Transcript The Doppler Wind Experiment

DWE: Initial Results
Michael Bird
(Radiostronomisches Institut, Universität Bonn)
And the DWE Team
HSWT#29, Florence
February 28, 2005
DWE data: Huygens Mission
f
Channel A
Channel B
df/dt
df/dt
6 hours
28 February 2005
f
3.67 hours
HSWT#29, Florence
2
No power!
28 February 2005
HSWT#29, Florence
3
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
28 February 2005
75°
60°
45°
30°
15°
240°
210°
Track of Orbiter
180°
150°
120°
Probe
0°
-15°
-30°
Track of
Sub-Earth
Point
-45°
-60°
-75°
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GBT
28 February 2005
Parkes
HSWT#29, Florence
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Huygens Radio Tracking Net
10:18 UTC-GRT
28 February 2005
12:30 UTC-GRT
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GRT
GBT
Huygens!
(~ -171 dBm)
Flux density: 125 Jy
28 February 2005
HSWT#29, Florence
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GBT Detection
28 February 2005
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Watching Huygens from JPL
28 February 2005
HSWT#29, Florence
9
Huygens Frequency: GBT + Parkes
28 February 2005
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Huygens Frequency: GBT + predicts
28 February 2005
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Huygens Frequency: Parkes + Predicts
predicted
impact
28 February 2005
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Parkes: Huygens Impact on Titan
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Doppler Components
GBT
(1) Raw Doppler
(2) Only Huygens
Motion
(3) Huygens Descent
Velocity
(4) Huygens Horizontal
Velocity
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Integrate wind velocity
to obtain:
Huygens
Eastward Drift
During Descent
28 February 2005
DWE
DISR
Difference
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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)
28 February 2005
HSWT#29, Florence
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Wind Shear and Stability
28 February 2005
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Richardson Number
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Thermal Gradients
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