>> Hello, and welcome to NASA's
Jet Propulsion Laboratory
in Pasadena, California,
I'm Preston Dyches.
 We are at the end of an era
 in planetary exploration.
  In less than two days,
  NASA's Cassini spacecraft
 will make its
 fateful, final plunge
 into the atmosphere of Saturn
 collecting data until
 the very last moment,
  as it ends its 13 year
  tour of the Saturn system.
  The purpose of
  our briefing today
 is to provide background on
 how we got here with Cassini,
along with preparations
for the final plunge,
and some of the science
that the Cassini team
  hopes to accomplish as
  Cassini heads into Saturn.
Our participants for
the briefing today are,
 from NASA headquarters
 in Washington,
the Director of NASA's Planetary
 Science Division, Jim Green.
 Up next, we have the
 Program Manager for Cassini
here at JPL, Earl Maize.
To his left, the Cassini Project
Scientist, Linda Spilker.
  And finally, Team
  Lead for Cassini's
ion and neutral mass
spectrometer instrument,
or INMS, from Southwest
Research Institute
 in San Antonio, Hunter Waite.
Alright, a reminder to reporters
dialed in on the phones,
 please dial star one to get in
 the queue to ask a question.
  And members of the public
  as well as the media
 can ask questions
 online via Twitter,
 using the hashtag #AskNASA.
 And with that, let's turn it
 over to Jim to get started.
>> Thank you very much, Preston.
You know, we're here at
a very historic time,
 but it really started
 with the Voyagers,
 Voyager One and Two, as we
 see here in the auditorium,
 a full scale Voyager, passing
 through the Saturn system,
 begging us to go back.
 And of course, in
 2004, Cassini made it
 to the Saturn system.
 And as you can see, Cassini,
 this is a smaller scale model,
 but if you can imagine
 the antenna size
 on Voyager being
 the same as Cassini,
this is a very capable,
large spacecraft
 that has been making
 fabulous measurements
  within the Saturn system.
My first slide, please.
  Of course, Saturn, one of
  the beautiful gas giants
  in our solar system,
  with the beautiful rings.
 Studying the planet itself
 has been incredibly important.
 The cloud dynamics and
 the storms that occur,
 and in fact while Cassini was
 there, a storm that lasted
 more than nine months raged
 in its northern hemisphere.
 Next slide, please.
 Of course, as we were able
 to get to higher latitudes,
we were able to look
down at the polar region
 and see other
 spectacular things.
  The hint of this hexagon
  pattern on the north pole
 was really observed
 first by the Voyagers,
 but we're now back to see
 that up close and personal.
The size of this whole hexagon,
 which is actually a jetstream
 on the outer rim of it,
  is about twice the
  size of our Earth.
 In addition to that,
 we had opportunities
 to begin to look at the moons.
  And here, other surprises
  were well in store for us.
 As seen in this image,
 this is Enceladus.
 This is a small moon just
 outside the rings of Saturn,
 and what we thought
 was an icy ball.
 When we observed the
 Southern Hemisphere,
 and geysers of water spewing
 out into the Saturn system,
it amazed us and began
changing the way we view
 the habitability or potential
 habitability of moons
 in the outer part
 of our solar system.
  My next image, of course,
  is the beautiful Titan.
This moon is bigger
than the planet Mercury.
 It has an atmosphere at twice
 our atmospheric pressure.
 If it was orbiting the
 Sun and not Saturn,
  we would call it a planet.
 It's truly a magnificent body.
 The Voyagers could
 only see the haziness
  of this beautiful
  object, but with Cassini,
our ability to penetrate through
that haze with our radars,
 and seeing what the surface
 structures and features are,
and the DSA Huygens
probe going all the way
 down to the surface,
 revolutionized
 our understanding of
 this spectacular moon.
This is the only other
body in the solar system
that has liquid on its surface.
  Its seas are about the
  size of our own Black Sea.
Now, they're not full of water,
  but they're full
  of liquid methane.
This is a spectacular
world in its own right.
 Next slide, please.
 Of course, Saturn has
 more than 60 moons.
Can't see them all, but
we saw approximately
 two dozen of them in addition
 to Enceladus and Titan.
Beautiful moons, with
all sorts of structures.
Those that even, in fact, modify
the structure of the rings,
creating divisions, or
elements that accrete material,
 and we begin to see all those
processes up close and personal.
  But one of the real stars
  of the show is Titan.
 Our ability to fly by Titan,
 which is about 20 Saturn radii
away from Saturn, allows
us to use the very basic
 principle of gravity
 assists to change
  the plane of Cassini's
  orbit, provide new views,
  and therefore observe in
  beautiful different ways.
The next animation
shows you these flybys.
 Now what we normally
 do on flybys
  is just get a little idea
  of what that body is,
 but these flybys have
 revolutionized our opportunity
 to use this concept
 for other missions.
We now know from these
flybys how to construct
 a global view of
 this beautiful world,
 and we're using it on
 the clipper mission
 that's going to Jupiter and
 viewing the moon Europa.
 Cassini has enabled us to make
those future missions possible.
 My next slide, please.
  Americans had a wonderful
  view of an eclipse,
 where the moon passed in
 front of the sun last month.
  Millions of people
  appreciate now
 what eclipses are all about.
  From our view on Cassini,
  this is the eclipse,
 with Saturn moving
 in front of the Sun.
  This allows in the low
  light of blocking the Sun,
 opportunities to see
 in greater detail
 the ring structure
 and other elements.
  In fact, we were even able
  to see distant planets,
 and the Earth, in a beautiful
 set of mosaic images
that have been stitched
together, as shown here.
  That outer ring that you
  see is called the E ring.
We're able to illuminate
it in ways that tells us
that Enceladus' geysers,
water being spewed out,
 is creating this ring.
Now because of the
importance of Enceladus
 that Cassini has shown
 us, and of Titan,
 another potential world that
 could be habitable for life,
 perhaps not like we
 know it, but perhaps
  completely different
  than ours, we had to make
  decisions on how to
  dispose of the spacecraft.
And that led us,
inevitably, to the plan
of taking Cassini and
plunging it into Saturn.
Because of planetary protection,
and our desire to go back to
Enceladus and go back to Titan,
go back to the Saturn
system, we must protect
 those bodies for
 future exploration.
 Next slide, please.
 Well, in the visible camera,
 we've seen more
 than 450,000 images.
  Every one of them,
  in their own way,
 are absolutely spectacular.
 But we made the
 decision to go through
 and pick the top 100 images,
 videos, and animations,
and create an ebook,
something that allows us
 to go back and view
 what we accomplished,
 and the beautiful observations
 that this mission has done.
 You can download this ebook in
  several formats at
  nasa.gov/ebooks.
 So with that, let's learn
 how we plan to plunge Cassini
 into Saturn, and what we will
 learn from that experience.
 So let me turn it
 over to Earl Maize,
 the Project Manager
 for Cassini, Earl?
 >> Excuse me, thank you, Jim.
It's been such a unique
and incredible privilege
and pleasure to operate
this spacecraft,
that before I go
into its demise,
I'd like to talk just
a little bit about some
 of its many accomplishments.
 As Jim pointed out,
 almost half a billion,
 I'm sorry, half a
 million images taken,
4.9 billion miles logged
on this spacecraft,
  635 gigabytes of
  data played back.
 Now that, by modern
 standards, is not a whole lot
  bigger than a flash
  drive, but you gotta think
  about 80s technology from
  a billion miles away,
and that all of a sudden
becomes pretty amazing.
 We had 162 targeted flybys,
 and as Jim pointed out,
 we've been using Titan
 to great advantage,
  and there have
  been 127 of those.
 Could I have the
 first graphic please?
 Just to show you this
 incredible spacecraft.
 Now as it's half, twice
 again, the size of the model
  in this auditorium
  if you're here,
 but it's absolutely splendid,
 just built for Saturn.
And of course, that's the iconic
 north pole of Saturn below it.
  Now that is an animation,
  we did not take
 a selfie stick with us,
 although we could have put one
 on the RPWS antenna
 in hindsight.
 That again was something that
 the 90s didn't know about,
 so we'll have to live onward.
But again, it's just been almost
flawless operations in both
the instruments and the
spacecraft engineering systems,
 and then the ground
 support itself, again,
  has just, I think
  made this mission,
 not only do we
 have an environment
  that just is overwhelming
  with abundance
 of scientific
 mysteries and puzzles,
 we've had a spacecraft and a
 team that could exploit it.
  So again, I will probably
  come back to that point,
  but it's just been an
  amazing, amazing mission.
So what are we gonna do?
Let's get to the last few hours.
Could I have the next animation?
 This is the so-called
 ball of yarn.
 What we do, as Jim pointed
 out, we have a main engine,
 and it's a great main
 engine, but we've got Titan,
and Titan is a
phenomenal main engine.
  Every time we flyby Titan,
  every time we flyby Titan,
 we get a little bit
 better view of Titan,
 and we get a little bit better
 view of the Saturn system.
  Every one of those
  course changes,
 every orbit change there
 is, Titan's doing it for us,
and it's done for us for
294 different orbits.
 127 times we've made
 major orbital changes,
 and Titan's been at the
 center of every one of them.
 So that's the ball of yarn,
  and if I could to
  go the next one,
 let me just show you
 what Titan did for us.
 This is April.
All the time we've
been outside the rings,
 and being very careful with
 the rings, and with the dust,
because we really didn't
understand the environment well.
  But for the grand finale,
  in order to exploit
  every last ounce of our
  propellant and the science
 that Saturn offered inside,
 we've been what we've
 been calling the proximal
 orbits, or the grand finale.
  Titan gave us one last
  little nudge back in April
 and pushed us, the
 Cassini spacecraft,
 between the rings and
 the planet itself,
and we've been
skirting back and forth
 in that sense for 22
 times since April.
 Our last one, unfortunately,
 was Saturday morning,
 or Saturday evening, actually,
 we got the callback
 on Saturday morning.
 We don't normally communicate
 with the spacecraft
 during these passages,
 because the science
 is so precious,
 we are busy gathering that.
 So the call home was Saturn
 morning, we were here,
  got the call home,
  spacecraft's fine,
 it did it again the
 way it always has.
 Monday we got the kiss
 goodbye from Titan.
 119,000 kilometer altitude
 flyby from Titan took about
39 meters per second of velocity
away from the spacecraft,
slowed it down just
enough that what's going
 to happen on Friday is
 absolutely inevitable.
 So if I could go to that next
 animation, just to show this.
There is a graphic here,
see that Titan flyby?
 Now that's behind me,
 I should be pointing.
 That little Titan flyby was
 enough to put us into Saturn.
  It was just distant
  enough, just close enough,
 and just the right orientation
 to seal Cassini's fate.
 So what's gonna happen next?
 Could I get the next
 graphic, please?
  We made contact with
  Cassini for the last time,
 for the penultimate
 time, we ceased
contact about 6:50 this morning.
 After the Titan flyby, we
 got a call home last night,
 we were all in the
 mission support area,
 waiting for telemetry.
 As it has done over
 and over again,
Cassini came in on time
and in perfect shape.
It got the flyby that it needed,
 it got the velocity
 change it needed,
 and it's now on its
 way into Saturn.
But before it goes, at
about 6:50 this morning,
 it turned off of Earth back
 to the job it's been at
  for the last 13 years,
  observing Saturn's system.
It's gonna be taking
the last set of pictures
  of some of the prime
  targets that it's visited
over the many years that
it's been at Saturn.
And we'll be able to share those
 with you sometime on Friday.
They'll be coming back tomorrow,
 at about 2:45 tomorrow
 afternoon, Cassini's
 gonna turn back,
 and play back those
 final sets of images.
 We figure that should
 take about 11 hours,
 so at about one
 o'clock in the morning
 of Friday, September
 15th, we will,
 the solid state recorders
 onboard Cassini will be empty,
 and we will then
 reconfigure Cassini
  for its very final
  transmissions.
 What we're gonna do is,
 Cassini is normally a mission
 that stores things on data,
 like it's doing right now,
  we're not in contact, we
  could look all we wanted,
 and Cassini's off busy
 doing its own thing,
  stores it on the recorders
  and plays it back later.
  It's doing that right now.
 But next Friday morning,
 we're going to turn Cassini
into what we call, essentially,
a bent pipe transmission system.
 Everything that comes
 from the instruments
 is going to go right into the
 recorder and right back out.
 So there'll be a
 few seconds' delay,
but it's essentially now
a real time instrument.
And that's to enable the
sampling instruments,
  particularly the ion and
  neutral mass spectrometer,
 to get data as deep
 into the atmosphere
  as Cassini will permit it.
 We've taken our data rate down
 to as low as we can handle,
 so that no matter what antenna
 we've got on the ground,
 we'll be able to receive it.
So if it's a rainy day in at
the, in Canberra, in Australia,
  where we'll be tracked,
  then we'll be able to have
  a better chance of
  getting the data.
We've also got antennas both
at the DS End Tracking stations
 on the east side of Australia,
 but also we've got the
 New Norcia DSA station
 standing at the ready
 on the west side.
 So if we've got a rainy day
 over the entire continent,
well we're out of luck.
 But the best we can do,
 we've got ourselves covered.
We will turn, at that
point also, to make sure
 that the high gain antenna,
 the large dish you see there,
 is pointed directly
 at the Earth,
 and that we've
 rotated the spacecraft
 so that the ion neutral
 mass spectrometer's aperture
  is pointing directly into
  the oncoming atmosphere.
  So essentially, it's
  getting just a full blast
  of the atmosphere
  as it comes in.
 So how are we gonna,
 the last few minutes?
 Cassini is not built
 for atmosphere, as
 you might imagine.
 We're a deep vacuum
 kind of probe.
That's not to say it
hasn't seen atmosphere.
 We've flown in the
 atmosphere of Titan,
we've used the thrusters
to battle the torques
and the drag forces that
we've had to deal with,
 and they've been
 very effective at it.
 So we know how to fly into
 a little bit of atmosphere,
  and we've been doing that
  for the last five orbits.
 We've actually been
 dipping our toes down
  into Saturn's atmosphere
  for the last five orbits,
 and the thrusters have
 had to fight back,
at what we call a duty
cycle, at a 100 percent,
they're working as hard
as they possibly can,
 they've been up into the 40s.
 So we really have been working
the atmospheric
effects to some extent.
 We have a good sense of these.
 But these are really
 tiny thrusters.
  They're built to
  move a school bus
 by just kind of tapping it.
 So you know, they're just
 not gonna be able to do that.
 I think, I'm kidding,
 one eighth pound.
So this is just, you're
touching something,
 pressing on it a little bit's
 about an eighth of a pound.
  You can imagine what
  those thrusters have to do
  in order to deal with the
  atmosphere of Cassini.
 So before I go on to
 the next animation,
 let me just point out
 one final moment here.
 At 4:55 AM Pacific Daylight
 Time, loss of signal.
And what's gonna
happen is the thrusters
 will eventually be
 overpowered by the atmosphere,
 we won't watch Cassini burn
 up, what we'll watch it do
is slowly turn away
from us, and we'll watch
 the indicator on the
 radio science displays
 that will go down flat, and
 essentially loss of signal.
The mission will be over
within a minute later.
 It's going so fast,
 and the atmosphere
 is thickening so quickly that
 Cassini will be vaporized
in a few, I think may
100, maybe two minutes,
  but I think more like one.
 So it's really, it's
 just inevitable.
  It's going in very
  fast, very steep.
 Let's go to the next image,
 just for fun, to see.
 There's the timeline of the
 last 90 seconds of Cassini.
  Every 10 seconds,
  tick mark there.
  And that really, that
  tick mark, as you can see,
 the final one on my right
 is, or on my left up there,
 I believe, is where
 we lose signal.
So you can see, very
very tenuous atmosphere.
 Where essentially, the analog
 of that might be on Earth,
that's about where the
International Space Station is,
 relative to density.
It's very very thin air.
 But Cassini's going so
 fast, and the thrusters are
 so modest for this
 sort of requirement,
 it's just not gonna
 last much longer.
  But you can see that about
  70 seconds, 60 seconds in,
 the thrusters are
 gonna start to fight.
  For the last minute or
  so, they will be fighting
 the atmosphere
 increasingly, increasingly,
 as it tries to turn Cassini
 into a more aerodynamically
 compatible shape, and
 eventually they will overcome.
 So if I could see the
 last graphic, please.
  This is an animation, so
  there's Cassini coming in.
  This is about that point.
And you can see, we're
starting, this is again,
 a bit of a artistic license
 here, but the thrusters,
 as you can see down off those
 extensions on the bottom,
 are fighting
 extremely hard to keep
 the antenna pointed
 directly at the Earth.
 And you see, it's gonna
 start to feel the vibration
 of some of the
 atmospheric torques.
 But it will fight, and it
 will fight, and it will fight.
 The mass spectrometer's
 pointing into the atmosphere,
 the antenna is
 pointing at the Earth,
and it's gonna do that
for as it possibly can.
  Those of you that have
  been following this story
  for a little while
  might have noticed
that we've been a little
bit ambivalent about
when Cassini's actually
going to lose signal.
 One of the wonders and
 mysteries of Saturn
is that we are always surprised.
 And we thought we knew what
 the atmosphere was all about.
We had models that told
us, that perhaps we were
  not going to get enough
  atmosphere to even satisfy
 the ion and mass requirements
 during the last five orbits.
We had plans to pop down
into the atmosphere,
and if it was too thick,
we had plans to pop up,
and pop up again, and pop down,
 in order to get this
 thing fine-tuned.
 Well it turned out to
 be absolutely perfect,
against all of our predictions.
 We had all these
 contingencies planned,
and we threw them away.
 But what that tells
 us, also not only
did we not know the atmosphere,
  but the atmosphere affects
  when you're gonna go in.
Every time you go into the
atmosphere and get slowed down,
 well you go ina
 little bit earlier.
 So what started at 5:08 is now
 at 4:55:06 AM Pacific Time.
  And that's our story,
  and we're sticking to it.
 [audience laughing]
 So with that, I'd like to turn
 the mic over to Linda Spilker
  to tell you about some of
  the just amazing science
that we're going to get
in these last few hours.
  >> Well, thank you
  very much, Earl.
 Being part of the Cassini
 mission for the entire mission
 has been an
 incredible privilege,
both for me and for many of the
scientists on board Cassini.
 We've had an incredible 13
 year journey around Saturn,
 returning data like
 a giant fire hose,
 just flooding us with data.
 In fact, if you
 imagine all that data
  as a million piece puzzle,
  Cassini has been slowly
 putting together the pieces,
 we have some of the border,
 some of the regions,
 and we're trying to
put together the picture
of the Saturn system,
 but we don't have a picture
 on the cover to guide us,
 to tell us what that final set
of data will finally look like.
And what's really great
about the grand finale
  is it's adding incredible
  new puzzle pieces
 to help us better understand
 the Saturn system.
  And as Earl said,
  lots of surprises.
 Many of the things we
 thought we knew about Saturn
 are more complicated than
 we originally had imagined.
If we look at the first graphic,
 this is an example of looking
 at Saturn from the outside in.
 That's what we're doing with
 the grand finale orbits.
If you look at that blue
figure on your right,
  that's the auroral
  oval at Saturn.
 The particles come in,
 hit the atmosphere,
 cause this wonderful aurora.
 Just underneath it,
 you have the hexagon
 with the hurricane inside it.
If you look on the bottom
right, you can see an image now
  in the infrared where you
  can see the heat energy
 coming out from
 inside of the planet.
 And finally, that beautiful
 image with the hexagon,
 so we're looking at
 different levels from Saturn,
almost like we've taken
a magnifying glass
 to the planet and the rings.
 We've also been looking at
 the interior, and in a sense,
pulling back the
curtain with our gravity
and magnetic field
data, to see what Saturn
is like on the inside, as well.
Well as Earl mentioned,
we're going to be taking
 our last images, we hope about
 eight o'clock tomorrow night
 to have the images up
 on our raw image site.
 If we go to the next graphic.
 In that last period of
 time, looking around Saturn,
what we're doing is we're taking
our final picture postcards
 of the Saturn system, looking
 at our favorite targets
 to put these images in
 our Cassini scrapbook.
 So we're going to take, if
 you look at the upper left,
 a mosaic of Saturn and
 the rings in color.
Basically, our last look
at the entire system.
Upper right, that's
Titan, we're gonna take
some goodbye pictures of Titan,
last look to see if there's
any weather or clouds going on.
 In the lower left, that's
 the outer edge of the A ring,
and that bright feature
is created by a grouping
 of particles that
 we've nicknamed Peggy.
 We've been watching since 2012
 to see if Peggy might break
 free of the rings and become
 a moon in her own right,
 so we're gonna take a last
 look, see what Peggy's up to.
  In the center, we're
  gonna watch Enceladus set
 behind the northern
 limn of Saturn,
 so very appropriate,
 Enceladus setting.
 Get a look at the propellers,
 that's on the lower right,
 these objects that are trying
  to open up gaps
  in Saturn's rings.
Not quite big enough to do that.
But you can only see those
with a spacecraft like Cassini.
 And then, in our
 final moments of data,
 we're gonna look on the dark
 side of Saturn at the point
 where Cassini will be
 plunging into the atmosphere,
  looking in the near
  infrared, the ultraviolet,
 trying to get some
 pictures of Cassini's
 final home inside the
 planet Saturn itself.
  Now if we go to
  the next graphic,
this just came down last night.
 This is one of our looks at
 Titan from the goodbye kiss.
The north pole, you can
see the lake region,
 we're looking at the
 north pole of Titan,
  looking through the haze.
The haze has cleared remarkably
  as summer solstice
  has approached.
 And then if we go to
 the final graphic,
 these are the instruments that
 will be on and sending back
data during those final
moments with Cassini.
  And we have eight
  of them, including
the gas ion and neutral
mass spectrometer,
 the magnetospheric
 imaging experiment,
the radio science system will be
 sending back its last
 gravity measurements.
 The radio and plasma
 wave antennas,
  and then the ultraviolet
  and infrared spectrometers
will also be taking data
in that time period.
The magnetometer and the
dust analyzer, as well.
Now in these very final seconds,
we'll be plunging deeper
into the atmosphere
 of Saturn than we've
 ever gone before.
In fact, you can
think of Cassini
 as becoming the
 first Saturn probe.
  And to tell you more about
  sniffing the atmosphere
 of Saturn, I turn it
 over to Hunter Waite,
 and he's the
 principal investigator
  for the ion and neutral
  mass spectrometer, Hunter?
>> Thanks, thanks Linda.
  The ion neutral
  mass spectrometer
  is actually the sensitive
  nose of the spacecraft.
 If we go to the next
 graphic, and zoom in on INMS,
  you can also see it here.
  Gas enters into this front
  portion of the instrument,
  and inside, the molecular
  composition is determined.
  And that's, so we
  have to be pointed
  in the forward direction,
  in the direction motion
  of the spacecraft, as
  Earl's already indicated.
  We've done this
  on many occasions,
 we explored the atmosphere
 of Titan in the same manner,
 we've explored the
 plumes of Enceladus
  with the ion neutral mass
  spectrometer as well,
 and found out about
 the composition there,
  and made some inferences
  about the internal ocean.
And now, we get a
chance to actually look
 at the atmosphere that's
 created in the rings itself,
 and the atmosphere of Saturn.
 So we're sampling both
 in this last stage.
  If you go to the next
  graphic, there's some idea
  of the sampling
  that we're doing.
  So the five dots indicate
  the five previous orbits,
  where we were at
  the lowest point,
  or closest to the
  atmosphere so far.
  Earlier, we were closer
  to the rings, and we were,
  well we were close to the
  rings, there's kinda like
 three bands that
 we actually sample.
 So we've had a chance to look
 more at the ring atmosphere,
 and to look and progressively
 see more and more
  of the atmosphere
  of Saturn itself.
 And you can see that
 line on the graphic,
 it's called
 well-mixed atmosphere.
That's where the
atmosphere becomes kinda
 homogenous in terms
 of composition.
 And we're not gonna
 quite make it there,
 but we'll make it close,
 and in that period of time,
 we'll be able to make
 our cleanest sample
  of the atmosphere
  of Saturn itself.
 So if we go to the final
 graphic, this is a very pretty
 picture of the rings,
 and of the atmosphere.
 You can see kind of a haze,
 which is the atmosphere,
 just above the
 edge of the planet.
 And one of the most important
 scientific things that we're
  trying to figure out is a
  concept called ring rain.
 And this concept was
 introduced in the early 80s
 to actually explain
 some observations
 that we made by both Pioneer
 and Voyager as they flew by.
 And this particular ring
 rain was actually water vapor
 and ice grains from the rings
 falling into the atmosphere,
 and making modifications to
 the atmosphere and ionosphere.
 Well, as Cassini has
 always delivered,
 ring rain is much more
 extensive than that,
 it's much more complicated,
 we're getting great new data,
we're trying to find out
exactly what is coming
  from the rings and what
  is due to the atmosphere.
  And that final plunge
  will allow us to do that.
 The other thing that we'll
 do during that period of time
 as we move closer to
 the mixed atmosphere,
 we'll be able to look at
 some important constituents
 that we know are there, and
 we've been measuring them,
 but we'll get a better idea of
 the hydrogen to helium ratio.
And this is important in
terms of the formation
and evolution of Saturn itself.
  So we have an extensive
  set of science objectives
 that we're going to execute
 on this final plunge,
  and we're looking
  forward to getting
 the data in near real time.
  Thanks, I'll pass
  it back to Earl.
  >> Thanks, Hunter.
  After nearly four decades
  of planning, execution,
 implementation, and execution,
 we are now within 48 hours
  of the end of the
  Cassini mission.
 The work of three space
 agencies, 17 member nations,
hundreds of suppliers,
thousands of engineers,
scientists, and support
staff are about to come
  to a fiery end high above
  the clouds of Saturn.
 The current Cassini team,
 or family as it has become,
comprised of hundreds of
engineers, scientists,
 and support staff, has
 worked for many years
 to bring us to this point,
 and has done a phenomenal job.
  As I emphasized
  at the beginning,
 this is about a
 spacecraft and a team
that has just been
absolutely the best one
  you could ever ask
  for in both cases,
 and it's coming to an
 end, unfortunately.
  We'll be saddened,
  there's no doubt about it,
 at the loss of such
 an incredible machine.
 But I think all of us, we're
 going to have a great sense
 of pride in, a little
 bit corny perhaps,
a mission accomplished.
  We set out to do something
  at Saturn, we did it,
 we did it extremely well, and
 we delivered more and more,
 and we've left the world
 informed, but still wondering.
And that, I couldn't ask for me.
 We gotta go back, we know it.
 We've been gathering all week.
We'll be staffing up the
mission control center tomorrow,
 standing vigil through
 the night as we
prepare to say goodbye,
both from here,
  and a large crowd of our
  team members at Cal Tech,
 as our faithful traveler from
 Earth makes its final goodbye.
 So thank you,
 Cassini, and farewell.
 >> Alright, well
 thank you very much
to our speakers,
just phenomenal.
  We're gonna go ahead and
  open it up for questions,
  first of all to reporters
  here in the auditorium.
Please wait for the mic,
 and give us your
 name and affiliation.
Any questions here?
We'll start down front.
 >> Hi, Irene Klotz
 with Aviation Week.
 The last image that's gonna
 be taken from Titan, is it,
 from Cassini, is it the image
 of where it's going to impact?
  And what is the speed that
  Cassini will be traveling
 relative to Saturn
 in the final descent?
  >> I think the answer is
  yes to the first question.
  >> Yes, the final
  image is the place
  where Cassini will plunge.
 It'll be dark, but that'll be,
we'll take an image there, yes.
 >> And in miles per
 hour, we're going
 about 76,000 miles per hour.
>> We'll actually have
an image with our visual
 and infrared mapping
 spectrometer,
 and that image can sense
 the heat of Saturn as well.
  So we may see some details
 of the atmosphere in
 the near infrared.
 >> Thanks, and the 4:55:06,
 that's Pacific Daylight Time,
  what is the actual
  time on with the
 >> It's about an
 hour and 21 minutes.
 It takes the signal
 an hour and 20,
sorry 23 minutes, to get
from Saturn to Earth.
 But as far as we're
 concerned, what we see
and what we live with is
the signal from Cassini.
  So in that last
  signal comes down,
 that's when things'll
 happen for us.
 >> Okay, another question here
 in the audience, down front.
>> Frederick Castel, journalist.
Two questions, when you
look at the ephemeris
of the different moons,
do we see some kind
 of Pioneer effect on
 the Saturn system?
 And the other question
 is, on the long term,
  for next mission,
  future mission,
 what's the strategy
 about plutonium?
 >> I'll start with
 the Pioneer effect,
but I'm going to let
Jim handle the next one.
No, we have not.
Because we have so many
different perturbations
 in the system from the moons,
 from our own thrusting,
 from the thermal pressures
 of the RTG, even more subtle,
 we're just too busy perturbing
 that trajectory to actually
 be able to see something as
 subtle as the Pioneer effect.
It's just too much going
on in the Saturn system.
 >> Several years ago,
 we were able to work
 with the administration and
 Congress to get the approval
  to restart the production
  of plutonium-238.
 We've already done a number of
 tasks, and in 2019 we'll get
back into the production
on a regular basis.
  We also have approximately
  30 kilograms plus
  of plutonium available to
  us for future missions.
  The next plutonium
  mission that we've planned
  is a Mars mission,
  it's Mars 2020.
 But I think we're
 in really good stead
 for the next several decades.
 Our plan is to keep
 a stock of plutonium
and not let that be a
mission limiting factor.
>> Okay, other questions
here in the audience?
Right here, we'll go
inside and then outside.
>> Hi, thank you for doing this.
Will we be able to tell anything
from the livestream data
 on the way into the
 atmosphere right away?
  And if not, how long
  will it be before we know
 a vague idea of what
 it's telling us?
 >> Well, the data the
 operations team lead
for the INMS tells me
that she will display it
 20 minutes after
 the time we take it.
So we're going to get
it streamed to us from,
  down link to JPL,
  be transferred to
  Southwest Research
  Institute, and then we'll
 have it on a computer
 down at Cal Tech.
  >> Understanding it might
  take a little bit longer.
>> It could, but
that's our plan.
  >> Lee Hokes, Wall
  Street Journal.
You mentioned that Cassini has,
among its many accomplishments,
 enabled a series of
 missions to come.
I wonder if you'd expand
on that for a moment.
>> Well, as I mentioned
earlier, the concept
of the gravity assists
that we were able to get
 with Titan allowed
 our instruments to get
 a global view of
 that beautiful moon.
  That's really spectacular,
  because that means,
 when we take it to the
 Jupiter environment
 where the radiation
 belt is really harsh
  all through the area where
  the Galilean moons are,
 we want to be able to
 get in and get out.
  And so then, if
  we orbit Jupiter,
 we can do multiple
 flybys of the moons,
  and the one we're
  planning to do is Europa,
and from those multiple flybys,
 actually create a global view
  of that moon as if
  we were in orbit.
 And so Cassini has really
 pioneered that whole concept,
 and that will be our
 first next attempt
 in using that to great effect.
>> Alright, actually we're
gonna go to the phones now for a
 couple of questions, but we'll
 come back to the auditorium.
  I think we have Marsha
  Dunn, from the AP, Marsha?
>> Marsha: Yes, can you hear me?
>> Sure.
  >> Marsha: Yes, for either
  Jim or Earl or both,
there seems to be a, the
outpouring of love for
 Cassini seems to be growing
 in these last hours and days.
 I'm wondering if you
 had a chance to hear
 the Cassini opera from
 the Planetary Society.
 What did you think about that?
And how do you feel
hearing from the public,
  who's so sorry to
  see Cassini go?
  >> I have heard
  the opera tribute
from the Planetary
Society, and I loved it.
 It's very heartwarming to us.
 As a matter of fact,
 we've recently posted
a letter from a six year
old boy who invited us
to his Cassini party
in Florida on the 15th.
 Feeling the love, if
 I can be so corny,
is just very heartening.
 Because it's part of
 what we try to do,
 is to extend everybody
 out to Saturn.
  It's not science for, you
  know, in the ivory tower,
 it's for humanity, and it's
 for everybody to get on,
 ride, come with us,
 is just phenomenal.
 So I'm very heartened by that.
  I wish, well never
  mind, I don't even
  want to go there,
  one more orbit.
 So it is where it is,
 we've gotten this,
 and again I couldn't
 be more heartened
 by the outpouring we've had.
>> Absolutely, you know
the Cassini family,
  as Earl mentioned,
  is those people
 that have worked many years,
 decades, to get to this point,
 and we are absolutely
 delighted to have
 an extended family to
 share the experiences
 that have really enabled
 enormous science to be done.
  In fact, you know,
  really the science
 is not done until we share it.
This is really just the
beginning of a number
 of discoveries that
 the data will reveal,
 as we try to figure out
 what the physical phenomena
 are that are being described
 in those observations.
Those will live on for
many decades afterwards,
and already they're
beckoning us to go back.
  You know, between Voyager
  and Cassini was 30 years.
  And I believe that will be
  much shorter the
  next time around.
 >> Okay, we're
 gonna take a couple
of questions from social media.
We've got Jason Townsend
from NASA headquarters.
Jason, what's going on?
>> Indeed, there's a lot
of interest online here.
 Our first question here
 comes from Salma on Twitter,
who asks, "Will Cassini
completely evaporate
 "in the atmosphere
 of Saturn, or will it
"crash into the
surface of the planet?"
 >> It will be
 completely vaporized,
like many meteorites hit Earth.
If there's a surface at Saturn,
  it's at a hellishly hot
  pressure and temperature,
  and anything from Cassini
  will vaporize long before.
 >> Wonderful, lots of
 other questions here,
  asking about images here.
  So Evelyn on Twitter asks,
  "Will Cassini be able
  "to take a close-up image
  of Saturn as it plunges?"
  >> No, we don't
  have the data rate
to support sending back
images in real time.
  So the instruments that I
  showed you did not include
 the cameras for those final
 few moments for the plunge.
 So we'll be getting
 those images back,
 the final image will be of the
 place where Cassini will go,
but it'll be from
about 14 hours earlier.
 >> Alright, next
 question here comes
  from Twitter user
  Bilemon, who asks,
"Would it be possible to
use a low gain antenna
  "at a very low bit
  rate to monitor
  "a heartbeat from Cassini
  just a little longer?"
 [audience laughing]
 >> I'll repeat that
 for the audience.
The spacecraft engineer
is in the second row,
  and the answer is
  a resounding no.
 If we had done
 that, we would have
 given up some science data.
 And really, for a few seconds'
 more to get those last
 packets of spectrometer data
 was much more important.
 >> Okay, we're gonna
 go back to the phones.
 I think we've got Leo Enwright
 from Irish Television.
 Leo, can you hear us?
>> Leo: Yeah, thanks very much.
In fact, my question
isn't entirely unrelated
 to the last one,
 because I'm wondering,
there has been some speculation
that a good telescope
on Earth, and I presume a league
 with one would be able
 to see this happen.
  Is that the case?
 >> Well, we're going to try
 and look with telescopes
 from the Earth,
 we're just not sure.
 This flash will be occurring
 on the day side of Saturn,
 and we've done some
 calculations about brightness.
 We think it's not very likely,
  but we're sure
  gonna look anyway.
>> Okay, one more
question on the phones.
 I'm gonna, I think
 we've got Dave Mosher
 from Business Insider.
 >> Dave: Can you guys hear me?
 >> Yeah, we sure can.
  >> Dave: Alright great, I
  actually had a follow up
  to the previous question,
  and one more new one.
 Do we know which observatories
 in the Southern
 Hemisphere or wherever
  on Earth are gonna be
  trying to see this thing?
 That's my first question, for
 whoever can best answer it.
And then, sorta related to that,
 but about the data
 that's coming back.
I just checked the
forecast for Australia,
and it does look like
there's a little clouds
and rain in the forecast
for the next few days.
 I'm curious if you guys are
 worried about that at all,
or if you're confident that
you're gonna get this data back.
  >> Well the
  observatories we're gonna
 be using are mostly
 in Australia.
 Australia, of course, Canberra
 has a great view of Cassini.
  Also, we're gonna be using
  some smaller telescopes,
 we're gonna try and
 look from India,
 from China, possibly
 from Taiwan.
We're really encouraging
our amateurs, too,
  to get out there and look
  with their telescopes.
  We don't have any
  giant telescopes
 in that region where
 we can see Cassini.
 So we're just saying
 hey everybody,
  go out and take a look,
  and we'll see what we see.
 >> We have every confidence
  that we're gonna
  get the data back.
  It's gonna take a
  pretty hellacious
rainstorm to take out the data.
  We've got our data rates
  down at a very low level.
 If we can maintain
 the 70 meter antenna,
we have a lot of margin.
If we do lose the 70 meter dish,
 then our margin is
 a little bit lower,
 but we're still, I
 believe, comfortable.
 Worst case, we still have
 the New Norcia complex over
  on the other side
  of the continent
that is not really
prepared to decommutate
  our telemetry immediately,
  but all the data
 will be on the ground,
 and we can build
 the right system to
 take it back apart.
 So we'll get the data, it's
 just a question of how soon.
 >> Okay, thanks guys.
  We're gonna go
  back to social for
a couple more questions, Jason?
 >> Alright, Twitter
 user Jason asks,
"When will a spacecraft
visit Saturn again?"
 >> So that's for me.
 [audience laughing]
  I sorta begged
  for that question.
 The observations by
 Cassini have been
 so remarkable for Enceladus
 and Titan that indeed,
 last year we announced the
 inclusion of those two objects
 in our focused science
 program called New Frontiers.
 Those proposals are in, and
 currently under evaluation,
  and they do indeed
  include proposals
 to go back to Titan
 and Enceladus.
 So we'll look through
 this competition and
 see what happens.
 >> Okay, you've got another
 question there, Jason?
>> Sure, this one comes
from Pietro, who asks,
 "If you could go back and
 change something in Cassini,
"an instrument or skill,
what would it be?"
>> Hunter, you wanna take that?
 [audience laughing]
  Okay, if I could
  go back and change
 some instruments on
 Cassini, I think I'd select
flying some more capable
mass spectrometers.
You know, if we had
known about the geysers
 on Enceladus ahead of time,
 that would have perhaps
  guided us, something to go
  back and perhaps look for,
  amino acids, fatty acids,
  possible evidence of life.
So if I could change one thing,
  it'd be to carry
  some spectrometers
that could do some work
for looking for life.
 >> I wouldn't have
 touched a damn thing.
 [audience laughing]
 You know, we went in with
 everything we possibly could.
 We had the Swiss Army knife,
 and now we know so much more,
now we can fine tune it.
 But this spacecraft, like I
 said, I couldn't have asked
 for anything, I couldn't
 have asked for anything more.
>> Alright, we're gonna come
back to the room, I think Emily.
 >> Hi, I'm Emily Loctawalla
 from the Planetary Society,
  with a couple of
  science questions.
 Hunter, I'm wondering
 if you could tell us
 a little bit more
 about that ring rain
 concept that you're
 trying to test,
  and what you're
  learning about it.
 And Linda, I know that
 there's a science team
 meeting going on this week,
 I'm wondering if you can
share any of the early exciting
  results from the
  proximal mission.
>> Well, the ring rain
concept, as I mentioned,
 was first introduced
 in the 1980s,
and it was a concept of
material from the rings,
  mainly water vapor
  and ice grains,
 descending into the atmosphere
 and causing changes
 in the atmosphere.
  And we have measured that,
  and we do see the water.
 But we see other
 constituents as well.
  So it's much more complex
  than we imagined before.
 And we'll be, you
 know, we're trying to,
 we're traveling at 31
 kilometers per second,
  and gas is coming into
  our instrument very fast,
  and with a lot of energy.
And so there's potential
to break it apart.
So we're working very
carefully to understand
 that before we go out and tell
 the public what we're seeing.
 >> Yes Emily, we're
 having one of our
project science group meetings,
 in fact it's the 73rd
 meeting we are having
 of this group since
 we first got started.
 And there have just been
 some tremendous presentations
about the grand finale science,
some of it only days old.
  And what I can tell you is
  that many of our models,
  we're finding out,
  are too simple,
  or just out and out wrong.
And so the scientists
are carefully looking at
  and calibrating their
  data, and comparing notes,
and discussing it, and
there's nothing to make
a scientist happier than finding
out hey, my model is wrong,
  I have to sorta start
  over and work it through.
So we have a lot of very
very happy scientists.
  We're meeting down at Cal
  Tech, and so hopefully
in the coming months
we'll have some answers.
 But in particular, the
 interior of the planet
  is very different
  than we expected,
its gravity field is not at all
what we expected
from our models.
 Also, the magnetic
 field, we're finding
that the rotation axis of Saturn
 and the magnetic field axis
 are almost perfectly aligned.
 Everything we think
 we know tells us
 that if you don't have
 at least a small tilt,
  you can't maintain
  those currents
 that sustain a magnetic field.
 So we have some more thinking
 and some more work to do.
>> Okay, questions here?
 I think there's one
 in the third row.
 >> Hi, Robert Perlman
 Collect Space.
Not that there'd be any
way of verifying this,
but has there been any modeling
or any even best guesses
 of how Cassini's
 going to come apart?
 And what might be the
 last piece to survive?
>> Yes, there's been
very thorough analysis,
a piece by piece deconstruction,
if you will, of Cassini.
 And we believe that
 the final components
  to be destroyed will be
  the aero shell components
 that are wrapped
 around, Cassini has
  these radioactive
  power supplies.
 And each little slug of
 plutonium is wrapped around,
is wrapped with iridium,
and then they're
put inside an aero
shell, in order to avoid
 any possible release during
 a launch accident or reentry.
And the iridium has a
very high melting point,
and the material around
them is even higher.
So those will be
the last pieces.
 Other than that, taking those,
 the parts of the spacecraft
 that will be shielded away
 will last a little bit longer.
 But, you know, a lot of
 the spacecraft is aluminum,
it's going to melt very quickly.
 A lot of it's carbon fiber and
 Mylar and things like that,
  and they're gonna
  go very quickly.
 >> Okay, how about some
 more social media questions?
 >> Sure, here's
 two good ones here.
The first one comes from
user Anshell, who asks
 "What is the last bit of data
 "that we will receive
 from Cassini?"
 >> The very last bit
 of data will include
the ion and neutral
mass spectrometer data,
  but they come down in
  packets, so we don't know
 if the INMS packet
 will be the last one,
 or a magnetometer
 packet, or whatever.
 But they'll be coming
 back as quickly
  as we can send them back.
 So we'll find out
 with that final bit.
>> Well actually, and we'll
see the radio signal dissipate.
 So our very last
 bit of science data,
  if we don't get a
  complete packet,
  could very well be
  the radio science.
>> Alright, lots of folks are
asking about what happens next.
 So Lisa here says, "What
 happens to the team working
"with Cassini Saturn
after the mission's end?
  "Are they just reassigned
  to new projects
  "or missions at NASA, or
  are they off job hunting?"
 [audience laughing]
 >> Well most of the engineers,
 there is an active planetary
 program here at JPL,
  and a lot of our engineers
  have already kind
 of half semi migrated over
 to these other opportunities.
 We're not having big layoffs
 or anything like that.
  There's lots of
  work for everyone.
 Some of us have some
 paperwork to do.
 [audience laughing]
And not just me.
 [audience laughing]
 So there's a lot of
 documentation, and of course,
 the science data, to the
 extent that it can be funded
by research grants will
continue for decades.
 So those opportunities
 for both our current
 and young scientists
 will be at least
 for another couple
 of decades, gotta be.
  >> Right, and the Cassini
  scientists are funded
 for the next year,
 basically to make sure
they carefully calibrate
and understand all
 of this grand finale
 data, to put it
 in the planetary data system.
 And from there,
 it'll be accessible
to future scientists, you know.
 Who knows how many PhD
 theses will be written
 in the coming decades
 with Cassini data?
 >> Indeed, you know, Cassini's
 really given everyone
 on the job training on
 operating spacecraft
and keeping our instruments
healthy and analyzing the data,
  and so we have a cadre of
  highly capable scientists,
  engineers, that we'll keep
  busy for many decades.
 You know, planetary
 program is doing well.
  We have tremendous support
  by the administration
 and Congress, we have missions
 that we're planning now.
 And we really have a
 very bright future.
  >> Alright, we've got time
  for another quick followup
 from Leo Enwright from
 Irish Television, Leo?
>> Leo: I've a question for
Earl and Linda about Enceladus,
 which is a tiny
 moon not much bigger
  than Ireland, I
  have to point out.
  And it's just astonishing
  that it's so active.
 Earl, do you know,
 do you have any idea
  of the chances
  that Cassini would
 have actually collided
 with this tiny moon?
 And for Linda, really,
 if you wouldn't mind
 just telling us on
 the scale of things
that you've seen in your
extraordinary career,
  I mean where does
  Enceladus fit in
 as the amazing
 surprise, as it were?
>> Well, we didn't do the math,
actually I take that back,
  we did do the math several
  times for Enceladus,
and as long as we could control
the spacecraft, no problems.
 But we had a big challenge
 in an uncontrolled spacecraft
 not hitting within a chance
 of one in a million Enceladus
 in the next 50 years.
 The issues are, of course,
 that once it's uncontrolled,
you've got Titan out
there pushing it around,
 it could push it just about,
 as you saw in those graphics,
 just about anywhere
 you'd want it to go,
 and Enceladus was a
 good sized target.
 So we didn't do the
 actual math for any
  of those others to
  convince ourselves
that an uncontrolled spacecraft
either had to be well
 outside of Saturn, I mean
 way way outside, or inside.
 >> Well let me answer
 the second part.
  For Enceladus, I would
  say Enceladus' discoveries
  made by Cassini
  are certainly one
 of the most astonishing set
  of discoveries for
  planetary science.
To find that there's
an ocean world so tiny,
  with the possibility of
  life, so far from the Sun,
10 times further from
the Sun than the Earth,
 has opened up our paradigm of
 where you might look for life,
both within our own solar system
 and in the exoplanet
 systems beyond.
  So these ocean
  worlds, Enceladus,
  Titan also has a liquid
  ocean, has really changed
our thinking about
where to look for life.
 >> Okay, well actually
 I think that's about
all the time we have for
today for our briefing.
 Thanks again to our
 speakers, and to all
  of you for your questions.
 Here's how you can
 watch Cassini coverage
 that NASA television
 has to offer
 over the next couple of days.
 Tomorrow, September 14th,
 we'll have a speaker program
as part of our NASA
social event on Cassini,
from one to two PM Pacific time,
that's four to five PM Eastern.
 Then on Friday, we'll
 have live commentary
 from Mission Control from four
 to five-thirty AM Pacific,
 that's seven to
 eight-thirty Eastern.
 And following loss
 of signal, we'll have
 a post-mission
 briefing right here,
 starting at
 six-thirty AM Pacific.
  You can watch live
  at NASA.gov/live.
  More info about Cassini
  is available at NASA.gov,
and you'll find a
detailed online toolkit
 about Cassini's grand finale
 and end of mission on the
mission website at
saturn.jpl.NASA.gov/grandfinale.
 And I think we've got
 a couple more minutes
 before the end of the hour,
 we'll end now with a replay
of some of the images and video
we've shared during
our presentation today.
  Thank you so much
  for joining us.
 [audience applauding]
