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Cassini Radio Occultation of Saturn's Rings and Atmosphere: Preliminary Results

Cassini Radio Occultation of Saturn's Rings and Atmosphere: Preliminary Results. Essam Marouf & Richard French. for the Cassini Radio Science Team. Cassini CHARM Presentation. May 31, 2005. Twelve Main Cassini Science Instruments. Microwave Remote Sensing Radio Science Subsystem (RSS)

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Cassini Radio Occultation of Saturn's Rings and Atmosphere: Preliminary Results

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  1. Cassini Radio Occultation of Saturn's Rings and Atmosphere: Preliminary Results Essam Marouf & Richard French for the Cassini Radio Science Team Cassini CHARM Presentation May 31, 2005

  2. Twelve Main Cassini Science Instruments • Microwave Remote Sensing • Radio Science Subsystem (RSS) • Cassini Radar (RADAR) • Optical Remote Sensing (ORS) • Composite Infrared Spectrometer (CIRS) • Imaging Science Subsystems (ISS) • Ultraviolet Imaging Spectrograph (UVIS) • Visual and Infrared Mapping Spectrometer (VIMS) • Fields, Particles, and Waves • Cassini Plasma Spectrometer (CAPS) • Cosmic Dust Analyzer (CDA) • Dual Technique Magnetometer (MAG) • Ion and Neutral Mass Spectrometer (INMS) • Magnetospheric Imaging Instrument (MIMI) • Radio & Plasma Wave Science (RPWS)

  3. Downlink  Radio Science Subsystem (RSS): Downlink Configuration From Cassini To the Deep Space Network (DSN) - Atomic Frequency Standard - X, S: 70 m - Ka, X: 34 m BWG Three Sinusoids Coherentin Phase (Crystal Oscillator-- USO) l (cm) Pt (W) SNR (dB-Hz) Ka 0.94 7 41 X 3.6 19 51 S 13 10  Goldstone, CA: 70 m Cassini RSS

  4. S/C Saturn From S/C q0 DSN q0 To DSN Titan Downlink Configuration is Used to Conduct: 1-Atmospheric / Ionospheric Occultations of Saturn and Titan 2- Ring Occultations 3- Bistatic-Scattering From Titan’s Surface Cassini RSS

  5. Hubble Space Telescope French et al., 2003

  6. Cassini Orbital Tour of the Saturn System 75 Saturn Orbits; 45 Titan Encounters (July 1, 2004 to June 30, 2008) D. Seal, 2004

  7. Rev 7 Rev 44 Occultation Sequence: revs 7 to 14 180° Transfer Sequence: revs 44, 46 20° ≤ B ≤ 24° B ~ 15° Rev 63 Rev 46 High Inc Sequence Orbits 56 to 67 6 ≤ B ≤ 10° Typical Ring Occultation Track Geometry (15 m tick-marks) Cassini RSS

  8. Catching the Open Rings Cassini Tour 14 |Ring-Opening-Angle| (|B°|) I0 t B I Year Rev 7 Occultation Track Cassini RSS

  9. Rev 7 Radio Occultation Track: May 2-3, 2005 View From the Earth Live Moveable Block (LMB) ERT UTC PT Cassini 10 m ingress BL BL egress 04:23 21:23 03:53 ERT 20:53 PDT 06:00 23:00 10:36 03:36 10:06 03:06 08:00 01:00 08:32 01:32 06:40 23:40 Cassini RSS 06:50 G: DSS 14, 25, 26 11:10 C: DSS 43, 34 02:45

  10. * Water-Ice Ring Particles *Millimeters to Several Meters Main Size Population * Tens of meters thick Artist Conception!

  11. Direct Signal Scattered Signal Observables Scattered Signal B Direct, or Coherent, Signal • Direct Signal • radial ring structure • Particle sorting by size • Thickness of ring edges • Scattered Signal • Particle size distribution • Vertical ring profile • Particle packing and clustering • Physical ring thickness Cassini RSS

  12. Radio Occultation: Profiling of Radial Ring Structure I0 Cassini ISS Saturn’s Rings I0 esin(B) Voyager RSS

  13. Planet Saturn and its Remarkable Ring System (~300,000 km across; ~distance from the Earth to the Moon ) Hubble Space Telescope

  14. Rings Structure Ring C Ring B Cassini Division RingA Ring F Cassini ISS

  15. Saturn’s Inner and Outer Ring C Cassini ISS

  16. OPACITY,[3.6] 125 km SIGNAL LOSS (dB) Interesting Ring Structure Exists at Every Spatial Scale Inner Ring C Cassini ISS 1500 km 4 km res - Colombo Gap - Titan Ringlet - W-Features Voyager RSS 200 m res Titan -1:0 Bending Wave 100 m resolution is not luxury !

  17. Observations are Diffraction-Limited Voyager RSS Fresnel Diffraction by the Inner Edge of the Encke Gap Voyager ISS

  18. Finite Observation Interval W (km); T (sec) Holographic Reconstruction -W /2 W /2 O Ring F Example F = 15 km DR = 200 m Signal phase must remain stable over T Voyager RSS Radius (km)

  19. B Cassini RSS: Achievable Radial Resolution DR = 100 m Threshold Optical Depth tTH(SNR=1) Resolution DR (m) Cassini RSS

  20. Occultations at Multiple Longitudes: Dynamical Ring Structure Narrow Eccentric Ringlets Bending Waves Uranus’ Ring  Density Waves Mimas 5:3 Optical Depth,  [3.6] Signal Loss (dB) Voyager RSS

  21. Occultations at Multiple Longitudes: Detection of Embedded Satellites Encke Gap Pan’s Wake Cassini ISS Voyager RSS

  22. Cassini Rev 7: Optical Depth Profiles of Ring C (X, 10 km Res) Cassini RSS

  23. Cassini Rev 7: Optical Depth Profiles of Ring C, S/X/Ka (R/G/B) Cassini RSS

  24. Cassini Rev 7: Optical Depth Profiles of Ring B (X, 10 km Res) Cassini RSS

  25. Cassini Rev 7: Optical Depth Profiles of Ring B, S/X/Ka (R/G/B) Cassini RSS

  26. Cassini Rev 7: Optical Depth Profile of Ring A (X, 10 km Res) Cassini RSS

  27. Cassini Rev 7: Density Waves in Outer Ring A (Ka, 1.4 km Res) Cassini RSS

  28. Cassini Rev 7: Optical Depth Profiles of Ring A, S/X/Ka (R/G/B) Cassini RSS

  29. Small Particles in Ring A (PIA07875) Cassini RSS

  30. Radio Occultation: Unraveling Saturn’s Rings (PIA07873) Cassini RSS

  31. Multiple Eyes of Cassini (PIA07874) • http://photojournal.jpl.nasa.gov/catalog/PIA07873 • http://photojournal.jpl.nasa.gov/catalog/PIA07872 • http://photojournal.jpl.nasa.gov/catalog/PIA07875 • http://photojournal.jpl.nasa.gov/catalog/PIA07960 • http://photojournal.jpl.nasa.gov/catalog/PIA07874

  32. Direct Signal Scattered Signal Observables Scattered Signal B Direct, or Coherent, Signal • Direct Signal • radial ring structure • Particle sorting by size • Thickness of ring edges • Scattered Signal • Particle size distribution • Vertical ring profile • Particle packing and clustering • Physical ring thickness Cassini RSS

  33. Scattered Signal: Doppler Contours Cassini RSS

  34. Scattered Signal: Meter-Size “Particles” amax = 3, 5, 10 m F (kHz) Cassini RSS

  35. Cassini Rev 7: Outer Ring B Direct & Scattered Signals Cassini RSS

  36. Rev 7 Radio Occultation Track: May 2-3, 2005 View From the Earth Live Moveable Block (LMB) ERT UTC PT Cassini 10 m ingress BL BL egress 04:23 21:23 03:53 ERT 20:53 PDT 06:00 23:00 10:36 03:36 10:06 03:06 08:00 01:00 08:32 01:32 06:40 23:40 Cassini RSS 06:50 G: DSS 14, 25, 26 11:10 C: DSS 43, 34 02:45

  37. TITAN EXTENDED ATMOSPHERE Cassini ISS

  38. Atmospheric Limb-Track Maneuver “Virtual” Earth “Apparent” Line of Sight Refracted Ray Path “Actual” Earth Geometric Line of Sight Actual Virtual Saturn or Titan Adapted from D. Wait 05/07/04

  39. RSS Saturn Atmosphere Signal Level (dB) Cassini RSS

  40. RSS Saturn Atmosphere Signal Level (dB) Cassini RSS

  41. RSS Saturn Atmosphere Signal Level (dB) Cassini RSS

  42. RSS Saturn Atmosphere Signal Level (dB) Cassini RSS

  43. RSS Saturn Atmosphere Signal Level (dB) Cassini RSS

  44. RSS Saturn Atmosphere Signal Level (dB) Cassini RSS

  45. Cassini/CIRS: Flasar et al. (2005) Zonal winds: u (m/s) Winds derived from the thermal wind equation showstrong vertical decay at low latitudes, but the cloudsobserved by HST & Cassini/ISS would have to be >130 km above those seen by Voyager if changing cloudheights explain the changes in observed wind speeds. 250 km Cloud tracking by HST and Cassini ISSsuggests that Saturn’s equatorial windshave changed or the cloud tops have changed. – Latitude Are Saturn’s Winds Changing?

  46. RSS Saturn Ionosphere Frequency Residual Hz Cassini RSS

  47. RSS Saturn Ionosphere Altitude (1bar) km Cassini RSS

  48. RSS Saturn Ionosphere Frequency Residual Hz Cassini RSS

  49. RSS Saturn Ionosphere Altitude (1bar) km Cassini RSS

  50. To profile radial ring structure with resolution ≤ 100 m; characterize structure variability with azimuth, wavelength, ring-opening-angle, and time To determine physical particle properties (size distribution, bulk density, surface density, thickness, viscosity) To study ring kinematics and dynamics (morphology, interaction with embedded and exterior satellites), and to investigate ring origin and evolution Scientific Objectives: Ring Occultations Cassini RSS

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