May 23 2005
From The Space Library
NASA announced results of the Cassini probe's first radio occultation observations of Saturn's rings, atmosphere, and ionosphere, which had taken place on 3 May. Scientists had labeled the seven main rings in the order of discovery; however, from the planet outward, the rings are labeled D, C, B, A, F, G, and E. During the experiment, Cassini had been occulted~hidden~behind the planet's rings. The craft had simultaneously transmitted Ka, X, and S, three radio signals of different frequencies~the first occultation experiment to do so. NASA's ground-based Deep Space Network had received the signals, but their passage through Saturn's ring material had affected their strength~the denser the ring, the weaker the signal. Cassini's radio signals had revealed Saturn's ring structure with clarity never before seen, in particular the structure of ring B, which had eluded previous robotic explorers. Cassini had revealed ring B's composition as a thick, 5,000-kilometer-wide (3,100-mile-wide) core, containing several bands of material nearly 4 times as dense as that found in ring A, and nearly 20 times as dense as ring C. Cassini had also shown that the structure of ring B varies dramatically, contrasting sharply with the relatively flat structure of ring A and the wavy structure of ring C. (NASA, “Cassini Radio Signals Decipher Structure of Saturn's Rings,” news release 05-130, 23 May 2005, http://www.nasa.gov/home/hqnews/2005/may/HQ_05130_Cassini.html (accessed 14 September 2009); David Whitehouse, “Cassini Makes Detailed Ring Map,” BBC News, 25 May 2005.)
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