the NASA programme which in 1977 sent two spacecraft into space to investigate certain planets. Voyager 1 discovered rings around the planet Jupiter in 1979 and flew past Saturn the following year. It sent back to earth the first close photographs of both planets. Voyager 2 has had the longest journey in the history of spacecraft. It passed Jupiter in 1979, Saturn in 1981, Uranus in 1986 and Neptune in 1989. Both spacecraft are travelling towards the region beyond the influence of the Sun.