Voyager 1 is a spacecraft launched on 5 September 1977 to investigate the outer Solar system. It flew past Jupiter in March 1979 and Saturn in November 1980, then continued outward on an extended mission to study the environment beyond the planets.[ref]
Voyager 1 Mission Overview by NASA. Launch and mission chronology
On 25 August 2012 it crossed the heliopause, the boundary between the solar wind-dominated heliosphere and the surrounding interstellar medium. This boundary concerns the plasma environment; it is not a boundary beyond which the Sun's gravity vanishes. Its scientific instruments include detectors of charged particles, a magnetometer and a Voyager plasma-wave instrument. Together, measurements of particles, magnetic fields and plasma waves allow a moving probe to investigate a remote environment that cannot be sampled in a terrestrial laboratory.[ref]
Voyager 1 Mission Overview by NASA. Interstellar mission and science instruments
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