Ulysses Craft Reaches Jupiter, Prepares for Rendezvous With Sun : Space: It will pass through intense radiation surrounding planet, using its gravity to alter course.

The Ulysses spacecraft reached Jupiter’s neighborhood and began a maneuver to use the giant planet’s gravity to fling itself into an orbit that will carry it over the poles of the sun--the first spacecraft ever to achieve that.

The $750-million NASA-European Space Agency craft will make its closest approach to Jupiter next Saturday but there will be no pictures because it is not carrying cameras. Instead, the craft is loaded with instruments that will study the sun in 1994 and 1995.

Scientists have long wanted to study the polar regions of the sun to see what they reveal about solar dynamics, but getting there is no easy matter. It takes too much energy to launch a spacecraft into an orbit that carries it out of the plane around the sun’s equator--in which the planets orbit--so it is impractical to fly a direct route.

Ulysses was launched in a longer but more energy-efficient course to reach its final destination. The craft is about 416 million miles from Earth, and it will pass within 280,000 miles of Jupiter’s north pole next Saturday, according to flight controllers at NASA’s Jet Propulsion Laboratory in Pasadena.

Jupiter’s powerful gravity will force the spacecraft to dive at an 80-degree angle, sweep around the planet and head on back toward the sun. That trajectory will carry Ulysses beneath the sun’s south pole in 1994. The spacecraft is to spend four months studying the sun’s southern polar region, as the sun’s gravity bends the craft’s course around the far side of the star and up over the north pole the following year.

During its passage around the poles, Ulysses will study the sun, its magnetic fields, and the stream of particles blasting off the sun at speeds of up to 1 million m.p.h.

The Jupiter flyby is of concern to mission planners because the gaseous planet is surrounded by intense radiation and charged particles.

“It’s a risky business for any spacecraft traveling through Jupiter’s environment,” said Edgar Page, the European Space Agency’s science coordinator at JPL.

Scientists will take advantage of the Jupiter encounter to study the giant planet and the space around it.

“We’re trying to do all the science we can,” said John Simpson, professor of physics at the University of Chicago, who leads a team of scientists from five nations responsible for several instruments aboard the spacecraft. Simpson and his colleagues would like to know more about the intense radiation that surrounds Jupiter. Some instruments that will be used to study the sun can be used to gather data during the Jupiter flyby.

Ulysses has nine primary instruments aboard, and when they are finally able to focus on the sun they will collect data that no other spacecraft has been able to get.

Ulysses’ Journey The Ulysses spacecraft has begun its 17-day encounter with Jupiter, and it will use that planet’s gravitational field to slingshot itself into a polar orbit around the sun. The maneuver will make Ulysses the first spacecraft to pass over the sun’s poles.