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File:Saturn's rings in visible light and radio.jpg


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English: Saturn's rings in visible light and radio


English: Cassini instruments provide complementary information about the structure of Saturn's rings. Narrow and wide angle cameras provide images in the visible region of the electromagnetic spectrum much like a digital camera does. The images have information about how the ring structure differs both with distance from the planet and with position around the equatorial circle. However, resolution is usually limited to few kilometers at best.

Radio and stellar occultations of the rings also provide important information about ring structure, but only along a one-dimensional track through the rings. The radial resolution can be as fine as 50 meters (164 feet). An "image" is then constructed by assuming circular symmetry over the ring region of interest. Colour is usually added to encode other information related to the observed structure.

This image compares structure of Saturn's rings observed by these two approaches. The upper half is a natural color mosaic of images of the illuminated side of the rings by the Cassini narrow-angle camera (see PIA06175). The bottom simulated image is constructed from a radio occultation observation conducted on May 3, 2005. For another view created using this process, see PIA07872. Colour in the lower image is used to represent information about ring particle sizes.

Three simultaneous radio signals of 0.94, 3.6, and 13 centimeter wavelength (Ka-, X-, and S-bands) were sent from Cassini through the rings to Earth. The observed change of each signal as Cassini moved behind the rings provided a profile of the distribution of ring material as a function of distance from Saturn, or an optical depth profile. This simulated image was constructed from the measured optical depth profiles.

Shades of purple, primarily over most of the middle ring, the B ring, and the inner portion of the outer ring, the A ring, indicate regions where there is a lack of particles less than 5 centimeters (about 2 inches) in diameter. Green and blue shades indicate regions where there are particles of sizes smaller than 5 centimeters (2 inches) and 1 centimeter (less than one third of an inch), respectively, primarily in the outer A ring and within most of the inner ring, the C ring. The saturated broad white band near the middle of the B ring is the densest region of the rings, over which two of the three radio signals were blocked at 10-kilometer (6-mile) resolution, preventing accurate colour representation. From other evidence in the radio observations, all ring regions appear to be populated by a broad range particle size distribution that extends to boulder sizes (several to many meters across).

The Cassini-Huygens mission is a cooperative project of NASA, the European Space Agency and the Italian Space Agency. The Jet Propulsion Laboratory, a division of the California Institute of Technology in Pasadena, manages the mission for NASA's Science Mission Directorate, Washington, D.C. The Cassini orbiter was designed, developed and assembled at JPL. The radio science team is based at JPL. The imaging team is based at the Space Science Institute, Boulder, Colo.

For more information about the Cassini-Huygens mission visit For more information on the radio science team visit The imaging team homepage is at

Français : Les instruments de la sonde Cassini fournissent des information différentes et complémentaires sur la structure des anneaux de Saturne. Les appareils photo à grand angle et à longue focale font des photos d'une façon très comparable à celle d'un appareil numérique. Ces images permettent de voir la structure des anneaux à la fois en fonction de la distance à la planète et le long du plan équatorial. Cependant la résolution est limitée à quelques kilomètres.

Les ondes radio et les occultations stellaires permettent d'obtenir une bien meilleure résolution (50 mètres), mais uniquement dans le sens radial. Une image est reconstruite en supposant que les anneaux ont une symétrie radiale dans la zone considérée. De la couleur est souvent ajoutée pour donner d'autres informations sur la structure observée.
Cette image compare la structure des anneaux de Saturne observée avec ces deux méthodes différentes. L'image du haut est une image en vraies couleurs obtenues avec la caméra à longue focale. L'image du bas a été construite après l'observation d'une occultation d'une source radio par les anneaux de la planète réalisée le 3 Mai 2005. La couleur sur l'image du bas donne des informations sur la taille des particules constituant les anneaux.

La mission Cassini-Huygens est une mission conjointe de la NASA, de l'ESA et de l'ISA. L'orbiteur Cassini et ses caméras ont été conçus et construit au JPL à Passadena, en Californie. Le centre de traitement des images est à Boulder, au Colorado (États-Unis).
中文: 土星光环
Date Visible light image taken 2004-12-12; radio data acquired 2005-05-03; combined image released 2005-05-23
Author NASA/JPL/Space Science Institute
Shuttle.svg This image or video was catalogued by Jet Propulsion Lab of the United States National Aeronautics and Space Administration (NASA) under Photo ID: PIA07874.
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