Spacecraft Uses Venus’ Gravity to Boost Speed, Shorten Voyage

The Cassini spacecraft came so close to Venus Sunday that it was able to add 16,300 mph to its velocity, shortening its scheduled trip to Saturn.

The international space mission of NASA, the European Space Agency and the Italian Space Agency passed within 176 miles of Venus on Sunday morning, completing a “gravity assist” in which Cassini uses a planet’s gravity like a slingshot.

“All indications are that the spacecraft did exactly what we expected,” said Ronald Draper, deputy program manager at NASA’s Jet Propulsion Laboratory in Pasadena.

A second Venus “gravity assist” is set for June 24, 1999, followed by a close pass of Earth in August 1999 and another past Jupiter in 2000. Each will add speed to allow Cassini to arrive at Saturn on July 1, 2004.

Cassini, now moving at 87,000 mph, was launched in October on a seven-year, 2.2-billion-mile voyage. The plutonium-powered spacecraft will spend four years exploring Saturn, its rings and frozen moons. The craft is carrying the European Space Agency’s Huygens probe, which will land on Titan, the largest of those moons.

A radar system eventually will produce images of Titan, the only moon in the solar system with a thick nitrogen atmosphere that is similar to Earth’s.