Cassini-Huygens Mission to SaturnOverview

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JPL Overview

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

Mission Overview

Christiaan Huygens (1629-1695) Dutch scientist, who discovered the true nature of Saturn’s rings, and in 1655, Titan

Giovanni Domenico Cassini (1625-1712), Italo-French astronomer, who discovered several of Saturn’s satellites: Iapetus, Rhea, Tethys and Dione. In 1675, he discovered what is today called “Cassini Division” the gap in-between the two

main rings of Saturn

Huygens and CassiniHuygens and CassiniThe The ScientistsScientists and the Machinesand the Machines

Cassini Orbiter & Huygens Probe

Launched on October 15, 1997 from KSC

7 year cruise on VVEJGA trajectory

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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:

Optical Remote Sensing (ORS)CIRS: Composite Infrared SpectrometerISS: Imaging Science SubsystemUVIS: Ultraviolet Imaging SpectrographVIMS: Visual and Infrared mapping Spectrometer

Microwave Remote SensingRADAR: Cassini RadarRSS: Radio Science Subsystem

Magnetospherie and Plasma Science (MAPS)CDA: Cosmic Dust AnalyzerINMS: Ion and Neutral Mass SpectrometerMAG: Dual Technique MagnetometerMIMI: Magnetospheric Imaging InstrumentRPWS: Radio and Plasma Wave Science

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)

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Tour Overview4 year Prime Mission– 75 orbits– 45 targeted Titan flybys– 8 targeted icy satellite flybys

5 Science Objectives– Titan– Saturn– Rings– Icy Satellites– Magnetosphere

Tour (Petal) movie

#1: Huygens on Titan

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

Huygens Separation & EntryRelease: December 24, 2004Decent: January 14, 2005Data Collection:

•Decent: 2h 27m•Surface: 1h 12m•Radiometric: 5h 52m

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The Huygens Descent

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The Surface of Titan

Arial view of Titan

Huygens “News”

#2: Enceladus

Slide 22

National Geographic, 1981

Enceladus, July 14, 2005Enceladus, July 14, 2005

175 km flyby!!

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

Enceladus Flyby: 12 November 2005

GEYSER COMPOSITIONGEYSER COMPOSITION(Waite (Waite et al.et al. 2006; Hansen 2006; Hansen et al.,et al., 2006)2006)

H2O 91 ± 3 % wt.

CO2 3.2 ± 0.6 % wt.

N2 4 ± 1 % wt.*

CH4 1.6 ± 0.4 % wt.

CO < 0.9 % wt

NH3, HCN, C2H2, C3H8 < 0.5 % wt. (i.e., detected)

*Inferred from a combination of INMS and UVIS data

HH22OO 91 91 ±± 3 % wt. 3 % wt.

COCO22 3.2 3.2 ±± 0.6 % wt. 0.6 % wt.

NN22 4 4 ±± 1 % wt.*1 % wt.*

CHCH44 1.6 1.6 ±± 0.4 % wt.0.4 % wt.

COCO < 0.9 % wt< 0.9 % wt

NHNH33, HCN, C, HCN, C22HH22, C, C33HH88 < 0.5 % wt. (< 0.5 % wt. (i.ei.e., detected)., detected)

*Inferred from a combination of INMS and UVIS data*Inferred from a combination of INMS and UVIS data

Slide 30

Why the South Pole?Nimmo and Pappalardo (2006)

• Low-density silicate or icediapir can be sufficient toovercome the equatorialbulge and reorient Enceladus

• Resulting stresses may be consistent with the observedtectonic patterns

• Few mgal gravity anomaly: mightbe detectable by Cassini?

Avg Earth87 mW/m2

EnceladusSouth Polar Terrain250 mW/m2

Tiger Stripes13,000 mW/m2

Planetary Heat FlowPlanetary Heat Flow

Yellowstone2500 mW/m2

Slide 34

16 MW16 MW160 MW160 MWTidal heating, solid ice rigidity, Q = 20

0.00470.0206Orbital Eccentricity

3.9 RS3.1 RSDistance from Saturn

1.61.2Density

504 km420 kmDiameter

EnceladusMimasBistable tidal heating?

• Enceladus is warm, dissipative, stays warm.• Mimas is cold, rigid, stays cold.

Need a way to “kick start”Enceladus initially

NASA/JPL/SSI

“Mimas Paradox”

#3: Titan from Space

Titan: the most EarthTitan: the most Earth--like body in the Solar Systemlike body in the Solar Systemmid-latitude streaksdetached haze

lakes

aeolian patterns

few craters

river channelsmountainshuge cloud system

wind driven dunes

drainage channels

ISS mapTitan @ 938 nm

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

RADAR map (TA-T30)

87°W 20°N

16°W 11°N

Impact basin (above) is about 450 km in diameter Impact crater (left) is about 80 km in diameter

100 km

Impact Craters

Cryovolcano and surface flows

“Cat Scratches” = Dunes?

Longitudinal DunesArabian Peninsula

Dunes probably consist of wind-blown hydrocarbon particles

Lucky Number 13

Circular feature Guabonito may not

be an impact crater after all

Wispy terrain to east of Shikoku(Great Britain) resembles dunes

seen in earlier SAR data

This complex area of hilly terrain and erosional channels is located atop Xanadu, the continent-sized region

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A Titan Lake?

Cassini had seen several “suspiciouslylacustrine features”…

…until finally Cassini found the Titan equivalent of Minnesota.

detached haze150 km higherthan observed

by Voyager

Titan's Atmospheric Variability

South-polar convective clouds

mid-latitude streaksSeasonalchanges inweatherpatterns

complex, variable haze structure

VIMS images of mid-latitude clouds

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 strongconnections to neutral chemistry; these are still being explored.

#4: Saturn Orbit Insertionand the

Rev 28 occultation Images

SOI Trajectory

X

Saturn Orbit Insertion Ring Plane Crossing

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Approach picture from Cassini:

May 10, 2004

Dist: 27 million km.

Pixel: 161 km.

Moon: Prometheus

Cassini ISS image: Space Science Institute (Boulder), NASA/JPL.

F

Cassini Division

ABC

Encke GapW~350 km

The main rings

Complex Rings

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Rev 28 Occultation

For the first time, we can see all the rings clearly in a single image!

No need for these artist’s renditions anymore.

E-Ring G-RingF-Ring

A-RingB-Ring C-Ring

CassiniDivision

D-Ring

There is a lot going on in this image, so let’s take a closer look….

On the planet, we see the light blocked by the rings

Out here, we see the light scattered by the rings

C DBA CD

ACD

B

C

The non-trivial relationship betweenbrightness and amount of material leads to strange images….

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