Ulysses adjusted its course toward Jupiter on Friday using a maneuver designed to increase the amount of time the spacecraft will spend studying the sun's poles.

The probe ignited its thrusters to slightly change the course, said Franklin O'Donnell, spokesman for the National Aeronautics and Space Administration's Jet Propulsion Laboratory."This is just to tweak the trajectory for the maximum amount of time over the sun's poles," he said.

The latest mid-course correction and four days of thruster firings that began Oct. 15 will add a week to the time the $250 million Ulysses spends orbiting the sun's high latitudes during its five-year, $750 million joint mission by NASA and the European Space Agency.

Ulysses was launched from the space shuttle Discovery on Oct. 6. On Feb. 8, 1992, the spacecraft will use Jupiter as a "gravity slingshot" to leave the plane in which all of the planets orbit the sun. That will allow Ulysses to fly almost over the sun's south pole in 1994 and north pole in 1995.

O'Donnell said another trajectory maneuver may be needed in the weeks before Ulysses whizzes around Jupiter.