From Wikipedia:
The Voyager 1 spacecraft is a 722-kilogram (1,592-lb) robotic American space probe launched by NASA on September 5, 1977, to study the outer Solar System and eventually interstellar space. Operating for 33 years, 8 months, and 10 days, the spacecraft receives routine commands and transmits data back to the Deep Space Network. It is the first probe to leave the Solar System and is the farthest man made object from Earth.
Part of the Voyager program with its sister craft Voyager 2, 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 November 20, 1980, after encountering the Jovian system in 1979 and the Saturnian system in 1980. It was the first probe to provide detailed images of the two largest planets and their moons.