Voyager 2

context: en: 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).Voyager 2 discovered previously unknown Neptunian rings, and confirmed six new moons: Despina, Galatea, Larissa, Proteus, Naiad and Thalassa. While in the neighborhood of Neptune, Voyager 2 discovered the "Great Dark Spot", which has since disappeared, according to observations by the Hubble Space Telescope. The Great Dark Spot was later hypothesized to be a region of clear gas, forming a window in the planet's high-altitude methane cloud deck.With the decision of the International Astronomical Union to reclassify Pluto as a dwarf planet in 2006, the flyby of Neptune by Voyager 2 in 1989 became the point when every known planet in the Solar System had been visited at least once by a space probe.
qas: question: zh_tw: 旅行者 2 號何時最接近海王星？
answers: en: text: August 25, 1989

context: en: On July 25, 2012, Voyager 2 was traveling at 15.447 km/s relative to the Sun at about 99.13 astronomical units (1.4830×1010 km) from the Sun, at −55.29° declination and 19.888 h right ascension, and also at an ecliptic latitude of −34.0 degrees, placing it in the constellation Telescopium as observed from Earth. This location places it deep in the scattered disc, and traveling outward at roughly 3.264 AU per year. It is more than twice as far from the Sun as Pluto, and far beyond the perihelion of 90377 Sedna, but not yet beyond the outer limits of the orbit of the dwarf planet Eris.
qas: question: zh_tw: 旅行者 2 號尚未超越什麼？
answers: en: text: Eris

context: en: The closest approach to Saturn occurred on August 26, 1981.While passing behind Saturn (as viewed from Earth), Voyager 2 probed Saturn's upper atmosphere with its radio link to gather information on atmospheric temperature and density profiles. Voyager 2 found that at the uppermost pressure levels (seven kilopascals of pressure), Saturn's temperature was 70 kelvins (−203 °C), while at the deepest levels measured (120 kilopascals) the temperature increased to 143 K (−130 °C). The north pole was found to be 10 kelvins cooler, although this may be seasonal (see also Saturn Oppositions).
qas: question: zh_tw: 北極會更冷多少？
answers: en: text: 10 kelvins

context: en: Voyager 2 is a space probe launched by NASA on August 20, 1977, to study the outer planets. Part of the Voyager program, it was launched 16 days before its twin, Voyager 1, on a trajectory that took longer to reach Jupiter and Saturn but enabled further encounters with Uranus and Neptune. It is the only spacecraft to have visited either of these two ice giant planets.
qas: question: zh_tw: 旅行者 2 號是何時發射的？
answers: en: text: August 20, 1977