Identical to Pioneer 6, Pioneer 7 was put into heliocentric orbit at 0.814 x 0.985 AU to study the solar magnetic field, the solar wind, and cosmic rays at widely separated points in solar orbit.
On ... 7 September 1968, the spacecraft was correctly aligned with the Sun and Earth to begin studying Earth's magnetic tail.
In 1977, eleven years after its launch, Pioneer 7 registered the magnetic tail 19.3 million kilometers out, three times further into space than recorded previously.
On 20 March 1986, the spacecraft flew within 12.3 million kilometers of Halley's Comet and monitored the interaction between the cometary hydrogen tail and the solar wind.
As with Pioneer 6 and Pioneer 8, NASA continues to maintain intermittent contact with Pioneer 7, more than thirty years after its mission began. On 31 March 1995, for example, the plasma analyzer was turned on during 2 hours of contact with the ground.
Information provided by http://solarsystem.nasa.gov/missions/profile.cfm?Sort=Alpha&Alias=P...