slide 1 of 45 prof. john zarneckiraes – 22 nd march 2005 the cassini-huygens mission to saturn and...
TRANSCRIPT
Prof. John Zarnecki RAeS – 22nd March 2005 Slide 1 of 45
The Cassini-Huygens Mission to Saturn and Titan
Professor John C. Zarnecki
Prof. John Zarnecki RAeS – 22nd March 2005 Slide 2 of 45
Saturn and Titan
Prof. John Zarnecki RAeS – 22nd March 2005 Slide 3 of 45
Saturn
Most distant planet visible with the naked eye 2nd largest planet in the solar system Gas giant – primarily Hydrogen and Helium 34 known moons at present 1.5 billion km mean distance from the sun, 10 x more distant than the
Earth Unique complex ring system
Prof. John Zarnecki RAeS – 22nd March 2005 Slide 4 of 45
Titan
Saturn’s largest moon
Discovered by Christiaan Huygens in 1655
Diameter of 5150 km
Atmospheric pressure of 1.5 bar
Surface temperature ~ 96 K (-177°C)
Prof. John Zarnecki RAeS – 22nd March 2005 Slide 5 of 45
Why Titan?
Only planetary satellite with atmosphere (column mass ~ 10
x value for Earth)
Surface – obscured by photochemical haze
Atmosphere – mainly N2 with CH4 and an array of
hydrocarbons and nitriles
Indirect evidence for surface seas/lakes (i.e. a methane
‘source’)
A ‘primordial atmosphere’ (but frozen!) → an ancient earth?
Prof. John Zarnecki RAeS – 22nd March 2005 Slide 6 of 45
The Cassini/Huygens Mission
Prof. John Zarnecki RAeS – 22nd March 2005 Slide 7 of 45
The Cassini Spacecraft
Joint ESA/NASA mission
Launched 15th October 1997
6.7 m high 2125 kg at launch After a 7 year (4 billion
km) journey, Cassini arrived at Saturn in July 2004.
Prof. John Zarnecki RAeS – 22nd March 2005 Slide 8 of 45
The Gravity Assist Trajectory
Prof. John Zarnecki RAeS – 22nd March 2005 Slide 9 of 45
Saturn Orbit Insertion
Prof. John Zarnecki RAeS – 22nd March 2005 Slide 10 of 45
The Huygens Probe
Determine atmospheric composition
Study aerosol properties and cloud physics
Characterise the upper atmosphere
Imaging the surface for the first time
Determine the physical properties of the surface material
Prof. John Zarnecki RAeS – 22nd March 2005 Slide 11 of 45
IndustryLogicaCMG – Mission critical on-board software, including Probe
control software, Cassini/Huygens communications relay software and in flight software maintenance.
Martin Baker Space Systems – Parachute systems and related structural components, mechanisms and pyrotechnics.
Irvin Aerospace – Sub-contractor to Martin Baker responsible for definition of each of the three disk gap band parachutes.
IGG Component Technology - Centralised procurement and testing of electrical, electronic and electromechanical components.
SciSys – Mission control system development and operational support.
Prof. John Zarnecki RAeS – 22nd March 2005 Slide 12 of 45
List of Instruments1. Huygens Atmospheric Structure
Instrument (HASI) Fulchignoni, Paris, France.
2. Gas Chromatograph Mass Spectrometer (GCMS) Niemann, NASA, USA
3. Aerosol Collector and Pyrolyser (ACP) Israel, CNRS, France.
4. Descent Imager/Spectral Radiometer (DISR) Tomasko, Arizona, USA
5. Doppler Wind Experiment (DWE) Bird, Bonn, USA
6. Surface Science Package (SSP) Zarnecki, OU, UK.
Prof. John Zarnecki RAeS – 22nd March 2005 Slide 13 of 45
Prof. John Zarnecki RAeS – 22nd March 2005 Slide 14 of 45
The Surface Science Package(SSP)
Prof. John Zarnecki RAeS – 22nd March 2005 Slide 15 of 45
SSP Flight Integration
Prof. John Zarnecki RAeS – 22nd March 2005 Slide 16 of 45
SSP Sensor Description
Prof. John Zarnecki RAeS – 22nd March 2005 Slide 17 of 45
Selected Properties Measured by SSP
Prof. John Zarnecki RAeS – 22nd March 2005 Slide 18 of 45
ATMOSPHERESOLIDMUDLIQUID
Prof. John Zarnecki RAeS – 22nd March 2005 Slide 19 of 45
ACC-I (Internal Accelerometer)
Piezoelectric accelerometer Max ~100 g detection Impact dynamics measurement
(deceleration)
Prof. John Zarnecki RAeS – 22nd March 2005 Slide 20 of 45
ACC-E (Penetrometer)
Piezoelectric force transducer
Protrudes from probe base
First instrument to touch Titan’s surface
Impact measurement of penetration through the surface layer (mechanical properties of the surface)
Prof. John Zarnecki RAeS – 22nd March 2005 Slide 21 of 45
TIL (Probe Attitude)
Measures tilt relative to 1 axis
Electrolytic liquid in a glass vial
Fluid movement relative to electrodes → tilt angle
Prof. John Zarnecki RAeS – 22nd March 2005 Slide 22 of 45
API-V (Speed of Sound)
2 piezoelectric transducers generate ultrasonic pulse
Alternate Tx/Rx mode Arranged facing each
other Time taken for pulse
to be detected → speed of sound in the Titan atmosphere (molecular mass)
Prof. John Zarnecki RAeS – 22nd March 2005 Slide 23 of 45
API-S (Sounder)
10 resonant piezoelectric plates
Simultaneously form a 20° acoustic beam
Orientated towards the surface
Surface profile echoes Ocean/lake sounder
Prof. John Zarnecki RAeS – 22nd March 2005 Slide 24 of 45
THP (Thermal Properties)
Thin wire technique 50 µm Pt wire pulsed with
high current
RΩ(t) measured Thermal conductivity
derived (gas mixture components)
Prof. John Zarnecki RAeS – 22nd March 2005 Slide 25 of 45
DEN (Density)
Archimedes’ principle Float suspended in
chamber
Buoyancy in immersed liquid measured by strain gauges → density
Prof. John Zarnecki RAeS – 22nd March 2005 Slide 26 of 45
REF (Refractometer)
Critical angle refractometer Linear photodiode array and
specially designed prism
Refractive index of immersed liquid measured (light-dark transition)
Prof. John Zarnecki RAeS – 22nd March 2005 Slide 27 of 45
PER (Permittivity and Conductivity)
Stacked parallel plates
Capacitance measured Permittivity and conductivity
of the liquid measured
Prof. John Zarnecki RAeS – 22nd March 2005 Slide 28 of 45
Landing On Titan
Prof. John Zarnecki RAeS – 22nd March 2005 Slide 29 of 45
Arrival and Descent
Prof. John Zarnecki RAeS – 22nd March 2005 Slide 30 of 45
Possible Landing Scenarios
Prof. John Zarnecki RAeS – 22nd March 2005 Slide 31 of 45
High Altitude Images
Altitude 16.2 km, 40m per pixel resolution
Credits: ESA/NASA/University of Arizona
Altitude 8 km, 20m per pixel resolution
Prof. John Zarnecki RAeS – 22nd March 2005 Slide 32 of 45
High Altitude Images
Credits: ESA/NASA/University of Arizona
Altitude 16.2 km, 40 m per pixel resolution
Prof. John Zarnecki RAeS – 22nd March 2005 Slide 33 of 45
A View from 10 km
Credits: ESA/NASA/University of Arizona
Prof. John Zarnecki RAeS – 22nd March 2005 Slide 34 of 45
Views at the surface
Credits: ESA/NASA/University of Arizona
Prof. John Zarnecki RAeS – 22nd March 2005 Slide 35 of 45
The Impact on the Surface
Prof. John Zarnecki RAeS – 22nd March 2005 Slide 36 of 45
The Impact on the Surface
Prof. John Zarnecki RAeS – 22nd March 2005 Slide 37 of 45
Impact Simulations Over 100 vertical and
oblique drops into 16 different substrate materials.
Coarse Gravel Sand
SiliBeads Crème Brulee Drop Test Rig
Prof. John Zarnecki RAeS – 22nd March 2005 Slide 38 of 45
Impact Simulations
Prof. John Zarnecki RAeS – 22nd March 2005 Slide 39 of 45
Impact Simulations
Prof. John Zarnecki RAeS – 22nd March 2005 Slide 40 of 45
Impact Dynamics – First Look
• ACC-I (deceleration):35ms deceleration pulse, peak 15g – Huygens probe decelerated over circa 16cm; Model comparison suggests material with uniform strength vs. depth, ~10
N cm-2
• ACC-E (penetration force):50N resistance with some variation – possibly a pebble strike, possible sub-surface granular structure on cm scale or finer
Prof. John Zarnecki RAeS – 22nd March 2005 Slide 41 of 45
API-S Surface Detection
Prof. John Zarnecki RAeS – 22nd March 2005 Slide 42 of 45
API-V
Speed of sound increases with temperature at lower altitude
Prof. John Zarnecki RAeS – 22nd March 2005 Slide 43 of 45
SSP Data Summary
• SSP has received ALL of its Science Data via Channel B.
• All SSP sensors have given the expected output for the atmospheric and surface conditions encountered.
• We have data up to T0 + 13,046secs (3hrs, 37mins, 26secs).
• Data from surface for 1hr, 9 mins, 36secs
Prof. John Zarnecki RAeS – 22nd March 2005 Slide 44 of 45
17 January 2005L.Gurvits and the Huygens VLBI Tracking Team
Doppler (wind and more….) measurements
Huygens carrier at Green Bank, Mk5 VLBI
Prof. John Zarnecki RAeS – 22nd March 2005 Slide 45 of 45
Acknowledgements
• SSP Science Team• Huygens Science Team• ESA• NASA• Polish Academy of Sciences• University of Manchester• Rutherford Appleton Laboratory• Particle Physics and Astronomy Research
Council