Longest surviving interplanetary spacecraft

The unmanned space probe Pioneer 6 was launched on 16 December 1965. After it achieved its Solar orbit between Earth and Venus, it was able to successfully determine the structure and flow of the Solar wind - the million-mile-an-hour stream of charged particles from the Sun. Although no longer being used to collect science data, Pioneer 6 is still functioning, 35 years after its launch. During the Apollo lunar landings, the Pioneers provided hourly reports of solar activity to Apollo mission control. The information guarded against the unexpected arrival of intense showers of solar protons which could have been dangerous to astronauts on the Moon. Pioneer 6 was the first of a fleet of five interplanetary missions to study the Sun. Four of the five were successful.