Cassini Begins Saturn Quest Seven Years After Launch

A SPACE craft the size of a bus began a historic four-year mission to explore Saturn and its moons yesterday.

The Cassini probe slipped through two of Saturn’s rings and set itself in orbit around the giant planet.

The joint US-European mission, the most complex and ambitious unmanned space expedition ever, is expected to provide important information on the evolution of planets.

The (pounds) 1.6bn quest includes the first orbit of Saturn and the most distant landing on any interplanetary body.

Cassini has taken seven years to complete its 2.2bn-mile journey through space. Huygens, a European Space Agency lander carried by the spacecraft, will parachute down to the surface of Saturn’s cloud- covered moon Titan early next year.

When Cassini reached Saturn it was expected to be travelling at 70,700mph. The brakes were applied by firing the probe’s main engine for 96 minutes for “a crucial orbit insertion manoeuvre”, cutting its speed to allow entry into orbit around Saturn.

The spacecraft passed through a gap between two of Saturn’s rings, called F and G, before swinging close to the planet and beginning the first of 74 orbits.

Over the next four years, it will have 52 close encounters with seven of Saturn’s 31 known moons.

Cassini has already visited one moon, an icy outpost of the Saturnian system called Phoebe. It flew past the moon at a distance of 1243 miles on June 11, sending back detailed pictures of its heavily scarred and cratered surface.

Saturn’s most famous feature is its glorious rings, which Cassini will scan from a distance of just over 9000 miles. Scientists are anxious to know how the rings, which may only be about 100 million years old, came into being.

One theory is that they were created from an object that was captured and torn apart by Saturn’s powerful gravity.

Professor Ian Halliday, of the Particle Physics and Astronomy Research Council, which runs the UK Astronomy Technology Centre in Edinburgh, said: “Saturn is hailed as the jewel of the solar system. It has fascinated us for centuries. Right now we stand on the threshold of a wealth of scientific discovery.”

Other instruments will study the Saturn’s atmosphere, the planet’s turbulent weather, and its magnetic field.

Britain is playing a key role with half the 12 instruments on board Cassini, and two of the six on the Huygens probe.

Landing on Titan will be the high point of the mission. On Christmas Day, Huygens will detach itself from Cassini and head towards the moon, arriving three weeks later.

Professor Carl Murray, of London’s Queen Mary University, said: “This is a remarkable achievement. The arrival of the Cassini- Huygens spacecraft at Saturn heralds a new age in our understanding of this majestic planet.”