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1993-04-23
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PUBLIC INFORMATION OFFICE
JET PROPULSION LABORATORY
CALIFORNIA INSTITUTE OF TECHNOLOGY
NATIONAL AERONAUTICS AND SPACE ADMINISTRATION
PASADENA, CALIF. 91109. TELEPHONE (213) 354-5011
FOR IMMEDIATE RELEASE
A team of scientists from NASA's Voyager Project ì
ì
have determined the rotation period of Saturn -- the length ì
ì
of a Saturn day -- using bursts of radio signals from the ì
ì
planet recorded by the two Voyager spacecraft.
The new Saturn day is 10 hours, 39 minutes, 24 ì
ì
seconds long. The determination was made by Michael Kaiser ì
ì
and Michael Desch of NASA's Goddard Space Flight Center in ì
ì
Greenbelt, Maryland, and James Warwick and Jeffrey Pearce of ì
ì
Radiophysics Inc. in Boulder, Colorado. They are members of ì
ì
the Voyager Planetary Radio Astronomy Team headed by Warwick.
Warwick's team recorded radio signals from a ì
ì
variety of sources in the sky during January and February ì
ì
1980, when Voyager 1 was more than 380 million kilometers ì
ì
(236 million miles) from Saturn, and Voyager 2 was more than ì
ì
554 million kilometers (344 million miles) from the planet.
By gradually eliminating signals coming from the ì
ì
Sun, Jupiter and other sources, they determined that the ì
ì
signals they were receiving every 10 hours, 39.9 minutes ì
ì
originated at the north pole of Saturn, and were precisely ì
ì
controlled by the planet's rotating magnetic field.
Radio astronomers were able to pin down the ì
ì
rotation rate of Jupiter using this method several years ago. ì
ì
Scientists feel it is the most accurate method of determining ì
rotation. Although the Earth, Jupiter and Saturn are all ì
ì
emitters of radio signals, scientists do not as yet ì
ì
understand how the signals are generated.
Astronomers using Earth-based observations of the ì
ì
ringed planet had calculated the length of a day at about 10 ì
ì
hours, 15 minutes, but admitted their measurements lacked ì
ì
great accuracy.
Their problem was that the planet does not have a ì
ì
solid surface, observers can see only the tops of Saturn's ì
ì
clouds, and the clouds lack sharply defined features to allow ì
ì
accurate determination of the planet's rotation.
Voyager 1 is scheduled to make its closest approach ì
ì
to Saturn Nov. 12, 1980. Voyager 2 will pass the planet Aug. ì
ì
26, 1981.
The Voyager Project is managed for NASA's Office of ì
ì
Space Science by the Jet Propulsion Laboratory, California ì
ì
Institute of Technology.
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