The Galileo probe closed in on Earth Friday, hurtling toward a velocity-boosting flyby today just 600 miles above the Atlantic Ocean, the first of two such encounters needed to put the craft on course for distant Jupiter.

As of noon Friday, the $1.5 billion nuclear-powered probe was 584,539 miles from Earth, on track for a 3:35 p.m. EST Saturday flyby after a similar encounter with Venus on Feb. 10.As Galileo races by, Earth's gravity will bend the craft's trajectory and boost its speed 11,620 mph - from 67,240 mph to 78,860 mph relative to the sun.The action will fling the spacecraft out into the asteroid belt before it falls back toward a second Earth flyby in two years.

Passing a scant 200 miles above South Africa on Dec. 8, 1992, Galileo's velocity will be boosted 8,280 mph to a blistering 87,190 mph - fast enough to finally begin the long voyage to Jupiter, some 480 million miles from the sun.

Galileo was launched from the space shuttle Atlantis on Oct. 18, 1989, on an unprecedented mission to drop a probe into Jupiter's stormy atmosphere before going into orbit for humanity's first long-term study of the solar system's largest planet.

Sailing through a ballet of ever-changing orbits, Galileo's electronic ears and eyes will study Jupiter's atmosphere and its whirling moons in exquisite detail, beaming back close-up photographs 20 to 1,000 times better than the spectacular pictures taken by the Voyager probes.