Voyager 1 is speeding along at about 57,600 kph (35,790 mph) - fast enough to travel from the Earth to the Sun three and a half times in one year.
Both Voyagers carry a gold record 'greeting to the universe' (right) containing sounds and images selected to portray the diversity of life and culture on Earth.
Voyager 1 is in the process of escaping the solar system at a speed of about 523.6 million km per year, or about 1.4 million km per day.
Even at this tremendous speed, Voyager 1 will take at least 14,000 years (and maybe twice that or even longer) to emerge from the Oort cloud.
A 30-cm gold-plated copper disc, together with a needle and playing instructions, is mounted on the body casing. On it are recorded natural Earth sounds, 90 min of music, 115 pictures, and greetings in 60 languages.