The 2 1/2-story tall, six-ton spacecraft flew as close as 727 miles to Earth, passing over the South Pacific at 11:28 p.m. ET. The spacecraft is now moving about 12,000 mph faster than it was before flying by Earth, thanks to the use of a techinque known as gravity assist or the "slingshot effect," which uses the Earth's gravitational field to boost the craft's speed.

The final boost from giant Jupiter in December 2000 will bend Cassinis route and put it in position to be captured by Saturns gravity in 2004.

During the flyby of Earth, scientists turned on nine of Cassinis 12 instruments to study the planet and its moon. Collaborative observations were made by NASAs Polar and Wind Earth-monitoring satellites, as well as an interplanetary monitoring platform outside Earths magnetosphere (IMP-8) and ground based radars.

Cassini sliced through Earths magnetosphere in a position not normally studied by spacecraft, so scientists were interested in comparing the Cassini data with information collected at the same time by other Earth-monitoring spacecraft. Polar, for example, made ultraviolet observations of the aurora, which are caused by Earths magnetic field.

"We havent received the full amount of data yet, but we did put our instrument into the requested mode," said James Spann, one of the co-investigators for an ultraviolet imager aboard Polar.

Cassinis true mission, however, lies at Saturn. The spacecraft is scheduled to spend four years whirling around the giant gas planet, its 18 known moons and its elaborate system of rings.

The $3.3 billion program is jointly sponsored by NASA and the European Space Agency, which provided a probe that will parachute to the surface of Saturns moon Titan.

Cassini began its circuitous, 2.2-billion mile journey to Saturn on Oct. 15, 1997. It has made two swings around Venus and one around Earth and is scheduled for a Dec. 30, 2000, visit to Jupiter.