1. Dr. David H. Atkinson Dept. Electrical & Computer Engineering University of Idaho 8 April 2005 Measuring the Zonal Winds on Titan: The Huygens Probe Doppler Wind Experiment

2. Cassini/Huygens

3. HST

4. Voyager 1

7. Transmitter Ultrastable Oscillator (TUSO) Radar Altimeter Antennas GCMS Atmospheric Structure Instrument Descent Imager Surface Science Package Command Data Management Unit (CDMU) Accelerometers

8. Batteries PCDU ACP SSP GCMS

9. KSC, Cape Canaveral: 15 Oct 1997

11. Cassini SOI: 1 July at 02:36 UT

12. Christmas Day 2004

13. 14 January 2005 7 years, 3 months and 4 billion km from launch

14. Titan: Pre-Cassini/Huygens N2, CH4, and H2 atmosphere cause a mild greenhouse effect that raises the surface temperature by +21K. High altitude optically thick organic haze absorbs solar visible but is transparent to IR, cooling surface temp by about 9K. (anti-greenhouse effect).

15. Huygens’ Scientific Payload ACP - Aerosol Collector and Pyrolyser (G. Israel, France) –Collection of aerosols for chemical-composition analysis. GCMS - Gas Chromatograph and Mass Spectrometer (H. Niemann, NASA GSFC) –gas chemical analyser designed to identify and quantify various atmospheric constituents. DISR - Descent Imager & Spectral Radiometer (M. Tomasko, U. Arizona) –images and spectral measurements. Also spectra of the surface material will be acquired. DWE - Doppler Wind Experiment (M. Bird, U. Bonn) –Wind measurements using Probe/Orbiter radio signal HASI - Huygens Atmosphere Instrument (M. Fulchignoni, Italy) – physical and electrical properties of the Atmosphere SSP - Surface Science Package (J. Zarnecki, UK) –physical properties of the surface at the impact site

18. DWE Concept Goal: In situ determination of zonal wind speed along Huygens descent path Approach: Record Doppler effect on Huygens carrier signal => radial velocity Input parameters: 1.Huygens descent speed, meridional speed 2.Huygens starting position 3.Cassini position & velocity

19. Ultra-stable Oscillators (USOs) TUSO on Huygens Probe RUSO in Huygens Receiver on Cassini Orbiter DWE Hardware

25. No power!

26. Channel B Temperature Compensated Crystal Oscillator

27. 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. Huygens VLBI Network Facility Start UTCStop UTCComment GBT09:31:1012:15:00 DWE: Real time RSR detection VLBA Fort Davis09:31:1013:45:00 VLBA North Liberty09:31:1013:15:00 VLBA Owens Valley09:30:0914:49:14DWE: No nodding – on Titan continuously VLBA Pie Town09:30:1114:15:04DWE: No nodding – on Titan continuously VLBA Los Alamos09:31:1014:00:00 VLBA Brewster09:31:1014:48:00 VLBA Kitt Peak09:31:1014:15:00DWE VLBA Mauna Kea09:31:1016:00:00DWE Parkes12:26:2316:00:00DWE: Real time RSR detection Hobart11:13:1016:00:00 Ceduna10:13:1016:00:00 Mopra10:10:1016:00:00 Kashima09:31:1016:00:00 Shanghai10:01:1016:00:00 Urumqi11:31:1016:00:00Calibration only, no Huygens signal at 2040 MHz ATCA10:01:1016:00:00Calibration only, no Huygens signal at 2040 MHz Onsala19:01:1022:15:00 Wettzell21:46:1022:15:00

29. Parkes Telescope Australia Green Bank Telescope West Virginia

30. Huygens Radio Tracking Net 10:18 UTC-ERT12:30 UTC-ERT

31. Huygens! (~ -171 dBm) 10:18:15 UTC-GRT10:18:10 UTC-GRT Green Bank Telescope

32. Huygens Frequency: GBT + Parkes

33. 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)

34. Adieu, Huygens