TheCassini/Huygens
Mission
toSATURN

Dr. R. Srama
MPI Nuclear Physics, Heidelberg, Germany
University Stuttgart

Lord of the Rings

Kobe, March 2010

GALILEO TO KEPLER
1610

ALTISSIMUM PLANETAMTERGEMINUM OBSERVAVI„The most distant planet has a three-fold shape !“„Der entfernteste Planet hat eine dreifache Form“(discovery of Saturn‘s ring)

CHRISTIAAN HUYGENS• mathematician and physicist of thenetherlands• (*1629, †1695)• interpretation of Saturn‘s ring• discovery of the large moon titan(1655)

GIOVANNI CASSINI• french astronomer andmathematician• (*1625,†1712)• discovery of 4 Saturn moons andthe ring division

SATURN !
1 Saturn year :29.5 yRotation :10 h, 40 min
Distance to Sun :1400 Mkm
Diameter at equator :120.000 km
Mass :
95 x Earth
Volume :760 x Earth
Density :0.7 g/cm^3 (Earth 5.5)
Strong pole oblateness
Magnetic field :4x10-5 T at pole (Earth : 5x10-5 T)
Dipole field axis = rotation axis !
ring plane :27 tilted towards orbit plane

SATURN‘S INTERIOR
Atmosphere : 94 % H, 6% He
T at upper cloud boundary : 150 K
T at cloud lower boundary : 80 K
T in center : 20.000 K, 5x10^12 P (Earth: 3800 K)
emission of heat (inner heat source)heat flux 120% of solar irradiation

metal-silicate
corel-Hydrogenl-He
metl-H

WINDS OF SATURN(UP TO 500 M/S)MOON MYSTERIES• Pandora and Prometheus are shephard moons for ring
• Dione and Tethys have own moons• Janus and Epimetheus exchange their orbit• Iapetus has a dark and bright side
• Mimas has a huge impact crater (1/4 of surface)• Enceladus is active (ice geysers), highest albedo• Phoebe has a retrograde orbit, KB object caught by Saturn (?)

CASSINI/HUYGENSHigh Gain Antenna
Magnetometer-boom
Plasma wave antenna
Camera platform
RTG (Power)
Main engine

CASSINI SPACECRAFT

COSMIC DUST ANALYSERHUYGENS PROBECASSINI FACTS
Program partners : NASA, ESA, ASI
17 countries
international engineers and scientists: 5000
costs : 1.4 billion (pre-launch development)$ 710 M mission operations$ 54 M tracking$ 422 M launch vehicle$ 500 M ESA (Huygens)$ 160 M ASI$ 3.27 billion, U.S. $2.6, Europe $ 660 M

CASSINI BUS
dry mass 2.11 + 320 kg Huygens probe + 3.1 t propellent = 5.7 theight : 6.8 m, 4m antenna, boom 11 m
22.000 wire connections, 12 km cablinglargest interplanetary S/C ever launched
3 RTGs, 750 W + small radio-isotope heaters everywhere
Main Engine : Mono-methyl-hydrazin, N-tetraoxid oxidator
16 small thrusters (Hydrazin)
Inertial Reference Unit - perform turns/firings while retain knowledge ofown position
X Band, 20 W, Ka, S, Ku
ADA software, 2x2 Gbit Solid State Recorder,
1MB memory for command subsystem, 16 kB PROM
redundant computers
4 Gyros, cover for main engine
Main engine : 445 Newton, gimbaled to maintain vector if CoM changes

CASSINI TRAJECTORYCRUISE SCIENCE:NOT ONLY SATURN ...
Cassini searches for gravity waves with radio sciencesubsystem
Cassini confirms general relativity theory during
conjunction (Cassini - Sun - Earth) in June 2002 ,Nature 2003

EINSTEIN WAS RIGHT
frequency shift after corrections
correction for doppler shift
due tosolar radiation pressure
non-isotrope
heat emissionof RTGs, ...

JUPITER SCIENCE
2000

jupiter by cassini

DUST FROM JUPITER„Io Ashes“incoming electron can generate more
ectron, and the net current can turnl., 1997]. In general, grain charges are
e dusk side of the torus where thes higher.
ulations [Horányi et al., 1997] show
arting on the dawn side of Jupiterthe Io torus for some time whereas
he dusk side have a higher chance toa strong variation of the expected dust
time even if the dust ejection rate ofsensor area [Krüger et al., 1999] had to be taken into
account, which did not remain constant as Galileo moved
about Jupiter. The time-dependent sensor area was calculated by taking the trajectory of a 10 nm particle as a‘standard’ trajectory: particles of this size best explain theobserved impact directions of the streams [Grün et al.,1998]. When no flux is superimposed upon the Galileo
trajectory in Figure 1, the dust streams were either not in thewe analyze this six-year Galileo dust
variations with Jovian local time andions to current models.

2001„Io Ashes“ - Stream Particles• Origin: Io Volcanoes• Size: 5 ... 40 nm• Dynamics Dominated

2002

2000
1999

Measurements
Jupiterby EMatForces

al-spinning spacecraft with an antenna
lel to the positive spin axis (PSA).
ileo’s orbital tour about Jupiter therds Earth. The Galileo Dust Detector
ts twin on-board Ulysses, is a multionization detector [Grün et al., 1992]
micron – and micron – sized dust pard on the spinning section of Galileo andt by an angle of 60! from the PSA. DDSof view. During one spin revolution ofector scans the entire anti-Earth hemi-1998• Fast Enough to Escape
From Jovian System

1997• Allow to Monitor Io

1996

Activity

061218
Jovian Local Time (h)24Figure 2. Dust fluxes measured with DDS along 33 Galileo
orbits about Jupiter vs. local time. Spacecraft distance r fromKrüger
et al.,
GRL, 2003
Jupiter is indicated with red solid lines. Fluxes
werecorrectedSpeed of nano-dust : > 100 km/s
6 nm grains

Are the grains fast enoughfor a detection? YES.

A. GrapsIo‘s dust streams:
Probes of the magnetosphere
Probes for Io‘s activity

10 RJ

10 RJ
Dust grain potential [V]5 nm grain (silicate)Io as a Dust Source:
Nano-Dust Coupling to Magnetosphere

Side View

Top View
A. Graps

M. Horanyi

Io as a Dust Source in the Jovian System• Streams of electrically charged dust grains emanating from thejovian system (Grϋn et al., 1993)• 26 day periodicity (Krϋger et al., 2006)• Interaction with interplanetary magnetic field• Grain radii: ~ 10 nm, speeds > 300 km/sec (Zook et al., 1996)‫‏‬• Jupiter's magnetosphere: giant dust accelerator• Source: Io (Graps et al., 2000)‫‏‬• Confirmed during 2nd Jupiterflyby in 2004 (Krüger et al. 2006)‫‏‬• Stream formation due to CIR
and CME interaction(Flandes & Krüger, 2007)‫‏‬

H. Krüger

UlyssesDust Streams: A Monitor of Io's Volcanism
Average Io dust emission: ~0.1 - 1 kg s- 1
Small compared to ~1 ton s- 1 of plasma ejectedPeaks in dust emission coincide with largest
surface changes
Dust condensation in plumes


Krüger et al., 2003

Io, GalileoElectromagnetically Interacting Dust at Jupiter
Dust impact rate correlated withJupiter's 10h rotation period

GalileoParticle source: Io

Graps et al. 2000

Grün et al. 1998

Periodogram of Galileo data

Composition Of Io‘sVolcanic Matter

ARTICLE IN PRESSYICAR:7897[m5+; v 1.56; Prn:21/03/2006; 11:08] P.6 (1-13)
F. Postberg et al. / Icarus(••••) •••–•••ARTICLEIN•••PRESSYICAR:7897[m5+; v 1.56; Prn:21/03/2006; 11:08] P.6 (1-13)
F. Postberg et al. / Icarus ••• (••••) •••–•••

Rh+C+Na+O+C2+K+Si+S+/Cl+

Time of Flight

Io Ashes Mostly
NaCl Crystals
Postberg et al., Icarus, 2006

Cosmic Dust Analyser (CDA)
Dust detector on Cassini spacecraft:• dust mass/velocity: impact
ionisation detector• chemical composition: time of flightmass spectrometer• dust charge/velocity/impact angle:
charge sensitive entrance grids• high rate detector (HRD)

July 2008, Cospar

R. Srama

2

CDA measurement range,-.(/0• !"#$%&%'"()*")+(.5.,,(6/($5.(• 12$&($3""4+(((((((((((((.,5.75.,58(9(:;0,(6/($5.<• 12$&(/)$$+((((.,5.7(5(.,5.?(@• 12$&(=>)*9"+((0,57,(/)$$(*"$AB2&%A#• 12$&(=A/3A$%&%A#+(• C/3)=&(=A2#&%#9(*)&"+((((( .DE""65.,,,,D$.,,,(&%/"$(/A*"($"#$%&%'"&>)#(A3&%=)B(/")$2*"/"#&$

CDA finds one particle within one km!
July 2008, Cospar

R. Srama

3!"#$%!&'(#)&*+*,-./0!"#$%&'()&($*'+,-'+,./$0$1!23'/(4%.2(56/$78$)5)79:3/.$8276$%5.32)$;$"'/&7<(2=>$&76?7/'.7)$5):$:=)56'&/>$&73?-')+$@(.A(()$!0B/C!DE/$5):$:3/.$/.2(56$:=)56'&/$1%F$G(6?8>$H5.32(4I2'+')$78$?52.'&-(/:(.(&.(:$:32')+$.,(
5??275&,$.7$%5.32)'/$.,($#$2')+"'/&7<(2=$78$%5.32)$:3/.$/.2(56/!76?7/'.'7)$78.,(/($?52.'&-(/;$/'-'&5.(/!"#$%&''()*+,%-#*.*%

SIMULATION OF ESCAPING DUST STREAMSFROM SATURN (M. HORANYI)DUST STREAM MODELINGS. HsuSATURN APPROACH
Enceladus

Mimas
TethysPHOEBE
Flyby : 2004, June 11
ice-rich moon coverd
with dark material
bright crater edges
190 m/pixel

PHOEBE CRATER
80 M/PIXELA COMET LIKE OBJECT
CO2 indicatorfor KuiperBelt
originretrogradeorbit

ORBIT INSERTION

Saturn orbit insertion
2004-183

SATURN ORBIT INSERTION

Saturn‘s Atmosphere

ISS teamnear IR ,890nm
14. Dec. 2004
Distance:
595,000 km
Pixel : 32 km

SIZE DISTRIBUTION OF
RING PARTICLES

insideDIRTY RINGSRINGS IN THE UV
more transparency
more water ice

ENCKE GAP IN A
RING BY THE
MOON PANWAVES THROUGH
THE RING

200.000km, 1 km/pixelMOON - RING INTERACTION

Störungen der Ringteilchen durch Mondemoon causes"#$%&'(%)*+,(('-.$'//'-%(0.%gap
andchanges&'(%1#-&%+0-&%&0'%20-3.'0456'-%,*/%
eccentricity
7$'0+8,6-'-ofringparticles
7*$9'%:,6-+.;$*-3'-%

8'0(%)*+,(('-.$'//'-%'$6;6'-%<=9'-.$090.>.%calculation/&'$%20-3?,$.0@'4!

discovery ofA'44'%0+.%"#$4,*/'-&%
0--'$6,48%&'+%
small
embedded
1#-&#$80.+

moons by
A'44'%0+.%-,564,*/'-&%,*B'$6,48%&'+%
analysing
1#-&#$80.+
ring waves

#a0

außen

ring particles! = 3" #a0(Julian & Toomre 1966, Lin & Papaloizou 1979)

innen

DENSITY WAVES IN THE RINGWAVES IN THE UVUV STAR OCCULTATION

RING PLANE CROSSINGF RING WITH SHEPHERD MOONSPROMETEUS AND PANDORAF RINGSHEPHERD MOON PROMETHEUS (102 KM)

SHADOW OF EPIMETHEUS

MOON DAPHNIS (8 KM) ON INCLINED ORBIT WITHIN
THE 42-KILOMETER WIDE KEELER GAP (A RING)

1500 m tall = 150xthickness

NEON LASSOCHARGED PARTICLES STRIKE THE HYDROGEN ATMOSPHEREHEXAGON AT THE POLE

IAPETUS - DICHOTOMYEVAPORATION OF WATER ICE ON LEADING SIDE (MICROMETEOROID IMPACTS)

MANY MANY MORE ...
Titan lakes
Titan dunes
Rhea ring
Radiation belts
MAPS in-situ results

LAKES AND DUNES - TITAN

HUYGENS

COMPARE EARTH - TITAN

MODEL OF TITAN‘S ATMOSPHEREHUYGENS
PROBE (ESA)
Titan atmosphere,winds, composition,temp., pressures,...
Separation - 25. dec 2004
Titan atms entry: 14. Jan 2005
entry angle : 65° (+/- 3°)entry speed : 6.1 km/s
peak decceleration : 10-19 gpeak heating : 500-1500 kW/m^2
decent time : 2:30 hHUYGENS LANDING SITE

METHANE
SOURCES?

PREDICTION AND MEASUREMENTS OF TITAN‘SATMOSPHERE : GOOD AGREEMENTACCELEROMETER AT LANDING

HUYGENS LANDING SCENARIOSTITAN SURFACE
PREDICTION AND REALITYSCIENCE PLANNING !
EXAMPLE : CIRSOBSERVATION PLANNING

ROCKING CASSINI: DUST DYNAMICS

DUST DENSITYComparison : Optical measurements

The E-RingEnceladus : Source ofice grains (E ring)• Size: 499 km• Density: 1600 kg/m
• 70 km Ice Crust on3Rocky CoreENCELADUS
FLYBY
PLANNING

Ejecta Production
Meteoroid Impacts Splash up
Ejecta• Gravitationally Bound

Ejecta Populate Cloud

Sremcevic et al., Icarus, 2005

Mass Yield ~ 4000
Koschny & Grün, Icarus, 2001; Krivov et al., Icarus, 2003

• Some Ejecta Escape:• Feed Rings• Mass Loss
Mechanism

Discovery (MAG, INMS, CDA):

South Pole Ice Geysers
Dust Cloud

Dust Datapeak rate not at closest
approach

SPECIALSECTION
SPECIALSECSPECIALSECTIO
Dust Plume

Spahn et al., Science, 311, 2006

Geyser Grains Slower Than
Escape Speed
Grain Size

~5µm

~1µm

Hill Radius ~ 950 km

Escape Speed ~ 207 m/s

Snow on Enceladus !

Kempf et al., 2009

Salty icy grains : Direct Evidence for Subsurface Liquid Water Reservoir

Water + Rocky Core

Water Dissolves Akali SaltsZolotov, Geophys. Res. Lett., 34, 2007

Ice Grains Should be Salty!

Dust Composition
Cassini Dust Detector CDA

Geyser Water Ice Grain(H2O)H+(H2O)2H+(H2O)3H+(H2O)4H+(H2O)5H+(H2O)6H+Na+193755 73 91
Mass (u)109

TOF Mass spectra(Cassini-CDA)

H1 H2H3(H2O)xH+ 1a: 6.4km/s

23456789< 6 km/s
b: 10.3km/s

c: 14.3km/s
log Amplitude

Cluster lengthd: 14.6km/s

e: 16.2km/s

16 km/s(H2O)xRh+ 0
Time of Flight1234

Salty Ice Grains - measured in E ring
K+(NaCl)Na+(Na2CO3)Na+Co-Added CDA
Spectrum:Salt-rich Geyser
Ice Grains(6%)

Na+ (H20)Na+ (NaOH)Na+(NaOH)2Na+(NaOH)3Na+

Lab Spectrum:
Laser Dispersion
of Salt Water
20406080100120140

Postberg et al., Nature, 2009

Results from Dust Measurements:
Enceladus Ocean„Soda“ Ocean
Rich in Carbonates
pH ~ 9
Salinity ~1% (Earth 1...4%)
Postberg et al., Nature, 2009

ARTISTS WERE ALMOST RIGHTENCELADUS REALITY
thanks to:NASA/JPL
S. Kempf, G. Moragas-Klostermeyer
F. Postberg, E. Grün, M. Burton, M. Roy
S. Hsu, H. Krüger, M. Horanyi, U. Beckmann, P. Strub,
N. Altobelli, V. Sterken, J. Schmidt, F. Spahn, ...
Cassini-CDA project grant by DLR