Goals: Pioneer 7 was the second in a series of solar orbiters designed to measure, from widely separated points in space on a continuing basis, interplanetary phenomena such as the Sun's magnetic field, the solar wind, and solar and galactic cosmic rays.

Accomplishments: Pioneers 6, 7, 8, and 9 formed a ring of solar-weather stations, spaced approximately along Earth's orbit, whose measurements were used to predict solar storms. Pioneer 7 recorded Earth's magnetic tail more than 19 million km from the planet, 3 times further than previously recorded. During the visit by Halley's comet to the inner solar ssytem in 1986, the spacecraft observed the interaction between the comet's hydrogen tail and the solar wind.

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