II.

Spacecraft

The Voyager spacecraft were identical. Each weighed 815 kg (1,797 lb), and each was built from 65,000 individual parts. The spacecraft were designed with radiation-hardened parts, and the more sensitive parts were shielded to withstand radiation.

A set of 16 thrusters allowed each spacecraft to control attitude and correct trajectory. Each of these tiny assemblies produced a thrust of only 0.85 newton (3 oz) to allow the craft to perform delicate maneuvers. Because the spacecraft were to travel far from the Sun, they could not use solar panels to collect sunlight for power. Instead they used radioisotope thermoelectric generators, which produce electricity from the heat resulting from the radioactive decay of plutonium. The generators power the instruments, computer, radio, and other systems. The spacecraft are controlled and their data returned to Earth through the Deep Space Network, a global spacecraft-tracking system.

The Voyager spacecraft were equipped with instruments to conduct ten different scientific experiments. The instruments included television cameras, infrared and ultraviolet sensors, magnetometers, plasma detectors, and cosmic-ray and charged-particle sensors. In addition, the spacecraft radios were used to gather information about planetary atmospheres and ring systems.

A message was placed aboard the Voyager spacecraft to communicate with any extraterrestrial beings that might come into contact with the probes. The message was carried on a 30.5-cm (12-in) gold-plated copper phonograph record containing 115 images and a variety of natural sounds selected to portray the diversity of life forms and cultures on Earth. Musical selections from different cultures and eras; spoken greetings in 55 languages; and printed messages from Jimmy Carter, former president of the United States, and from Kurt Waldheim, former United Nations secretary general, were also included.