear ground. Notice how the B ring - the
brightness of the B ring is very, very different from the foreground and
in the background.

Whereas the A ring is about the same, the C ring is about the same. This
really indicates that the B ring also is full of these waves. And in the
foreground, we're actually seeing the light from the sun on the other
side getting blocked very effectively.

Whereas on the far side, the background it\'s getting through. So this
again, lots of little gaps we're seeing on the far side, not nothing at
all on the near side. It\'s very interesting results. So this
self-gravity weight structure just permeates the A and the B ring. You
can see that there's not much of it going on the C ring though.

Okay, I need to move on here. I'm starting to run a little bit behind.
Let me see. Let me check my time - 47. Okay I am running just a little
bit behind.

So I just want to mention that there is also ultra-fine structure that's
been seen, both in the cameras. In the upper panels here, these pictures
were taken only during Saturn orbit insertion when the spacecraft was
the closest as it would ever be to the ring. And what the cameras saw
was some parts of the ring - like let\'s see - the top pair of pictures
are both in the B ring.

And you can see the left of that top pair shows no fine scale structure.
The right of that top pair shows quite a bit of fine scale structure.
Same thing in the next pair of panels - the left of that pair - these
are now in the inner A ring - shows no fine scale structure. The right
shows lots of fine scale structure.

So this fine scale structure comes and goes and it's about to be a kind
of a process where the viscosity in the ring combined with its orbital
motion just creates these cyclical beats back and forth that are maybe
only ten times as - the radial scale of these things may be only ten
times the vertical thickness of the rings, so hundreds of meters again.

Lots of this structure is being observed now with the stellar
osciltation and the radial osciltation that's shown on the next slide.
This is kind of a complicated slide but I just want to illustrate to you
that we're mapping out how this very fine scaled structure comes and
goes on hundreds of meters of scale.

And it's very persistent as you go through the rings. These are
different paths through the A ring and the B ring, you can see the
kilometers at the bottom. And this sort of a double band of different
color that runs through these different features is an indication of
this very fine scaled structure. It's like a defraction pattern from a
slip defraction pattern. That's kind of what we're seeing here. So it's
very sensitive and just getting started to really map this stuff out.

Okay so, processes - I don't think I'm going to repeat all this. We
learned a lot about structure, microstructure - especially the
self-gravity wakes are just everywhere in the rings and we're really
starting to map all this out.

Okay - let's go on - next slide - and talk a little bit about moonlets
in the ring. This is sort of the third main topic here. This is a close
up of - actually there's two things here. On the left, you'll see the
Encke Gap in the A ring, on the right you see the Keeler Gap in the A
ring - the close up.

The Encke Gap's about 300 kilometers wide, the Keeler Gap's about 30
kilometers wide. We knew from Voyager data that there was a moonlet in
the Encke Gap. But the Cassini data is so much cleaner and so much more
beautiful, we're really mapping out - you see this wavy inner edge on
the Encke Gap here. It looks like a little bit of a sine wave here.

The physics of this is just like a rock in a stream. As the water flows
down the stream, flows over a rock, what do you see? You see a wake
downstream from the rock, okay. The wake is fixed to the rock. You look
at that shape, it's just fixed to rock.

The water is moving right through it. So that's exactly the same thing
we're seeing here. The rock is the moon. It's downstream off to the left
and these little sine wave wiggles in the edge of the ring are the wake.
If the pattern is fixed to the rock, the ring particles are moving
through that pattern.

But the detailed structure all over 360 degrees is this gap - it's very
complex. That's what this kind of saw tooth structure here - horizontal
band of saw teeth actually looks like. You know, there's no simple
pattern here, it's not a simple sinusoid and we would not expect it to
persist all the way around just from that moon called Pan that's in the
middle of the Encke Gap. So there's still some puzzles here.

One of Cassini\'s first real victories here though was the discovery of
this moon, Daphnis, on the right-hand side in the middle of the Keeler
Gap. And you can see the structure is very much the same. You see these
wakes going downstream of the moon.

And now what is downstream? You say, well but one's up top of it and
one's down below it. But they're both downstream because to the left of
the moon, that ring material is moving down to the right - relative to
the moon because it's moving faster than the moon.

To the right of the moon, the material is moving up because the moon is
actually moving past it. So both of these are downstream. The wakes are
both downstream in both cases.

And you can see from the movie graphic at the bottom, we're actually
starting to study this. And the agreement of the models is actually
quite good with the data. And even to the degree of this sort of peaky
looking structure in the Daphnis case that you do not see in the Pan
case is due primarily to the fact that Daphnis is actually on an
eccentric orbit and Pan is largely not.

So there's a lot we can learn from this. So there are actually moons in
the rings clearing gaps. And this physics is directly applicable to how
our planets of our solar system formed. Jupiter and Saturn, for
instance, are thought to have been able to, as soon as they grew, carve
out a gap in the solar nebula just like this - just exactly the same
physics - very much the same.

So we're learning a huge amount about planetary formation by studying
the physics well.

Next concept shows sort of a puzzle. Now here's a gap in the C ring
that's about the same width as the Keeler Gap, but we have not been able
to find a moon in that gap anywhere, in fact, in any of the empty gaps
in the rings anywhere. There's about five or six of them in the Cassini
Division. There's three or four of them in the C ring. We have not found
moonlets like this in any of these other gaps. So that is the puzzle.

Found some little funny things \-- what we call this fuzz here \-- but
no moon. So we're going to try very hard in the extended mission to
focus on these gaps and see how we can constrain this a little bit
better.

Okay, so here's the next slide. It's just really a beautiful picture
again, from the inner side of the ring. The red arrow indicates the C
ring. You can see it\'s just full of beautiful structure. The dark band
there sort of two-thirds the way out is an empty gap. No moonlet as yet.

All the - you can see it's almost symmetrically surrounded by these,
what we call plateau features. Nobody has a clue what causes those.
There's sort of a smooth sinusoidal wave going through the middle part
of the C ring, Nobody has a clue what causes that - still a mystery.

So we're going to be working on this data for quite a long time, trying
to pull out clues from the color, the brightness, the particle size -
all that we've got now that we never had before.

Okay, next slide. Very important result though, actually, in talking
about movements in the ring. Something we've been calling propeller
objects or shards. These are things that we still cannot see directly
but we infer their presence by how they disturb the surrounding
material.

So the panel at the upper right indicates both the theoretical model and
actual observation. And one part in the A ring, where if you were to put
an object that's only maybe 100 meters or a couple of hundred meters
across, so it's much smaller than those moons, Pan and Daphnis. It's way
too small to empty a gap. But it's much bigger than the typical ring
particle and so it's able to disturb all that material.

Now what it does is it kind of carves out two little empty zones, again,
a little bit downstream from it on either side and you detect these
things barely with the cameras.

So now we've been able, by digging into the data, that little double
bright dash structure is very diagnostic and probably almost 100 of
these things have been found now. That's indicated in the two lower
panels. And the really amazing thing is, they're not everywhere. They're
located only in several of discreet bands in the A ring.

So let's go to the next slide. Oops, this one doesn't show it. Oh yeah,
it does. So this shows the kind of data we're talking about here. You
can actually see several of these. So you can tell there's lots of these
things in the rings, okay. But you have to look very close and do the
analysis right, really estimate, you know, how big these things are. But
people have done this.

Next slide shows where these bands are. They're sort of in the middle
part of the A ring. And that's where they are. They are not found in the
spaces between those banks. They are not found outside the Keeler Gap or
in the inner part of the A ring or as far as we can tell, in the inner
part of the B ring or anywhere else.

So we're going to keep looking for these things but it's very
interesting to ask, what are these things. Are these things the
remnants, the broken up pieces of whatever moon got destroyed to form
the rings or did they maybe grow in place? This is a puzzle.

Okay, let's move on here. I want to talk a little bit more about the F
ring, which is really even more fascinating I think than the stuff I
showed you before. This is a close up of the F ring of just the main
strand. And you can see, it's got all these spikes and jets and funny
things going on. There's a whole 360 degrees basically.

These things - these spikes and jets as indicated by the model below on
the left-hand side are probably caused by individual objects probably
too small to see, generally, crossing through the F ring and hitting
it - colliding with it, knocking stuff out of orbit into these jets that
go in and out.

And then over time, they very slowly smear out and blur away and then
they're lost. Meanwhile, others are being created all the time. So this
calls for a whole tribe or population of objects on very eccentric
orbits that are eccentric enough to cross the F ring. And big enough not
to get stopped by the stuff that they hit.

So like a whole asteroid belt surrounding the F ring. The right-hand two
pictures indicate at least one example that this is what's going on.
There\'s a single object whose orbit has been measured - discovered in
2004. And here are two pictures. One - the top one shows it inside the F
ring, the bottom one shows it outside the F ring. So it's clearly the
same object, clearly crosses the F ring. In fact, it itself is
responsible for some of these spikes that are shown on the left.

So here you can even see, this object is like an arc. It's got a trail,
a rubble or debris - probably got knocked off this the last time it went
through the F ring and banged into something. So this whole zone is
probably just full of hundreds or thousands of these moonlets that are
just constantly on these eccentric orbits colliding with each other,
colliding with the F ring, maybe creating new F rings over time. We just
don't know. Fascinating environment with all these objects.

Okay, next slide. So this slide shows a couple of things. Let's see. I
guess the top - the green graphics towards the top of the page - I
mentioned to you already that we know from the density waves that these
little moons that are causing them are rubble piles. That is they're not
solid.

So here's an example on the right of what one of these rubble piles
might look like. You notice it's oblate, so that the figures on the left
are actual data. And what they show is this moon, Pan, which is the
middle of the Encke Gap, and this other moon Atlas, which is just
outside the A ring, you know, in the sort of flying saucer shape.

So they're definitely oblate objects. And in fact, you can show that the
shape of these things is very consistent with them just barely holding
on to this rubble under their own gravity, which they can do better with
these flattened oblate structures.

Okay, so these things grow by occasionally picking up an object but it's
not stuck by anything but gravity and can only grow to this envelope
shape. So what does this tell you? Like on the right, you can see maybe
there's some red thing in there, you know, but it's buried in this green
stuff.

We may never know just exactly what the composition is of these shards
or primordial moons are, if that's what they are - maybe they're rocks,
you know. But they're covered up in all this rubble of ice and that's
all we see. And that may be all we can see unless one of them undergoes
a collision and knocks off some more of this stuff.

So we hope to be able to watch with Cassini for quite a while - maybe
watch for one of these things.

Okay, let's move on. Okay, so just to summarize what we've learned about
these ring-satellite interactions. We've discovered one embedded
moonlet. That's Daphnis in the Encke Gap. We're puzzled by the lack of
moonlets in many other empty gaps in the C ring in the Cassini Division.

All of these moonlets have low densities, suggesting that they are
rubble piles and grew from a more dense central piece by creating
incoming material. Maybe this is true for the so-called propeller
objects - that\'s the third paragraph, that a unique population of
sub-kilometers size objects. They're only in three belts.

Maybe they grew in place or maybe they didn't. If they grew in place,
why are they only in three belts and not everywhere? So finally this
whole F ring complex is a dynamically interacting environment, probably
what's called orbital chaos. These orbits of these things are
continually being pumped and stirred up, colliding with the F ring
strands and maybe even with the shepherding satellites themselves. So
it's a very changing environment.

Okay, I'm going to try to go through this pretty quick. I just want to
point out from studying the dust and meteorites, that we have learned a
lot about dust. Not only have we learned that these streams of dust
grains leave the Saturn system - that is, they get charged and they get
blown away on the solar wind, but I think the most important thing,
really is the whole E ring and Enceladus story.

This is the supplier for the E ring, it goes way out to Titan and
inwards to Mimas. Its vertical structure is different from what we
thought. And one interesting thing about the E ring is - it's called
heliotropic in that it's eccentric but it's (unintelligible) - that is,
it's furthest distance away from the planet actually tracks the solar
direction.

So it doesn't process around in a normal Capillarian way. It's got this
permanently sunward pointing direction because of forcing by sunlight.

Okay, so let's move on to our - let's see. I think I'm going to skip
over this slide and the next one. These are some details about the E
ring. And I guess I'm going to go to the next word chart which describes
what we have not done which is very, very important.

That is it always has been a key objective that I mentioned before. We
have to measure the mass of meteorites that are hitting the rings to
really be able to figure out how old the rings are

And we had several ways we're going to try to do this. We're going to
try to do it in crews. Well that is kind of screwed up by pointing
restrictions, that were not foreseen before launch because we had a
redistribution of the instruments on the spacecraft in mid-stream.

We had a technique. We were going to look at impacts on the rings by
flashes of ultraviolet light. Well, that got screwed up by the fact that
most of that ultraviolet light was blocked by its own photosphere, if
you like. Most of these flashes probably happen but most of the light
comes out in visible wavelengths where we couldn't see it with the
ultraviolet experiment.

Another observation that's very powerful is during the Saturn orbit
excursion, one of the field and particle instruments, called the radio
and plasma wave spectrometer, detected dozens and dozens of these little
tones - sounds like tones on your touchtone phone. But they're tones at
plasma wave frequencies.

What they think this was is a spacecraft flying through cones of waves
that are propagating away from the rings that are caused - each one - by
an impact on the ring. So we can count impact on the rings. But what we
can't quite yet do is tell you how big of an object forms each one of
those cones and plasma waves.

So this is a real challenge for (Sirus), I'd say. And presuming in the
latter part of the mission we'll detect a lot more of these. But I think
as (Dave) will probably tell you, during the extended mission and
hopefully again in the extended extended mission, what we're going to do
is we're going to fly very close by some of these (icy) moons that
probably have halos of dust that are kicked up from their surface by
this incoming meteoroid mass.

And because you get about 1,000 times the amount of ejected mass from an
impact as the mass is a projectile, these moons act like little
amplifiers. So by flying through their dust halos, we can get a
measurement of how much mass is hitting their surfaces. So those are
very important measurements for later on in the mission.

Okay, last two slides really just cover a couple - I just really want to
talk about spokes here. I guess before I talk about spokes, this bottom
graphic here - the blue and red and green - illustrates this impact
effect that I talked about that the RPWS observed just during Saturn
orbit insertion, the vertical axis' frequency, horizontal axis' time.

So each one of these green-red specks up there is spacecraft flying
through a different plasma cone, okay. So you see this is very cool -
very unique measurement never seen before - like to do it later again in
the mission. And we'd like to know how big each one of those impacts was
that caused one of those blips.

Okay, so upper left here show the spokes as seen from Voyager. As you
all know certainly that during Cassini - almost all through the Cassini
mission, almost to today, we really were not seeing very many spokes.
And this led to some real new theoretical development which is indicated
in the panel at the upper right which sort of describes the model
whereby yes, we're creating dust, dust is getting pumped up off the
rings and if that dust could stay there, it would create a spoke.

But through most of Saturn's year, when the sun is high up above the
ring plane, sunlight photo sputters electrons off the main rings. So the
main rings become positively charged and there\'s this cloud of
electrons that surrounds the main ring.

Well any dust particle that gets popped off into this cloud of electrons
will pick up some of these electrons, become negatively charged. It
fields the positive fields from the main ring. It gets sucked right back
down onto the rings, just like the electrostatic precipitators they put
in smoke stacks. They charge these grains, they suck them right out of
the stream.

So what this graph shows is that at different elevation angles of the
sun, like the ones at the bottom where you see these parabolas, the
trajectory just goes up and comes right back down to the ring. Those are
the trajectories, the dust particles when the sun is high in the sky.
The dust particles just can't survive very long.

But then as the sun gets more and more edge on to the ring plane, as the
season approaches spring or fall like we are right now and like what
Voyager was, you can see these curves become more flat and the
trajectory or particles can actually go way up away from the ring and
escape and survive up there and be visible as a spoke particle.

So you can see where it says early 2007, what we were thinking based on
these early models was that by early 2007 we start to see the spokes
again. And to some degree we were but not really very many.

Next slide indicates that by now we're actually starting to see spokes
sort of almost in Voyager abundance. But we're starting to get very,
very close to equinox now. In fact, equinox is during - within about a
year and a half or so from now, two years and (Dave) will tell you about
that.

So we're going to have to revise these models. But generally speaking,
it seems like this is the right answer. That's why we weren't seeing
spokes with this charging effect due to the sun. We should start to see
them again in increasing numbers from now on out.

Okay, so that is more or less it. Overall, the rings really are -
Cassini has really driven this home. The rings are really dynamic and
time variable. They change as we watch them on time scales of weeks and
months, certainly years and decades going back to Voyager over the
duration of the Cassini missions. It's very important to have this time
baseline to watch all these changes.

From the standpoint of composition, we really do need to understand the
composition. The models all indicate because of this bombardment that
the composition is probably changed with time. We now know that the
atmosphere of the rings is oxygen - molecular and atomic.

Well as you all know, oxygen oxygenizes things so if there ever was any
metal in the ring, it could get transformed (in a rough). So this kind
of a radical new thought that's occurring to some of us as an
alternative to the traditional organics option, partly driven by the
fact that we're not seeing any of these CH spectral features, we're not
seeing any of the CO2 spectral features, this is what we tend to see in
these outer solar system objects that are rich in organics - we\'re not
seeing it. So it's a bit of a puzzle.

Okay, so the ring structure - well, you know, it's complex and we're
not, you know, we're really making huge progress on the wakes, the
self-gravity wakes - enormous amount of progress, spiral density waves -
enormous amount of progress. A lot of this other stuff still a little
bit stumped about what's causing it and we just have to get deeper in
and analyze the data.

Embedded moonlets - well certainly, there are more of them than one.
That theory is definitely confirmed. A bit of a puzzle why we're not
seeing them in C ring of the Cassini Division. And the whole F ring is
just a horse of a different color entirely. Orbital chaos, collisions,
very dynamic. We come back, you know, by the end of the Cassini mission,
it may look entirely different.

Okay, that's it for me. Thank you very much and I guess I could take a
few questions anyway.

(Jane Jones): Thanks a lot, Jeff. Yeah, if anybody has any questions, we
do only have 45 more minutes on the telecon and I'm sure that's plenty
of time for (Dave)'s talk. But if anybody has any questions for Jeff?

Woman: I have a question - (unintelligible) in Berkley, California. I
may have misunderstood you but is there a favored material that is
cometary material for the bombardment rather than chondrite?

Jeff Cuzzi: Let me see - did I - would you repeat that? Is there a
favored cometary material - I think you said that.

Woman: Is there a reason why cometary material other than chondrite
would actually be responsible for the bombardment?

Jeff Cuzzi: Oh, I see what you're saying. Well yes, the chondrites,
formally speaking, are from asteroids. And asteroids are probably too
far in to reach Saturn. So it's all primitive material. Chondrite
material is primitive in a lot of ways but it is lacking in the
volatiles. Of course, it's lacking in water, it's lacking, you know, in
the various organics generally.

Even what they call carbonaceous chondrites are only maybe up to 5% or
something like that - organic material. Whereas comets are 30% organic
material. So it's our solar system primitive material. It would be what
would form a chondrite if it were in the inner solar system.

But because Saturn's out at 10AU, the most likely thing is this being
bombarded by stuff from the outer solar system - centaurs, Kuiper Belt
material, cometary material and so on. Does that answer you question?

Woman: I have another question if nobody else does.

Jeff Cuzzi: Go ahead.

Woman: I think that (unintelligible) information, the gap is from
particles from our - something like meteors (unintelligible) meteors. Is
that correct?

Jeff Cuzzi: The gaps\...

Woman: Gap of knowledge - the gap of knowledge\...

Jeff Cuzzi: Oh, planetary information - yes. There's a big gap of
knowledge pretty much from meters to maybe even 100 kilometers.

Woman: So how does this help? I don't quite get that.

Jeff Cuzzi: Oh, well, I mean, it's helping at the larger scales as well.
There's a lot we don't understand still about tidal truncation of gaps.
But at the level - I guess what I did not say was at the level of these
self-gravity wakes - remember, I showed that movie with the self-gravity
wakes - that is another suggestion that's been advanced to help bridge
this gap between the meter size and the 100 kilometer size.

That is that the particles in the solar nebula undergo gravitational
instability just like these clumps in Saturn's rings. So again, it is
the same physics. And so the nebula has a different wrinkle in that
there's gas there and the gas does complicate the situation in a very
important way.

But actually learning how these self-gravity structures form in the
rings is an important validation of all the theories that we're applying
to the nebula as well.

Woman: Okay - thank you.

Jeff Cuzzi: So there really are those two things and - or three. The
physics of spiral density waves, the torques that are being applied, you
know, even though you might say that the major gap - and I agree with
you, by the way, that the major gap is in sort of this meter to 100
kilometer size. It doesn't mean we really understand everything else
perfectly.

So the idea before we studied these gaps - these tidal truncations with
Cassini - there was, you know, I mean, it was really only theory. You
know, the theory says these truncations should happen. Well here we have
the observation that it really does happen. And by the way, we have this
puzzle that we're seeing these empty gaps in the C ring - the Cassini
Division and we're not seeing the moonlets yet.

So maybe this is a clue that under certain circumstances gaps can be
caused by objects that are even smaller than we think. So we haven't
necessarily solved all these problems yet.

(Jane Jones): Okay, well I think now we'll move on to our second speaker
and thank Jeff Cuzzi for his great summary of the ring science.

Jeff Cuzzi: Thank you, (Jane). (Jane), I'm going to have to log off
because I have an appointment.

(Jane Jones): Okey-doke.

Jeff Cuzzi: Okay.

(Jane Jones): Thanks so much. So now we'll move on to our second part
and as we're wrapping up our four-year prime mission and beginning our
two-year extended mission, (Dave Seal), who is our Cassini Mission
planning lead will tell us all about the Equinox Mission, which is our
next two-year mission.

And with that, I think I'll just turn it over to you, (Dave).

(Dave Seal): Okay, thanks (Jane) and thanks everyone for sticking
around. I hope you're excited to hear about the extended mission. The
first part of which we call the Equinox Mission. As most of you probably
know, we're already actually in the Equinox Mission. We started it on
July 1 so we're almost two months in.

And we're all really excited here to be continuing on kind of in the
same - at the same pace that we have been with Cassini. This is really
the kind of thing that I think NASA really hopes for when it builds -
with any mission but particularly with a mission like Cassini, which we
tend to call a flagship mission because it's sort of a many eggs in one
basket kind of thing, you know.

If the mission had - if something had gone wrong with the mission, it
would be a great loss. But at the same time, it also has the potential
for great gains. And as with, you know, the Mars Rovers and really all
the mission that NASA plans, you know, we always build in margin to make
sure that we can complete our prime mission and satisfy all the science
objectives and really deliver the most bang for the buck and give the
taxpayers their money's worth.

And so it's quite likely with these missions that you end your prime
mission with some margin left over. And we've certainly done that. We
have margin in spades now and that's what we're able to use to deliver
sort of a double feature, you know, a second stage of science
observations.

And as Jeff sort of alluded many times in his talk, even just in one
discipline in the rings we have only scratched the surface on a number
of interesting scientific phenomena that happened in the Saturn system.
So it's really very worthwhile to keep going and to spend as much time
as we can there.

The cover page - as you see this is Page 51, at least on the PowerPoint.
Again, this is a spectacular image that Jeff showed, one of the
signature images of Saturn and included in the rings is an area that
we'll be investigating in the coming years.

The reasons why - I'm sure probably most of you are happy to have one,
just for its own sake, but certainly it was clear I think to us and I
think to headquarters that an extended mission made sense to build on
the many successes that we managed to accomplish during the primary
mission. Obviously arrival and the Huygens mission was successful.

The main - one of the key ingredients for a successful extended mission
is the fact that the spacecraft and the instruments are still very
healthy and all operating at full or near to full capacity. The other
key - one key component of that is the fact that we do have fuel which
I'll show a bit later to use for this mission.

Clearly we made some important discoveries that we're starting to
understand and further scientific observation is very important for
NASA's mission. Really the biggest argument to me in addition to these
is just the fact that Saturn is really the most target-rich environment
in the solar system with, you know, 60 named moons and others being
added as we speak to the list.

The ring system, you know, Saturn has more active dynamics arguably than
any other place in the solar system, what with atmospheric storms and
other phenomena, the magnetosphere being actively interacting with the
solar wind, Enceladus\' plume, Titan\'s atmosphere and the seasons
varying on many of these bodies it really is just a very rich
environment to study.

And also a key component that we don't often touch on is just how
complicated our tour really was during the prime mission and the fact
that we were able to prove that we can fly such a tour which is really
never - nothing like this has ever really been flown before.

You know, Galileo at Jupiter did have many flyby trajectories but not
nearly to the level in any way that Cassini has had with maneuvers
sometimes every couple of days, you know, flybys as little as a couple
of weeks apart and sometimes rarely even, you know, even closer in time
than that.

This really was a first in many ways for NASA being able to execute a
tour like this. So we've demonstrated that we can continue on
successfully with the margins and the abilities that we\'ve shown in the
prime mission.

Onto the next page, you know, we - to prepare for this mission, the
science community engaged in updating the science objectives based on
new discoveries as well as what we - what they felt really should be
covered in an extended mission. And you know, there really are a variety
of different science activities that we'll - we're planning to do and
are doing now.

They tend to fall into four categories. The first is really to try to
study Saturn\'s seasons. Saturn's full year in terms of its seasons
takes almost 30 years. So to have been there for four years, only four
out of 30 is kind of like studying one place on the Earth for just a
month or two.

You know, certainly if you were, I don't know, on the East Coast for
January and February, you might get a very limited perspective on what
the whole seasonal change and cycle and the nature of the place is. And
certainly that's true for Saturn as well.

There are a lot of spatial-related science objectives. There are some
portions geometrically of the Saturn system that we didn't get to spend
very much time in or didn't get to visit at all. Certainly the
magnetospheric scientists definitely want to sample the entire
environment all around Saturn in all directions to get a complete
picture of what's going on.

There's also a number of science objectives that are responding to
discoveries notable among them obviously Enceladus\' plume. Jeff
mentioned the (unintelligible) rings, the propellers, the new moonlets
that were discovered and their reactions, the activity in the F ring as
well as seasonal changes sort of - of new discovered lakes near the
poles of Titan definitely all fall into this - these categories.

And then some of the prime mission objectives need to be rounded out and
kind of tied off completely. So we have a full suite of science that's
on the same order as the science that we had for the prime mission to
accomplish.

The next chart - it's labeled 54 - there's a couple of charts here that
just kind of demonstrate why we can do what we plan to do. This chart
shows the power level in watts with time that the spacecraft's RTGs can
provide. As you can see, it does slowly degrade with time as the
material within the RTGs undergoes (unintelligible). We started out near
launch with almost 900 watts during tour that went from in the low 700s
to just about 700 watts exactly.

And during the Equinox Mission, as you can see here which is in purple
for the next - for the present and coming two years - that does continue
to degrade. We lose about one watt a month. However, even at 675 watts,
which you can see at the end of the Equinox Mission, we can certainly
operate all of the scientific instruments that are appropriate to
whatever discipline we're studying at the time all at the same time.

So, you know, if we're looking at the rings, we need all the remote
sensing instruments, they can all be on at the same time. You know, if
we're flying close to Saturn and we want to observe with those - with
some of those same instruments as well as take magnetospheric
measurements, all those instruments can still be on at more or less the
same time.

I think the only mode we have some problems with is one of the radio
science modes. But we've developed some unique workarounds to that. So
the power situation is really still very good.

If you look on the next page 55, this was our consumables or propellant
status as of the end of the prime mission. The big dark purple wedges
are what we estimated - what we had left over at the end of the prime
mission. So the pie chart in the upper right shows the bi-propellant,
that's the fuel system used to do the larger maneuvers where the four
smaller wedges, you know ,the light blue and the maroon, the yellow and
sort of teal are sort of what we used during the prime mission on a
yearly basis.

So you can see there was some really substantial additional amount left
over. And you can see the case is even better for hydrazine. This is
what we used to do the attitude control and smaller maneuvers where we
really have an enormous amount of hydrazine left compared to what we use
in a yearly basis during prime mission. So we're really in very good
shape and this is very impressive to headquarters that we had plenty of
resources in terms of the fuel to be able to continue on.

In terms of kind of, you know, the risk posture - the kind of risks that
we've taken during the prime mission - we have no plans to change that.
We're not going to take anymore risk with the spacecraft than we did in
the prime mission. It's still a priceless international asset and we
still want to continue studying Saturn with the same expected level of
success that we set during the prime mission.

There's a portion of the earlier picture and in terms of dust hazards,
we still plan to avoid those regions that we think are dangerous.
Clearly in the main ring system, we can't fly through it. If light can't
get through it, chances are we can't either.

The G ring is one of the faint rings which we tend to avoid the core of
it. But we have flown several times through the outskirts of Voyager and
Pioneer, as well through the G ring and didn't experience any
significant ill effects.

The E ring is completely composed of small particles so that's safe. And
there's some other faint rings in the new discovery category that
Cassini discovered that we continue to monitor. But obviously these are
faint rings and these are all components that we plan to study as close
as possible safely.

And the next chart 57, this kind of shows our plan for Titan which is
sort of - we continue on with more of the same in terms of altitudes.
This is one of the more visually stimulating pictures of Titan's
atmosphere. And you can see kind of drawn in where the surface would be
as well as really how far above even what you can see visibly, the
atmosphere extends in terms of what Cassini measures.

That haze you see in purple, we really do not get close to. It's far too
dense for us to fly through it. You know, Titan's atmosphere is
generally quite a bit more puffy than the Earth's is. So this would like
different if it was the Earth at the same relative size.

So we still plan to fly, do many flybys by Titan and through the 950 to
1050 kilometer altitude range, which is more than low enough for the gas
sniffers to do their job and continue to monitor Titan's atmospheric,
you know, behavior as the seasons progress.

It's also still a fine altitude for radar to continue to do synthetic
aperture studies of the surface as they've done all during the prime
mission.

Page 58, it's a bit complicated. Basically just what I wanted to show
here was kind of just touch on briefly the process we went through to
come up with the trajectory for the extended mission. All of the science
objectives that I touched on briefly earlier - those come out of the
working groups which are kind of pictured on the left there into one set
of objectives.

Those go into trajectory design. We then pass the trajectories out to
the science community and they analyze the trajectories with respect to
the objectives that we have come up. And then we work on exactly how the
key science objectives can be implemented and sort of iterated a number
of times to come up with a final trajectory, which really almost
exclusively everyone was very happy with.

And that's kind of what we wind up with and that's shown on Page 59 in
the two right-most columns. The four columns sort of on the left were
the prime mission. You can kind of see visually how many Titan flybys as
well as Enceladus and other (icy) satellite flyby tasks we had as well
as the number of orbits.

And you can see just immediately visually that the pace is certainly not
slacking off in any respect of the word. In fact, arguably the pace
picks up in the Equinox Mission compared to the prime mission. We still
have an average - at least as many Titan flybys as we had during the
prime mission. Clearly we had more in year three but we had less
respectively in the other three years of the prime mission.

But we're continuing to fly by Titan very often. We've stepped up the
frequency of Enceladus flybys. The first one of which we had just a few
weeks ago. And that is for the obvious reason of plume discovery being
so significant.

We also added, you know, close flybys of some of the other (icy)
satellites, sort of later on in the sixth year of the mission, when we
get back down into the equatorial plane. We're at high inclination right
now and it's generally easier to get those when you're in the equatorial
plane.

And in terms of the number of orbits, you know, those are clearly -
we're clearly going to be in rapid orbits and flying by Saturn
frequently - more frequently than in the prime mission really. So if
anything the pace is increasing for the Equinox Mission and we're
excited to be supporting that.

Page 60 kind of shows what we call the spaghetti plot but it's color
coded rather nicely to show sort of the different phases of the mission.
Again, you can see, even in the two years of the Equinox Mission, we're
really covering a very wide range of geometry around Saturn.

We start off as I said in high inclination. Those are the blue orbits.
The one in the upper left is sort of the top down picture. Whereas sort
of the one in the upper right you can kind of see how high that
inclination really is, flying sort of over the poles as much as
possible.

We have what's called a pie transfer. You can see it best sort of on the
bottom picture. It's that single green line where we hit Titan on one
side of its orbit in a nearly circular transfer, hit it again in the
other side of the orbit. It's an efficient way to kind of move from one
side of Saturn to the other then we can continue flying by Titan on
the - on the second, you know, on the second leg.

We then have some orbits of moderate inclination that's slowly
decreasing. Those are the orange ones. These are optimized for a few
things but prominent among them is viewing of Saturn rings during the
equinox. As Jeff alluded, this is - excuse me - this is a really
exciting time for the rings people because, you know, the sun passes
through the ring plane. So it will cast shadows of bending waves on
other parts of the rings. The rings guys may use this time to find new
moonlets because of the shadows they cast.

And there's generally a lot of interesting dynamics that can be observed
during this time period and it's very high priority for them. And again,
since Saturn's full set of seasons is nearly 30 years, this kind of
thing only happens twice a season. So this is the only time
realistically that we'll get to observe Saturn during this particular
geometry.

The red phase covers some (icy) satellite encounters. And again, as you
can see, that tends to be close to the equatorial plane from the upper
right plot. And then right at the very end, there's a couple of orbits
added for some key science objectives of getting ground tracks at high
latitude on Titan. And that's in particular - that means that when
you're flying by Titan at closest approach, you're passing over high
northern or southern latitudes of Titan.

And I believe that's partially desirable to study those - the new - the
lakes and to see if there's been environmental change since the first
images, radar and otherwise of those areas. As well as, I think start
to - I think there's tracks of both in the north and the south and to
sort of see how the two poles are different or similar is also an
important science objective.

Page 61 shows the inclination profile. Again as you can see, we start at
high inclination. We used the equinox time period to bring the
inclination down to moderate and then to low levels and then hit the
(icy) satellite encounters sort of near the end of the Equinox Mission.
And this plot is about two years wide. So this really covers the
complete Equinox Mission time period.

This plot shows the ground tracks. You can see sort of the several very
high northern ground tracks that are coming up sort of on the very top
in the red and then the yellow and blue on the bottom chart.

We also have - you can see on Page 63, you know a number of very close
Enceladus flybys. The 1E4 that's labeled here is the flyby that we just
implemented. We just accomplished earlier this month. We'll continue
with another step in even closer with E5 coming up shortly. And then
we'll just continue to - I mean, all of these encounters you can see go
through the plume to some level.

The really exciting ones are in 2010. That's E7 and E9. Those are the
two encounters that will fly very - really deep - probably deepest in
the plume of the entire mission, even after the Equinox Mission. It's
not terribly likely that we'll get much closer than that.

So this is a really exciting time for plume science as well to be
stepping in closer and closer to the source of the plumes, not only to
be able to image them move closely but perhaps more relevant is the
statement that we can sort of sniff out the composition and the density
profile of the plume directly, which is arguably the most illuminating
way to study the composition of the plume and to get a hint at what's
going underneath the surface.

So these - those encounters are exciting. Page 64 shows sort of some of
the osciltation profiles. This is the path of the spacecraft as it
passes behind Saturn on the top and Titan on the bottom. And I believe
those are 500 kilometer radii contours that are going out of Titan.

And you can see that there a number of osciltation tracks that pass
behind Saturn and a variety of latitudes and geometry. It's not only
going east west but also north south. And there are a handful that cut
all the way across the ring system as well. You can see them coming from
the left. It's a little easier to see them on the left than it is on the
right.

And Titan as well, you know, there's a number of osciltation tracks at
high northern latitude, there's a few at high southern latitude and
there's a couple that come in near the equator as well. So they're
definitely hitting all the - all of the objectives with the trajectory.

To spend the last few minutes talking about what happens after the
equinox - that's mainly what we're spending a lot of effort on now is
what happens after July of 2010. We do surprisingly still expect to have
some propellant margins and a healthy spacecraft then as well.

So there is a reasonable chance that NASA will approve a further
extension which hopefully you'll all be excited about. This picture on
Page 65 again tries to illuminate the seasonal case for Saturn. These
curves here show it's - this is a curve of the solar declamation - in
other words, the latitude of the sun as seen from Saturn.

On the Earth this would look similar. It would go from just about 20
degrees northern to - during our summer to just below 20 degrees
southern during our winter over the course of one-half of the season
from, say, you know, a northern winter to a northern summer.

And that's exactly the kind of thing that we're hoping to get most of
beyond the equinox. This is all proposed at this stage but really to see
a full set of seasons on Saturn and to see the changes that happen not
only on the planet itself but in the rings on Titan with Enceladus'
plume, etcetera, there really is we think a strong case that can be made
for really trying to go for a full half season.

And that would push us, if possible, all the way to sort of the middle
of the year on 2017 which is the northern summer solstice. That'll
really give us a complete set of a half season going all the way from
northern winter, as you can see its (unintelligible) on the left here.
You can see this is the view of Saturn from the Sun or from the Earth
where you can see that you're looking at sort of the southern hemisphere
more than the northern hemisphere.

The northern hemisphere is shadowed by the rings. It's colder. The same
is true for all of the satellites that are in orbit in Saturn's
equatorial plane. Their southern hemispheres are being illuminated more
than the northern hemispheres. Certainly for Titan that could have
climate implications with things like the lakes as well as maybe the
precipitation cycle or the cycle of the hydrocarbons in the atmosphere.

To observe Saturn through the equinox, which you can see sort of in the
fourth Saturn from the left where the rings are paper thin, all the way
to northern summer at the far right would really be a huge step forward
even beyond what we've done now in terms of studying seasonal changes on
Saturn.

And you can see, even on adding the Equinox Mission, it does give us a
significant boost but it really doesn't take us all the way to the full
half season. So this beyond the equinox time period is the time period
we're hoping to be able to attack and discuss with headquarters in the
coming months.

Page 66 takes some getting used to and it takes some absorption. But one
of the interesting things we discovered was that a lot of our fuel
expenditures were being done to try to pack in as much stuff as we could
with particular orbital geometries that were high priority for the prime
mission.

And as you can - might imagine, like if you're trying to fit in
activities in your day, you reach a point where it gets really expensive
to sort of work things in and you just, you know, you just have to spend
all your resources getting from one place to another to try to work
everything in.

And that's sort of the frantic level that we've been on. And this is -
there are really three drivers to this. One is for the prime and the
extended mission, having to densely interweave all of the different
science objectives in what is a short period of time for tour design -
in other words, four years for the prime mission, two years for the
Equinox Mission, that itself is expensive in terms of propellant.

You have to add extra maneuvers and do things faster than would be
convenient in terms of celestial mechanics. Also each encounter had its
own requests from the science community in terms of how to optimize it
to get the most science we possibly could and that added expenditures as
well that wouldn't have been necessary if we hadn't quite optimized it
quite too intensely.

That approach was very appropriate for the prime mission where we really
had to deliver as much science as possible in the shortest time period.
But for an extended mission, there are other options that can still get
nearly as much science without optimizing everything quite so intensely.
There is another explanation. There is another expenditure too which is
the first one listed in the bottom which is the closer you get to Saturn
at orbits that have some inclination, the more (unintelligible) it costs
you.

And this is just because Saturn is an oblate body that tends to want to
rotate the orbit and pull it because of its oblateness in ways that are
inconvenient for us in terms of our propellant expenditures.

So the close (paradoxes) where we studied the rings and the
magnetosphere very closely - some of those were very expensive. And if
we can avoid those in an extended mission, we can save fuel.

So all of these things led us to conclude that there really were ways to
do extended mission after the equinox very cheaply but still deliver
almost the same intensity of science that we did in the prime in the
Equinox Mission. And I think this is one of the cases to be made to NASA
and our partners is that we really can continue on past the equinox at a
high rate of science return not only per dollars spent but also per unit
of propellant spent. And that's kind of what this chart is meant to
illustrate.

Page 67 shows an update of where we expect to be at the end of the
Equinox Mission. In other words, in July of 2010. At this point, the
color blue is what's left over. So for the bi-propellant, you can see we
do have a pretty significant wedge of bi-prop left over for large
maneuvers. It's not quite as bit as it was for the Equinox Mission in
terms of what we had to work with.

Hydrazine again, is in very good shape. We expect to have quite a bit of
hydrazine left over. And these two together should be good if NASA does
approve such a mission if we can prove ourselves that such a mission is
worthwhile, this should provide us with at least a few years of
operability.

Again if we're frugal with this, we can still deliver a lot of science
over perhaps more than a few years and possibly get us most of the way
to the solstice.

At the very end\...

(David Lightwood): Can I ask a question?

(Dave Seal): Sure, Go ahead.

(David Lightwood): (David Lightwood), I'm not connected with anybody.
But what makes the propellants unusable?

(Dave Seal): Oh, sure. In each propellant system, you can't ever empty
it completely. It would kind of be like trying to empty your car's gas
tank completely. There's going to be some gasoline vapor floating
around, some gas stuck to the walls of the tank, possibly some in the
tubing that goes from the tank to the engine.

And it's basically the same situation for Cassini. There is some small
amount - it may not seem terribly small for the bi-propellant but it's a
complicated system with a lot of plumbing. There is some amount that
just - we just can't squeeze out of the tanks because it just - because
of the nature of the system.

(David Lightwood): Okay, thank you.

(Dave Seal): And that's our best estimate or what's unusable. It may be
better, it may be worse. But we're keeping a handle in it as best we
can.

(Matthew Otto): Question.

(David Lightwood): Thanks very much.

(Dave Seal): Sure.

(Matthew Otto): Question.

(Dave Seal): Sure.

(Matthew Otto): This is (Matthew Otto) again with the Saturn Observation
Campaign. I'm glad to see that you have a lot of consumables left over
after the primary mission. However, now I'm thinking about the other
additive control system which is the reaction wheels.

(Dave Seal): Sure.

(Matthew Otto): And traditionally in other space systems, for example,
Sky Lab, they've had problems with reaction wheels - actually on the RSS
also.

(Dave Seal): Right.

(Matthew Otto): With the wheels that have the tentacle problems. How are
the reaction wheels holding up on the Cassini?

(Dave Seal): The reaction wheels have been showing signs of degradation.
Actually perhaps degradation is the wrong word. But they have been
showing their age a bit. This really started even before we arrived at
Saturn.

It is certain that they will fail eventually or enough of them will fail
to render them unusable. But it's really hard to predict and we've had
many detailed technical meetings talking about this and trying to
predict exactly, you know, trying to determine what these signs mean in
terms of their lifetime, trying to predict when they may fail.

And it's really a very difficult - it's a really difficult thing to
predict.

(Matthew Otto): But for now they\'re\...

(Dave Seal): It's the moving part or the set of moving parts that we
worry about most.

(Matthew Otto): Right.

(Dave Seal): However if they do fail again, we do have the hydrazine
system with all of this margin at least at the end of the Equinox
Mission.

(Matthew Otto): And for now they're operating just fine apparently.

(Dave Seal): Yeah.

(Matthew Otto): Okay.

(Dave Seal): Yeah, the wheels are operating just fine. We've had - we've
really had no problems during tour where we have had to stop using them
and therefore lost any science. So we've really had no science losses in
tour just from the reactional wheel behaviors themselves.

So there's really, you know, there's no reason to expect that they're
going to fail tomorrow, next week, next month - probably even next year.
Five years from now - tough to say.

(Matthew Otto): Okay, thank you.

(Dave Seal): But, you know, I think we've - we continue to monitor them
so closely and still have a redundant wheel that we shouldn't - there's
no reason for us to expect that the Equinox Mission or even beyond the
Equinox Mission couldn't operate with the wheels still at a healthy
level.

(Matthew Otto): Well my opinion is the JPL engineers of many years ago
designed a very robust spacecraft. And I've always been amazed at how
well the Cassini has held up over all these years systems-wise.

(Dave Seal): Yeah, it's really staggering to us too how few problems
we've had. And you're right, that is a testament to two things - the
people that designed and built it well and tested the heck out of it and
made sure that everything was working and also the (unintelligible) team
that's flying it now really keeps a close eye on every system.

And even though they've been operating it for four years, you know, they
avoid complacency and continue to keep a close eye on everything and
make sure that anything out of the ordinary gets all of the proper
attention.

And their reaction - they'll certainly get their share of attention
compared to every other component of the spacecraft. And they are
monitored almost on a continuous day-to-day basis.

Well let me make sure I take a few minutes to talk about one of the
possibilities for the very end of the Cassini mission. There will be a
point where we have to end the mission for good. We hope that this point
is reached when we're nearly out of propellant and we're about to lose
control of the spacecraft, where there really is no reason to keep it
running.

And one of the most exciting things that we can do with this - hopefully
many years from now is the trajectory designers have discovered an
option where we can in one Titan flyby hop over the entire ring system
and fly between the main rings and the planet.

And this has got a lot of scientists excited, not only on Cassini but
also in the outer planet community at large. Some of you may know
there's a new mission called Juno that's approaching - that's, you know,
progressing in its development phase.

Their plan is to fly very close to Jupiter during the (unintelligible)
part of the orbit and getting as close as possible really allows them to
study the magnetosphere in great detail as well as things like the
gravitational harmonics of the planet and even the atmosphere to some
extent.

And that is certainly true for us, you know, because of the main rings
and because they're too dangerous to fly through it, we really have not
been able to get very close to the planet itself except during orbit
insertion.

There we were three-tenths of a Saturn radius above the surface which,
you know, if you eyeball it, it's still quite a distance away. And that
was as close as we were able to get. With this option, we can get
arbitrarily close down to really just skimming over the cloud tops

And for many of the disciplines - scientific disciplines that are active
in the project, this is really a very exciting prospect. Obviously
Saturn atmospheric scientists would love to sample that Saturn's
atmosphere in situ with out atmospheric instrument - the magnetospheric
guys would love to get this close. It opens up a whole suite of science
investigation that has been thought to be impossible up to this point.

The rings guys - Jeff mentioned that earlier alluded to them that we
could use these orbits to get a better estimate on the mass of the rings
and even maybe the mass distribution across the rings because we're just
getting so close to Saturn itself and to the rings. And so the - and as
well as studying the rings - at least the inner part of the rings more
closely, you know, from a substantially less distance.

All these are really exciting prospects to the scientists and I think
this may be an option that you hear more about in the coming years.
Certainly no one wants to think about the end of the spacecraft or the
end of the project but the good thing about this is, you know, we would
ideally do this when the end really was just over the horizon where
there really is no, you know, the spacecraft would die or run out of
fuel on its own.

And the great thing about this is really this can get us so much new and
unique science that this is really a very, very positive and attractive
thing to think about in terms of the future of Cassini.

To really, as the phrase goes, go out with a bang instead of a whimper
would really be, I think, the last and possibly the best feather in the
cap of the project.

And the last chart here is the image that (Buren Johnson) made. This is
just kind of a nice little closing image to picture Cassini sort of
being around there with the rings so close and spectacular and sort of
flying through the cloud tops of Saturn, perhaps seeing a storm here and
there as opposed to sort of the more plain hazy view.

But that's where we hope to end the project, with something as exciting
and scientifically productive as this.

So we have maybe a minute or two left. I'm happy to take anymore
questions people have. But thank you very much for your attention for
this fourth anniversary CHARM session.

Man: More questions for you on the consumables.

(Dave Seal): Sure.

Man: Back on - I guess it was Slide 54 you had the power output graph
for the RTG.

(Dave Seal): Right.

Man: At what point does the output drop below what it needs to keep the
spacecraft functional?

(Dave Seal): Nothing on this page.

Man: Okay, so that's way far out in the future.

(Dave Seal): Yeah, so really - realistically beyond where we expect to
still be around. Even at 600 watts, you see at 2017 or 2018. You can
still operate all of the basic systems - spacecraft systems. It's very
likely that between 2011 and 2017 we're going to have to start being
much more creative with what instruments can be on simultaneously. You
know, we're going to have to - maybe every two years, one more
instrument can operate at the same time.

So we're going to have to do things like only do camera observations and
then turn - put those to sleep or turn them off and only do
magnetospheric observations.

But all the basic spacecraft systems in terms of the flight computers,
the attitude-controlled computers that all the various devices, you
know, the thruster's reaction wheels - all of that can operate at any
power level that you see here.

Man: Thank you.

(Sunny Mario): (Sunny Mario) in Berkeley, California.

(Dave Seal): Hi.

(Sunny Mario): I have a question. What is the funding for the
(unintelligible) and the funding for the years after that?

(Dave Seal): NASA headquarters has already delivered us a plan for the
Equinox Mission that is essentially at the same level of funding that
we've received for the prime mission. So we should think of this as
really as a two-year addition to our prime mission. You know, you saw
the level of science intensity that we're planning. And our team size
and funding level is going to maintain - be maintained at about the same
level.

And that obviously is required to enable us to do the - to continue on
with the same level of science intensity. We're still working on exactly
what the scope and general plan is for the Solstice Mission - or what we
might call the Solstice Mission or the mission past the equinox. It
doesn't have a - any sort of official name yet. It's sort of the second
stage of the extended mission.

And we have some reviews coming up in the next 6 to 12 months with
headquarters to figure out exactly what that's going to be. We'll have -
we'll - there'll be releases from headquarters when we come to - so I'm
sure will be the right decision. But for now, there's really no solid
plan for any sort of funding profile for that yet.

(Sunny Mario): Can you give me a number for Equinox?

(Dave Seal): A number in terms of dollars? I don't have those figures at
my fingertips but I can - I wonder if they were in the press release
that we sent out with the Equinox. I'll talk to (Jane) about it after we
get offline and see if we can put something out there. But offhand I'm
not sure what our annual budget is for Equinox.

(Sunny Mario): It's roughly half as much as the primary mission.

(Dave Seal): Well the Equinox Mission is half as long. But the funding
profile per year is about the same as it was for the prime mission. So
it's at the 100% funding level compared to what we did for prime
mission.

(Sunny Mario): Okay. My other question is\....

(Jane Jones): Excuse me, we're just about running out of - we're over
our allotted two hours for the telephone call. So please just ask one
more question and then I'd like to thank (Dave) and turn the phone back
off.

(Sunny Mario): Okay, the last question then is, why would skimming the
clouds of Saturn be better than (unintelligible) at the end?

(Dave Seal): Well one of the major concerns at any end of mission is
what's called planetary protection. You know, because we do carry RTGs,
they do have the capacity for warming the environment around them even
if they impact on Titan at high speed.

And we don't want to contaminate Titan with maybe microbes or other bugs
or things that might still be floating around the spacecraft. Whereas,
coming - going into Saturn and going deep into Saturn's atmosphere is a
more attractive end of mission for that reason.

The other thing is, you know, we've already flown - the other
consideration is we've already flown deep in Saturn for, you know, as
deep as we can safely in Saturn's atmosphere. And I don't know if
there's a lot of really new science to be gained by ending the mission
there.

That might be more compelling argument scientifically or it might be
more palatable to the general public is that it's just not
scientifically that much of a bonus over what we've already done.
Whereas, hopping over the rings has really major science advances
possible for a variety of disciplines. And it makes it just that much
more scientifically attractive.

Okay.

(Jane Jones): Okay, well thank you, (Dave). That was awesome and I'm so
glad we have - we were able to get the Equinox Mission into a CHARM
right away, so that everybody knows kind of what's coming up for the
next - for all of us for the next two years.

And I don't know what our topic for next month is at this time, but
you'll be hearing about it soon. So all of you, look forward to having
you join us again next month - and thanks, (Dave), so much.

(Dave Seal): Thanks and goodbye everyone.

(Jane Jones): Okay, bye-bye everyone.

Man: Goodbye - see you next month.

END