NASA Voyager 2

NASA's Voyager 1 and 2 probes were launched in reverse order, so Voyager 2 is actually older. It rocketed into space on 20 August 1977, 16 days before its twin, and went on to visit Jupiter, Saturn, Uranus, and Neptune. It continues to send back measurements of the solar wind as it coasts out of the solar system towards interstellar space. Its radioactive power source should keep it alive until around 2025, by which point it will be 48 years old. On June 28, 2010, Voyager 2 completed 12,000 days of continuous operations since its launch on August 20, 1977. For nearly 33 years, the venerable spacecraft has been returning unprecedented data about the giant outer planets, the properties of the solar wind between and beyond the planets and the interaction of the solar wind with interstellar winds in the heliosheath. Having traveled more than 21 billion kilometers on its winding path through the planets toward interstellar space, the spacecraft is now nearly 14 billion kilometers from the sun. Traveling at the speed of light, a signal from the ground takes about 12.8 hours to reach the spacecraft.