Cassini spacecraft. Computer artwork of the Cassini spacecraft over Titan, one of the moons of the ringed planet Saturn (centre left). The image shows Cassini after it has just released the Huygens probe (not seen here) into Titans atmosphere. It is firing its retrorocket (far right) in order to slow itself down and enter Saturns orbit. Cassini will orbit Saturn for four years, and will study the planet, its rings, and its moons. It was launched in October 1997 and is expected to reach Saturn in July 2004. The Huygens probe will enter Titans atmosphere in November 2004. It will carry instruments down to Titan and send data back to Earth for up to 30 minutes.