Pioneer 7 was a space probe in the Pioneer program.
August 17, 1966 Launched from Cape Canaveral into solar orbit with a mean distance of 1.1 AU. March 20, 1986 Flew within 12.3 million kilometres of Halley's Comet and monitored the interaction between the cometary hydrogen tail and the solar wind. It discovered He+ plasma produced by charge exchange of solar wind He++ with neutral cometary material. March 31, 1995 Tracked successfully. The spacecraft and one of the science instruments were still functioning. Source