A Measurement of Titans Zonal Winds by the Huygens Doppler Wind Experiment:

1
A Measurement of Titans Zonal Winds by the
Huygens Doppler Wind Experiment
Michael Bird (Radiostronomisches Institut,
Universität Bonn) And the DWE Team
DPS Cambridge - Paper 2.01I Monday, 5 September
2005
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The DWE Team

• M.K. Bird, R. Dutta-Roy, Y. Dzierma
• Radioastronomisches Inst., Univ. Bonn,
  Auf dem Hügel 71, 53125 Bonn, Germany
• M. Allison
• NASA Goddard Inst. for Space Studies,
  2880 Broadway, New York, NY 10025
• D.H. Atkinson
• Dept. of Elec. Computer Engineering,
  Univ. of Idaho, Moscow, ID 83844
• S.W. Asmar, W.M. Folkner, D.V. Johnston, R.A.
  Preston
• Jet Propulsion Laboratory, Caltech, 4800
  Oak Grove Dr, Pasadena, CA 91109
• P. Edenhofer
• Institut für HF-Technik, Universität
  Bochum, 44780 Bochum, Germany
• D. Plettemeier
• Elektrotechnisches Institut, Technische
  Univ. Dresden, 01062 Dresden, Germany
• G.L. Tyler
• Center for Radar Astronomy, Stanford
  University, Stanford, CA 94305
• L.I. Gurvits, S.V. Pogrebenko, I.M. Avruch
• Joint Inst. for VLBI in Europe, P.O.
  Box 2, 7990 AA Dwingeloo, The Netherlands

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DWE Concept (1)

• Goal In situ determination of zonal wind speed
  along Huygens descent path

• Approach Record Doppler effect on Huygens
  carrier signal gt radial velocity

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DWE Concept (2)

• Input parameters
• Huygens descent speed,
• Huygens meridional speed
• Huygens starting position
• Cassini position velocity
• Earth-based station 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 Signal paths
Cassini
TCXO
TCXO
Channel B
Huygens Receivers
Huygens Data
TCXO TUSO
Channel A
TCXO RUSO
TCXO RUSO
Huygens Probe
NO POWER
Channel C
Earth
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DWE from Earth Geometry
Titan Disk

• Huygens antenna pointed only 30 from Earth
• Better SNR than for VLA detection of Galileo
  Probe at Jupiter
• Probe-Earth vector projection onto horizontal
  nearly antiparallel to Probe-Orbiter projection

?20º
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Huygens Radio Tracking Net
GBT
VLBA
PT
OV
VLBA
KP
MK
MK
Parkes
1018 UTC-GRT
1230 UTC-GRT
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Huygens Earth-Based Network
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GBT
Parkes
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101815 UTC-GRT
10
GBT 14 Jan 2005
Huygens! ( -171 dBm)
just noise
Flux density ? 125 Jy
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Huygens Frequency GBT Parkes
Cassini loss of link
26-min gap
Parkes
GBT
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Huygens Frequency GBT predicts
80-s gaps (VLBI)
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Huygens Frequency Parkes Predicts
80-s gaps (VLBI)
predicted impact
?f 26.4 Hz
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Zonal Wind Velocity
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Zonal Wind Height Profile
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DWE Preliminary Results

• 1. Zonal winds above boundary layer are
• PROGRADE
• 2. First in situ confirmation of
• TITANS SUPERROTATION
• 3. Huygens eastward drift 3.75º (166 km)
• 4. Low-velocity layer between 60-100 km
• Stong positive/negative wind shear
• Unexpected, presently unexplained
• 5. Considerable turbulence above 100 km
• 6. Near surface winds are weak (1 m/s)

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Huygens Ground Track DeterminationA Comparison
of DWE and DISR Results

• R. Dutta-Roy, B. Rizk, S.W. Asmar, D.H. Atkinson,
• M.K. Bird, M.W. Bushroe, E. Karkoschka,
• E.A. McFarlane, C. See, M.G. Tomasko,
• and the DWE and DISR Teams

DPS Cambridge - Poster 45.09 Wednesday, 7
September 2005
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A Preliminary Meteorological Interpretation of
Correlated Huygens DWE and HASI Data

• M. Allison, F. Ferri, M.K. Bird, M. Fulchignoni,
• S.W. Asmar, D.H. Atkinson, G. Colombatti, G.L.
  Tyler
• and the DWE and HASI Experiment Teams

DPS Cambridge - Poster 45.03 Wednesday, 7
September 2005