1
00:00:01,701 --> 00:00:04,971
- [Narrator] NASA's Jet
Propulsion Laboratory presents

2
00:00:04,971 --> 00:00:07,740
the Von Karman Lecture,
a series of talks

3
00:00:07,740 --> 00:00:11,678
by scientists and engineers
who are exploring our planet,

4
00:00:11,678 --> 00:00:15,048
our solar system, and
all that lies beyond.

5
00:00:15,048 --> 00:00:17,550
(light music)

6
00:00:27,627 --> 00:00:29,796
- Good evening, everybody.

7
00:00:30,796 --> 00:00:32,565
May the fourth be with you.

8
00:00:32,565 --> 00:00:34,601
(audience laughing)

9
00:00:34,601 --> 00:00:38,004
(applauding and whistling)

10
00:00:38,004 --> 00:00:38,838
Wow.

11
00:00:40,406 --> 00:00:42,909
I got a live long and prosper
sign right there in the back.

12
00:00:42,909 --> 00:00:44,744
Thank you for joining
us here at JPL,

13
00:00:44,744 --> 00:00:46,546
and thank you for
joining us at home,

14
00:00:46,546 --> 00:00:49,515
for the Von Karman lecture
series, now let's get to it.

15
00:00:49,515 --> 00:00:51,484
The Cassini mission
has revolutionized

16
00:00:51,484 --> 00:00:53,920
our understanding of Saturn,
from its complex rings

17
00:00:53,920 --> 00:00:57,823
or magnetic environment
to its menagerie of moons.

18
00:00:57,823 --> 00:01:00,593
Icy jets shoot from the
tiny moon Enceladus,

19
00:01:00,593 --> 00:01:02,661
liquid ethane and
methane dominate

20
00:01:02,661 --> 00:01:05,364
Titan's hydrocarbon
lakes and seas,

21
00:01:05,364 --> 00:01:08,034
and Hyperion has
a static charge.

22
00:01:08,034 --> 00:01:09,902
We look forward to the
puzzles Cassini will solve

23
00:01:09,902 --> 00:01:13,105
as it goes out in
a blaze of glory.

24
00:01:13,105 --> 00:01:14,340
Tonight our guests will reveal

25
00:01:14,340 --> 00:01:15,741
some of the recent
science discoveries

26
00:01:15,741 --> 00:01:18,344
and share the excitement
and challenges

27
00:01:18,344 --> 00:01:20,646
expected during
Cassini's final orbits.

28
00:01:20,646 --> 00:01:23,449
Now Dr. Earl Maize is the
Cassini program manager,

29
00:01:23,449 --> 00:01:26,585
a veteran of 32 years at JPL.

30
00:01:26,585 --> 00:01:28,387
He began his career
working on the navigation

31
00:01:28,387 --> 00:01:31,524
and engineering teams of the
Galileo mission to Jupiter.

32
00:01:31,524 --> 00:01:35,194
After Galileo's final Earth
flyby, he transferred to Cassini

33
00:01:35,194 --> 00:01:36,962
as a spacecraft
operations manager

34
00:01:36,962 --> 00:01:39,298
and then deputy program manager.

35
00:01:39,298 --> 00:01:40,866
He left the project
for eight years

36
00:01:40,866 --> 00:01:44,537
to hold management positions
in guidance, navigation,

37
00:01:44,537 --> 00:01:47,307
and control in avionics,
then returned to Cassini

38
00:01:47,307 --> 00:01:50,877
as program manager
in January of 2013.

39
00:01:50,877 --> 00:01:54,480
Dr. Linda Spilker is the
Cassini project scientist,

40
00:01:54,480 --> 00:01:56,382
and co-investigator
on the Cassini

41
00:01:56,382 --> 00:01:59,118
composite infrared
spectrometer team,

42
00:01:59,118 --> 00:02:02,555
and has worked on
Cassini since 1988.

43
00:02:02,555 --> 00:02:06,359
Since joining JPL
almost 40 years ago,

44
00:02:06,359 --> 00:02:09,929
her first and only job
out of college by the way,

45
00:02:09,929 --> 00:02:11,431
she has worked on
the Voyager project,

46
00:02:11,431 --> 00:02:14,033
the Cassini project, and
conducted independent research

47
00:02:14,033 --> 00:02:16,702
on the origin and evolution
of planetary ring systems

48
00:02:16,702 --> 00:02:19,038
while also supporting
proposals and concept studies

49
00:02:19,038 --> 00:02:22,007
for new missions to
the outer planets.

50
00:02:22,007 --> 00:02:24,176
She enjoys yoga and hiking,

51
00:02:24,176 --> 00:02:25,944
especially through her
favorite park, Yosemite,

52
00:02:25,944 --> 00:02:28,514
and is married with
three daughters and
five grandchildren.

53
00:02:28,514 --> 00:02:29,582
(murmuring)

54
00:02:29,582 --> 00:02:30,416
Right?

55
00:02:30,416 --> 00:02:31,884
(audience laughing)

56
00:02:31,884 --> 00:02:35,120
Ladies and gentlemen, Going
Out in a Blaze of Glory.

57
00:02:35,120 --> 00:02:37,557
(applauding)

58
00:02:53,539 --> 00:02:56,809
(slow, dramatic music)

59
00:02:59,244 --> 00:03:01,614
- [Narrator] A lone explorer,

60
00:03:02,781 --> 00:03:05,585
on a mission to reveal
the grandeur of Saturn,

61
00:03:05,585 --> 00:03:07,253
its rings and moons.

62
00:03:12,758 --> 00:03:16,896
After 20 years in space,
NASA's Cassini spacecraft

63
00:03:16,896 --> 00:03:18,831
is running out of fuel.

64
00:03:20,433 --> 00:03:23,469
And so, to protect
moons of Saturn

65
00:03:23,469 --> 00:03:27,073
that could have conditions
suitable for life,

66
00:03:27,073 --> 00:03:29,008
a spectacular end
has been planned

67
00:03:29,008 --> 00:03:32,345
for this long-lived
traveler from Earth.

68
00:03:35,047 --> 00:03:38,551
- [Announcer] Five,
four, three, two, one.

69
00:03:40,619 --> 00:03:43,222
And liftoff of the
Cassini spacecraft

70
00:03:43,222 --> 00:03:45,892
on its million mile
trek to Saturn.

71
00:03:45,892 --> 00:03:47,760
We have cleared the tower.

72
00:03:47,760 --> 00:03:49,596
Pitch program is in...

73
00:03:51,397 --> 00:03:55,134
- [Narrator] In 2004,
following a seven year journey

74
00:03:55,134 --> 00:03:59,305
through the solar system,
Cassini arrived at Saturn.

75
00:04:00,706 --> 00:04:03,876
- [Man] Light up the rockets.

76
00:04:03,876 --> 00:04:06,345
- [Narrator] The spacecraft
carried a passenger,

77
00:04:06,345 --> 00:04:10,817
the European Huygens probe,
the first human made object

78
00:04:10,817 --> 00:04:14,988
to land on a world in the
distant outer solar system.

79
00:04:17,923 --> 00:04:22,161
For over a decade, Cassini has
shared the wonders of Saturn

80
00:04:22,161 --> 00:04:26,332
and its family of icy moons,
taking us to astounding worlds

81
00:04:27,499 --> 00:04:31,270
where methane rivers
run to a methane sea,

82
00:04:31,270 --> 00:04:35,641
where jets of ice and gas are
blasting material into space

83
00:04:35,641 --> 00:04:37,944
from a liquid water ocean

84
00:04:37,944 --> 00:04:41,547
that might harbor the
ingredients for life.

85
00:04:43,249 --> 00:04:47,753
And Saturn, a giant world
rule by raging storms

86
00:04:47,753 --> 00:04:50,590
and delicate
harmonies of gravity.

87
00:04:53,425 --> 00:04:57,163
Now, Cassini has one
last, daring assignment.

88
00:05:06,205 --> 00:05:10,209
Cassini's grand finale
is a brand new adventure.

89
00:05:12,478 --> 00:05:16,649
22 dives through the space
between Saturn and its rings.

90
00:05:20,886 --> 00:05:24,657
As it repeatedly braves
this unexplored region,

91
00:05:24,657 --> 00:05:28,594
Cassini seeks new insights
about the origins of the rings

92
00:05:28,594 --> 00:05:31,464
and the nature of the
planet's interior,

93
00:05:31,464 --> 00:05:34,300
closer to Saturn
than ever before.

94
00:05:40,939 --> 00:05:45,111
On the final orbit, Cassini
will plunge into Saturn,

95
00:05:46,345 --> 00:05:49,915
fighting to keep its
antenna pointed at Earth

96
00:05:49,915 --> 00:05:52,352
as it transmits its farewell.

97
00:05:54,487 --> 00:05:57,890
In the skies of Saturn,
the journey ends.

98
00:06:01,560 --> 00:06:05,331
As Cassini becomes part
of the planet itself.

99
00:06:28,921 --> 00:06:31,324
(applauding)

100
00:06:48,975 --> 00:06:52,879
- Cassini is on a collision
course with Saturn.

101
00:06:54,513 --> 00:06:58,517
In the next four months,
every week we'll be coming

102
00:06:58,517 --> 00:07:01,186
a little bit closer, and
a little further away,

103
00:07:01,186 --> 00:07:03,823
until finally on September 15th,

104
00:07:03,823 --> 00:07:06,958
very early in the morning
here, about three AM,

105
00:07:06,958 --> 00:07:08,628
it will enter the atmosphere,

106
00:07:08,628 --> 00:07:11,697
going at about 75,000
miles per hour.

107
00:07:13,032 --> 00:07:16,068
At that speed, that
spacecraft won't last long.

108
00:07:16,068 --> 00:07:19,872
It will quickly lose
control, begin to melt,

109
00:07:19,872 --> 00:07:22,575
and eventually vaporize
into the very planet

110
00:07:22,575 --> 00:07:26,579
that it went to explore
some 20 years ago today,

111
00:07:27,880 --> 00:07:28,981
20 years ago.

112
00:07:30,416 --> 00:07:35,220
So, you might wonder, you
know, that such a hot idea?

113
00:07:35,220 --> 00:07:37,023
You've got a perfect spacecraft,

114
00:07:37,023 --> 00:07:39,992
you've been rewriting history
books and science texts

115
00:07:39,992 --> 00:07:42,795
ever since you got there,
and in fact even beforehand.

116
00:07:42,795 --> 00:07:46,765
Well, for the next
maybe 45 minutes or so,

117
00:07:46,765 --> 00:07:50,035
Linda and I are going to
try to at least explain why

118
00:07:50,035 --> 00:07:54,207
we not only think this is a
good idea, but a great idea.

119
00:07:58,010 --> 00:08:01,480
So quickly to the pad and
beyond, as the movie showed you,

120
00:08:01,480 --> 00:08:04,517
we launched in 1997,
absolutely flawless,

121
00:08:04,517 --> 00:08:08,020
a beautiful launch from
the cape on a Titan 4B,

122
00:08:08,020 --> 00:08:11,657
and six and a half years later,
after a very circuitous tour

123
00:08:11,657 --> 00:08:16,094
of the, well, middle
and outer solar system,

124
00:08:16,094 --> 00:08:19,431
we finally arrived at
Saturn on July 30th,

125
00:08:19,431 --> 00:08:21,901
June 30th, sorry, 2004,

126
00:08:21,901 --> 00:08:26,005
and had an absolutely
flawless orbit insertion.

127
00:08:26,005 --> 00:08:30,409
For the next 13 years, we
were doing pretty much this.

128
00:08:30,409 --> 00:08:31,878
(audience laughing)

129
00:08:31,878 --> 00:08:34,447
Now don't be alarmed,
this is something we call

130
00:08:34,447 --> 00:08:38,184
the ball of yarn, this
is the entire mission,

131
00:08:38,184 --> 00:08:42,788
all 293 orbits, some of which
we haven't finished yet,

132
00:08:42,788 --> 00:08:45,925
beginning with SOI
and continuing on.

133
00:08:45,925 --> 00:08:50,129
What happens here is that
for the last 12 years,

134
00:08:50,129 --> 00:08:53,299
we've been using
Cassini's rocket fuel

135
00:08:54,800 --> 00:08:58,471
and Saturn's largest
satellite, moon, Titan,

136
00:08:59,671 --> 00:09:02,040
which is a mission
designer's dream,

137
00:09:02,040 --> 00:09:05,110
to move us all through
this Saturn system.

138
00:09:05,110 --> 00:09:06,878
So we've been able to...

139
00:09:06,878 --> 00:09:08,614
Probably can't see it in here,

140
00:09:08,614 --> 00:09:11,017
but right in the middle of
all this there is Saturn.

141
00:09:11,017 --> 00:09:12,751
So we've been able
to actually go

142
00:09:12,751 --> 00:09:14,686
to these very highly
inclined orbits,

143
00:09:14,686 --> 00:09:16,088
so we come down over the tops

144
00:09:16,088 --> 00:09:17,923
and look at the rings
and look at the poles

145
00:09:17,923 --> 00:09:20,492
at these very long,
looping orbits

146
00:09:20,492 --> 00:09:22,494
out to examine the magnetosphere

147
00:09:22,494 --> 00:09:25,898
way outside of the
influence of Saturn itself,

148
00:09:25,898 --> 00:09:28,501
and then of course
these in tight orbits

149
00:09:28,501 --> 00:09:31,870
to investigate Enceladus
and the icy moons.

150
00:09:31,870 --> 00:09:35,974
So for the last 12 years,
up until last November,

151
00:09:35,974 --> 00:09:37,910
this is pretty much
what we've been up to.

152
00:09:37,910 --> 00:09:42,414
A fascinating tour, and an
amazing set of discoveries.

153
00:09:42,414 --> 00:09:45,150
We'll get to a little
bit of those later,

154
00:09:45,150 --> 00:09:48,287
and I think Linda will show
you even more as we move on.

155
00:09:48,287 --> 00:09:49,121
But,

156
00:09:50,556 --> 00:09:53,326
I want to jump
back to the reason

157
00:09:54,526 --> 00:09:56,328
that I started with
this whole premise,

158
00:09:56,328 --> 00:09:58,196
and why are you doing this?

159
00:09:58,196 --> 00:10:01,767
Well, Saturn's got
some ocean worlds.

160
00:10:01,767 --> 00:10:05,537
These are pictures, essentially
Voyager class pictures

161
00:10:05,537 --> 00:10:08,207
of the moon Enceladus and Titan,

162
00:10:09,375 --> 00:10:11,243
both mysterious
in their own ways,

163
00:10:11,243 --> 00:10:15,147
Titan enshrouded by
this veil of orange haze

164
00:10:15,147 --> 00:10:16,748
that we couldn't penetrate,

165
00:10:16,748 --> 00:10:19,118
and Enceladus
exceptionally bright,

166
00:10:19,118 --> 00:10:21,587
but quite small,
300 miles across,

167
00:10:21,587 --> 00:10:23,688
so essentially a
bright snowball.

168
00:10:23,688 --> 00:10:25,391
Well, by the time we were done,

169
00:10:25,391 --> 00:10:27,526
or Cassini was
done, I should say,

170
00:10:27,526 --> 00:10:30,729
I'll take some credit, but
not all of it by any stretch.

171
00:10:30,729 --> 00:10:32,464
(audience laughing)

172
00:10:32,464 --> 00:10:35,668
Enceladus had turned out to
not only be differentiated,

173
00:10:35,668 --> 00:10:39,839
but to have plumes, a warm
global saltwater ocean,

174
00:10:42,007 --> 00:10:43,776
and hydrothermal activity.

175
00:10:43,776 --> 00:10:45,644
And if you notice that we
just had a press release

176
00:10:45,644 --> 00:10:48,180
not too long ago that
there is atomic hydrogen

177
00:10:48,180 --> 00:10:49,681
out in these plumes.

178
00:10:49,681 --> 00:10:53,752
All the ingredients for life,
on this little tiny moon.

179
00:10:53,752 --> 00:10:57,055
Absolutely
Earth-shaking discovery.

180
00:10:57,055 --> 00:10:58,624
Sorry, that's a bad pun.

181
00:10:58,624 --> 00:10:59,959
(audience laughing)

182
00:10:59,959 --> 00:11:02,161
But really, just
everybody was floored.

183
00:11:02,161 --> 00:11:04,730
We had no idea this
was gonna happen.

184
00:11:04,730 --> 00:11:06,665
And then on top of that,

185
00:11:06,665 --> 00:11:10,836
Titan was revealed to have
lakes, a hydrologic cycle,

186
00:11:12,271 --> 00:11:14,172
of course it's not water,
it's methane and ethane,

187
00:11:14,172 --> 00:11:16,408
rain, clouds, rivers, estuaries,

188
00:11:16,408 --> 00:11:19,245
and it too has a
subsurface ocean.

189
00:11:20,645 --> 00:11:24,015
So we've got two places
that really just need to be

190
00:11:24,015 --> 00:11:27,152
kept as pristine
as we possibly can.

191
00:11:27,152 --> 00:11:30,589
And I gotta say that there's
something about Cassini

192
00:11:30,589 --> 00:11:32,758
that you know, while it
was a perfect spacecraft,

193
00:11:32,758 --> 00:11:35,394
it's not all that perfect.

194
00:11:35,394 --> 00:11:37,462
We're outta gas.

195
00:11:37,462 --> 00:11:39,198
There's very little fuel left.

196
00:11:39,198 --> 00:11:41,967
And what happens, even though
we were able to use Titan,

197
00:11:41,967 --> 00:11:44,903
as I showed in the other
slide, quite effectively

198
00:11:44,903 --> 00:11:46,838
to move around in
the Saturn system,

199
00:11:46,838 --> 00:11:49,541
we still need the propellant
to keep the spacecraft,

200
00:11:49,541 --> 00:11:52,144
you know, oriented and on track.

201
00:11:52,144 --> 00:11:53,979
So without propellant,
eventually it would be

202
00:11:53,979 --> 00:11:55,480
running out of control,

203
00:11:55,480 --> 00:11:58,884
and as we've come to discover
with Titan and Enceladus,

204
00:11:58,884 --> 00:12:03,555
an uncontrolled spacecraft
encountering these moons

205
00:12:03,555 --> 00:12:06,725
could eventually result
in an inadvertent impact,

206
00:12:06,725 --> 00:12:09,661
which would cause us all
sorts of embarrassment

207
00:12:09,661 --> 00:12:13,232
and some concern for
future exploration.

208
00:12:13,232 --> 00:12:14,066
So.

209
00:12:15,500 --> 00:12:19,037
We had to do something about
it, and what we decided to do

210
00:12:19,037 --> 00:12:20,972
was what we've called
the grand finale.

211
00:12:20,972 --> 00:12:24,309
So let me back up a
little bit and talk about,

212
00:12:24,309 --> 00:12:26,845
these are the final six
years of the mission,

213
00:12:26,845 --> 00:12:29,548
without the F-ring orbits.

214
00:12:29,548 --> 00:12:33,719
When we were discussing
various options for the...

215
00:12:36,088 --> 00:12:37,756
The eventual...

216
00:12:37,756 --> 00:12:40,326
There's no euphemistic
way to put this.

217
00:12:40,326 --> 00:12:42,528
The eventual
disposal of Cassini,

218
00:12:42,528 --> 00:12:44,930
a lot of different
options became available.

219
00:12:44,930 --> 00:12:47,966
But the one that just
absolutely was most compelling

220
00:12:47,966 --> 00:12:51,302
was to actually stay
inside the Saturn system,

221
00:12:51,302 --> 00:12:52,971
investigate as much as we can,

222
00:12:52,971 --> 00:12:54,740
use all of the gas
we possibly could,

223
00:12:54,740 --> 00:12:56,241
and then put it into Saturn.

224
00:12:56,241 --> 00:12:58,744
So this is what
we've settled on,

225
00:12:58,744 --> 00:13:01,046
and I think I'm gonna try
to continue to lead you

226
00:13:01,046 --> 00:13:03,882
towards the fact that this is
an absolutely phenomenal end

227
00:13:03,882 --> 00:13:05,351
to a great mission.

228
00:13:05,351 --> 00:13:08,520
So this again is the ball
of yarn, if you will,

229
00:13:08,520 --> 00:13:09,688
for the last six years.

230
00:13:09,688 --> 00:13:11,557
This began back in 2010.

231
00:13:11,557 --> 00:13:12,857
And what we've been doing,

232
00:13:12,857 --> 00:13:14,626
as you can see it
even better here,

233
00:13:14,626 --> 00:13:17,029
every one of these little
nodes, these little knots,

234
00:13:17,029 --> 00:13:18,730
is a crossing of titan,

235
00:13:18,730 --> 00:13:21,000
and Titan has been moving
us all through the system

236
00:13:21,000 --> 00:13:22,968
as it did for the
previous six years,

237
00:13:22,968 --> 00:13:26,539
and what happens next
though is really fun.

238
00:13:27,506 --> 00:13:29,674
We find a Titan orbit,

239
00:13:29,674 --> 00:13:31,176
and the mission
designers have just been

240
00:13:31,176 --> 00:13:32,978
absolutely brilliant with this,

241
00:13:32,978 --> 00:13:35,013
found a Titan that took
us into what we call

242
00:13:35,013 --> 00:13:36,615
the ring grazing orbits.

243
00:13:36,615 --> 00:13:39,184
These orbits
actually are in tight

244
00:13:39,184 --> 00:13:42,121
and are grazing
tantalizingly close

245
00:13:42,121 --> 00:13:44,289
to the F ring right here.

246
00:13:44,289 --> 00:13:47,159
20 of these, and we
just finished them up

247
00:13:47,159 --> 00:13:48,293
a little while ago.

248
00:13:48,293 --> 00:13:50,796
Absolutely phenomenal
set of orbits

249
00:13:50,796 --> 00:13:55,333
that have provided entirely
new insights into the rings,

250
00:13:55,333 --> 00:13:57,603
and some of the ring moons.

251
00:13:58,804 --> 00:14:01,240
Better than we've
ever been since SOI.

252
00:14:01,240 --> 00:14:04,242
Closer we've ever been
since the orbit insertion.

253
00:14:04,242 --> 00:14:06,612
We've never been in this
close again, before.

254
00:14:06,612 --> 00:14:07,446
So.

255
00:14:08,547 --> 00:14:11,116
Well, what do we do next?

256
00:14:11,116 --> 00:14:14,119
There's one more
Titan flyby coming.

257
00:14:16,321 --> 00:14:18,189
This is the final of
the F ring orbits.

258
00:14:18,189 --> 00:14:20,192
Now what I want you to look for

259
00:14:20,192 --> 00:14:22,728
is the Titan flyby that's
gonna come sneaking around here

260
00:14:22,728 --> 00:14:24,563
and give us one
last little push.

261
00:14:24,563 --> 00:14:27,999
This is the last orbit,
boom, around the F rings,

262
00:14:27,999 --> 00:14:29,801
now watch it, here it comes.

263
00:14:29,801 --> 00:14:31,670
Here comes Titan.

264
00:14:31,670 --> 00:14:34,606
Watch what's gonna
happen to our orbit.

265
00:14:34,606 --> 00:14:36,775
It's gonna such just
a little tiny bit

266
00:14:36,775 --> 00:14:38,777
of energy from Cassini.

267
00:14:38,777 --> 00:14:42,281
Just enough, just
enough to put it between

268
00:14:44,550 --> 00:14:47,352
the rings and the planet.

269
00:14:47,352 --> 00:14:50,422
The first of our ring
plane orbits she goes.

270
00:14:50,422 --> 00:14:52,491
And that's number one,

271
00:14:52,491 --> 00:14:55,694
we just did number two
yesterday, actually Tuesday,

272
00:14:55,694 --> 00:14:58,130
and we've got 20 more to go.

273
00:14:58,130 --> 00:15:01,399
Those are the grand
finale orbits.

274
00:15:01,399 --> 00:15:04,703
It's an absolute
pinnacle of astrodynamics

275
00:15:04,703 --> 00:15:08,540
and science achievement,
so very exciting.

276
00:15:08,540 --> 00:15:12,711
Let me just give you another
quick glimpse of these.

277
00:15:14,112 --> 00:15:16,281
This is gonna be all 22 of
them, so hang on for a while.

278
00:15:16,281 --> 00:15:17,816
(audience laughing)

279
00:15:17,816 --> 00:15:20,886
But what I wanted
to show you is that

280
00:15:22,321 --> 00:15:25,457
Titan has been our friend
and moving us all around

281
00:15:25,457 --> 00:15:29,094
for the last 13 years,
and we're calling

282
00:15:29,094 --> 00:15:33,232
this final Titan flyby
the goodbye kiss.

283
00:15:33,232 --> 00:15:35,634
It is coming in right now,

284
00:15:35,634 --> 00:15:38,403
and it's going to slow
down just a little bit

285
00:15:38,403 --> 00:15:40,138
after 22 of these,

286
00:15:40,138 --> 00:15:42,574
Titan's gonna come
swirling in from the side,

287
00:15:42,574 --> 00:15:44,576
there it goes right there,

288
00:15:44,576 --> 00:15:47,045
and what that's gonna
do is it's gonna steal

289
00:15:47,045 --> 00:15:48,980
just a little bit more energy.

290
00:15:48,980 --> 00:15:52,484
Just enough so that
Cassini is gonna go

291
00:15:52,484 --> 00:15:54,553
into the planet itself.

292
00:15:54,553 --> 00:15:59,158
That's the 75,000 mile
per hour hit a brick wall

293
00:15:59,158 --> 00:16:03,695
kind of encounter that the
spacecraft will not survive.

294
00:16:03,695 --> 00:16:07,566
And again, the point is
that we absolutely must

295
00:16:07,566 --> 00:16:09,701
put the spacecraft
into a position

296
00:16:09,701 --> 00:16:12,004
where it can't
inadvertently contact either

297
00:16:12,004 --> 00:16:16,441
Enceladus or Titan, or actually
any of the icy satellites

298
00:16:16,441 --> 00:16:21,179
which we believe are
also potential for
further exploration.

299
00:16:21,179 --> 00:16:23,248
So let's just see
how we do here.

300
00:16:23,248 --> 00:16:25,784
All right, so we've
got the orbits, right?

301
00:16:25,784 --> 00:16:27,486
We've got a challenging
new set of orbits,

302
00:16:27,486 --> 00:16:29,020
a whole new regime,

303
00:16:29,020 --> 00:16:31,856
but we've got an old spacecraft.

304
00:16:31,856 --> 00:16:33,992
So the first question
we've got to ask is

305
00:16:33,992 --> 00:16:36,628
can we teach the
spacecraft new tricks?

306
00:16:36,628 --> 00:16:37,895
It's gonna go into a new region,

307
00:16:37,895 --> 00:16:39,364
it's gonna do different things,

308
00:16:39,364 --> 00:16:41,933
and of course with any kind
of learning experience,

309
00:16:41,933 --> 00:16:43,435
there are constraints.

310
00:16:43,435 --> 00:16:46,705
We've got folks on the
science side who say,

311
00:16:46,705 --> 00:16:47,873
"look over here!

312
00:16:47,873 --> 00:16:48,974
"Look over here!

313
00:16:48,974 --> 00:16:51,110
"Saturn's really cool!"

314
00:16:51,110 --> 00:16:55,380
On the other side, they're
looking at the rings.

315
00:16:55,380 --> 00:16:57,049
"No, look over here."

316
00:16:57,049 --> 00:17:00,251
And then you've got
the engineers, I
consider myself one,

317
00:17:00,251 --> 00:17:02,153
that are saying
"you gotta be bold,

318
00:17:02,153 --> 00:17:05,056
"you gotta do, you know,
dare mighty things."

319
00:17:05,056 --> 00:17:07,926
Well wait a minute,
we gotta be careful.

320
00:17:07,926 --> 00:17:09,394
(laughs)

321
00:17:09,394 --> 00:17:12,030
It's dangerous over there,
and it's dangerous over there.

322
00:17:12,030 --> 00:17:13,866
So what's gonna happen?

323
00:17:13,866 --> 00:17:15,867
The spacecraft of
course is you know,

324
00:17:15,867 --> 00:17:17,336
"I'll do what you tell me.

325
00:17:17,336 --> 00:17:18,803
"Just gotta tell me, give
me the right orders."

326
00:17:18,803 --> 00:17:20,372
So it's a bit of confusion.

327
00:17:20,372 --> 00:17:22,674
Let me just try to
answer the question

328
00:17:22,674 --> 00:17:25,376
that we've tried to deal
with between the bold,

329
00:17:25,376 --> 00:17:28,947
the mighty things, and be
careful not to do anything

330
00:17:28,947 --> 00:17:29,782
too crazy.

331
00:17:31,617 --> 00:17:33,285
And that is the gap.

332
00:17:34,753 --> 00:17:35,820
(audience laughing)

333
00:17:35,820 --> 00:17:37,956
There is a very narrow gap.

334
00:17:37,956 --> 00:17:40,391
It's a billion miles
away, so 1200 kilometer,

335
00:17:40,391 --> 00:17:43,128
1200 mile gap is kinda narrow,

336
00:17:43,128 --> 00:17:47,065
and it's been a big deal
for us to worry about this.

337
00:17:47,065 --> 00:17:48,834
So let me just give you
a couple of animations

338
00:17:48,834 --> 00:17:50,868
that one of our mission
design engineers put together,

339
00:17:50,868 --> 00:17:52,503
which really I think give you

340
00:17:52,503 --> 00:17:54,039
an idea of what's going on here.

341
00:17:54,039 --> 00:17:56,809
This, or these
are the 22 orbits,

342
00:17:58,343 --> 00:18:00,345
and this is the final orbit,

343
00:18:00,345 --> 00:18:04,216
and here is actually pretty
nice and pretty accurate

344
00:18:04,216 --> 00:18:06,918
rendition of Saturn
and its rings,

345
00:18:06,918 --> 00:18:09,021
an artistic representation.

346
00:18:09,021 --> 00:18:13,524
Here is what it looks like
with a high contrast photo.

347
00:18:13,524 --> 00:18:16,895
So you can see, we are
flirting very close,

348
00:18:16,895 --> 00:18:20,199
the atmosphere on one side
and the dust on the other.

349
00:18:20,199 --> 00:18:24,236
So it's not quite as easy
a shot as it first appears.

350
00:18:24,236 --> 00:18:27,272
Now take a look at this
a little bit closer up,

351
00:18:27,272 --> 00:18:31,343
get a bit better view of
our ring plane crossings

352
00:18:32,577 --> 00:18:35,514
and our periapsis,
or minimum altitudes,

353
00:18:35,514 --> 00:18:38,650
which are all in the souther
hemisphere of Saturn.

354
00:18:38,650 --> 00:18:41,819
One last look, and you can
kinda look down the orbital path

355
00:18:41,819 --> 00:18:45,090
and you can just get a
sense of just how close

356
00:18:45,090 --> 00:18:46,992
these are to Saturn itself,

357
00:18:46,992 --> 00:18:50,162
and how much Titan, who's still
out there pushing us around,

358
00:18:50,162 --> 00:18:52,730
is moving these
various orbits around,

359
00:18:52,730 --> 00:18:55,133
and finally you see our
final orbit over on the end,

360
00:18:55,133 --> 00:18:57,835
it doesn't show up well
here, but it's there.

361
00:18:57,835 --> 00:18:59,471
So, what do you do with that?

362
00:18:59,471 --> 00:19:00,739
Well, first thing
we engineers do

363
00:19:00,739 --> 00:19:02,874
is we put that into
a XY chart, right?

364
00:19:02,874 --> 00:19:04,142
(audience laughing)

365
00:19:04,142 --> 00:19:05,277
What else would you do?

366
00:19:05,277 --> 00:19:06,645
It's data.

367
00:19:06,645 --> 00:19:08,913
And so here are our
minimum altitudes,

368
00:19:08,913 --> 00:19:11,583
and here are our
XY plane crossings,

369
00:19:11,583 --> 00:19:13,218
but then of course
what you want to do

370
00:19:13,218 --> 00:19:14,953
is put your boundaries on.

371
00:19:14,953 --> 00:19:17,489
And what we've done is
we've more or less decided

372
00:19:17,489 --> 00:19:20,025
that the extensible
edge of the D-ring

373
00:19:20,025 --> 00:19:23,661
is about 6400 kilometers
from the center of Saturn.

374
00:19:23,661 --> 00:19:27,032
And we picked some orbits that
we thought were pretty cool.

375
00:19:27,032 --> 00:19:29,301
They've got a lot of, you
know, moving around in here,

376
00:19:29,301 --> 00:19:30,769
they go down into
the atmosphere,

377
00:19:30,769 --> 00:19:32,937
and then finally down here
you'll notice our final orbit.

378
00:19:32,937 --> 00:19:34,839
But they do some things up here

379
00:19:34,839 --> 00:19:36,174
that are a little bit alarming.

380
00:19:36,174 --> 00:19:39,344
They take us up into the dust.

381
00:19:39,344 --> 00:19:43,048
So we had to figure out what
we're gonna do about that

382
00:19:43,048 --> 00:19:45,717
There's a high contrast
photo again of the dust,

383
00:19:45,717 --> 00:19:47,919
and there's that boundary,

384
00:19:47,919 --> 00:19:50,154
and there's the
range that we're in.

385
00:19:50,154 --> 00:19:52,156
So, we had to come up
with some sort of scheme

386
00:19:52,156 --> 00:19:53,658
as to how to deal with the dust.

387
00:19:53,658 --> 00:19:56,895
We modeled it completely,
we feel like it's safe,

388
00:19:56,895 --> 00:20:00,498
in all the models that
the ring scientists have,

389
00:20:00,498 --> 00:20:02,434
and we've got the best ring
scientists in the world,

390
00:20:02,434 --> 00:20:04,035
as you could imagine,
on the project,

391
00:20:04,035 --> 00:20:07,172
so we really didn't
have a lot of worry,

392
00:20:07,172 --> 00:20:09,007
but you never know, we've
never been there before,

393
00:20:09,007 --> 00:20:10,508
so we had to see
what was going on.

394
00:20:10,508 --> 00:20:12,543
And so there's the region
we were trying to avoid,

395
00:20:12,543 --> 00:20:16,148
and what we decided to
do for these up here

396
00:20:17,416 --> 00:20:18,616
was shield them.

397
00:20:18,616 --> 00:20:20,619
Now if you notice the
images of Cassini,

398
00:20:20,619 --> 00:20:23,088
it's got a large, well
it's right over there.

399
00:20:23,088 --> 00:20:26,991
There's a very large, saucer
shaped antenna on the front.

400
00:20:26,991 --> 00:20:28,994
Pretty solid piece of material,

401
00:20:28,994 --> 00:20:31,830
and almost all the
instruments are behind it.

402
00:20:31,830 --> 00:20:33,331
So if we go into the dust

403
00:20:33,331 --> 00:20:35,733
with that antenna
pointing into the dust,

404
00:20:35,733 --> 00:20:38,236
everybody's pretty
fine except of course

405
00:20:38,236 --> 00:20:41,439
for that long magnetometer
boom, which is exposed,

406
00:20:41,439 --> 00:20:43,641
but there's not a thing
we can do about that.

407
00:20:43,641 --> 00:20:45,610
So for these
crossings, we decided

408
00:20:45,610 --> 00:20:48,579
that we would protect
the spacecraft

409
00:20:48,579 --> 00:20:50,815
by hiding it in the shielding.

410
00:20:50,815 --> 00:20:53,185
Furthermore, since
we really didn't know

411
00:20:56,021 --> 00:20:54,485
where we were going,

412
00:20:56,021 --> 00:20:57,556
we just didn't know
what was in there,

413
00:20:57,556 --> 00:21:01,560
we decided to put a shield
on our first flyby as well.

414
00:21:01,560 --> 00:21:03,862
We've now completed that
flyby, and completed...

415
00:21:03,862 --> 00:21:05,796
Oh they're not
calling them flybys,

416
00:21:05,796 --> 00:21:06,964
they're ring plane crossings.

417
00:21:06,964 --> 00:21:08,666
Completed that one and that one,

418
00:21:08,666 --> 00:21:10,936
and I gotta happy to
say the spacecraft's

419
00:21:10,936 --> 00:21:12,203
come out just fine.

420
00:21:12,203 --> 00:21:14,072
So let me show you
just a little bit

421
00:21:14,072 --> 00:21:15,106
of what that looked like.

422
00:21:15,106 --> 00:21:17,609
This was our first crossing.

423
00:21:17,609 --> 00:21:19,143
Right?

424
00:21:19,143 --> 00:21:20,945
And you're gonna watch the
spacecraft reorient itself

425
00:21:20,945 --> 00:21:23,381
as it goes through the dust

426
00:21:23,381 --> 00:21:25,483
and point the antenna right into

427
00:21:25,483 --> 00:21:27,218
what we call the ram direction.

428
00:21:27,218 --> 00:21:28,987
That is the direction
of oncoming dust.

429
00:21:28,987 --> 00:21:31,389
And of course, being as
opportunistic as we can,

430
00:21:31,389 --> 00:21:32,490
the minute we're
through the dust,

431
00:21:32,490 --> 00:21:33,758
we turn the
spacecraft back around

432
00:21:33,758 --> 00:21:35,327
and start imaging
the planet again.

433
00:21:35,327 --> 00:21:36,961
So just for a few minutes

434
00:21:36,961 --> 00:21:38,796
on either side of the
ring plane crossing,

435
00:21:38,796 --> 00:21:41,632
we used the spacecraft
antenna as a shield

436
00:21:41,632 --> 00:21:43,969
for the rest of the instruments.

437
00:21:43,969 --> 00:21:45,303
That went perfectly fine.

438
00:21:45,303 --> 00:21:47,973
Now, you want to see some drama,

439
00:21:49,173 --> 00:21:51,409
it's not this, it's me
trying to make it work.

440
00:21:51,409 --> 00:21:54,412
(audience laughing)

441
00:21:54,412 --> 00:21:56,781
I'm gonna see if we can do this.

442
00:21:56,781 --> 00:21:57,616
This is...

443
00:21:59,084 --> 00:22:00,518
Let me explain a
little bit first,

444
00:22:00,518 --> 00:22:02,888
because I'm gonna, yeah,
I'm gonna mess it up.

445
00:22:02,888 --> 00:22:04,056
This is the...

446
00:22:06,524 --> 00:22:10,595
What we call the radio
plasma wave spectral analysis

447
00:22:10,595 --> 00:22:12,997
of the ring plane crossing,

448
00:22:12,997 --> 00:22:16,234
and what happens is as dust
strikes the spacecraft,

449
00:22:16,234 --> 00:22:19,637
it creates a plasma,
it's an ionized gas,

450
00:22:19,637 --> 00:22:21,239
and our antenna
can pick them up,

451
00:22:21,239 --> 00:22:23,274
and so the more
dust you run into,

452
00:22:23,274 --> 00:22:25,610
the more energetic,
more plasma you get,

453
00:22:25,610 --> 00:22:27,512
and you get exactly
what you think you see.

454
00:22:27,512 --> 00:22:29,113
This is time,

455
00:22:29,113 --> 00:22:31,349
and this is in a certain sense

456
00:22:31,349 --> 00:22:33,585
a measure of the
plasma or energy.

457
00:22:33,585 --> 00:22:35,654
And so you see a very peak

458
00:22:35,654 --> 00:22:37,322
right here at the
ring plane crossing.

459
00:22:37,322 --> 00:22:40,658
This happened during one of
our F ring grazing orbits,

460
00:22:40,658 --> 00:22:44,830
and it was just classic, you
know, ring grazing material.

461
00:22:46,498 --> 00:22:49,067
So what I want to do
if I can get this,

462
00:22:49,067 --> 00:22:53,104
if I can find my mouse
here, oh, there it is.

463
00:22:53,104 --> 00:22:56,140
So this is the sound
file of what we consider

464
00:22:56,140 --> 00:22:58,476
a normal dust crossing.

465
00:22:58,476 --> 00:23:01,046
And you can see the
little line going through.

466
00:23:01,046 --> 00:23:03,715
(static sounds)

467
00:23:41,152 --> 00:23:42,353
So you can so both,

468
00:23:42,353 --> 00:23:45,823
hear both of the
low level particles,

469
00:23:45,823 --> 00:23:47,592
kind of the smaller particles,

470
00:23:47,592 --> 00:23:50,594
every now and then you hear a
larger bip of a more energetic

471
00:23:50,594 --> 00:23:54,566
or a larger particle
striking the antenna.

472
00:23:54,566 --> 00:23:57,402
That was with the high
gain antenna shielding us.

473
00:23:57,402 --> 00:23:59,137
So here's what we saw

474
00:24:00,571 --> 00:24:02,974
during our first
proximal orbit passage.

475
00:24:02,974 --> 00:24:07,312
After all these dire
concerns about the dust,

476
00:24:07,312 --> 00:24:09,914
I'm not gonna spend
a whole lot of time

477
00:24:09,914 --> 00:24:12,184
trying to find this audio file

478
00:24:12,184 --> 00:24:13,918
that doesn't sound
like anything,

479
00:24:13,918 --> 00:24:16,521
because this was
absolutely silent.

480
00:24:16,521 --> 00:24:19,224
We had the noise turned up
so we could find something,

481
00:24:19,224 --> 00:24:22,694
turns out that all of this
drama about the D ring

482
00:24:22,694 --> 00:24:25,830
and all that dust in between
that gap was actually

483
00:24:25,830 --> 00:24:27,798
just a big empty.

484
00:24:27,798 --> 00:24:30,335
We don't quite understand it.

485
00:24:30,335 --> 00:24:31,936
Well, I should say
the ring scientists

486
00:24:31,936 --> 00:24:33,271
are still befuddled by it.

487
00:24:33,271 --> 00:24:34,905
There shouldn't be
that little dust there,

488
00:24:34,905 --> 00:24:36,474
but something's
cleaned it all out.

489
00:24:36,474 --> 00:24:39,643
So I think as one of our
mission design folks quipped,

490
00:24:39,643 --> 00:24:42,614
Saturn has swept the
doorstep free for us.

491
00:24:42,614 --> 00:24:43,781
(audience laughing)

492
00:24:43,781 --> 00:24:45,282
Like a good host.

493
00:24:45,282 --> 00:24:48,687
So indeed, so far, we've had
perfect ring plane crossings,

494
00:24:48,687 --> 00:24:51,489
and the drama about any dust
issues or things like that

495
00:24:51,489 --> 00:24:53,492
seemed to be for naught.

496
00:24:54,859 --> 00:24:57,428
Okay, so we've just
talked a little bit about

497
00:24:57,428 --> 00:24:59,764
how to avoid the dangers
using the high gain antenna

498
00:24:59,764 --> 00:25:00,998
and things like that.

499
00:25:00,998 --> 00:25:04,068
Now what about look over
here, look over there?

500
00:25:04,068 --> 00:25:07,272
We've had 22 orbits, sounds
like a lot, but the instruments,

501
00:25:07,272 --> 00:25:08,807
we've got 11
functioning instruments

502
00:25:08,807 --> 00:25:11,475
and five other investigations
that try to share instruments,

503
00:25:11,475 --> 00:25:13,945
and there's a huge amount
of conflict between this.

504
00:25:13,945 --> 00:25:16,414
And so it was very hard
when we started working on

505
00:25:16,414 --> 00:25:19,484
this years ago, that the
instruments figured out new ways

506
00:25:19,484 --> 00:25:23,088
to use an cooperate
on these 22 orbits.

507
00:25:23,088 --> 00:25:25,823
For example, we have
the gravity folks

508
00:25:25,823 --> 00:25:27,325
that are doing gravity science,

509
00:25:27,325 --> 00:25:29,593
they want to have the antenna
pointing to the Earth,

510
00:25:29,593 --> 00:25:31,562
they want to have it rock solid

511
00:25:31,562 --> 00:25:32,764
because they're
trying to measure

512
00:25:32,764 --> 00:25:35,533
incredibly subtle
variations in the signal

513
00:25:35,533 --> 00:25:37,768
as it passes between
the rings and Saturn.

514
00:25:37,768 --> 00:25:40,004
The magnetometer
folks want to roll,

515
00:25:40,004 --> 00:25:42,072
because they want to
spin that big boom

516
00:25:42,072 --> 00:25:44,409
through as much space
as they possibly can

517
00:25:44,409 --> 00:25:47,078
in order to get the best
magnetic field data.

518
00:25:47,078 --> 00:25:50,515
Well they found a way
to spin on an axis

519
00:25:50,515 --> 00:25:53,918
that keeps the radio bore sight
directly pointed at Earth,

520
00:25:53,918 --> 00:25:57,488
and so they get to spin
and gravity science gets

521
00:25:57,488 --> 00:25:58,690
the benefit of their...

522
00:25:58,690 --> 00:26:00,291
Again, a beautiful
collaboration.

523
00:26:00,291 --> 00:26:02,560
We figured out a way
to repurpose the INMS

524
00:26:02,560 --> 00:26:04,428
to become an atmospheric probe.

525
00:26:04,428 --> 00:26:07,399
The spacecraft can now use
the data that's on board,

526
00:26:07,399 --> 00:26:09,367
normally stored on board and
shoot it down immediately,

527
00:26:09,367 --> 00:26:11,402
so as we're burrowing
in the atmosphere,

528
00:26:11,402 --> 00:26:13,271
we're sampling data to
the very last instant.

529
00:26:13,271 --> 00:26:15,206
There are bunches
of examples of that.

530
00:26:15,206 --> 00:26:18,276
So let me just go
to this last slide.

531
00:26:19,744 --> 00:26:22,947
This again is all of
the periapsis passages,
all along here.

532
00:26:22,947 --> 00:26:26,050
As you can see, they
are spread around,

533
00:26:26,050 --> 00:26:28,052
but we really had a tremendous
amount of contention

534
00:26:28,052 --> 00:26:32,957
and what happened is that
almost all of them shared.

535
00:26:32,957 --> 00:26:36,294
Instruments are collaborating
on all those circled orbits,

536
00:26:36,294 --> 00:26:38,930
there's a collaboration
between the radio science

537
00:26:38,930 --> 00:26:41,432
and magnetometer, between
dust and mass spectrometers,

538
00:26:41,432 --> 00:26:42,266
between...

539
00:26:42,266 --> 00:26:43,468
It goes on and on.

540
00:26:43,468 --> 00:26:45,803
So we've maximized
every piece of science

541
00:26:45,803 --> 00:26:47,872
that we can get out
of these orbits.

542
00:26:47,872 --> 00:26:48,973
And with that...

543
00:26:48,973 --> 00:26:49,907
(laughs)

544
00:26:49,907 --> 00:26:51,609
The amount of time I've wasted.

545
00:26:51,609 --> 00:26:55,713
Here is the Cassini poised
for its first flyby,

546
00:26:55,713 --> 00:26:58,583
and I'm gonna segue into
the grand finale objectives,

547
00:26:58,583 --> 00:27:02,386
some of the unique
science, and Linda Spilker.

548
00:27:02,386 --> 00:27:04,722
Thank you for your patience.

549
00:27:04,722 --> 00:27:07,158
(applauding)

550
00:27:12,796 --> 00:27:14,666
Okay, well I'm Linda Spilker,

551
00:27:14,666 --> 00:27:16,767
and I'm the Cassini
Project Scientist,

552
00:27:16,767 --> 00:27:18,168
and I have a really cool job.

553
00:27:18,168 --> 00:27:20,571
I get to coordinate
amongst 300 scientists

554
00:27:20,571 --> 00:27:22,506
spread around the world

555
00:27:22,506 --> 00:27:26,577
to get the best science possible
for the Cassini mission.

556
00:27:26,577 --> 00:27:28,780
And I've been lucky enough
to be with this mission

557
00:27:28,780 --> 00:27:30,281
for a long time.

558
00:27:30,281 --> 00:27:33,984
It's been almost 30 years
that I've worked on Cassini.

559
00:27:33,984 --> 00:27:36,454
In fact, my oldest
daughter Jennifer

560
00:27:36,454 --> 00:27:40,525
just started kindergarten when
I started working on Cassini,

561
00:27:40,525 --> 00:27:44,395
and now she's married and she
has a daughter of her own.

562
00:27:44,395 --> 00:27:47,665
And what's so amazing
is how quickly

563
00:27:47,665 --> 00:27:50,467
those 30 years have flown by.

564
00:27:50,467 --> 00:27:52,770
And in fact, here's sort of...

565
00:27:52,770 --> 00:27:55,006
Basically I've been
on the Cassini mission

566
00:27:55,006 --> 00:27:56,808
for one Saturn orbit.

567
00:27:56,808 --> 00:27:59,277
It takes Saturn about 30
years to go around the sun

568
00:27:59,277 --> 00:28:00,511
a single time.

569
00:28:00,511 --> 00:28:03,013
And so what's show here
are the mission phases

570
00:28:03,013 --> 00:28:05,149
as a function of Saturn orbit.

571
00:28:05,149 --> 00:28:08,552
So you can see, as Earl
said, we arrived in 2004,

572
00:28:08,552 --> 00:28:10,855
had a four year prime mission,

573
00:28:10,855 --> 00:28:12,457
two year equinox mission,

574
00:28:12,457 --> 00:28:14,992
we're now in our seven
year solstice mission,

575
00:28:14,992 --> 00:28:18,396
and we're at the very tail
end, as Earl showed you.

576
00:28:18,396 --> 00:28:20,831
We had just finished
our ring grazing orbits,

577
00:28:20,831 --> 00:28:24,669
and we're now two dives
into the grand finale.

578
00:28:26,137 --> 00:28:27,771
So what I'm gonna do is I'm
gonna step back and show you

579
00:28:27,771 --> 00:28:30,874
some amazing pictures
and science results

580
00:28:30,874 --> 00:28:33,544
from those ring grazing orbits.

581
00:28:33,544 --> 00:28:36,780
We basically pulled
Cassini's orbit in very close

582
00:28:36,780 --> 00:28:38,882
to Saturn's F ring,
which is nestled

583
00:28:38,882 --> 00:28:40,484
right against the main rings,

584
00:28:40,484 --> 00:28:43,087
giving us a chance to
get incredible pictures.

585
00:28:43,087 --> 00:28:44,722
In fact, if you look
in the blue region,

586
00:28:44,722 --> 00:28:47,325
we can get incredible
pictures of tiny little moons

587
00:28:47,325 --> 00:28:50,828
that orbit in the gaps in
the rings, next to the rings,

588
00:28:50,828 --> 00:28:54,999
and the best pictures ever
of the rings themselves.

589
00:28:56,167 --> 00:28:58,035
So here you can see
a couple of gaps,

590
00:28:58,035 --> 00:29:00,038
the wider gap over on the left,

591
00:29:00,038 --> 00:29:02,674
that's the Encke gap and
inside of the Encke gap

592
00:29:02,674 --> 00:29:04,709
is the moon Pan.

593
00:29:04,709 --> 00:29:06,777
Now Pan was actually
discovered in the Voyager data

594
00:29:06,777 --> 00:29:09,547
but not until 10 years
after the Voyager flyby

595
00:29:09,547 --> 00:29:12,950
where Mark Showalter
put together the images

596
00:29:12,950 --> 00:29:15,419
and figured out there was a
moon and where to look for it.

597
00:29:15,419 --> 00:29:18,789
The next gap out includes a
little tiny moon named Daphnis.

598
00:29:18,789 --> 00:29:22,293
Cassini discovered
Daphnis in 2005.

599
00:29:22,293 --> 00:29:26,831
And finally out hugging the
edge of the A ring is Atlas,

600
00:29:26,831 --> 00:29:29,233
and Atlas was discovered in
the Voyager data as well,

601
00:29:29,233 --> 00:29:31,469
so to really see these
little tiny moons

602
00:29:31,469 --> 00:29:33,470
it takes a spacecraft.

603
00:29:33,470 --> 00:29:34,572
So let's take a look at those.

604
00:29:34,572 --> 00:29:36,574
First let's look at Pan.

605
00:29:38,042 --> 00:29:39,744
Here's a movie that we took
with the Cassini spacecraft,

606
00:29:39,744 --> 00:29:42,980
these are raw images, you can
see cosmic ray hits and so on.

607
00:29:42,980 --> 00:29:45,550
But here, I'll back it
up and show it again,

608
00:29:45,550 --> 00:29:48,386
we went zooming
by this tiny moon.

609
00:29:49,587 --> 00:29:50,855
And you can see,
it looks unusual.

610
00:29:50,855 --> 00:29:52,924
It's not, doesn't
look like a potato,

611
00:29:52,924 --> 00:29:54,726
it doesn't look
like a round moon,

612
00:29:54,726 --> 00:29:57,194
in fact, here's a
couple views of Pan,

613
00:29:57,194 --> 00:30:01,065
Pan's about 20 miles
across at its equator,

614
00:30:01,065 --> 00:30:04,569
it's nestled in a 200
mile wide Encke gap,

615
00:30:06,003 --> 00:30:07,471
and you can see it also
has this very interesting

616
00:30:07,471 --> 00:30:11,042
equatorial ridge or
skirt of particles.

617
00:30:11,042 --> 00:30:13,143
And what it does is in
accumulating particles

618
00:30:13,143 --> 00:30:15,045
from the edges of the Encke gap,

619
00:30:15,045 --> 00:30:17,415
and they go around the
equator of the moon,

620
00:30:17,415 --> 00:30:19,817
and sometimes those particles
actually slide down.

621
00:30:19,817 --> 00:30:21,819
It's hard to see here,
but there's actually,

622
00:30:21,819 --> 00:30:25,056
you can see a landslide of
particles in a couple of places

623
00:30:25,056 --> 00:30:27,759
where they slide down
onto the main central

624
00:30:27,759 --> 00:30:29,159
frozen moon itself.

625
00:30:29,159 --> 00:30:33,331
You can see tiny little
craters, some ridges inside of,

626
00:30:33,331 --> 00:30:36,234
along this ridge here, so
very interesting and unique.

627
00:30:36,234 --> 00:30:38,436
In fact, one of the Cassini
scientists said, "hmm,

628
00:30:38,436 --> 00:30:41,772
"that reminds me of
cheese dumplings."

629
00:30:41,772 --> 00:30:44,107
So you can see the edges
on these cheese dumplings,

630
00:30:44,107 --> 00:30:46,511
so a very very unusual shape.

631
00:30:48,145 --> 00:30:50,281
Well it's moving on to Daphnis,

632
00:30:50,281 --> 00:30:51,682
Daphnis is much smaller.

633
00:30:51,682 --> 00:30:54,017
Daphnis is only
six miles across.

634
00:30:54,017 --> 00:30:57,822
And it's holding open
a 25 mile wide gap.

635
00:30:57,822 --> 00:30:59,457
Turns out that these
moons are big enough

636
00:30:59,457 --> 00:31:01,825
they literally shove
aside the ring particles

637
00:31:01,825 --> 00:31:04,996
and create a gap that
goes all the way around

638
00:31:04,996 --> 00:31:07,031
Saturn's rings, so
if you're a big guy,

639
00:31:07,031 --> 00:31:08,933
you get in the rings and
you say "move out of my way"

640
00:31:08,933 --> 00:31:10,735
and you can create a gap.

641
00:31:10,735 --> 00:31:13,604
Daphnis also as well
as Pan creates waves

642
00:31:13,604 --> 00:31:15,372
along the edge of the gap.

643
00:31:15,372 --> 00:31:17,275
Here's another view of
those waves you can see

644
00:31:17,275 --> 00:31:19,543
actually a tiny tendril
of ring particles

645
00:31:19,543 --> 00:31:21,512
that Daphnis has pulled out,

646
00:31:21,512 --> 00:31:23,113
and just like the
waves in an ocean

647
00:31:23,113 --> 00:31:26,384
you can see this wave going
along and slowly damping out,

648
00:31:26,384 --> 00:31:28,919
and the particles
actually sheering apart.

649
00:31:28,919 --> 00:31:31,522
So just very beautiful,
very close up views,

650
00:31:31,522 --> 00:31:35,693
incredible detail in the
rings themselves as well.

651
00:31:37,962 --> 00:31:40,163
Let me go in the
right direction.

652
00:31:40,163 --> 00:31:42,200
And this is a movie of Atlas.

653
00:31:42,200 --> 00:31:46,370
Now Atlas is the moon, it is
about 26 kilometers across

654
00:31:46,370 --> 00:31:49,073
and only 11 miles
north to south.

655
00:31:49,073 --> 00:31:52,109
And so you can see here's
a close up view of Atlas,

656
00:31:52,109 --> 00:31:54,679
it's not washed out
like this on my screen

657
00:31:54,679 --> 00:31:57,181
but it's much smoother,
very few craters,

658
00:31:57,181 --> 00:32:00,184
there's a big icy
particle in the center.

659
00:32:00,184 --> 00:32:02,086
It turns out these
moons can't accumulate

660
00:32:02,086 --> 00:32:03,721
ring particles forever.

661
00:32:03,721 --> 00:32:06,390
They get out to a certain
size and then their gravity

662
00:32:06,390 --> 00:32:08,592
gets balanced by
Saturn's gravity.

663
00:32:08,592 --> 00:32:10,527
So any ring particles
that try and stick

664
00:32:10,527 --> 00:32:12,596
get pulled away by
Saturn's gravity.

665
00:32:12,596 --> 00:32:16,801
So Atlas has grown pretty much
to the biggest size it can

666
00:32:16,801 --> 00:32:18,870
around its equator.

667
00:32:18,870 --> 00:32:21,806
And here are the three
moons shown to scale.

668
00:32:21,806 --> 00:32:23,707
There's a scale
bar of six miles,

669
00:32:23,707 --> 00:32:25,877
so you can see
Daphnis truly is tiny,

670
00:32:25,877 --> 00:32:29,880
and it really took Cassini's
very stable, good cameras

671
00:32:29,880 --> 00:32:32,550
to be able to find tiny Daphnis.

672
00:32:33,718 --> 00:32:35,119
Now here's one of my
favorite pictures,

673
00:32:35,119 --> 00:32:37,421
this is going all
the way back to 2009,

674
00:32:37,421 --> 00:32:39,924
the sun was edge
on to the rings,

675
00:32:39,924 --> 00:32:42,059
and at that point in time,

676
00:32:42,059 --> 00:32:43,961
basically the sun's edge on,

677
00:32:43,961 --> 00:32:45,496
at that point in time,
anything that sticks

678
00:32:45,496 --> 00:32:48,299
above or below the rings
will cast a shadow.

679
00:32:48,299 --> 00:32:50,968
And that's called equinox,
and so you can see shadows,

680
00:32:50,968 --> 00:32:53,504
many many shadows,
cast by objects

681
00:32:53,504 --> 00:32:56,273
probably a third to
half a mile in size,

682
00:32:56,273 --> 00:32:58,542
probably accumulations
of particles,

683
00:32:58,542 --> 00:33:00,945
maybe bigger particles as well.

684
00:33:00,945 --> 00:33:03,681
But we've never been able
to really resolve or see

685
00:33:03,681 --> 00:33:07,117
one of those particles,
up until very recently.

686
00:33:07,117 --> 00:33:09,119
This is the same view
now turned sideways,

687
00:33:09,119 --> 00:33:10,621
here's the edge of the B ring,

688
00:33:10,621 --> 00:33:12,422
you see all of this speckling,

689
00:33:12,422 --> 00:33:14,658
and those are
individual clumps now

690
00:33:14,658 --> 00:33:18,462
that we can resolve at
the edge of the B ring.

691
00:33:18,462 --> 00:33:20,697
Incredibly detailed structure.

692
00:33:20,697 --> 00:33:22,967
We were thinking as we
got to higher resolution

693
00:33:22,967 --> 00:33:24,902
the ringlets would just
appear to get wider

694
00:33:24,902 --> 00:33:27,404
and we'd see more
structure, but instead,

695
00:33:27,404 --> 00:33:29,073
we see more and more ringlets.

696
00:33:29,073 --> 00:33:31,575
Every time we get closer,
the ringlet that's there

697
00:33:31,575 --> 00:33:33,411
divides into more and into more

698
00:33:33,411 --> 00:33:36,214
and it's just an incredible
detailed structure.

699
00:33:36,214 --> 00:33:38,048
I got this picture
from Matt Tiscarino,

700
00:33:38,048 --> 00:33:40,051
and he tried
something very clever.

701
00:33:40,051 --> 00:33:43,420
He realized if you could fold
the picture over essentially,

702
00:33:43,420 --> 00:33:46,523
along a line that's
perpendicular to the rings

703
00:33:46,523 --> 00:33:48,326
and subtract the two halves,

704
00:33:48,326 --> 00:33:51,328
anything that's different
as you go along the azimuth

705
00:33:51,328 --> 00:33:53,598
in this direction
along the rings

706
00:33:53,598 --> 00:33:56,333
would show up as
additional speckling.

707
00:33:56,333 --> 00:33:58,068
So he did just that, and
you can see of course

708
00:33:58,068 --> 00:34:00,871
the edge of the B ring has
lots of these little speckles,

709
00:34:00,871 --> 00:34:03,841
it's very different as you
go from one place to another,

710
00:34:03,841 --> 00:34:06,510
slowly dies away, but then
there's a couple of other places

711
00:34:06,510 --> 00:34:09,413
that have a lot of
speckles in them too,

712
00:34:09,413 --> 00:34:11,448
and very sort of hidden
away in that other image,

713
00:34:11,448 --> 00:34:14,151
but you can see them now,
and so now we have to explain

714
00:34:14,151 --> 00:34:16,787
why can you get
clumping so far away

715
00:34:16,787 --> 00:34:18,322
from the edge of the B ring?

716
00:34:18,322 --> 00:34:21,391
So lots of new science in
just a handful of pictures

717
00:34:21,391 --> 00:34:24,795
that have come back in
the ring grazing orbits.

718
00:34:24,795 --> 00:34:26,663
And then of course these
very interesting objects

719
00:34:26,663 --> 00:34:28,266
called propellers.

720
00:34:28,266 --> 00:34:31,101
If you're a tiny moon, you're
not big enough to make a gap,

721
00:34:31,101 --> 00:34:33,303
what these propeller
objects are trying to do,

722
00:34:33,303 --> 00:34:35,139
there's an object
in the middle here

723
00:34:35,139 --> 00:34:37,107
trying to open up a gap.

724
00:34:37,107 --> 00:34:39,009
It gets a partial gap,

725
00:34:39,009 --> 00:34:41,312
those are the two arms
of the propellers,

726
00:34:41,312 --> 00:34:42,446
and we had a lot of fun,

727
00:34:42,446 --> 00:34:44,682
we named the propellers
after aviators.

728
00:34:44,682 --> 00:34:48,819
So you'll find an Earhart, in
this case it's Santos Dumont.

729
00:34:48,819 --> 00:34:51,188
And you're seeing a view
on the lit and unlit side.

730
00:34:51,188 --> 00:34:54,057
This is about a mile
across in width here,

731
00:34:54,057 --> 00:34:57,261
the object is probably a
quarter mile or so in size,

732
00:34:57,261 --> 00:35:00,431
and so these objects are like
the seeds that you would have

733
00:35:00,431 --> 00:35:03,600
in a disc from which
the solar system formed.

734
00:35:03,600 --> 00:35:06,870
So Saturn's rings are
really a laboratory

735
00:35:06,870 --> 00:35:09,106
where we can watch
dust interacting,

736
00:35:09,106 --> 00:35:11,775
how you could grow larger
objects, planetesimals,

737
00:35:11,775 --> 00:35:14,244
that could go on to
form a solar system.

738
00:35:14,244 --> 00:35:16,413
So studying the rings
gives us ideas about

739
00:35:16,413 --> 00:35:18,249
how our solar system formed

740
00:35:18,249 --> 00:35:22,119
and how you could get solar
systems around other stars.

741
00:35:22,119 --> 00:35:25,423
So very exciting
to look at as well.

742
00:35:25,423 --> 00:35:26,958
And this is a very
interesting picture.

743
00:35:26,958 --> 00:35:31,628
This dot here, it isn't a star,
it's not a cosmic ray hit,

744
00:35:31,628 --> 00:35:33,164
that's the Earth.

745
00:35:33,164 --> 00:35:36,467
That we turned the Cassini
cameras on April 12th

746
00:35:36,467 --> 00:35:38,803
to take our last
picture of Earth

747
00:35:38,803 --> 00:35:43,040
in between the edge of the
A ring and Saturn's F ring.

748
00:35:43,040 --> 00:35:45,042
And if you look very
carefully and blow it up,

749
00:35:45,042 --> 00:35:46,744
there's the moon.

750
00:35:46,744 --> 00:35:48,678
So you're actually seeing
the Earth and the moon,

751
00:35:48,678 --> 00:35:50,580
and what if you're on the Earth,

752
00:35:50,580 --> 00:35:53,383
this was over the middle
of the Atlantic Ocean

753
00:35:53,383 --> 00:35:55,018
when we snapped this picture.

754
00:35:55,018 --> 00:35:57,287
So it's a very special time,

755
00:35:57,287 --> 00:35:59,223
we have to use Saturn
to cover up the sun

756
00:35:59,223 --> 00:36:02,326
so we can turn our delicate
cameras close enough to the sun,

757
00:36:02,326 --> 00:36:05,729
but the sun's covered to
take this very unique image.

758
00:36:05,729 --> 00:36:08,098
So this is our farewell picture,

759
00:36:08,098 --> 00:36:10,601
our last picture of the Earth.

760
00:36:15,806 --> 00:36:18,876
Now Earl showed this, this is
the historic first passage,

761
00:36:18,876 --> 00:36:21,578
this is the start
now, the grand finale,

762
00:36:21,578 --> 00:36:23,580
going in between the
rings and the planet,

763
00:36:23,580 --> 00:36:28,585
flying in a place
that no spacecraft
has ever flown before,

764
00:36:28,585 --> 00:36:29,719
and that's very exciting because

765
00:36:29,719 --> 00:36:32,289
every time you go someplace new,

766
00:36:32,289 --> 00:36:34,391
you're going to make
new discoveries,

767
00:36:34,391 --> 00:36:36,327
and that's exactly
what Cassini did.

768
00:36:36,327 --> 00:36:38,495
You're riding along with
the Cassini spacecraft,

769
00:36:38,495 --> 00:36:40,063
here's what it might feel like

770
00:36:40,063 --> 00:36:41,899
as you're peering over
the edge of the antenna

771
00:36:41,899 --> 00:36:45,236
to dive in between the
rings and the planet.

772
00:36:45,236 --> 00:36:48,306
You're going at
76,000 miles an hour,

773
00:36:49,440 --> 00:36:52,576
and it only takes you
an hour to go from

774
00:36:52,576 --> 00:36:55,912
over one pole of
Saturn to over another,

775
00:36:55,912 --> 00:36:57,681
and then you come back
out the other side,

776
00:36:57,681 --> 00:37:00,284
and you do this every
six and a half days.

777
00:37:00,284 --> 00:37:02,186
So you're coming
in very quickly,

778
00:37:02,186 --> 00:37:03,954
you can see the background
of the Milky Way,

779
00:37:03,954 --> 00:37:06,089
you come out the other side,

780
00:37:06,089 --> 00:37:09,560
you can see the sun
here as you go on out,

781
00:37:09,560 --> 00:37:12,863
so just a very exciting
time in the mission.

782
00:37:12,863 --> 00:37:16,199
So, what did we see
on that first dive?

783
00:37:16,199 --> 00:37:17,868
We actually on this first dive,

784
00:37:17,868 --> 00:37:20,437
we used the high gain antenna
to protect the spacecraft,

785
00:37:20,437 --> 00:37:23,941
but we rotated to point
the cameras at Saturn.

786
00:37:23,941 --> 00:37:26,010
We started at
Saturn's north pole

787
00:37:26,010 --> 00:37:29,847
and we just kept taking
pictures every 17 seconds

788
00:37:29,847 --> 00:37:33,150
from the north pole
down toward the equator.

789
00:37:33,150 --> 00:37:35,085
And here you can see
views of some of those.

790
00:37:35,085 --> 00:37:37,688
Here's the giant
vortex, hurricane-like,

791
00:37:37,688 --> 00:37:39,857
right at the north pole.

792
00:37:39,857 --> 00:37:42,459
Some of these clouds
that are better resolved

793
00:37:42,459 --> 00:37:43,960
than we've seen before,

794
00:37:43,960 --> 00:37:46,196
here's the edge of
the giant hexagon,

795
00:37:46,196 --> 00:37:49,733
a six-sided jet stream that's
two Earth diameters across

796
00:37:49,733 --> 00:37:51,635
centered on the north pole,

797
00:37:51,635 --> 00:37:53,671
then down to some
of the other images.

798
00:37:53,671 --> 00:37:56,073
So I'm gonna show you some
of the other additional ways

799
00:37:56,073 --> 00:37:57,574
to look at this data.

800
00:37:57,574 --> 00:38:00,510
One is here, here is what
the spacecraft was doing

801
00:38:00,510 --> 00:38:03,781
as we were taking those
pictures and looking at Saturn.

802
00:38:03,781 --> 00:38:05,248
So you can see that
we're going down,

803
00:38:05,248 --> 00:38:07,451
you can watch those
little picture frames

804
00:38:07,451 --> 00:38:09,520
getting smaller and
smaller and smaller,

805
00:38:09,520 --> 00:38:12,489
as we go down it, you'll
see shortly a turn

806
00:38:12,489 --> 00:38:14,224
as we point the
high gain antenna

807
00:38:14,224 --> 00:38:16,559
down into the
direction of particles,

808
00:38:16,559 --> 00:38:18,062
but we're still taking pictures,

809
00:38:18,062 --> 00:38:21,532
we're still taking science
data all of the way through.

810
00:38:21,532 --> 00:38:23,200
Here's another view,

811
00:38:23,200 --> 00:38:25,169
I like this view
because the red dot

812
00:38:25,169 --> 00:38:26,804
is showing you where
you are on Saturn,

813
00:38:26,804 --> 00:38:29,206
and here's those pictures
as if you're gazing out

814
00:38:29,206 --> 00:38:33,376
of a tiny window looking
down on the planet.

815
00:38:33,376 --> 00:38:35,178
So you can see all of
the detailed structure.

816
00:38:35,178 --> 00:38:37,147
These are all up on our web page

817
00:38:37,147 --> 00:38:40,717
if you want to go and
take a look at those.

818
00:38:40,717 --> 00:38:43,020
There's the turn for
the high gain antenna.

819
00:38:43,020 --> 00:38:46,089
And it'll stop here
shortly and then just to,

820
00:38:46,089 --> 00:38:48,358
you know, this is just
really an up close view

821
00:38:48,358 --> 00:38:51,128
of those first pictures
that game back.

822
00:38:51,128 --> 00:38:53,597
And we were gathered
on Wednesday night,

823
00:38:53,597 --> 00:38:56,133
it was just, you know,
a little over a week ago

824
00:38:56,133 --> 00:38:59,169
we were gathered to
wait for the first,

825
00:38:59,169 --> 00:39:01,505
you know, dive to come through,

826
00:39:01,505 --> 00:39:03,340
it was actually on April
26th, which was my birthday,

827
00:39:03,340 --> 00:39:05,075
and what a great
birthday present

828
00:39:05,075 --> 00:39:08,211
to make it through successfully
through the rings, so.

829
00:39:08,211 --> 00:39:09,146
(applauding)

830
00:39:09,146 --> 00:39:11,147
That was really a good day.

831
00:39:11,147 --> 00:39:13,384
And as we watch these
pictures come back,

832
00:39:13,384 --> 00:39:16,353
lots of us were here until
about two in the morning or so,

833
00:39:16,353 --> 00:39:18,722
one of the leading
Saturn scientists

834
00:39:18,722 --> 00:39:22,092
said "I've never seen
anything like it in my life.

835
00:39:22,092 --> 00:39:23,661
"I don't know what it is."

836
00:39:23,661 --> 00:39:25,629
And that's half the
fun, you go there,

837
00:39:25,629 --> 00:39:28,298
you're not sure what
you're gonna find.

838
00:39:28,298 --> 00:39:29,900
Now this is the second dive,

839
00:39:29,900 --> 00:39:31,602
what you're seeing
here is a movie,

840
00:39:31,602 --> 00:39:33,603
it's showing the
Cassini spacecraft

841
00:39:33,603 --> 00:39:36,474
along this orbital
cycle a few times.

842
00:39:36,474 --> 00:39:38,609
Well here, let me back
it up, it'll cycle again.

843
00:39:38,609 --> 00:39:39,910
Here's Cassini.

844
00:39:39,910 --> 00:39:41,478
This is the magnetic
field lines,

845
00:39:41,478 --> 00:39:43,180
the strength is color coded,

846
00:39:43,180 --> 00:39:45,048
and we're turning
the spacecraft.

847
00:39:45,048 --> 00:39:46,783
This is showing you an hour,

848
00:39:46,783 --> 00:39:50,954
and we're turning Cassini the
whole way through that time.

849
00:39:50,954 --> 00:39:54,291
And that's to calibrate the
magnetometer and get that data,

850
00:39:54,291 --> 00:39:57,027
and we were clever enough
to add just the right instep

851
00:39:57,027 --> 00:39:59,563
in that turn to have
the cosmic dust analyzer

852
00:39:59,563 --> 00:40:01,665
looking in the direction
of the ring plane.

853
00:40:01,665 --> 00:40:03,600
Our hope was it would
sample the ring particles

854
00:40:03,600 --> 00:40:04,968
and give us composition,

855
00:40:04,968 --> 00:40:07,438
but as Earl said,
it's pretty empty,

856
00:40:07,438 --> 00:40:11,008
and so there wasn't a
lot to see for that time.

857
00:40:11,008 --> 00:40:12,709
Here are some pictures
that came back,

858
00:40:12,709 --> 00:40:15,111
I just went to the web and
pulled off a few of them.

859
00:40:15,111 --> 00:40:17,681
This is a star, and this
is what happens when a star

860
00:40:17,681 --> 00:40:21,151
gets overexposed and the
camera is extra bright.

861
00:40:21,151 --> 00:40:25,456
Here's the F ring, and then
here's part of Saturn's A ring.

862
00:40:25,456 --> 00:40:28,958
Another one of the F ring,
it's very kinky and clumpy,

863
00:40:28,958 --> 00:40:30,794
very unusual, and we
took a very long movie

864
00:40:30,794 --> 00:40:33,530
as we flew through on
this particular pass

865
00:40:33,530 --> 00:40:35,032
of Saturn's F ring.

866
00:40:35,032 --> 00:40:37,468
Let me give you some of the
highlights of the science

867
00:40:37,468 --> 00:40:40,670
that we're going to be doing
in the remaining 20 dives

868
00:40:40,670 --> 00:40:42,672
between Saturn and the rings.

869
00:40:42,672 --> 00:40:45,709
Well of course it involves the
planet itself and the rings.

870
00:40:45,709 --> 00:40:47,044
If we start with the rings,

871
00:40:47,044 --> 00:40:48,745
one of the things
that Cassini can do

872
00:40:48,745 --> 00:40:52,516
is for the very first time
measure the mass of the rings.

873
00:40:52,516 --> 00:40:55,953
Right now that mass is
uncertain to 100 percent,

874
00:40:55,953 --> 00:40:57,220
we don't know what it is.

875
00:40:57,220 --> 00:40:58,955
But by diving in between
Saturn and the rings,

876
00:40:58,955 --> 00:41:01,624
we get just the mass
of Saturn by itself.

877
00:41:01,624 --> 00:41:03,493
Earlier in the mission, we have

878
00:41:03,493 --> 00:41:05,496
the mass of Saturn
plus the rings,

879
00:41:05,496 --> 00:41:07,698
subtract the two, you get
the mass of the rings.

880
00:41:07,698 --> 00:41:10,367
Now if the rings are more
massive than we expect,

881
00:41:10,367 --> 00:41:12,102
then they could've
perhaps formed

882
00:41:12,102 --> 00:41:14,071
at the same time as Saturn.

883
00:41:14,071 --> 00:41:16,006
They could've been
massive enough

884
00:41:16,006 --> 00:41:18,775
to have survived the
micro-meteoroid bombardment

885
00:41:18,775 --> 00:41:22,246
and erosion that took place
to be there 'til today.

886
00:41:22,246 --> 00:41:24,615
Less massive, they
must be young.

887
00:41:24,615 --> 00:41:26,350
Perhaps only 100
million years old,

888
00:41:26,350 --> 00:41:29,886
a small fraction of the
age of the solar system,

889
00:41:29,886 --> 00:41:32,489
perhaps forming from a comet
or a moon that got too close,

890
00:41:32,489 --> 00:41:34,525
Saturn's gravity
ripped it apart,

891
00:41:34,525 --> 00:41:37,361
those pieces went
on to form the ring.

892
00:41:37,361 --> 00:41:39,796
We still hope to get the
composition of the rings,

893
00:41:39,796 --> 00:41:41,764
we just have to
get a ring particle

894
00:41:41,764 --> 00:41:44,167
into our cosmic dust analyzer.

895
00:41:44,167 --> 00:41:46,269
Then for the planet itself
and also for the rings,

896
00:41:46,269 --> 00:41:47,971
we get some of the
best pictures ever

897
00:41:47,971 --> 00:41:50,841
of the hexagon, of the
storms at the poles,

898
00:41:50,841 --> 00:41:53,477
you've seen one swath,
we're gonna do that again,

899
00:41:53,477 --> 00:41:55,412
perhaps get some color,

900
00:41:55,412 --> 00:41:57,581
exquisite pictures
of those inner rings,

901
00:41:57,581 --> 00:42:01,351
who knows what we'll find
when we take a closer look.

902
00:42:01,351 --> 00:42:03,753
Then of course on
the last five orbits,

903
00:42:03,753 --> 00:42:07,491
we're literally dipping our
toe into Saturn's atmosphere,

904
00:42:07,491 --> 00:42:09,259
and our ion and neutral
mass spectrometer

905
00:42:09,259 --> 00:42:12,229
will be tasting the composition.

906
00:42:12,229 --> 00:42:14,265
It's mostly hydrogen, but
there are other things

907
00:42:14,265 --> 00:42:15,498
there as well.

908
00:42:15,498 --> 00:42:17,801
And so for the first
time directly sampling

909
00:42:17,801 --> 00:42:20,637
the upper atmosphere
of the planet.

910
00:42:20,637 --> 00:42:22,005
There's a radiation belt there.

911
00:42:22,005 --> 00:42:23,773
We know from Saturn
orbit insertion

912
00:42:23,773 --> 00:42:25,575
there's a very weak
radiation belt,

913
00:42:25,575 --> 00:42:28,345
not nearly as strong as the
main belt outside of the rings,

914
00:42:28,345 --> 00:42:30,447
so we hope to characterize
the radiation belt

915
00:42:30,447 --> 00:42:33,784
and the plasma
environment in that gap

916
00:42:33,784 --> 00:42:36,386
between the planet
and the rings.

917
00:42:36,386 --> 00:42:38,355
Then of course we're gonna
study the magnetic field,

918
00:42:38,355 --> 00:42:42,693
these blue lines coming out
from Saturn in exquisite detail.

919
00:42:42,693 --> 00:42:44,027
One of the things
we still don't know

920
00:42:44,027 --> 00:42:45,662
is the length of a Saturn day.

921
00:42:45,662 --> 00:42:48,832
How fast does Saturn
rotate on its interior,

922
00:42:48,832 --> 00:42:49,933
because when you
look at the outside,

923
00:42:49,933 --> 00:42:51,435
all you see are clouds.

924
00:42:51,435 --> 00:42:53,704
And different latitudes
rotate at different rates,

925
00:42:53,704 --> 00:42:55,839
and so we want to know
what's the rate of rotation.

926
00:42:55,839 --> 00:42:59,075
It's around 10 hours,
maybe 10 hours 20 minutes.

927
00:42:59,075 --> 00:43:00,577
What is it?

928
00:43:00,577 --> 00:43:02,646
And we're hoping if the
magnetometer data shows us

929
00:43:02,646 --> 00:43:04,815
the magnetic field is
tilted just a little bit,

930
00:43:04,815 --> 00:43:08,017
it'll swivel around
like a giant lighthouse,

931
00:43:08,017 --> 00:43:10,554
giving us the length of a day.

932
00:43:10,554 --> 00:43:11,855
We also want to know

933
00:43:11,855 --> 00:43:13,523
where does the magnetic
field originate?

934
00:43:13,523 --> 00:43:15,024
The atmosphere is
gas at the top,

935
00:43:15,024 --> 00:43:18,628
that hydrogen compresses to be
a molecular hydrogen liquid,

936
00:43:18,628 --> 00:43:21,231
compresses some more
until it becomes metallic,

937
00:43:21,231 --> 00:43:24,067
it's metallic in a phase
where currents can flow

938
00:43:24,067 --> 00:43:25,502
and generate a magnetic field.

939
00:43:25,502 --> 00:43:28,271
We think it's about
half a Saturn radius in,

940
00:43:28,271 --> 00:43:30,540
about a million
atmospheres of pressure.

941
00:43:30,540 --> 00:43:32,576
That's what our models tell us.

942
00:43:32,576 --> 00:43:34,277
So we'll get a
chance to find out,

943
00:43:34,277 --> 00:43:36,947
see what the inside
of the planet is like.

944
00:43:36,947 --> 00:43:39,149
We'll study the
aurora in more detail,

945
00:43:39,149 --> 00:43:40,917
particles come in
along the field lines,

946
00:43:40,917 --> 00:43:43,120
crash into that
area, create aurora,

947
00:43:43,120 --> 00:43:45,222
and they're pink,
pink and purple,

948
00:43:45,222 --> 00:43:47,591
because it's hydrogen
that's glowing and emitting

949
00:43:47,591 --> 00:43:50,427
in the aurora on Saturn.

950
00:43:50,427 --> 00:43:53,363
And then finally, looking
at the interior itself,

951
00:43:53,363 --> 00:43:55,065
with our gravity measurements,

952
00:43:55,065 --> 00:43:58,202
the size of a rocky core,
is it one Earth in size?

953
00:43:58,202 --> 00:43:59,736
Two Earths in size?

954
00:43:59,736 --> 00:44:01,205
What's the boundary like?

955
00:44:01,205 --> 00:44:02,672
How deep do the winds go?

956
00:44:02,672 --> 00:44:05,208
Is it 300 miles, 3000 miles?

957
00:44:05,208 --> 00:44:08,245
When do you start to
feel the winds peter out?

958
00:44:08,245 --> 00:44:10,781
And we think with the gravity
measurement irregularities

959
00:44:10,781 --> 00:44:15,318
we'll be able to pin down
the location of those winds.

960
00:44:15,318 --> 00:44:18,188
Then of course on
that final orbit,

961
00:44:18,188 --> 00:44:20,123
we go into Saturn.

962
00:44:20,123 --> 00:44:22,525
And that's gonna be
really I think a tough,

963
00:44:22,525 --> 00:44:25,461
a tough day, to say
goodbye to this spacecraft

964
00:44:25,461 --> 00:44:26,963
that's been around for so long.

965
00:44:26,963 --> 00:44:28,464
And when you think about it,

966
00:44:28,464 --> 00:44:31,335
with Cassini's final heartbeat,

967
00:44:31,335 --> 00:44:34,637
that's humankind's
last intimate,

968
00:44:34,637 --> 00:44:36,373
personal connection with Saturn,

969
00:44:36,373 --> 00:44:39,042
that connection will be cut.

970
00:44:39,042 --> 00:44:40,744
And we'll no longer be able to

971
00:44:40,744 --> 00:44:42,245
see those little tiny moons

972
00:44:42,245 --> 00:44:45,549
that I showed you pictures of
tonight, or Saturn's F ring,

973
00:44:45,549 --> 00:44:49,119
because you see, they'll
be lost in the glare

974
00:44:49,119 --> 00:44:50,687
of Saturn and its rings.

975
00:44:50,687 --> 00:44:53,656
Except for once every 15 years

976
00:44:53,656 --> 00:44:56,860
when the rings are
edge-on to the sun

977
00:44:56,860 --> 00:44:58,662
and the rings go dark.

978
00:44:58,662 --> 00:45:01,264
Then we'll get a chance
to catch a glimpse

979
00:45:01,264 --> 00:45:05,101
of these little tiny worlds
that Cassini revealed.

980
00:45:05,101 --> 00:45:08,539
But we have 20 more
dives through that gap

981
00:45:10,274 --> 00:45:11,708
before we get to the end.

982
00:45:11,708 --> 00:45:14,311
So we have a lot
more new, exciting,

983
00:45:14,311 --> 00:45:16,546
incredible science ahead.

984
00:45:16,546 --> 00:45:19,749
So join us, check our web page,

985
00:45:19,749 --> 00:45:21,584
look at the great
pictures coming down,

986
00:45:21,584 --> 00:45:24,554
and enjoy these final heady days

987
00:45:24,554 --> 00:45:26,724
of Cassini's grand finale.

988
00:45:27,858 --> 00:45:29,159
Thank you very much.

989
00:45:29,159 --> 00:45:31,562
(applauding)

990
00:45:41,871 --> 00:45:43,573
Earl and I would be
happy to take questions

991
00:45:43,573 --> 00:45:45,342
if you wouldn't
mind please using

992
00:45:45,342 --> 00:45:47,010
the microphone in the back,

993
00:45:47,010 --> 00:45:48,611
and that way everyone
will be able to hear you,

994
00:45:48,611 --> 00:45:51,448
so if you can go in the
back and use the microphone,

995
00:45:51,448 --> 00:45:53,117
that would be great.

996
00:45:58,789 --> 00:45:59,990
Go ahead.

997
00:45:59,990 --> 00:46:01,791
- Yeah, in the early '70s,

998
00:46:01,791 --> 00:46:04,761
I along with two now retired
colleagues developed the model

999
00:46:04,761 --> 00:46:06,897
for the gravitational
attraction of a disk,

1000
00:46:06,897 --> 00:46:09,799
which a Voyager navigator
said was rather critical

1001
00:46:09,799 --> 00:46:12,635
to Voyager actually
to go to Uranus

1002
00:46:12,635 --> 00:46:15,038
instead of some random place.

1003
00:46:15,038 --> 00:46:16,907
I'm kind of surprised that

1004
00:46:16,907 --> 00:46:19,276
partial derivatives
of your trajectory

1005
00:46:19,276 --> 00:46:21,978
with respect to the
mass of the rings

1006
00:46:21,978 --> 00:46:24,548
using that model don't
give you better information

1007
00:46:24,548 --> 00:46:27,284
than 100 percent
of an error bar.

1008
00:46:28,652 --> 00:46:30,220
- Well sort of the
question is, you know,

1009
00:46:30,220 --> 00:46:32,022
you needed to know
the mass of the rings

1010
00:46:32,022 --> 00:46:33,790
to have sent Voyager
on to Uranus,

1011
00:46:33,790 --> 00:46:36,759
so why don't we know them
better from our navigation data?

1012
00:46:36,759 --> 00:46:39,529
Well, if you look at it,
the mass of the rings

1013
00:46:39,529 --> 00:46:44,267
compared to the mass of
Saturn is absolutely tiny.

1014
00:46:44,267 --> 00:46:46,002
So in a certain sense, you know,

1015
00:46:46,002 --> 00:46:47,570
the rings are kind
of in the noise

1016
00:46:47,570 --> 00:46:49,839
because Saturn is so massive.

1017
00:46:49,839 --> 00:46:51,574
So even after all, you know,

1018
00:46:51,574 --> 00:46:55,178
we have it down much
more precisely than
we had for Voyager,

1019
00:46:55,178 --> 00:46:58,748
but it's still a
large error bar.

1020
00:46:58,748 --> 00:47:00,751
- Another question also,

1021
00:47:00,751 --> 00:47:04,821
I assume that when the line
of sight between the Earth

1022
00:47:04,821 --> 00:47:07,390
and the spacecraft
passes through Saturn,

1023
00:47:07,390 --> 00:47:09,259
that you are getting information

1024
00:47:09,259 --> 00:47:13,063
of the atmospheric composition
using microspectrometry.

1025
00:47:13,063 --> 00:47:14,297
- Right, right.

1026
00:47:14,297 --> 00:47:15,531
That's a very good point.

1027
00:47:15,531 --> 00:47:17,033
There are other kinds
of things we'll be doing

1028
00:47:17,033 --> 00:47:19,269
with the spacecraft, we can
actually use the radio signal

1029
00:47:19,269 --> 00:47:21,905
occulted by Saturn to get
occultations of the atmosphere,

1030
00:47:21,905 --> 00:47:25,809
of the rings themselves, and
do a lot of other science

1031
00:47:25,809 --> 00:47:27,610
focused on Saturn as well.

1032
00:47:27,610 --> 00:47:29,045
We'll actually get
radar in the rings

1033
00:47:29,045 --> 00:47:30,547
for the first time too.

1034
00:47:30,547 --> 00:47:32,148
And we've been doing that
throughout the mission,

1035
00:47:32,148 --> 00:47:34,717
using the radio beam or
stars to get occultations

1036
00:47:34,717 --> 00:47:37,287
of the planet and of the rings.

1037
00:47:39,689 --> 00:47:41,992
- Hey, I'm curious if you
could talk at all about

1038
00:47:41,992 --> 00:47:44,628
how you made the determination
that it was gonna be safe

1039
00:47:44,628 --> 00:47:46,362
to pass between the
rings and Saturn.

1040
00:47:46,362 --> 00:47:47,897
I know you talked
a little bit about

1041
00:47:47,897 --> 00:47:50,333
the ring scientists did a
lot of work in determining

1042
00:47:50,333 --> 00:47:52,702
that the dust environment
would be low enough

1043
00:47:52,702 --> 00:47:53,970
Cassini could survive,

1044
00:47:53,970 --> 00:47:55,571
but since it had never
been explored before,

1045
00:47:55,571 --> 00:47:57,941
how could you make that
with enough confidence

1046
00:47:57,941 --> 00:48:00,943
to say yeah, we'll
risk it and let's go?

1047
00:48:00,943 --> 00:48:03,380
- Well we had a model,
and what we did is,

1048
00:48:03,380 --> 00:48:05,582
Earl showed it earlier,
we took a picture

1049
00:48:05,582 --> 00:48:07,250
of the innermost
part of the rings

1050
00:48:07,250 --> 00:48:10,320
with Saturn's shadow
going across it.

1051
00:48:10,320 --> 00:48:12,922
And we know the shadow was
very black and very dark,

1052
00:48:12,922 --> 00:48:15,458
we looked at our image,
we stretched it to see

1053
00:48:15,458 --> 00:48:18,828
where that boundary went
relative to the shadow.

1054
00:48:18,828 --> 00:48:22,565
But in the images, all you see
are the tiny dust particles.

1055
00:48:22,565 --> 00:48:25,735
So we felt we understood
the dust very well.

1056
00:48:25,735 --> 00:48:28,672
But the bigger particles, if
there aren't very many of them,

1057
00:48:28,672 --> 00:48:29,939
you don't see them.

1058
00:48:29,939 --> 00:48:31,774
So we were just
sort of assuming,

1059
00:48:31,774 --> 00:48:33,677
okay, let's assume
it's sort of like

1060
00:48:33,677 --> 00:48:36,145
when we go through the
E ring or the G ring,

1061
00:48:36,145 --> 00:48:39,082
just little particles
and extrapolate in.

1062
00:48:39,082 --> 00:48:41,651
Our extrapolations told us
we should have less dust

1063
00:48:41,651 --> 00:48:44,520
than we saw in the E ring
or the ring grazing orbits,

1064
00:48:44,520 --> 00:48:47,090
but there was nothing
in the model to say

1065
00:48:47,090 --> 00:48:49,025
there'd be no dust.

1066
00:48:49,025 --> 00:48:50,861
So but part of it,
the bigger particles,

1067
00:48:50,861 --> 00:48:52,929
that was a risk.

1068
00:48:52,929 --> 00:48:55,531
A risk though worth taking.

1069
00:48:55,531 --> 00:48:56,533
- Thank you.

1070
00:48:58,468 --> 00:49:00,203
- Thanks for the great talk.

1071
00:49:00,203 --> 00:49:02,872
I had a question
for each of you.

1072
00:49:02,872 --> 00:49:05,542
First question, on the animation

1073
00:49:06,943 --> 00:49:10,947
depicting Cassini's first
travel through the ring plane,

1074
00:49:10,947 --> 00:49:13,115
it appeared that the mag boom

1075
00:49:13,115 --> 00:49:16,386
was rotated towards the D ring,

1076
00:49:16,386 --> 00:49:18,221
is that accurate?

1077
00:49:18,221 --> 00:49:20,924
And would there be
any difference between

1078
00:49:20,924 --> 00:49:23,560
particulate risk on
either orientation?

1079
00:49:23,560 --> 00:49:24,728
- No.

1080
00:49:24,728 --> 00:49:26,395
When you're pointing
into the ram,

1081
00:49:26,395 --> 00:49:29,766
you know, the mag boom
is equally exposed,

1082
00:49:29,766 --> 00:49:31,734
and so that was a
preferential attitude

1083
00:49:31,734 --> 00:49:34,471
for the magnetometer itself.

1084
00:49:34,471 --> 00:49:36,406
- Yeah, if you look at the
Cassini model over here,

1085
00:49:36,406 --> 00:49:38,808
you can see the mag boom,
that big golden boom,

1086
00:49:38,808 --> 00:49:41,277
it doesn't matter how
you point the space...

1087
00:49:41,277 --> 00:49:43,113
Well, for the high gain antenna

1088
00:49:43,113 --> 00:49:44,547
protecting the rest
of the spacecraft,

1089
00:49:44,547 --> 00:49:47,083
the mag boom was
hanging out there.

1090
00:49:47,083 --> 00:49:48,618
Yeah.

1091
00:49:48,618 --> 00:49:51,487
- Second question, on the
equinox slide that you had,

1092
00:49:51,487 --> 00:49:54,791
there's a lot of
vertical perturbations,

1093
00:49:54,791 --> 00:49:58,061
and it looked like they were
all 90 degrees from ring plane.

1094
00:49:58,061 --> 00:50:00,564
What are the
mechanics behind that?

1095
00:50:00,564 --> 00:50:02,665
- In that image I
showed from equinox,

1096
00:50:02,665 --> 00:50:07,070
the sun direction was shining
from above, shining down,

1097
00:50:07,070 --> 00:50:09,572
and so that small piece
of the rings that you saw,

1098
00:50:09,572 --> 00:50:11,207
it made them look
like, you know,

1099
00:50:11,207 --> 00:50:14,210
all the shadows were going
out in a single direction.

1100
00:50:14,210 --> 00:50:16,712
Why the clumps happened to
be at the edge of the B ring,

1101
00:50:16,712 --> 00:50:19,115
there's a resonance keeping
the edge from spreading

1102
00:50:19,115 --> 00:50:21,784
and maybe the clumping,
there's a lot of clumping

1103
00:50:21,784 --> 00:50:24,153
that happens in that
region as the particles,

1104
00:50:24,153 --> 00:50:26,423
like a crowded freeway,
they're trying to merge over

1105
00:50:26,423 --> 00:50:28,891
and they can't, so they're
starting to clump together.

1106
00:50:28,891 --> 00:50:30,559
- But the main question was on

1107
00:50:30,559 --> 00:50:32,529
the vertical extension of that.

1108
00:50:32,529 --> 00:50:36,666
If a moon is traveling by,
and caused perturbation,

1109
00:50:36,666 --> 00:50:39,002
wouldn't that be
bent or inclined

1110
00:50:39,002 --> 00:50:41,471
as opposed to straight
out of ring plane?

1111
00:50:41,471 --> 00:50:43,406
- Well, everything
pretty much with Saturn,

1112
00:50:43,406 --> 00:50:44,908
that's a very
interesting question,

1113
00:50:44,908 --> 00:50:46,676
the rings on average are
only about 10 feet thick,

1114
00:50:46,676 --> 00:50:49,779
and Saturn's oblateness
tends to keep everything

1115
00:50:49,779 --> 00:50:51,915
very very coplanar.

1116
00:50:51,915 --> 00:50:54,717
So they don't tend to
have inclined orbits.

1117
00:50:54,717 --> 00:50:56,620
There are other places in the
rings with inclined orbits,

1118
00:50:56,620 --> 00:50:58,054
bending waves, et cetera,

1119
00:50:58,054 --> 00:51:00,589
but not generally
across the rings

1120
00:51:00,589 --> 00:51:02,458
not at the edge of the B ring.

1121
00:51:02,458 --> 00:51:03,293
- Thank you.

1122
00:51:03,293 --> 00:51:04,127
- Yeah.

1123
00:51:05,295 --> 00:51:08,331
- Yes, all the orbits
of the spacecraft

1124
00:51:08,331 --> 00:51:11,434
that I saw here, it looked
extremely elliptical.

1125
00:51:11,434 --> 00:51:14,638
Is there a way that you could've
obtained a circular orbit,

1126
00:51:14,638 --> 00:51:18,040
and if so, could you have
continued the mission

1127
00:51:18,040 --> 00:51:22,878
by attaining the circular
orbit within the ring gap,

1128
00:51:22,878 --> 00:51:24,113
considering now that you know

1129
00:51:24,113 --> 00:51:25,648
that there's very few
particles in there,

1130
00:51:25,648 --> 00:51:28,385
and then you wouldn't have
run into much resistance,

1131
00:51:28,385 --> 00:51:30,286
and if it eventually
decayed its orbit

1132
00:51:30,286 --> 00:51:31,921
like a satellite around Earth,

1133
00:51:31,921 --> 00:51:34,124
it would just crash
into the planet anyway,

1134
00:51:34,124 --> 00:51:37,493
and it wouldn't present
any hazard to the moons.

1135
00:51:37,493 --> 00:51:40,096
- Well, I think a circular
orbit's always an option,

1136
00:51:40,096 --> 00:51:43,366
but not a very scientifically
interesting one.

1137
00:51:43,366 --> 00:51:46,202
One of the things we really
did have to, you know,

1138
00:51:46,202 --> 00:51:49,806
if you're going to use
Titan as a circularizer,

1139
00:51:49,806 --> 00:51:51,541
and that's really the only
way we could've done it,

1140
00:51:51,541 --> 00:51:53,309
you're gonna have to
come back to Titan,

1141
00:51:53,309 --> 00:51:54,577
there's no way to avoid it,

1142
00:51:54,577 --> 00:51:56,179
so you're essentially
going to be

1143
00:51:56,179 --> 00:51:58,148
in some sort of
Titan-like orbit,

1144
00:51:58,148 --> 00:52:00,383
and if you're going
to be doing that,

1145
00:52:00,383 --> 00:52:02,552
you're eventually
gonna have to deal with

1146
00:52:02,552 --> 00:52:03,853
the fact that you're
out of propellant

1147
00:52:03,853 --> 00:52:06,155
and in an orbit you
don't want to be in,

1148
00:52:06,155 --> 00:52:07,857
with Titan messing with you.

1149
00:52:07,857 --> 00:52:09,325
There were some other options

1150
00:52:09,325 --> 00:52:13,129
for very large elliptical
orbits that were also stable,

1151
00:52:13,129 --> 00:52:15,899
but the scientific
value of those

1152
00:52:17,267 --> 00:52:20,670
relative to these grand
finale orbits was so marginal

1153
00:52:20,670 --> 00:52:24,173
that they were dismissed
almost immediately.

1154
00:52:24,173 --> 00:52:25,941
- Right, in fact, the
scientists kind of looked down

1155
00:52:25,941 --> 00:52:27,810
this table of options
of what we could do

1156
00:52:27,810 --> 00:52:30,179
and they saw the grand finale
and they said "that's it,

1157
00:52:30,179 --> 00:52:33,083
"end of discussion, we don't
need to talk about it anymore,"

1158
00:52:33,083 --> 00:52:34,517
so they liked that.

1159
00:52:34,517 --> 00:52:36,386
- Yeah, granted that
because of the way

1160
00:52:36,386 --> 00:52:38,121
the mission proceeded,
it's no longer an option,

1161
00:52:38,121 --> 00:52:41,557
but if you'd known when
you started the mission

1162
00:52:41,557 --> 00:52:43,259
what you know now, would
it have been possible

1163
00:52:43,259 --> 00:52:46,129
to end the mission with the
spacecraft in a circular orbit

1164
00:52:46,129 --> 00:52:48,565
within the ring gap?

1165
00:52:48,565 --> 00:52:49,999
- Oh, within the ring gap.

1166
00:52:49,999 --> 00:52:51,401
I don't think so,

1167
00:52:52,435 --> 00:52:54,904
simply because
there's, where are you,

1168
00:52:54,904 --> 00:52:57,140
you're going to have to find
something to circularize you

1169
00:52:57,140 --> 00:52:59,976
at both periapsis
and at the apoapsis,

1170
00:52:59,976 --> 00:53:02,045
and I'm not quite sure...

1171
00:53:03,480 --> 00:53:05,681
I'm not gonna stick my
neck out on that, though.

1172
00:53:05,681 --> 00:53:07,584
Again, if you're using Titan,

1173
00:53:07,584 --> 00:53:09,452
and that's really the
only thing we've got,

1174
00:53:09,452 --> 00:53:12,455
you're gonna have to end up
coming back out to Titan again.

1175
00:53:12,455 --> 00:53:13,690
- So there's no way...

1176
00:53:13,690 --> 00:53:15,091
You couldn't carry
enough fuel to do that,

1177
00:53:15,091 --> 00:53:16,025
you'd have to--

1178
00:53:16,025 --> 00:53:16,859
- Well that would be the thing,

1179
00:53:16,859 --> 00:53:18,795
and no, I don't think...

1180
00:53:18,795 --> 00:53:21,564
Well, I'll let Linda speak
to the scientific merits

1181
00:53:21,564 --> 00:53:23,299
of carrying that much propellant

1182
00:53:23,299 --> 00:53:25,902
and then using it to go inside
the rings and stay there.

1183
00:53:25,902 --> 00:53:29,338
But you could, I
mean, conceivably

1184
00:53:29,338 --> 00:53:31,140
you could take enough
propellant to go in

1185
00:53:31,140 --> 00:53:33,876
and actually once you've
got periapsis inside,

1186
00:53:33,876 --> 00:53:37,213
then do a breaking burn to
take apoapsis in as well.

1187
00:53:37,213 --> 00:53:39,315
But that's a lot of propellant.

1188
00:53:39,315 --> 00:53:40,650
- That's a lot of propellant,

1189
00:53:40,650 --> 00:53:42,418
or you could try
aerocapture or aerobraking,

1190
00:53:42,418 --> 00:53:43,853
but until Cassini flew there,

1191
00:53:43,853 --> 00:53:45,788
we had no idea how
clear it would be.

1192
00:53:45,788 --> 00:53:47,290
- Okay, thank you.

1193
00:53:50,193 --> 00:53:51,027
- Hi.

1194
00:53:52,495 --> 00:53:56,199
I was wondering, do you use
plutonium to power Cassini?

1195
00:54:00,303 --> 00:54:01,604
- Yes we do.

1196
00:54:01,604 --> 00:54:03,907
But we use plutonium in
a very interesting way,

1197
00:54:03,907 --> 00:54:08,311
because plutonium,
that's P238, is very hot.

1198
00:54:08,311 --> 00:54:10,813
And so all we're doing
is using the heat

1199
00:54:10,813 --> 00:54:13,516
from its radioactive
decay to fire,

1200
00:54:13,516 --> 00:54:17,086
to power little
thermoelectric cells.

1201
00:54:17,086 --> 00:54:19,421
We have three of them
on the spacecraft,

1202
00:54:19,421 --> 00:54:20,957
you can look at the model later

1203
00:54:20,957 --> 00:54:22,792
and see them at the bottom,
they're these black things.

1204
00:54:22,792 --> 00:54:25,027
And so it's the
heat from plutonium

1205
00:54:25,027 --> 00:54:26,729
that give us the electricity.

1206
00:54:26,729 --> 00:54:28,130
And that's all we use it for,

1207
00:54:28,130 --> 00:54:31,935
we actually use chemical
rocket fuel for the propellant,

1208
00:54:31,935 --> 00:54:35,538
and the plutonium,
well, as a good example,

1209
00:54:36,672 --> 00:54:38,575
Voyager's coming
up on its 40th year

1210
00:54:38,575 --> 00:54:40,977
and they're still going
fine on plutonium.

1211
00:54:40,977 --> 00:54:44,680
Cassini has lots of
electricity, just no propellant.

1212
00:54:44,680 --> 00:54:46,149
- Yeah, if you look
at the Voyager model,

1213
00:54:46,149 --> 00:54:48,784
that big black object
off to one side,

1214
00:54:48,784 --> 00:54:50,987
Cassini has three of those.

1215
00:54:50,987 --> 00:54:53,056
And that's what
contains the plutonium

1216
00:54:53,056 --> 00:54:57,227
that the heat is used to power
Voyager and to power Cassini.

1217
00:54:59,128 --> 00:55:02,265
- Another question is
do you have an idea

1218
00:55:02,265 --> 00:55:05,768
of what the pentagon
could be made of?

1219
00:55:05,768 --> 00:55:08,938
- Oh, what the hexagon at
the north pole is made of?

1220
00:55:08,938 --> 00:55:11,774
Well it's a jet stream,
so it's made of gas,

1221
00:55:11,774 --> 00:55:13,343
but going around very fast.

1222
00:55:13,343 --> 00:55:16,279
That edge of the hexagon
is like a giant racetrack,

1223
00:55:16,279 --> 00:55:18,314
and the clouds just
race around there faster

1224
00:55:18,314 --> 00:55:20,483
than just about any place else.

1225
00:55:20,483 --> 00:55:24,354
Why it has six sides, and
what keeps six sides on it,

1226
00:55:24,354 --> 00:55:26,389
we have no idea.

1227
00:55:26,389 --> 00:55:27,390
- Thank you.

1228
00:55:30,126 --> 00:55:32,662
- Yeah, I was wondering
if the ring gaps

1229
00:55:32,662 --> 00:55:37,233
seem to be always caused by
moons that clear out the debris,

1230
00:55:37,233 --> 00:55:39,568
or maybe moons that
were once there

1231
00:55:39,568 --> 00:55:41,137
and were ejected at some point,

1232
00:55:41,137 --> 00:55:44,506
are are they like dynamic
and constantly changing?

1233
00:55:44,506 --> 00:55:45,808
- Well initially with the rings,

1234
00:55:45,808 --> 00:55:48,878
we thought that the
gaps had to have moons,

1235
00:55:48,878 --> 00:55:51,347
because we saw Pan
in the Encke gap,

1236
00:55:51,347 --> 00:55:53,683
then we discovered
Daphnis in the Kieler gap,

1237
00:55:53,683 --> 00:55:55,318
but there are gaps
in the C ring,

1238
00:55:55,318 --> 00:55:57,954
some of the gaps have
ringlets inside of it,

1239
00:55:57,954 --> 00:56:00,756
and we looked, and we
looked, and we looked,

1240
00:56:00,756 --> 00:56:05,494
we didn't find any moons in
any of the gaps in the C ring.

1241
00:56:05,494 --> 00:56:09,032
So there's some process that
we don't understand quite yet

1242
00:56:09,032 --> 00:56:12,735
that can keep gaps
open without moons.

1243
00:56:12,735 --> 00:56:15,238
So if you have a good
idea, let us know.

1244
00:56:15,238 --> 00:56:16,072
(audience laughing)

1245
00:56:16,072 --> 00:56:17,073
- Thank you.

1246
00:56:18,407 --> 00:56:19,576
- Howdy.

1247
00:56:19,576 --> 00:56:21,044
I actually had two
really quick questions.

1248
00:56:21,044 --> 00:56:24,647
One was about Pan, that
odd ridge-shaped feature

1249
00:56:24,647 --> 00:56:27,983
on its equator, do you know
like the consistency of that,

1250
00:56:27,983 --> 00:56:29,418
is it more like a rocky material

1251
00:56:29,418 --> 00:56:32,054
or more of like something
equivalent to sand?

1252
00:56:32,054 --> 00:56:35,325
- Okay, well the rings are
made 99 percent of water ice.

1253
00:56:35,325 --> 00:56:38,227
And so, and that's
also true of the moons.

1254
00:56:38,227 --> 00:56:40,363
And we can also,
through some mechanisms,

1255
00:56:40,363 --> 00:56:44,200
figure out how porous, you
know, how porous it is.

1256
00:56:44,200 --> 00:56:46,469
An ice cube would be
not porous at all,

1257
00:56:46,469 --> 00:56:48,738
a snowball would
be quite porous.

1258
00:56:48,738 --> 00:56:50,806
Pan is much more
toward a snowball

1259
00:56:50,806 --> 00:56:52,675
than it is toward an ice cube.

1260
00:56:52,675 --> 00:56:55,011
There's a lot of porous
space in between,

1261
00:56:55,011 --> 00:56:56,479
and it's water ice.

1262
00:56:56,479 --> 00:56:57,980
- Okay.

1263
00:56:57,980 --> 00:57:01,951
And my second question was in
regards to the final orbit.

1264
00:57:01,951 --> 00:57:06,222
Right now the final orbit is
perpendicular to the rings.

1265
00:57:06,222 --> 00:57:08,924
Was it ever considered
to do a orbit

1266
00:57:08,924 --> 00:57:11,527
more parallel to the rings?

1267
00:57:11,527 --> 00:57:14,330
Was that every a consideration?

1268
00:57:14,330 --> 00:57:15,998
- Do you want to answer
that, the navigator?

1269
00:57:15,998 --> 00:57:17,500
- Well...

1270
00:57:17,500 --> 00:57:18,935
- That's a good question,
they did find something.

1271
00:57:18,935 --> 00:57:20,536
- It's a great question.

1272
00:57:20,536 --> 00:57:22,972
But what happened,
actually when we

1273
00:57:22,972 --> 00:57:24,173
first started with Cassini,

1274
00:57:24,173 --> 00:57:26,075
we didn't think we could
do what we've done.

1275
00:57:26,075 --> 00:57:29,245
So the techniques, the
astrodynamic techniques

1276
00:57:29,245 --> 00:57:32,148
and the numerical techniques
have been evolving,

1277
00:57:32,148 --> 00:57:33,616
and we actually do now know

1278
00:57:33,616 --> 00:57:36,385
based on some work from
the Cassini navigation team

1279
00:57:36,385 --> 00:57:40,756
that we could have these
so-called ring skirting orbits,

1280
00:57:40,756 --> 00:57:44,293
but by that time,
interestingly enough,

1281
00:57:44,293 --> 00:57:47,997
we developed the Cassini
project, the nav team developed

1282
00:57:47,997 --> 00:57:52,701
these responses more as we ran
out of propellant too early.

1283
00:57:52,701 --> 00:57:56,473
By that time we had invested
so much time and energy

1284
00:57:56,473 --> 00:58:00,209
and our propellant reserves
in getting ourselves

1285
00:58:00,209 --> 00:58:02,511
into these grand finale orbits

1286
00:58:02,511 --> 00:58:04,146
that it really wasn't an option.

1287
00:58:04,146 --> 00:58:06,015
But it's out there, and
we're actually seeing

1288
00:58:06,015 --> 00:58:08,951
maybe some mission proposals
next time around to do that.

1289
00:58:08,951 --> 00:58:11,086
- Right, when Cassini
launched, we had no idea

1290
00:58:11,086 --> 00:58:13,589
you could dive in between
the rings and the planet.

1291
00:58:13,589 --> 00:58:15,791
And that just took the
evolution of software

1292
00:58:15,791 --> 00:58:17,993
and of the right
people to find that.

1293
00:58:17,993 --> 00:58:20,195
It's actually a group at
Purdue first found it,

1294
00:58:20,195 --> 00:58:23,065
then people here at JPL
were the ones that actually

1295
00:58:23,065 --> 00:58:26,302
came up with and finished
the grand finale orbits.

1296
00:58:26,302 --> 00:58:30,072
- So it's possible that
the next Saturn mission

1297
00:58:30,072 --> 00:58:32,441
will be more ring-focused or
something along those lines.

1298
00:58:32,441 --> 00:58:36,311
- There's almost a ring
hovering type mission now

1299
00:58:36,311 --> 00:58:39,315
that the astrodynamics
allow it to happen,

1300
00:58:39,315 --> 00:58:41,851
just need to get it started.

1301
00:58:41,851 --> 00:58:43,319
- So just to sort
of answer that,

1302
00:58:43,319 --> 00:58:44,520
the priorities if we were
to go back to Saturn,

1303
00:58:44,520 --> 00:58:46,488
NASA has a New
Frontiers program,

1304
00:58:46,488 --> 00:58:49,892
and in it there are three
possible Saturn missions.

1305
00:58:49,892 --> 00:58:51,794
One is a Saturn probe,

1306
00:58:51,794 --> 00:58:54,297
send a probe deep into
Saturn's atmosphere,

1307
00:58:54,297 --> 00:58:57,866
measure noble gases in the
composition as you go down,

1308
00:58:57,866 --> 00:59:00,135
the next is Titan as a target,

1309
00:59:00,135 --> 00:59:04,406
orbit Titan, land on Titan,
float in Titan's methane seas,

1310
00:59:04,406 --> 00:59:06,675
and the third is to
go back to Enceladus.

1311
00:59:06,675 --> 00:59:09,545
So those are the
three major targets.

1312
00:59:09,545 --> 00:59:12,081
New Frontiers is a
much smaller budget

1313
00:59:12,081 --> 00:59:14,116
than a big flagship
like Cassini,

1314
00:59:14,116 --> 00:59:17,119
but at least there's three
of them, three possibilities.

1315
00:59:17,119 --> 00:59:18,854
In November they'll down select,

1316
00:59:18,854 --> 00:59:20,923
I think they got
40 some proposals,

1317
00:59:20,923 --> 00:59:22,591
go down to three to five,

1318
00:59:22,591 --> 00:59:24,726
and then further down select
probably a year after that,

1319
00:59:24,726 --> 00:59:27,296
so we'll see if Saturn
is still in the mix,

1320
00:59:27,296 --> 00:59:28,798
going back to Saturn,

1321
00:59:28,798 --> 00:59:31,133
but it's still, you know, it's
probably 30 years from now

1322
00:59:31,133 --> 00:59:32,468
until we get back.

1323
00:59:32,468 --> 00:59:33,635
It's a long trip.

1324
00:59:33,635 --> 00:59:34,503
- Fingers crossed.

1325
00:59:34,503 --> 00:59:35,404
- Yeah.

1326
00:59:35,404 --> 00:59:36,406
- Thank you.

1327
00:59:37,472 --> 00:59:40,008
- Hi, I have a two-parter also.

1328
00:59:40,008 --> 00:59:44,614
First question is, how
long out are you able to

1329
00:59:44,614 --> 00:59:46,182
plan for this trip?

1330
00:59:46,182 --> 00:59:48,951
Like a 30 year mission,
how long are you able...

1331
00:59:48,951 --> 00:59:50,986
I mean, do you start off
with like a five year plan,

1332
00:59:50,986 --> 00:59:53,422
and then you, you
know, figure that out,

1333
00:59:53,422 --> 00:59:54,823
and then after
another five years,

1334
00:59:54,823 --> 00:59:55,924
you do another five year plan?

1335
00:59:55,924 --> 00:59:58,695
Like how much out do you end up

1336
00:59:58,695 --> 01:00:00,229
before you're like
re-evaluating?

1337
01:00:00,229 --> 01:00:01,764
- You pretty much
plan end to end,

1338
01:00:01,764 --> 01:00:03,866
you plan, you know, when
you're gonna launch,

1339
01:00:03,866 --> 01:00:05,968
how long the cruise
is gonna take,

1340
01:00:05,968 --> 01:00:08,070
and what your prime
mission would be like,

1341
01:00:08,070 --> 01:00:10,773
and that's part of the
package that you put together

1342
01:00:10,773 --> 01:00:14,209
and give to NASA for the
missions that you want to fly.

1343
01:00:14,209 --> 01:00:17,480
So when we first got,
Cassini started in 1990,

1344
01:00:17,480 --> 01:00:20,049
we picked the instruments,
built the spacecraft,

1345
01:00:20,049 --> 01:00:21,784
we knew it would
launch, you know,

1346
01:00:21,784 --> 01:00:23,185
we had some launch
slips and things,

1347
01:00:23,185 --> 01:00:24,386
but when it launched in '97,

1348
01:00:24,386 --> 01:00:27,055
we knew exactly when
it would get to Saturn,

1349
01:00:27,055 --> 01:00:30,726
and we knew exactly what those
four years would look like.

1350
01:00:30,726 --> 01:00:33,528
- The solstice mission
that I showed you

1351
01:00:33,528 --> 01:00:35,898
actually was planned in 2009,

1352
01:00:35,898 --> 01:00:39,368
right down to almost
the final set of orbits.

1353
01:00:39,368 --> 01:00:41,403
Now there are certainly some
tweaks and modifications,

1354
01:00:41,403 --> 01:00:45,575
but we really take the long
view on that final set.

1355
01:00:46,943 --> 01:00:50,613
- So I'm also curious, the
crash into Saturn with Cassini,

1356
01:00:50,613 --> 01:00:54,684
was there a plan B, and
why wasn't plan B chosen?

1357
01:00:56,418 --> 01:00:59,888
- Probably plans A through
F, maybe through H,

1358
01:00:59,888 --> 01:01:01,723
and again, it's the science.

1359
01:01:01,723 --> 01:01:03,559
- Right, yeah, the
science drove it,

1360
01:01:03,559 --> 01:01:05,694
and more than that, you
know, the fuel light's on,

1361
01:01:05,694 --> 01:01:07,296
it's red and it's blinking,

1362
01:01:07,296 --> 01:01:09,465
and it's saying, you know,
you're almost out of gas,

1363
01:01:09,465 --> 01:01:11,167
in fact we don't use
the main engines,

1364
01:01:11,167 --> 01:01:14,036
we use use the
hydrazine reservoir now,

1365
01:01:14,036 --> 01:01:15,438
and it really was the fuel,

1366
01:01:15,438 --> 01:01:17,940
healthy spacecraft,
great instruments,

1367
01:01:17,940 --> 01:01:21,243
you know, we just need a way
to refuel, and we'd be fine.

1368
01:01:21,243 --> 01:01:22,245
- Thank you.

1369
01:01:23,979 --> 01:01:26,516
- Do we understand why
the Saturnian system

1370
01:01:26,516 --> 01:01:29,819
is so complex compared
with another solar system,

1371
01:01:29,819 --> 01:01:34,089
or any other planetary
system in our solar system?

1372
01:01:34,089 --> 01:01:36,191
- Well the Saturn
system looks complex,

1373
01:01:36,191 --> 01:01:37,626
you've got the main planet,

1374
01:01:37,626 --> 01:01:39,562
you've got the
rings, and 62 moons,

1375
01:01:39,562 --> 01:01:42,565
but the Jovian system has
complexities of its own,

1376
01:01:42,565 --> 01:01:44,600
as do the systems of
Uranus and Neptune,

1377
01:01:44,600 --> 01:01:47,169
we just haven't studied
Uranus and Neptune

1378
01:01:47,169 --> 01:01:50,139
as well as we've studied
the Saturn system, you know.

1379
01:01:50,139 --> 01:01:52,308
Saturn just has these
great big wonderful rings,

1380
01:01:52,308 --> 01:01:54,744
but so do Jupiter,
Uranus, and Neptune,

1381
01:01:54,744 --> 01:01:56,245
they have rings too,

1382
01:01:56,245 --> 01:01:58,581
they have fascinating moons,
maybe not quite as many,

1383
01:01:58,581 --> 01:02:02,751
but there's a lot of complexity
with those outer planets.

1384
01:02:02,751 --> 01:02:04,820
- In other words,
it just happened.

1385
01:02:04,820 --> 01:02:06,455
- Yeah, we don't know,
that's a good question.

1386
01:02:06,455 --> 01:02:09,558
Why the moons ended up,
the order and the masses,

1387
01:02:09,558 --> 01:02:11,627
that's a really good question.

1388
01:02:11,627 --> 01:02:13,996
- The same question
for both of you,

1389
01:02:13,996 --> 01:02:16,299
there have been many
surprises on this mission,

1390
01:02:16,299 --> 01:02:19,001
what was the biggest
surprise for you?

1391
01:02:19,001 --> 01:02:22,471
- You take that, what's
the biggest surprise?

1392
01:02:22,471 --> 01:02:25,308
- I guess I've still got
to go back to Enceladus.

1393
01:02:25,308 --> 01:02:28,111
I mean there's just
something absolutely magical

1394
01:02:28,111 --> 01:02:29,712
about this...

1395
01:02:29,712 --> 01:02:32,582
I mean, again, it's just
totally out of the blue

1396
01:02:32,582 --> 01:02:35,317
that it would be as
dynamic as it is,

1397
01:02:35,317 --> 01:02:37,754
and not only dynamic
in a geological sense,

1398
01:02:37,754 --> 01:02:40,356
but to have all the
chemistry going on as well.

1399
01:02:40,356 --> 01:02:43,292
I mean that's just
rewritten the book.

1400
01:02:43,292 --> 01:02:46,462
It's promoted itself
from a class zero

1401
01:02:47,863 --> 01:02:49,499
to a class three object,

1402
01:02:49,499 --> 01:02:52,334
and by those I mean
planetary protection terms,

1403
01:02:52,334 --> 01:02:54,469
it is something that, you know,

1404
01:02:54,469 --> 01:02:56,839
once in a lifetime you'll
be walking down the trail

1405
01:02:56,839 --> 01:02:59,107
and you find a ruby.

1406
01:02:59,107 --> 01:03:00,876
It's just amazing.

1407
01:03:00,876 --> 01:03:03,412
- Yeah, I mean, Enceladus
was a complete surprise.

1408
01:03:03,412 --> 01:03:05,515
A moon 300 miles across,

1409
01:03:05,515 --> 01:03:08,750
we thought for certain
it would be frozen solid.

1410
01:03:08,750 --> 01:03:11,286
And to fly by and
see active geysers

1411
01:03:11,286 --> 01:03:14,122
coming out of four
fractures at the south pole,

1412
01:03:14,122 --> 01:03:16,458
mostly water vapor and
water ice particles,

1413
01:03:16,458 --> 01:03:20,295
but you found organics,
you found carbon dioxide,

1414
01:03:20,295 --> 01:03:23,999
methane, ammonia,
then the global ocean

1415
01:03:23,999 --> 01:03:26,034
that was round the rocky core,

1416
01:03:26,034 --> 01:03:28,203
hydrothermal vents
on the sea floor,

1417
01:03:28,203 --> 01:03:30,572
that hydrogen coming
out has enough energy

1418
01:03:30,572 --> 01:03:33,042
in combination with methane,

1419
01:03:33,042 --> 01:03:35,244
in fact the scientists
did a calculation,

1420
01:03:35,244 --> 01:03:36,812
there's enough
hydrogen coming out,

1421
01:03:36,812 --> 01:03:38,980
the energy there
is the equivalent

1422
01:03:38,980 --> 01:03:41,917
of 300 cheese pizzas per hour

1423
01:03:41,917 --> 01:03:43,085
(audience laughing)

1424
01:03:43,085 --> 01:03:44,586
coming out of, you
know, out of Enceladus.

1425
01:03:44,586 --> 01:03:47,356
If you wanted microbes, you
had a lot of hungry microbes.

1426
01:03:47,356 --> 01:03:49,826
You have a lot of food
there for them to eat.

1427
01:03:49,826 --> 01:03:52,628
So basically, I think
one of Cassini's legacies

1428
01:03:52,628 --> 01:03:54,363
will be we've changed
the way we look

1429
01:03:54,363 --> 01:03:56,164
at where you can find life.

1430
01:03:56,164 --> 01:03:58,801
It doesn't have to be
in that Goldilocks zone

1431
01:03:58,801 --> 01:04:00,235
where the Earth is,
where you can have

1432
01:04:00,235 --> 01:04:01,704
liquid water on the surface.

1433
01:04:01,704 --> 01:04:04,907
It could be beneath the icy
crusts of worlds like Enceladus,

1434
01:04:04,907 --> 01:04:08,010
Europa, Titan, and
perhaps other worlds,

1435
01:04:08,010 --> 01:04:09,812
so I think that's
probably the biggest

1436
01:04:09,812 --> 01:04:13,648
shift in our thinking, where
do you go to look for life.

1437
01:04:13,648 --> 01:04:16,385
And if we found life
in Enceladus's ocean,

1438
01:04:16,385 --> 01:04:17,953
it would be remarkable,

1439
01:04:17,953 --> 01:04:20,822
to think that life could form
underneath the icy crust,

1440
01:04:20,822 --> 01:04:22,924
it would be totally
a different path

1441
01:04:22,924 --> 01:04:25,461
from the life that we
took on our planet,

1442
01:04:25,461 --> 01:04:27,697
and by the same token
if we didn't find life

1443
01:04:27,697 --> 01:04:31,267
in Enceladus's ocean, that
would be remarkable as well,

1444
01:04:31,267 --> 01:04:33,802
because it would show you
here you have this habitat,

1445
01:04:33,802 --> 01:04:37,405
you have these ingredients, and
yet life didn't get started.

1446
01:04:37,405 --> 01:04:39,975
And so maybe life on
the Earth is special.

1447
01:04:39,975 --> 01:04:43,245
So either way, whatever the
answer to that question,

1448
01:04:43,245 --> 01:04:44,947
whether it's
Enceladus or Europa,

1449
01:04:44,947 --> 01:04:48,383
it will be remarkable,
whatever that answer.

1450
01:04:48,383 --> 01:04:49,385
- Thank you.

1451
01:04:52,154 --> 01:04:53,889
- Two questions.

1452
01:04:53,889 --> 01:04:56,992
One, is there a contingency plan

1453
01:04:56,992 --> 01:05:00,596
if any of these last orbits
throw a wrench in the works

1454
01:05:00,596 --> 01:05:03,098
or a surprise, sort of
like not finding dust,

1455
01:05:03,098 --> 01:05:05,234
maybe you find something
you weren't expecting,

1456
01:05:05,234 --> 01:05:06,902
and the second question is,

1457
01:05:06,902 --> 01:05:10,239
in the sort of
contingency planning,

1458
01:05:10,239 --> 01:05:13,642
is there any thought
or imagination

1459
01:05:13,642 --> 01:05:15,944
as to what happens when you
put a little bit of plutonium

1460
01:05:15,944 --> 01:05:19,581
on a planet that probably
didn't have it to begin with?

1461
01:05:19,581 --> 01:05:20,883
- You want to take
the first part,

1462
01:05:20,883 --> 01:05:21,884
I'll take the second part.

1463
01:05:21,884 --> 01:05:23,118
- Sorry, I got--

1464
01:05:23,118 --> 01:05:24,286
- Oh, okay, the
contingency plans.

1465
01:05:24,286 --> 01:05:27,422
Once we got the
final flyby of Titan,

1466
01:05:27,422 --> 01:05:29,225
127th flyby,

1467
01:05:29,225 --> 01:05:31,993
we were pointed to what we
call a ballistic trajectory,

1468
01:05:31,993 --> 01:05:33,996
and if something
happened to Cassini,

1469
01:05:33,996 --> 01:05:37,699
the bits and pieces or
whatever or the damaged Cassini

1470
01:05:37,699 --> 01:05:39,702
would follow the same orbits,

1471
01:05:39,702 --> 01:05:42,705
ending up in Saturn
on September 15th.

1472
01:05:42,705 --> 01:05:44,105
So we don't have to
do anything else,

1473
01:05:44,105 --> 01:05:46,408
and that's why NASA's
planetary protection

1474
01:05:46,408 --> 01:05:48,677
really liked this set of orbits.

1475
01:05:48,677 --> 01:05:50,513
We could get in
there, take the risk,

1476
01:05:50,513 --> 01:05:54,917
something happens, the mission
is still gonna end with that.

1477
01:05:54,917 --> 01:05:57,519
As far as putting
plutonium into Saturn,

1478
01:05:57,519 --> 01:05:59,621
if you look at the
mass of Cassini

1479
01:05:59,621 --> 01:06:03,025
compared to the mass of
Saturn, it's pretty tiny.

1480
01:06:03,025 --> 01:06:04,827
And one thing that's
kinda cool to think about,

1481
01:06:04,827 --> 01:06:07,963
we're putting a little
piece of Earth into Saturn.

1482
01:06:07,963 --> 01:06:10,399
So yeah, and we're
going really fast,

1483
01:06:10,399 --> 01:06:11,933
and it's gonna be very hot,

1484
01:06:11,933 --> 01:06:13,535
so if we do have
any microbes there,

1485
01:06:13,535 --> 01:06:14,737
they're gonna be toast.

1486
01:06:14,737 --> 01:06:17,039
(audience laughing)

1487
01:06:17,039 --> 01:06:18,040
- Thank you.

1488
01:06:19,975 --> 01:06:21,877
- I have two more questions.

1489
01:06:21,877 --> 01:06:23,679
(audience laughing)

1490
01:06:23,679 --> 01:06:27,015
One question would
be what would you do

1491
01:06:27,015 --> 01:06:30,019
if you lost connection
with Cassini?

1492
01:06:31,419 --> 01:06:32,287
- You want to take that, Earl?

1493
01:06:32,287 --> 01:06:33,722
- We would keep looking.

1494
01:06:33,722 --> 01:06:35,190
(audience laughing)

1495
01:06:35,190 --> 01:06:38,894
Cassini, and I don't mean to
be glib, but what happens if...

1496
01:06:38,894 --> 01:06:42,798
Cassini has a tremendous
amount of what we call

1497
01:06:42,798 --> 01:06:45,701
fall protection
software built into it.

1498
01:06:45,701 --> 01:06:48,537
So if we were to lose
contact with Cassini,

1499
01:06:48,537 --> 01:06:51,506
we have to talk to Cassini
and Cassini has to talk to us.

1500
01:06:51,506 --> 01:06:54,042
If for example we lost contact

1501
01:06:54,042 --> 01:06:56,444
and Cassini didn't hear from us,

1502
01:06:56,444 --> 01:06:58,581
it would start
looking for the Earth,

1503
01:06:58,581 --> 01:07:01,016
and meanwhile we're starting
to look for Cassini,

1504
01:07:01,016 --> 01:07:03,652
so we'd go through days and
days and potentially weeks

1505
01:07:03,652 --> 01:07:07,956
of allowing Cassini to
turn on different hardware,

1506
01:07:07,956 --> 01:07:10,859
different radios, point
its antenna different ways,

1507
01:07:10,859 --> 01:07:13,595
meanwhile we're using all the
antennas all over the Earth

1508
01:07:13,595 --> 01:07:15,130
to try to re-command it.

1509
01:07:15,130 --> 01:07:19,301
So if indeed it happened because
Cassini failed in some way,

1510
01:07:20,803 --> 01:07:22,871
then we of course
wouldn't hear back,

1511
01:07:22,871 --> 01:07:26,241
but it would be a long
time before we gave up.

1512
01:07:26,241 --> 01:07:28,077
- We probably wouldn't
give up 'til the end.

1513
01:07:28,077 --> 01:07:30,445
(audience laughing)

1514
01:07:30,445 --> 01:07:32,214
- My second question is,

1515
01:07:32,214 --> 01:07:36,385
are you going to start another
mission after Cassini ends?

1516
01:07:37,719 --> 01:07:40,055
- Well, there's another
mission in the works to Europa.

1517
01:07:40,055 --> 01:07:41,790
It's called the Europa Clipper.

1518
01:07:41,790 --> 01:07:43,759
And so NASA has
selected to go back

1519
01:07:43,759 --> 01:07:45,961
to this other ocean world

1520
01:07:45,961 --> 01:07:48,697
and to study it and
learn more about it,

1521
01:07:48,697 --> 01:07:51,066
for possible future missions
there's even a proposal

1522
01:07:51,066 --> 01:07:54,035
for a Europa lander, to find
a place where there might be

1523
01:07:54,035 --> 01:07:57,038
plumes on Europa, put a
lander down on the surface,

1524
01:07:57,038 --> 01:08:01,109
and sample and look for
life coming from that plume.

1525
01:08:01,109 --> 01:08:02,611
So that's sort of
next on the books.

1526
01:08:02,611 --> 01:08:03,846
I hope there's a lot more.

1527
01:08:03,846 --> 01:08:05,280
I want to go back to
Uranus and Neptune

1528
01:08:05,280 --> 01:08:07,882
and back to Saturn
and Enceladus, so.

1529
01:08:07,882 --> 01:08:09,217
Hopefully there's a lot more.

1530
01:08:09,217 --> 01:08:10,219
- Thank you.

1531
01:08:11,753 --> 01:08:14,756
- Do you want to read some
of the questions there?

1532
01:08:14,756 --> 01:08:16,124
- Thank you.

1533
01:08:16,124 --> 01:08:18,327
Following the goodbye kiss,

1534
01:08:18,327 --> 01:08:21,230
will you have control
over the angle of descent

1535
01:08:21,230 --> 01:08:23,332
into Saturn's atmosphere?

1536
01:08:24,700 --> 01:08:27,369
You're saying no, you won't
really know the angle?

1537
01:08:27,369 --> 01:08:29,705
- Well, we'll know
this one thing,

1538
01:08:29,705 --> 01:08:31,239
'til the very last second,

1539
01:08:31,239 --> 01:08:33,842
we'll be pointing the high
gain antenna at the Earth.

1540
01:08:33,842 --> 01:08:36,078
And that's our goal, and
then while we do that,

1541
01:08:36,078 --> 01:08:38,280
the other axis is pointing

1542
01:08:38,280 --> 01:08:39,948
the ion and neutral
mass spectrometer

1543
01:08:39,948 --> 01:08:41,983
in the direction of
Saturn's atmosphere.

1544
01:08:41,983 --> 01:08:44,620
So we have picked
that orientation.

1545
01:08:44,620 --> 01:08:47,589
Send back the most data,
the longest possible time.

1546
01:08:47,589 --> 01:08:49,924
- The spacecraft will be
controlling its attitude

1547
01:08:49,924 --> 01:08:52,528
until it can't, and so
we will know it's...

1548
01:08:52,528 --> 01:08:54,329
And it will not only
be controlling it,

1549
01:08:54,329 --> 01:08:55,931
it'll be telling us what it is.

1550
01:08:55,931 --> 01:08:57,298
Again, until it can't.

1551
01:08:57,298 --> 01:08:59,167
- Would the hope be
that it goes in maybe

1552
01:08:59,167 --> 01:09:00,869
a little more
shallow than steep,

1553
01:09:00,869 --> 01:09:02,071
just to give you a
few more seconds?

1554
01:09:02,071 --> 01:09:03,272
- No, it's going in.

1555
01:09:03,272 --> 01:09:04,540
It's going in.

1556
01:09:04,540 --> 01:09:06,842
It's not gonna skip out,
it's not gonna skip out.

1557
01:09:06,842 --> 01:09:09,344
- If it comes out, we're
gonna be both very embarrassed

1558
01:09:09,344 --> 01:09:11,647
and having to deal with a
very damaged spacecraft.

1559
01:09:11,647 --> 01:09:12,647
(audience laughing)

1560
01:09:12,647 --> 01:09:13,649
- Thank you.

1561
01:09:16,552 --> 01:09:19,188
- I'm not quite sure how to
ask this question, but...

1562
01:09:19,188 --> 01:09:20,422
- Great shirt, by the way.

1563
01:09:20,422 --> 01:09:21,257
- Oh, thanks.

1564
01:09:21,257 --> 01:09:22,090
- Absolutely.

1565
01:09:22,090 --> 01:09:24,426
Thumbs up on the shirt.

1566
01:09:24,426 --> 01:09:26,061
- How do I say this?

1567
01:09:26,061 --> 01:09:29,731
So there's a lot of
talk about the science,

1568
01:09:29,731 --> 01:09:32,334
but what I'm curious
to know is that

1569
01:09:32,334 --> 01:09:36,004
this is technology that we
had 20 years ago, right?

1570
01:09:36,004 --> 01:09:39,541
When it launched,
and so now it's 2017,

1571
01:09:39,541 --> 01:09:43,211
and so, and it
feels like Cassini,

1572
01:09:43,211 --> 01:09:47,515
the analogy that I think
of is like a jazz musician.

1573
01:09:47,515 --> 01:09:50,052
It feels like you're
just kind of riffing.

1574
01:09:50,052 --> 01:09:52,120
And you're kinda
just going around

1575
01:09:52,120 --> 01:09:53,989
and not necessarily
making it up,

1576
01:09:53,989 --> 01:09:56,091
but you have like a hunch
and you kinda go for it.

1577
01:09:56,091 --> 01:09:58,660
Knowing what we
know now, you know,

1578
01:09:58,660 --> 01:10:01,997
like what will we bring to
the next jam session, I guess?

1579
01:10:01,997 --> 01:10:05,434
Like what technology
has evolved, or what
have we learned,

1580
01:10:05,434 --> 01:10:07,536
or what kind of technology
do we wish we had

1581
01:10:07,536 --> 01:10:11,507
on Cassini that we'll have
for Europa Clipper, I suppose.

1582
01:10:11,507 --> 01:10:12,774
- Right, right.

1583
01:10:12,774 --> 01:10:15,944
Certainly had we known
the potential for life

1584
01:10:15,944 --> 01:10:18,013
in Enceladus's ocean, if
we knew it had an ocean,

1585
01:10:18,013 --> 01:10:21,316
we would've carried more
capable mass spectrometers.

1586
01:10:21,316 --> 01:10:23,485
That we have mass
spectrometers kind of like

1587
01:10:23,485 --> 01:10:27,990
100 atomic mass units,
100 protons' worth
of molecular size,

1588
01:10:27,990 --> 01:10:30,658
that's not nearly enough
to look for fatty acids,

1589
01:10:30,658 --> 01:10:32,861
amino acids, evidence for life.

1590
01:10:32,861 --> 01:10:34,863
So you would carry
mass spectrometers,

1591
01:10:34,863 --> 01:10:36,731
instruments that
could do the sampling

1592
01:10:36,731 --> 01:10:38,266
that could help answer the...

1593
01:10:38,266 --> 01:10:40,168
You're getting free samples,
so take advantage, you know,

1594
01:10:40,168 --> 01:10:42,404
and check it out, and who knows

1595
01:10:42,404 --> 01:10:44,339
with the camera
technologies, you know,

1596
01:10:44,339 --> 01:10:45,940
our cameras may not be as good

1597
01:10:45,940 --> 01:10:47,342
as the cell phone
cameras of today.

1598
01:10:47,342 --> 01:10:49,410
So you could do a lot
more with the cameras,

1599
01:10:49,410 --> 01:10:52,914
the spectrometers, all
kinds of instruments

1600
01:10:52,914 --> 01:10:54,415
with the technologies today,

1601
01:10:54,415 --> 01:10:57,052
and we'd have a lot of
more orbit choice, too,

1602
01:10:57,052 --> 01:10:59,021
we could do, you know,
skim across the rings,

1603
01:10:59,021 --> 01:11:00,522
finding this unique orbit,

1604
01:11:00,522 --> 01:11:02,390
maybe go inside
and come back out,

1605
01:11:02,390 --> 01:11:04,025
now that we know it's clear.

1606
01:11:04,025 --> 01:11:06,328
You know, we could do maybe
a lot of things differently.

1607
01:11:06,328 --> 01:11:08,797
Carry two probes, maybe a
Titan orbiter, you know,

1608
01:11:08,797 --> 01:11:10,766
a lot you could do.

1609
01:11:10,766 --> 01:11:12,000
- Okay, great.

1610
01:11:12,000 --> 01:11:14,069
Thank you so much.

1611
01:11:14,069 --> 01:11:15,570
- Do you want to, okay.

1612
01:11:15,570 --> 01:11:17,005
After this, we're gonna ask a
couple question from online,

1613
01:11:17,005 --> 01:11:18,506
yeah.

1614
01:11:18,506 --> 01:11:22,011
- One of the objectives that
you named for this final dive

1615
01:11:23,245 --> 01:11:25,780
is to keep Titan pristine,

1616
01:11:25,780 --> 01:11:28,383
but Huygens has already
gone into Titan.

1617
01:11:28,383 --> 01:11:31,753
So how, was there
special protection done?

1618
01:11:31,753 --> 01:11:33,555
Or was it done on the assumption

1619
01:11:33,555 --> 01:11:35,957
that we weren't going to
find as much as we did there?

1620
01:11:35,957 --> 01:11:37,859
- You know, I think
that's a fair comment,

1621
01:11:37,859 --> 01:11:41,797
and we really have to
be very careful about

1622
01:11:41,797 --> 01:11:43,932
Titan's classification.

1623
01:11:43,932 --> 01:11:47,936
It still is, and was what
we call a category two,

1624
01:11:47,936 --> 01:11:52,540
which means that the
probability of contamination

1625
01:11:52,540 --> 01:11:56,978
influencing future
investigations is very very low.

1626
01:11:56,978 --> 01:12:01,383
But nonetheless, you
know, Huygens soft-landed,

1627
01:12:01,383 --> 01:12:02,684
you're absolutely right,

1628
01:12:02,684 --> 01:12:05,187
it wasn't cleaned any
more than Cassini was,

1629
01:12:05,187 --> 01:12:06,989
it wasn't decontaminated,

1630
01:12:06,989 --> 01:12:09,724
and so it could've potentially
left microbes on the surface,

1631
01:12:09,724 --> 01:12:11,993
but again, we're
bringing plutonium,

1632
01:12:11,993 --> 01:12:14,529
lots of it onto the
surface, potentially,

1633
01:12:14,529 --> 01:12:18,032
and again, it's something
that we need to take

1634
01:12:18,032 --> 01:12:20,869
every reasonable
precaution to avoid.

1635
01:12:20,869 --> 01:12:25,040
But Enceladus went from a
category one or even maybe zero

1636
01:12:26,674 --> 01:12:29,744
to category three, which means
that the probability of us,

1637
01:12:29,744 --> 01:12:31,246
our requirements
on the probability

1638
01:12:31,246 --> 01:12:34,048
of inadvertently striking
it are much more stringent,

1639
01:12:34,048 --> 01:12:36,017
and that's really the driver.

1640
01:12:36,017 --> 01:12:39,121
Titan, at the time
it seemed fine,

1641
01:12:39,121 --> 01:12:41,957
and you know, you
can't undo what we did,

1642
01:12:41,957 --> 01:12:43,492
and the classification
hasn't changed,

1643
01:12:43,492 --> 01:12:46,061
but it still looks
different now than it did.

1644
01:12:46,061 --> 01:12:48,196
- Right, you could
still land on Titan,

1645
01:12:48,196 --> 01:12:49,664
the way it's categorized now.

1646
01:12:49,664 --> 01:12:53,668
In part, the icy crust is so
thick above the ocean of Titan,

1647
01:12:53,668 --> 01:12:57,338
which is where we'd worry
about Earth kinds of life,

1648
01:12:57,338 --> 01:12:59,007
but that is, you
know, so that's why

1649
01:12:59,007 --> 01:13:00,875
it's stayed a category two.

1650
01:13:00,875 --> 01:13:02,177
And there's no direct contact,

1651
01:13:02,177 --> 01:13:04,246
we don't see any
geysers or you know,

1652
01:13:04,246 --> 01:13:07,048
jets or anything coming
out from Titan's surface.

1653
01:13:07,048 --> 01:13:08,416
- Okay, thank you.

1654
01:13:08,416 --> 01:13:12,487
- We've got a few questions
from the internet.

1655
01:13:12,487 --> 01:13:15,990
Ocean McIntire, and
this is for you Linda,

1656
01:13:15,990 --> 01:13:18,259
are there any suspected
reasons for the lack,

1657
01:13:18,259 --> 01:13:19,594
in fact they're all for you.

1658
01:13:19,594 --> 01:13:21,797
Any suspected reasons
for the lack of dust

1659
01:13:21,797 --> 01:13:23,531
within the ring gap?

1660
01:13:23,531 --> 01:13:24,733
- Wow, that's a great question.

1661
01:13:24,733 --> 01:13:26,167
Why no dust?

1662
01:13:26,167 --> 01:13:29,003
That's a really good
question, we don't know.

1663
01:13:29,003 --> 01:13:31,439
We're hoping with
a few more orbits,

1664
01:13:31,439 --> 01:13:33,008
we can, and a little bit
more time, figure that out.

1665
01:13:33,008 --> 01:13:34,276
But a complete surprise,

1666
01:13:34,276 --> 01:13:36,244
of all the things we
would have guessed,

1667
01:13:36,244 --> 01:13:39,948
no dust was not even
on the list, so.

1668
01:13:39,948 --> 01:13:43,518
- And then the dynamics
for polar activity,

1669
01:13:43,518 --> 01:13:45,787
or inactivity look impressive.

1670
01:13:45,787 --> 01:13:47,922
Can you elaborate?

1671
01:13:47,922 --> 01:13:50,658
- Okay, for polar activity.

1672
01:13:50,658 --> 01:13:52,460
- Yeah, about polar activity.

1673
01:13:52,460 --> 01:13:54,963
- Okay, I think we're probably
talking about the hexagon

1674
01:13:54,963 --> 01:13:58,066
and the vortices,
the hurricane-like
vortices at the poles.

1675
01:13:58,066 --> 01:14:00,869
You know, Saturn is
spinning, it's mostly gas,

1676
01:14:00,869 --> 01:14:03,438
we know hurricanes on
Earth tend to migrate,

1677
01:14:03,438 --> 01:14:05,140
you know, toward the poles,

1678
01:14:05,140 --> 01:14:06,941
they don't ever make it there
because they're out of energy,

1679
01:14:06,941 --> 01:14:09,811
but we have those two
hurricane-like features

1680
01:14:09,811 --> 01:14:12,580
right at the poles, and the
energy source for the hexagon

1681
01:14:12,580 --> 01:14:15,384
for that jet stream, that's
a really good question.

1682
01:14:15,384 --> 01:14:17,585
We're hoping our
pictures and new data

1683
01:14:17,585 --> 01:14:19,054
will help us figure that out.

1684
01:14:19,054 --> 01:14:20,455
- I think that must be
the inactivity references

1685
01:14:20,455 --> 01:14:22,724
to the stability
of that hexagon.

1686
01:14:22,724 --> 01:14:24,126
- Right, it's been
there at least 30 years,

1687
01:14:24,126 --> 01:14:25,126
Voyager discovered it, so.

1688
01:14:25,126 --> 01:14:26,561
- And then here's a fine one,

1689
01:14:26,561 --> 01:14:28,696
here's a good fitting question.

1690
01:14:28,696 --> 01:14:31,366
AJ asks, will there
be a followup mission

1691
01:14:31,366 --> 01:14:33,001
to Saturn in the future?

1692
01:14:33,001 --> 01:14:34,436
- Oh, I certainly hope so.

1693
01:14:34,436 --> 01:14:37,539
To Saturn, to Enceladus,
to Saturn, Titan,

1694
01:14:37,539 --> 01:14:38,973
there's so much we've left,

1695
01:14:38,973 --> 01:14:41,643
so many questions
that we now have open

1696
01:14:41,643 --> 01:14:42,977
for a future mission.

1697
01:14:42,977 --> 01:14:44,813
So thank you very much,
thank you for coming.

1698
01:14:44,813 --> 01:14:47,249
(applauding)