HSWT#29, Florence February 28, 2005
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Transcript of HSWT#29, Florence February 28, 2005
HSWT#29, FlorenceFebruary 28, 2005
DWE: Initial Results
Michael Bird
(Radiostronomisches Institut, Universität Bonn)
And the DWE Team
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DWE data: Huygens Mission
6 hours 3.67 hours
f f
df/dt df/dt
Channel A Channel B
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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
0°
15°
30°
45°
60°
75°
-15°
-30°
-45°
-60°
-75°
Track ofSub-Earth
Point
Track of OrbiterProbe
180°210°240° 150° 120°
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GBT Parkes
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Huygens Radio Tracking Net
10:18 UTC-GRT 12:30 UTC-GRT
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GRT
GBT Huygens!(~ -171 dBm)
Flux density: 125 Jy
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GBT Detection
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Watching Huygens from JPL
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Huygens Frequency: GBT + Parkes
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Huygens Frequency: GBT + predicts
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Huygens Frequency: Parkes + Predicts
predictedimpact
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Parkes: Huygens Impact on Titan
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GBT
(1) Raw Doppler
(2) Only Huygens Motion
(3) Huygens Descent Velocity
(4) Huygens Horizontal Velocity
Doppler Components
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Huygens Eastward DriftDuring Descent
DWEDISR
Difference
Integrate wind velocityto obtain:
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DWE: Preliminary Results• Zonal winds above boundary layer are
PROGRADE
• Low-velocity layer between 60-80 km – Stong positive/negative wind shear– ‘Unexpected’, but evident in some GCMs
• Considerable turbulence above 100 km
• Near surface winds are weak (~ 1-2 m/s)
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Wind Shear and Stability
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Richardson Number
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Thermal Gradients