Following a mid-course correction in 1987, "Voyager 2"s closest approach to Neptune occurred on August 25, 1989. Through repeated computerized test simulations of trajectories through the Neptunian system conducted in advance, flight controllers determined the best way to route "Voyager 2" through the Neptune-Triton system. Since the plane of the orbit of Triton is tilted significantly with respect to the plane of the ecliptic, through mid-course corrections, "Voyager 2" was directed into a path about 4950 kilometers (3000 mi) above the north pole of Neptune. Five hours after "Voyager 2" made its closest approach to Neptune, it performed a close fly-by of Triton, the larger of Neptune's two originally known moons, passing within about 40,000 kilometers (25,000 mi).