The Voyager 2 spacecraft is an unmanned interplanetary space probe launched on August 20, 1977. Both the Voyager 2 and the Voyager 1 space probes were designed, developed, and built at the Jet Propulsion Laboratory near Pasadena, California. Identical in form and instruments with its sister Voyager program craft Voyager 1, Voyager 2 was launched on a slower, more curved trajectory that allowed it to be kept in the plane of the Ecliptic (the plane of the Solar System) so that it could be sent on to Uranus and Neptune by means of utilizing gravity assists during its fly-by of Saturn in 1981 and of Uranus in 1986. Because of this chosen trajectory, Voyager 2 could not take a close-up look at the large Saturnian moon Titan as its sister space probe had. However, Voyager 2 did become the first and only spacecraft to make the spaceflight by Uranus and Neptune, and hence completing the Planetary Grand Tour. This is one that is made practical by a seldom-occurring geometric alignment of the outer planets (happening once every 175 years).
The Voyager 2 space probe has made the most productive unmanned space voyage so far, visiting all four of the Outer Planets and their systems of moons and rings, including the first two visits to previously unexplored Uranus and Neptune. Voyager 2 had two sensitive vidicon cameras and an assortment of other scientific instruments to make measurements in the ultraviolet, infrared, and radio wavelengths, as well as ones to measure subatomic particles in outer space, including cosmic rays. All of this was accomplished at a fraction of the amount of money that was later spent on more advanced and specialized space probes Galileo and Cassini–Huygens. Along with the earlier NASA Pioneer 10 and Pioneer 11, sister probe Voyager 1, and the more recent New Horizons, Voyager 2 is an interstellar probe in that all five of these are on one-way trajectories leaving the Solar System.