| Voyager 1 |
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One of a pair of almost identical planetary probes launched by the USA in 1977. The other was Voyager 2. The Voyager missions were possible only because of a chance favourable alignment of the outer planets, Jupiter, Saturn, Uranus and Neptune, occurring just once in more than a hundred years. Between them, the two spacecraft were able to explore these four planets, their environs and satellite systems. The gravitational "sling-shot" technique was used to accelerate the craft from one encounter to the next. The missions were immensely successful, making numerous discoveries and returning huge quantities of data as well as visual images. The instruments on the Voyagers consisted of two groups. One set was designed to sample the craft's environment and these remained in operation constantly, even between planetary encounters. They measured magnetic field, low-energy charged particles, cosmic rays and the characteristics of the local plasma. The other instruments were a wide-angle (3°) camera, a close-up (0.4°) camera, a Michelson interferometer to analyse infrared emission from planetary atmospheres, an ultraviolet spectrometer, a photopolarimeter to measure light intensity and its state of polarization, and a detector for radio emission from planetary magnetospheres. The main communication dish was 3.7 metres in diameter and a plutonium-238 power source was used. Voyager 1 was launched on 5 September 1977. Its closest encounter with Jupiter was on 5 March 1979 at 350,000 kilometres (217,500 miles) and that with Saturn was on 12 November 1980 at 124,000 kilometres (77,000 miles). It entered the jovian system close to Io and Callisto and the saturnian system near Titan, Rhea and Mimas. After the encounter with Saturn, it left the plane of the solar system to travel on into interstellar space. See also: Voyager Interstellar Mission. |