Trajectory of the Cassini probe. Computer graphic of the flight path of the unmanned Cassini probe sent by NASA to Saturn. It launched from Earth (left) in October 1997 and orbited the inner solar system twice, flying past Venus in April 1998 and July 1999, and Earth in August 1999, to gain speed to reach Jupiter (lower centre) in December 2000 and Saturn (right, 1.5 billion kilometres from the Sun) in July 2004. It travelled over 3.5 billion kilometres in 6 years and nine months. At Saturn, the probe examined the ring system and moons, and released the Huygens probe to study the atmosphere and surface of Saturn's largest moon Titan.