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Cassini Cameras Spot Powerful Lightning Storm on Saturn

16 February 2006

Amateur astronomers helped the international mission's investigation

After NASA's Cassini spacecraft detected radio bursts from Saturn in January indicating a rare, powerful atmospheric storm, Cassini imaging scientists spotted the storm by looking for it in the dark.

The Cassini-Huygens mission to Saturn is a cooperative project of NASA, the European Space Agency and Agenzia Spaziale Italiana, the Italian space agency.

When Cassini detected lightning-generated radio noise from the storm, the spacecraft was at a place in its orbit where it was unable to image the sunlit side of Saturn, according to a February 14 press release from the Space Science Institute in Colorado, whose flight operations branch manages the Cassini spacecraft’s visible camera instrument.

Instead, imaging scientists searched for the southern hemisphere storm in images of the planet's night side. A small amount of sunlight reflecting off Saturn's rings and illuminating the night side was enough to make features in the atmosphere visible.

"It's really the only large storm on the whole planet," says Andrew Ingersoll, a member of the Cassini imaging team.

"It's in the right place,” he added, “and it appeared at the right time to match the radio emissions, so it has to be the right storm."

The new storm’s latitude matches that of the "dragon storm," a powerful emitter of radio noise that Cassini imaged in 2004.

The new storm lies in a region of the southern hemisphere that scientists call storm alley because of the high storm activity level Cassini observed there. The storm’s north-south dimension is about 3,500 kilometers.

Earth-based amateur astronomers, who could see Saturn's dayside with their telescopes when Cassini could not, have also helped Cassini's investigation of the storm.

Saturn storm images are available at http://ciclops.org, http://saturn.jpl.nasa.gov, and http://www.nasa.gov/cassini.

Text of the Space Science Institute press release follows:

(begin text)

Space Science Institute
(Boulder, Colorado)
Press release, February 14, 2006

Cassini cameras spot powerful new lightning storm on Saturn

Following the recent detection of Saturnian radio bursts by NASA's Cassini spacecraft that indicated a rare and powerful atmospheric storm, Cassini imaging scientists have spotted the storm in an unlikely fashion: they looked for it in the dark.

When lightning-generated radio noise from the storm was detected by Cassini on January 23, the spacecraft was at a place in its orbit where it was unable to image the sunlit side of Saturn. Instead, imaging scientists searched for the southern hemisphere storm in images of the planet's night side. Fortunately, the small amount of sunlight reflecting off Saturn's rings and illuminating the night side is enough to make features in the atmosphere visible.

Images showing the storm can be found at http://ciclops.org, http://saturn.jpl.nasa.gov and http://www.nasa.gov/cassini.

The storm is located on the side of Saturn that faces the spacecraft when the radio emissions are detected; Cassini does not observe the radio emissions for half a Saturnian day when the storm is on the planet's other side.

The latitude of the new storm matches that of the "Dragon storm," which was a powerful emitter of radio noise and was imaged by Cassini in 2004. It lies in a region of the southern hemisphere referred to as "storm alley" by scientists because of the high level of storm activity observed there by Cassini. The storm's north-south dimension is about 3,500 kilometers (2,175 miles).

"It's really the only large storm on the whole planet," says Andrew Ingersoll, a member of the Cassini imaging team. "It's in the right place and it appeared at the right time to match the radio emissions, so it has to be the right storm," he said.

Cassini's investigation of the storm has also been aided by the efforts of Earth-based amateur astronomers, who were able view Saturn's dayside with their telescopes when Cassini could not. The amateurs' images of Saturn provided the first visual confirmation of the storm, now revealed in detail by the new views from Cassini.

The Cassini-Huygens mission is a cooperative project of NASA, the European Space Agency and the Italian Space Agency. The Jet Propulsion Laboratory (JPL), a division of the California Institute of Technology in Pasadena, manages the Cassini-Huygens mission for NASA's Science Mission Directorate, Washington. The Cassini orbiter and its two onboard cameras were designed, developed and assembled at JPL. The imaging team consists of scientists from the U.S., England, France, and Germany. The imaging operations center and team leader (Dr. C. Porco) are based at the Space Science Institute in Boulder, Colo.

The Space Science Institute (SSI) is a nonprofit, public benefit corporation formed in 1992. Our purpose is to create and maintain an environment where scientific research and education programs can flourish in an integrated fashion. SSI has five major branches: Research, Flight Operations, Education, Business Operations, and Information Systems and Technology (IST). SSI’s research program encompasses the following areas: space physics, earth science, planetary science, and astrophysics. The flight operations branch manages the Cassini spacecraft’s visible camera instrument and provides spectacular images of Saturn and its moons and rings to the public.

(end text)

(Distributed by the Bureau of International Information Programs, U.S. Department of State. Web site: http://usinfo.state.gov)