The US-European space probe Cassini began late Wednesday its crucial maneuver, which scientists call Saturn orbit insertion, with its main engine to burn for the spacecraft to slow to be captured by Saturn's gravity field.

The process began at 10:36 p.m. EDT (0236 GMT Thursday) and is planned to end at 12:12 p.m. EDT (0412 GMT Thursday). Cassini is expected to begin orbiting Saturn at 11:54 p.m. EDT (0354 GMT Thursday) if all proceeds as planned. It will become the first man-made object that ever orbits Saturn and its 31 icy moons.

Before this, Cassini's high-gain antenna was oriented forward in order to shield the spacecraft from impact during an expected 90-minute and 158,000-km flight through the ring plane of Saturn, the sixth planet from Sun.

Nuclear-powered Cassini is planned to complete 76 orbits in the next four years or more and make 52 close passes at seven of Saturn's 31 known moons. It will fly closest to Saturn during the first orbit, to be within 80,230 km from the planet's center and about 19,980 km from its cloud tops.

The first images taken by Cassini are expected to reach Earth at about 8 a.m. EDT (1200 GMT) on July 1.

Cassini is 6.6 meters long, 3.9 meters wide and weighs 5,670 kg.It carries 12 scientific instruments and probe Huygens which is developed by the European Space Agency. Huygens, about 2.7 meters in diameter and 317 kg in weight, will be released from Cassini on Dec. 25 and enter Titan's atmosphere on Jan. 14.

Titan, the largest moon of Saturn, is believed to have a "pre-biotic" environment and its investigation can reportedly help understand how the primitive Earth evolved into a life-bearing planet.

Cassini was launched from Cape Canaveral, Florida, on Oct. 15, 1997, and has completed a 3.5 billion-km interplanetary journey. The 3.3 billion-US dollar Cassini-Huygens project was first proposed in 1982 and is joined by NASA, the European Space Agency and the Italian Space Agency. About 260 scientists are involved in the project.