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Ulysses Spacecraft Zooms Near Jupiter in Fifth Probe to Visit Planet

February 8, 1992

PASADENA, Calif. (AP) _ The U.S.-European Ulysses space probe swooped past Jupiter today, flying through radiation belts and using the planet’s gravity so it can become the first spacecraft to study the sun’s poles.

″We are absolutely elated,″ said Willis Meeks, NASA’s manager of the $750 million Ulysses project at Jet Propulsion Laboratory.

Ulysses made its closest approach to Jupiter a few seconds before 4:01 a.m. PST today, flying about 235,000 miles over the planet’s cloud tops at a speed of 61,249 mph, said Don Meyer, the deputy mission operation manager.

Engineers confirmed the flyby happened 37 minutes and 15 seconds later - the time it took the spacecraft’s radio signal to travel 416 million miles to Earth, Meeks said.

″There was a lot of handshaking, a lot of smiles, a lot of jubilation,″ he added. Mission controllers also played the theme music from the film ″2001: A Space Odyssey.″

About an hour after the flyby, Ulysses zoomed into Jupiter’s ″torus,″ a doughnut-shaped ring of sodium, oxygen and sulfur particles ejected into orbit around Jupiter by sulfur-spewing volcanoes on the Jovian moon Io.

The spacecraft’s radio signal was beamed through the ring toward Earth, providing information about the makeup of the torus, said Ed Smith, NASA’s Ulysses project scientist.

The main purpose of Ulysses’ close encounter with Jupiter was to use the planet as a gravity slingshot, hurling the spacecraft southward out of the plane in which the planets orbit the sun.

That will put Ulysses in position to accomplish its main goal: observing the sun’s south polar regions during June-September 1994 and north polar latitudes the following year.

The joint mission by the European Space Agency and the National Aeronautics and Space Administration ″marks a new era of space exploration″ because studying the sun’s polar regions ″will be like filling in parts of a puzzle that we just have not seen before,″ Meeks said.

During Ulysses’ flight near Jupiter, it is studying unexplored regions of the gargantuan magnetic field that surrounds the solar system’s largest planet. The formal encounter period started Jan. 31 and ends Feb. 16. Scientists plan to discuss Ulysses’ preliminary findings at Jupiter during a Tuesday news conference.

The solar system’s strongest radiation belts are trapped within Jupiter’s magnetic field. There was a small chance the bombardment would make Ulysses shut off most of its instruments and go into a protective ″safe mode,″ although it is shielded to withstand much stronger radiation. Engineers were prepared to restore full spacecraft operations if that happened.

The spacecraft entered Jupiter’s radiation belts Friday, said Edgar Page, the European Space Agency’s Ulysses science coordinator.

Ulysses is the fifth spacecraft to visit Jupiter. Pioneers 10 and 11 and Voyagers 1 and 2 flew past Jupiter during the 1970s. Unlike those spacecraft, Ulysses isn’t equipped to take pictures.

Page said Ulysses has detected an old puzzle first noted during the Voyager flybys: a blast of high-energy electrons - negatively charged particles - shooting off Jupiter about every nine hours and 55 minutes.

That’s the length of a Jovian day, the time Jupiter takes to spin once on its axis. Page said scientists can’t explain what causes the particle blasts or why they coincide with Jupiter’s rotation.

Ulysses was launched from space shuttle Discovery on Oct. 6, 1990. It will be the first spacecraft to fly above the sun’s poles. But it never will be closer to the sun than it was on the launch pad. All it needs to do is leave the plane of the planets so it can observe the sun’s poles from a distance.

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