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Saturns Thermal Emission at 2.2-cm Wavelength as Imaged by the Cassini RADAR RadiometerWe present well-calibrated, high-resolution maps of Saturn's thermal emission at 2.2-cm wavelength obtained by the Cassini RADAR radiometer through the Prime and Equinox Cassini missions, a period covering approximately 6 years. The absolute brightness temperature calibration of 2% achieved is more than twice better than for all previous microwave observations reported for Saturn, and the spatial resolution and sensitivity achieved each represent nearly an order of magnitude improvement. The brightness temperature of Saturn in the microwave region depends on the distribution of ammonia, which our radiative transfer modeling shows is the only significant source of absorption in Saturn's atmosphere at 2.2-cm wavelength. At this wavelength the thermal emission comes from just below and within the ammonia cloud-forming region, and yields information about atmospheric circulations and ammonia cloud-forming processes. The maps are presented as residuals compared to a fully saturated model atmosphere in hydrostatic equilibrium. Bright regions in these maps are readily interpreted as due to depletion of ammonia vapor in, and, for very bright regions, below the ammonia saturation region. Features seen include the following: a narrow equatorial band near full saturation surrounded by bands out to about 10deg planetographic latitude that demonstrate highly variable ammonia depletion in longitude; narrow bands of depletion at -35deg latitude; occasional large oval features with depleted ammonia around -45deg latitude; and the 2010-2011 storm, with extensive saturated and depleted areas as it stretched halfway around the planet in the northern hemisphere. Comparison of the maps over time indicates a high degree of stability outside a few latitudes that contain active regions.
Document ID
20140016850
Acquisition Source
Goddard Space Flight Center
Document Type
Reprint (Version printed in journal)
External Source(s)
doi:10.1016/j.icarus.2013.06.008
Authors
Janssen, M. A. (Jet Propulsion Lab., California Inst. of Tech. Pasadena, CA, United States)
Ingersoll, A. P. (California Inst. of Tech. Pasadena, CA, United States)
Allison, M. D. (NASA Goddard Inst. for Space Studies New York, NY, United States)
Gulkis, S. (Jet Propulsion Lab., California Inst. of Tech. Pasadena, CA, United States)
Laraia, A. L. (California Inst. of Tech. Pasadena, CA, United States)
Baines, K. H. (Jet Propulsion Lab., California Inst. of Tech. Pasadena, CA, United States)
Edgington, S. G. (Jet Propulsion Lab., California Inst. of Tech. Pasadena, CA, United States)
Anderson, Y. Z. (Jet Propulsion Lab., California Inst. of Tech. Pasadena, CA, United States)
Kelleher, K. (Jet Propulsion Lab., California Inst. of Tech. Pasadena, CA, United States)
Oyafuso, F. A. (Jet Propulsion Lab., California Inst. of Tech. Pasadena, CA, United States)
Date Acquired
December 2, 2014
Publication Date
June 21, 2013
Publication Information
Publication: Icarus
Publisher: Elsevier
Volume: 226
Issue: 1
Subject Category
Astrophysics
Report/Patent Number
GSFC-E-DAA-TN15186
Funding Number(s)
CONTRACT_GRANT: 10-CDAP10-0051
Distribution Limits
Public
Copyright
Public Use Permitted.
Keywords
composition
Structure
Atmosphere
Saturn
Atmospheres
Atmospheres

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