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 200510

Huygens DWE

GBT Parkes

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 200513

Huygens DWE

Huygens Frequency: GBT + predicts

80-s gaps(VLBI)

Cambridge DPS, 5 Sep 200514

Huygens DWE

Huygens Frequency: Parkes + Predicts

predictedimpact

f = +26.4 Hz

80-s gaps(VLBI)

Cambridge DPS, 5 Sep 200515

Huygens DWE

Zonal Wind Velocity

Cambridge DPS, 5 Sep 200516

Huygens DWE

Zonal Wind Height Profile

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

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 45.03Wednesday, 7 September 2005