The international Cassini-Huygens spacecraft was launched on October 15, 1997 and had a marathon 7-year 2-billion mile journey to the distant planet Saturn. The 23-foot tall, 14-foot wide, 6-ton spacecraft is the largest most sophisticated outer planet spacecraft ever built, and is in its third year of operation in orbit around the planet Saturn. Cassini-Huygens has been returning extraordinary data about the entire Saturn system: the spectacular rings; the numerous icy satellites with a variety of unique surface features; the giant planet itself; a huge magneto-sphere teeming with particles that interact with the rings and moons; and the intriguing moon Titan, which is slightly larger than the planet Mercury, and whose hazy atmosphere is denser than that of Earth. This talk will be an overview of the Cassini-Huygens mission to Saturn with a summary of the top science returns of its first three years in orbit. The Minnesota Space Grant Consortium, run out of the Department of Aerospace Engineering and Mechanics at the University of Minnesota, hosts Trina Ray of NASA JPL on January 22, 2008.

1. Cassini-Huygens Mission to Saturn
Overview
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2. JPL Overview

3. NASA’s Jet Propulsion Laboratory,
managed by the California Institute
of Technology, is the world leader in
robotic exploration of the solar
system.
http://photojournal.jpl.nasa.gov

4. Mission Overview

5. Huygens and Cassini
The Scientists and the Machines
Giovanni Domenico Cassini
Christiaan Huygens
(1625-1712), Italo-French
(1629-1695) Dutch
astronomer, who discovered
scientist, who
several of Saturn’s satellites:
discovered the true
Iapetus, Rhea, Tethys and
nature of Saturn’s
Dione. In 1675, he
rings, and in 1655,
discovered what is today
Titan
called “Cassini Division” the
gap in-between the two
main rings of Saturn

6. Cassini Orbiter & Huygens Probe

7. Launched on October
15, 1997 from KSC
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7 year cruise on
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VVEJGA trajectory

8. Cassini Spacecraft
Cassini Spacecraft Specs
• Height: 6.8 m (22 ft)
• Diameter: 4 m (13 ft)
• Mass: 2125 kg (2.8 tons)
(fueled+probe): 5700 kg (6
tons)
• Power: 700 Watts at SOI
• .5 GB recorder
• Huygens Probe:
320 kg (~700 lbs)
Cassini Instruments:
Magnetospherie and Plasma Science (MAPS)
Optical Remote Sensing (ORS)
CDA: Cosmic Dust Analyzer
CIRS: Composite Infrared Spectrometer
INMS: Ion and Neutral Mass Spectrometer
ISS: Imaging Science Subsystem
MAG: Dual Technique Magnetometer
UVIS: Ultraviolet Imaging Spectrograph
MIMI: Magnetospheric Imaging Instrument
VIMS: Visual and Infrared mapping Spectrometer
RPWS: Radio and Plasma Wave Science
Microwave Remote Sensing
RADAR: Cassini Radar
RSS: Radio Science Subsystem

10. Cost
• Cassini total cost $3 billion
– $2.5 B NASA for Cassini, $0.5 B ESA for Huygens
– Spread over ~20 y -> $150 M/y
– Cassini 0.5% of NASA annual budget ($16.8 B)
• NASA annual budget $16.8 B
– 1.7% of U.S. discretionary spending ($982 B)
– 0.6% total U.S. budget ($2800 B)

12. Tour Overview
4 year Prime Mission
– 75 orbits
– 45 targeted Titan flybys
– 8 targeted icy satellite flybys
5 Science Objectives
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Titan
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Saturn
–
Rings
–
Icy Satellites
–
Magnetosphere
–
Tour (Petal) movie

13. #1: Huygens on Titan

14. Why Titan?
• Diameter – 5150km; larger than Mercury and Pluto
• Only planetary satellite with a dense atmosphere
• Surface: P: 1.5 X Earth’s; T: 94 K (-179 C)
• Composition – Nitrogen (N2); Methane (CH4) and
rich array of hydrocarbons (CxHx) and nitriles
(HCN)
• Surface – obscured by photochemical haze
• Murky atmosphere may be similar to that which
existed on Earth before life formed.
• Most Earth-like body in the solar system: rivers,
lakes, seas, mountains, dunes, channels, winds,
volcanos, thick atmosphere - chemically complex

15. Huygens Separation & Entry
Release: December 24, 2004
Decent: January 14, 2005
Data Collection:
•Decent: 2h 27m
•Surface: 1h 12m
•Radiometric: 5h 52m
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16. The Huygens
Descent
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17. The Surface of Titan

18. Arial view of Titan

19. Huygens “News”

20. #2: Enceladus

22. National Geographic, 1981
Slide 22

24. Enceladus, July 14, 2005
175 km flyby!!

26. Two UVIS stellar occultations. The one in July identified a
local atmosphere around the south pole.

28. Enceladus Flyby: 12 November
2005

29. GEYSER COMPOSITION
(Waite et al. 2006; Hansen et al., 2006)
H2O 91 ± 3 % wt.
2
CO 2 3.2 ± 0.6 % wt.
N2 4 ± 1 % wt.*
2
CH4 1.6 ± 0.4 % wt.
4
CO < 0.9 % wt
(i.e.,
(i.e.,
NH3, HCN, C2H2, C3H8 < 0.5 % wt. (i.e., detected)
3 22 38
*Inferred from a combination of INMS and UVIS data

30. Why the South Pole?
Nimmo and Pappalardo (2006)
• Low-density silicate or ice
diapir can be sufficient to
overcome the equatorial
bulge and reorient Enceladus
• Resulting stresses may be
consistent with the observed
tectonic patterns
• Few mgal gravity anomaly: might
be detectable by Cassini?
Slide 30

31. Planetary Heat Flow
Enceladus
Avg Earth South Polar Terrain
87 mW/m2 250 mW/m2
Tiger Stripes
Yellowstone
13,000 mW/m2
2500 mW/m2

34. “Mimas Paradox”
NASA/JPL/SSI
Mimas Enceladus
Bistable tidal heating?
Diameter 420 km 504 km • Enceladus is warm,
dissipative, stays warm.
Density 1.2 1.6
• Mimas is cold, rigid, stays
Distance from Saturn 3.1 RS 3.9 RS
cold.
Orbital Eccentricity 0.0206 0.0047
Need a way to “kick start”
Tidal heating, solid 16 MW
160 MW Enceladus initially
ice rigidity, Q = 20
Slide 34

35. #3: Titan from Space

37. Titan: the most Earth-like body in the Solar System
detached haze mid-latitude streaks
drainage
channels
huge cloud system mountains
river channels
wind driven dunes
aeolian patterns
lakes
few craters

38. ISS map
Titan @ 938 nm

39. VIMS map (r = 5 µm; g = 2 µm; b = 1.6 µm)

40. RADAR map (TA-T30)

41. 87°W 20°N
Impact basin (above) is
100 km about 450 km in diameter
Impact crater (left) is
about 80 km in diameter
16°W 11°N
Impact Craters
Cryovolcano and surface flows

42. Cat Scratches” = Dunes?
Longitudinal Dunes
Arabian Peninsula
Dunes probably consist of wind-blown
hydrocarbon particles

43. Wispy terrain to east of Shikoku
Lucky (Great Britain) resembles dunes
seen in earlier SAR data
Number 13
Circular feature
Guabonito may not
be an impact
crater after all
This complex area of hilly terrain and
erosional channels is located atop
Xanadu, the continent-sized region
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44. A Titan Lake?
Cassini had seen several “suspiciously
lacustrine features”…

45. …until finally Cassini found the Titan
equivalent of Minnesota.

47. Titan's Atmospheric Variability
mid-latitude streaks
Seasonal
detached haze
changes in
150 km higher
weather
than observed
patterns
by Voyager
South-polar convective clouds
VIMS images of mid-latitude clouds
complex, variable haze structure

48. What Would the INMS Measure in Other
Ionospheres?
We have discovered that Titan has the most chemically complex
ionosphere in the solar system. There are likely strong
connections to neutral chemistry; these are still being explored.

50. #4: Saturn Orbit Insertion
and the
Rev 28 occultation Images

51. SOI Trajectory

52. Saturn Orbit Insertion Ring Plane Crossing
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53. Approach picture from
Cassini:
May 10, 2004
F
Dist: 27 million km.
Pixel: 161 km.
Moon: Prometheus
A
C B
Cassini ISS image: Space
Science Institute (Boulder),
NASA/JPL.
Encke Gap
W~350 km
The main rings
Cassini Division

54. Complex Rings
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56. Rev 28 Occultation

57. For the first time, we can see all the rings clearly in a single image!
D-Ring
E-Ring Cassini
G-Ring
F-Ring Division
A-Ring
B-Ring C-Ring
There is a lot going
on in this image, so
let’s take a closer
look….
No need for these artist’s renditions anymore.

58. Out here, we
see the light
scattered by
the rings
A CD B D
C On the planet,
we see the light
blocked by the
rings
C
B
CD
A
The non-trivial relationship between
brightness and amount of material
leads to strange images….

61. Come join us! http://saturn.jpl.nasa.gov