Occultation Science from the Sixties to Present

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Occultation Science from the Sixties to
Present T. P. Yunck and W. G. Melbourne Jet
Propulsion Laboratory California Institute of
Technology OPAC-1 Graz, Austria 16-20
September 2002
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Origins-I Optical Occultation
Stellar Occultation by Venus
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Venus passing behind the Moon
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Moon-Saturn Occultation
November 2001
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Moon-Saturn Occultation
Entry
November 2001
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Moon-Saturn Occultation
Exit
November 2001
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Pseudo Optical Occultation of Jupiter Rings
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Grazing Stellar Occultation at Jupiter
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Pluto Stellar Occultation
July 20, 2002
The only planet not yet visited by a spacecraft
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Images of Pluto and Charon
Constructed from Occultation Measurements
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Origins-II Planetary Radio Occultation
Mariner IV at Mars July 1965
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Mariner IV Occultation at Mars Two Competing
Proposals
Amazing facts At 10 cm wavelength, 1 free
electron will cancel the refractive effect of 2.5
x 1011 CO2 molecules.
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Mariner IV Mars 15 July 1965 ( JPL wirephoto )
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Mariner IV Occultation at Mars Earliest Results
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Mariner IV Occultation at Mars Refined Results
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Mariner V at Venus 19 October 1967
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Mariner V Occultation at Venus Separate Stanford
JPL Experiments
Amplitude and phase based retrievals
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Mariner V Occultation at Venus Temperature
Profile Comparison
Fjeldbo et al., 1971
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Pioneer Venus Orbiter 1979-1982
Data taken over multiple seasons
First recovery of zonal winds from pressure
contours
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Outer Planets I Jupiter and Saturn
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Outer Planets Occultation Retrieval Challenges
Uncertain composition and mixing Uncertain
rotation rates Pronounced oblateness
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Saturns Strange Moon Voyager Occultation of
Titan
High altitude methane clouds
Surface pressure was unknown to within a factor
of 1000 (answer 1.5 bars)
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Saturn Ring Occultation
The rings act as a vast, thin, complex
diffraction screen.
Sampling of the phase-amplitude hologram allows
detailed recon-struction of the ring structure
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Saturn Ring Occultation
This inverse Fresnel filtering improves
resolu-tion by x50-90 over the 15 km Fresnel
limit
Marouf, Tyler, Rosen, 1986
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Outer Planets II Uranus and Neptune
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Uranian Rings
Voyager Stellar Occultation
Voyager Radio Occultation
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Neptunian Rings
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Occultation Subjects A Group Portrait
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An Observation on the Terrestrial Planets
This atmosphere is too thin
This atmosphere is too thick
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Just
right
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What took so long?
Need a lot of transmitters and a lot of LEO
receivers GPS did not fit the paradigm One-way
only Need flight USOs? Dithered GPS signal
Need classified receiver? Suppressed GPS
carrier Crude pseudorange only? Multipath a
major concern Need high-gain antennas?
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Earth Occultation Early Concepts
Fishbach, 1965 Stellar occultation from LEO
Lusignan et al., 1969 Radio sounding with
tandem LEOs at a fixed separation
Gurvich and Krasilnikova, 1987 Navigation
satellites for sensing Earth atmosphere
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GPS Geoscience Instrument EOS-A, EOS-B and Space
Station (1988-1992)
Three Antennas 18 Channels Full Sky View
POD Geodesy Ionosphere Mapping Atmospheric
Occultation
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The GPS-MET Experiment on MicroLab-I 1995 - ?
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CHAMP
SAC-C
GRACE
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EQUARS C/NOFS NPOESS (3) METOP ACE
(4) TerraSAR-X ?
Coming Attractions
COSMIC/Rocsat3 (6)