Pioneer 6 was the first of four NASA spacecraft designed to study interplanetary phenomena in space. The spacecraft successfully provided simultaneous scientific measurements at widely dispersed ... locations in heliocentric orbit. It returned the first data on the tenuous solar atmosphere and later recorded the passage of Comet Kohoutek's tail in 1974.
Along with Pioneers 7, 8, and 9, the spacecraft formed a ring of solar weather stations spaced along Earth's orbit. Measurements by the four Pioneers were used to predict solar storms for approximately 1,000 primary users, including the Federal Aviation Administration; commercial airlines; power companies; communication companies; military organizations; and entities involved in surveying, navigation, and electronic prospecting.
By December 1990, Pioneer 6 had circled the Sun twentynine times (traveling 24.8 billion kilometers) and had been operational for twenty years -- a record for a deep space probe. Its original slated lifetime had been only six months.
On 15 December 1996, the spacecraft's primary transmitter failed, but during a track on 11 July 1996, ground controllers switched on the backup transmitter.
Of the spacecraft's six scientific instruments, two (the plasma analyzer and the cosmic-ray detector) still continue to function.
NASA maintains contact with the spacecraft once or twice each year. For example, 1 hour's worth of scientific data was collected on 29 July and 15 December 1995 (although the primary transmitter failed soon after that), and again on 6 October 1997, more than thirty years after launch. The probe's solar arrays continue to deteriorate, although the transmitters can be turned on at perihelion when the solar flux is strong enough to provide sufficient power.
On 8 December 2000, to commemorate its thirty-fifth anniversary of operation, ground controllers established successful contact with the spacecraft for about 2 hours.
Information provided by http://solarsystem.nasa.gov/missions/profile.cfm?Sort=Alpha&Alias=P...