Venus Flyby Update

April 29, 1998

Cassini spacecraft navigators reported that Sunday's successful flyby of Venus was on time and on target.

"The accuracy achieved by our navigators is roughly equivalent to shooting a basketball from Los Angeles to London and making a swish shot," said Richard Spehalski, Cassini Program Manager at NASA's Jet Propulsion Laboratory.

As planned, Cassini flew 284 kilometers (176 miles) above the Venusian surface at 6:52:14 Pacific Daylight Time, (Earth-received time) on April 26. Because of Venus' distance (136 million kilometers or 85 million miles from Earth), it took Cassini's radio signals 7 minutes to travel to Earth.

The tug of Venus' gravity gave the Cassini spacecraft a boost in speed of about 7 kilometers per second (about 4 miles per second). This will help the spacecraft reach Saturn in July 2004. Leaving Venus, Cassini was moving at more than 141,000 kilometers per hour (87,000 miles per hour) relative to the Sun.

The Venus flyby is the latest of dozens of similar "gravity-assist" flybys of planets and moons performed by JPL-controlled spacecraft over the past three decades. Cassini will perform three more similar gravity-assist flybys: Venus again in June of 1999, Earth in August of 1999, and Jupiter in December 2000. All the flybys use the gravitational pull of the target planets to impart more speed to the spacecraft to help it reach Saturn. The Venusian flyby was the lowest-altitude gravity-assist planetary pass Cassini will make in its mission.

Science instruments on the spacecraft searched for lightning in Venus' atmosphere during the flyby, and the radar instrument onboard was activated to test a bounced signal off Venus' surface.

After it enters orbit around Saturn in 2004, Cassini will study the ringed planet, its moons and ring system for at least four years. It will also deliver a scientific probe called Huygens to parachute to the surface of Saturn's largest moon, Titan.

Additional information about Cassini-Huygens is online at

Cassini will begin orbiting Saturn on July 1, 2004, and release its piggybacked Huygens probe about six months later for descent through the thick atmosphere of the moon Titan. Cassini-Huygens is a cooperative mission of NASA, the European Space Agency and the Italian Space Agency. JPL, a division of the California Institute of Technology in Pasadena, manages the mission for NASA's Office of Space Science, Washington, D.C.

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