A Measurement of Titan´s Zonal Winds by the Huygens Doppler Wind Experiment: Michael Bird...
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A Measurement of Titan´s Zonal Winds by the Huygens Doppler Wind Experiment:
Michael Bird(Radiostronomisches Institut, Universität Bonn)
And the DWE Team
DPS Cambridge - Paper 2.01IMonday, 5 September 2005
Cambridge DPS, 5 Sep 20052
Huygens DWE
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
Cambridge DPS, 5 Sep 20053
Huygens DWE
DWE Concept (1)
• Goal: In situ determination of zonal wind speed along Huygens descent path
• Approach: Record Doppler effect on Huygens carrier signal => radial velocity
Cambridge DPS, 5 Sep 20054
Huygens DWE
DWE Concept (2)
• Input parameters:1. Huygens descent speed, 2. Huygens meridional speed3. Huygens starting position4. Cassini position & velocity5. Earth-based station position & velocity
Cambridge DPS, 5 Sep 20055
Huygens DWE
DWE Hardware
• TUSO on Huygens Probe
Ultra-stable Oscillators (USOs)
• RUSO in Huygens Receiver on Cassini
+
Cambridge DPS, 5 Sep 20056
Huygens DWE
Cassini
TCXOTCXO
TCXORUSO
TCXOTUSO
Channel B
Channel A
Earth
“Channel C”
Huygens Signal paths
Huygens DataHuygensReceivers
HuygensProbe
NO POWER
TCXORUSO
Cambridge DPS, 5 Sep 20057
Huygens DWE
DWE from Earth: Geometry• 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
0°
15°
30°
45°
60°
75°
-15°
-30°
-45°
-60°
-75°
Track ofSub-Earth
Point
Track of OrbiterProbe
180°210°240° 150° 120°
20º
Titan Disk
Cambridge DPS, 5 Sep 20058
Huygens DWE
Huygens Radio Tracking Net
10:18 UTC-GRT 12:30 UTC-GRT
GBT
VLBA
MK
KP
PTOV
MK
Parkes
VLBA
Cambridge DPS, 5 Sep 20059
Huygens DWE
Huygens Earth-Based NetworkFacility Start
UTCStop UTC Comment
GBT 09:31:10 12:15:00 DWE: Real-time RSR detection
VLBA Fort Davis 09:31:10 13:45:00
VLBA North Liberty 09:31:10 13:15:00
VLBA Owens Valley 09:30:09 14:49:14 DWE: No nodding – on Titan continuously
VLBA Pie Town 09:30:11 14:15:04 DWE: No nodding – on Titan continuously
VLBA Los Alamos 09:31:10 14:00:00
VLBA Brewster 09:31:10 14:48:00
VLBA Kitt Peak 09:31:10 14:15:00 DWE
VLBA Mauna Kea 09:31:10 16:00:00 DWE
Parkes 12:26:23 16:00:00 DWE: Real-time RSR detection
Hobart 11:13:10 16:00:00
Ceduna 10:13:10 16:00:00
Mopra 10:10:10 16:00:00
Kashima 09:31:10 16:00:00
Shanghai 10:01:10 16:00:00
Cambridge DPS, 5 Sep 200511
Huygens DWE
GBT: 14 Jan 2005 Huygens!(~ -171 dBm)
Flux density 125 Jy
10:18:15 UTC-GRT10
just noise
Cambridge DPS, 5 Sep 200512
Huygens DWE
Huygens Frequency: GBT + Parkes
26-min gap
GBT
Parkes
Cassiniloss of link
Cambridge DPS, 5 Sep 200514
Huygens DWE
Huygens Frequency: Parkes + Predicts
predictedimpact
f = +26.4 Hz
80-s gaps(VLBI)
Cambridge DPS, 5 Sep 200517
Huygens DWE
DWE: Preliminary Results1. Zonal winds above boundary layer are PROGRADE2. First in situ confirmation of TITAN’S SUPERROTATION3. 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 km6. Near surface winds are weak (~1 m/s)
Huygens Ground Track Determination:A 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 45.09Wednesday, 7 September 2005