Huygens at Titan

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Huygens at Titan
Michael Bird
Radioastronomisches Institut Universität Bonn
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Outline

• getting there
• 14 January 2005
• lifting Titans veil
• Huygens DWE an update

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getting there
the journey is the destination.
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Cassini/Huygens
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Cassini/Huygens
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KSC, Cape Canaveral 15 Oct 1997
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Cassini SOI 1 July at 0236 UT
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Christmas Day 2004
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14 January 2005
7 years, 3 months and 4 billion km from launch
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Huygens Descent on Titan
From Atmospheric Entry
To Touchdown on Surface
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Huygens Targetting Error
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Huygens Landing Error
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Huygens Descent Scenario
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Huygens events (UTC) One Way Light Time 1 h 07
m 06 s
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Huygens Mission Intervals Predicted vs. Actual
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lifting Titans veil
Yet do thy cheeks look red as Titans face
W. Shakespeare
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Titan Pre-Cassini/Huygens (1)

• PTitan orbit 15.9 d, PSaturn orbit 29.4 yr,
  obliquity 27
• Bulk density 1.88 g cm-3, Callisto
  Ganymede (50 ice, 50 rock)
• Atmospheric Composition N2 0.77
  0.92 (0.97)
• 
  Ar 0.05 0.17 (lt0.001)
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  CH4 0.03 0.07 (0.023)
• 
  other hydrocarbons and nitriles
• Haze from photodissociation of CH4 ? 2-5 in
  visible, ? lt 1 in near-IR.
• Tsurface 94 K, Psurface 1.5 bar.
• Tropopause (42 km) T 71 K Scale height in
  troposphere 20 km

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Titan Pre-Cassini/Huygens (2)
Optically Thick Aerosol Haze
Mild Greenhouse Effect
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Huygens Investigations
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HASI atmospheric profiles
temperature
pressure
Psurf 1.463 bar
Tsurf 93.8 K
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GCMS Atmospheric Constituents
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ACP Schematic
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SSP Impact on Surface
wet sand or clay
(crème brûlée)
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DISR first images
drainage canals fluvial activity
dry lakebed
fluid CH4
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DISR Selected Details
methane springs?
water ice shoals?
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DISR side-looking imager
h 8 km
res 20 m
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DISR 360 Panorama
ground fog
h 8 km ?s 20 m horizontal velocity 1-2 m s-1
landing site
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DISR on the surface
orange tint from reflectance spectra
mouse
5 cm
85 cm
dirty water ice, not hydrocarbon ice
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Huygens Doppler Wind Experiment An Update
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DWE Concept

• Goal In situ determination of zonal wind speed
  along Huygens descent path
• Approach Record Doppler effect on Huygens
  carrier signal gt radial velocity
• Input parameters
• Huygens descent speed, meridional speed
• Huygens starting position
• Cassini position velocity

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DWE Hardware
Ultra-stable Oscillators (USOs)

• TUSO on Huygens Probe
• RUSO in Huygens Receiver on Cassini

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Huygens Doppler PCO1
TUSO/RUSO
TCXO/TCXO
3 hours
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No power!
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DWE from Earth Geometry

• Huygens antenna pointed only 30 from Earth
• Better SNR than for Galileo Probe detection at
  Jupiter
• Probe velocity projection in direction to Earth
  nearly antiparallel to projection in direction to
  Orbiter

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GBT
Parkes
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Earth-based DWE Huygens Frequency
Impact on surface
Change of parachutes
GBT
Parkes
Time (SPM)
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prograde zonal wind
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VLBI network as seen from Titan 14 Jan 2005
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VLBI station visibility
entry
landing
orbiter
battery
Parkes
GBT
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Huygens Art Contest
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Lebe Wohl, Huygens