HSWT#29, FlorenceFebruary 28, 2005

DWE: Initial Results

Michael Bird

(Radiostronomisches Institut, Universität Bonn)

And the DWE Team

28 February 2005 2HSWT#29, Florence

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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28 February 2005 18HSWT#29, Florence

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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28 February 2005 20HSWT#29, Florence

Wind Shear and Stability

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Richardson Number

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Thermal Gradients