The Voyager 2 spacecraft is a 722-kilogram (1,592 lb) space probe launched by NASA on August 20, 1977 to study the outer Solar System and eventually interstellar space. Operating for 34 years, 8 months and 5 days as of today (25 April 2012), the spacecraft receives routine commands and transmits data back to the Deep Space Network.
Part of the Voyager program with its identical sister craft Voyager 1, the spacecraft is currently in extended mission, tasked with locating and studying the boundaries of the Solar System, including the Kuiper belt, the heliosphere and interstellar space. The primary mission ended December 31, 1989 after encountering the Jovian system in 1979, Saturnian system in 1980, Uranian system in 1986, and the Neptunian system in 1989. It was the first probe to provide detailed images of the outer gas giants.
Each Voyager space probe carries a gold-plated audio-visual disc in the event that either spacecraft is ever found by intelligent life-forms from other planetary systems. The discs carry photos of the Earth and its lifeforms, a range of scientific information, spoken greetings from the people (e.g. the Secretary-General of the United Nations and the President of the United States, and the children of the Planet Earth) and a medley, “Sounds of Earth”, that includes the sounds of whales, a baby crying, waves breaking on a shore, and a variety of music.
As the probes are extremely small compared to the vastness of interstellar space, the probability of a space-faring civilization encountering them is very small, especially since the probes will eventually stop emitting any kind of electromagnetic radiation. If they are ever found by an alien species, it will most likely be far in the future as the nearest star on Voyager 1’s trajectory will only be reached in 40,000 years.
Carl Sagan noted that “The spacecraft will be encountered and the record played only if there are advanced space-faring civilizations in interstellar space. But the launching of this ‘bottle‘ into the cosmic ‘ocean’ says something very hopeful about life on this planet.” Thus the record is best seen as a time capsule or a symbolic statement rather than a serious attempt to communicate with extraterrestrial life.