The Ulysses spacecraft, speeding toward Jupiter on a roundabout mission to explore the sun's poles in 1994-95, is firing its thrusters this week to adjust its course, NASA says.

"Everything is proceeding as planned. There hasn't been a single hiccup or glitch of any kind," Franklin O'Donnell, who is a spokesman for NASA's Jet Propulsion Laboratory, said after the four-day maneuver started Monday.Ulysses was released from the shuttle Discovery on Oct. 6 on a 1.86 billion-mile mission during which it will use the gravity of Jupiter, the solar system's biggest planet, to sling it into orbit over the sun's poles.