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The Voyager program is a continuing American scientific program that employs two robotic probes, ''Voyager 1'' and ''Voyager 2'', to study the outer Solar System. They were launched in 1977 to take advantage of a favorable alignment of Jupiter, Saturn, Uranus, and Neptune, and are now exploring the outer boundary of the heliosphere. Although their original mission was to study only the planetary systems of Jupiter and Saturn, ''Voyager 2'' continued on to Uranus and Neptune, and both ''Voyagers'' are now tasked with exploring interstellar space. Their mission has been extended three times, and both probes continue to collect and relay useful scientific data. On August 25, 2012, data from ''Voyager 1'' indicated that it had become the first human-made object to enter interstellar space, traveling "further than anyone, or anything, in history". , ''Voyager 1'' was moving with a velocity of relative to the Sun.〔(【引用サイトリンク】title=Voyager Mission Operations Status Report # 2013-05-31, Week Ending May 31, 2013 )〕 ''Voyager 2'' is expected to enter interstellar space within 2016, and its plasma spectrometer should provide the first direct measurements of the density and temperature of the interstellar plasma.〔 〕 Data and photographs collected by the ''Voyagers’'' cameras, magnetometers, and other instruments revealed previously unknown details about each of the giant planets and their moons. Close-up images from the spacecraft charted Jupiter’s complex cloud forms, winds, and storm systems and discovered volcanic activity on its moon Io. Saturn’s rings were found to have enigmatic braids, kinks, and spokes and to be accompanied by a myriad of “ringlets.” At Uranus ''Voyager 2'' discovered a substantial magnetic field around the planet and 10 additional moons. Its flyby of Neptune uncovered three complete rings and six hitherto unknown moons as well as a planetary magnetic field and complex, widely distributed auroras. ''Voyager 2'' is still the only spacecraft to have visited the ice giants. The ''Voyager'' spacecraft were built at the Jet Propulsion Laboratory in Southern California, and they were paid for by the National Aeronautics and Space Administration (NASA), which also paid for their launchings from Cape Canaveral, Florida, their tracking, and everything else concerning the space probes. ==History== The two ''Voyager'' space probes were originally conceived as part of the Mariner program, and they were thus named ''Mariner 11'' and ''Mariner 12''. They were then moved into a separate program named ''Mariner Jupiter-Saturn'', later renamed the ''Voyager Program'' because it was thought that the design of the two space probes had progressed sufficiently beyond that of the ''Mariner'' family that they merited a separate name.〔('' Chapter 11 "Voyager: The Grand Tour of Big Science" ) (sec. 268.), by Andrew,J. Butrica, found in ''From Engineering Science To Big Science'' ISBN 978-0-16-049640-0 edited by Pamela E. Mack, NASA, 1998〕 The ''Voyager Program'' was similar to the Planetary Grand Tour planned during the late 1960s and early 70s. The Grand Tour would take advantage of an alignment of the outer planets discovered by Gary Flandro, an aerospace engineer at the Jet Propulsion Laboratory. This alignment, which occurs once every 175 years, would occur in the late 1970s and make it possible to use gravitational assists to explore Jupiter, Saturn, Uranus, Neptune, and Pluto. The Planetary Grand Tour was to send several pairs of probes to fly by all the outer planets (and Pluto) along various trajectories, including Jupiter-Saturn-Pluto and Jupiter-Uranus-Neptune. Limited funding ended the Grand Tour program, but elements were incorporated into the ''Voyager'' Program, which fulfilled many of the flyby objectives of the Grand Tour except a visit to Pluto. ''Voyager 2'' was the first to launch. Its trajectory was designed to allow flybys of Jupiter, Saturn, Uranus, and Neptune. ''Voyager 1'' was launched after ''Voyager 2'', but along a shorter and faster trajectory that was designed to provide an optimal flyby of Saturn's moon Titan, which was known to be quite large and to possess a dense atmosphere. This encounter sent ''Voyager 1'' out of the plane of the ecliptic, ending its planetary science mission.〔(【引用サイトリンク】url=http://voyager.jpl.nasa.gov/faq.html )〕 Had ''Voyager 1'' been unable to perform the Titan flyby, the trajectory of ''Voyager 2'' could have been altered to explore Titan, forgoing any visit to Uranus and Neptune. ''Voyager 1'' was not launched on a trajectory that would have allowed it to continue to Uranus and Neptune, but could have continued from Saturn to Pluto without exploring Titan.〔(【引用サイトリンク】 title=What If Voyager Had Explored Pluto? )〕 During the 1990s, ''Voyager 1'' overtook the slower deep-space probes ''Pioneer 10'' and ''Pioneer 11'' to become the most distant human made object from Earth, a record that it will keep for the foreseeable future. Even the ''New Horizons'' probe, which had a higher velocity than ''Voyager 1'' at launch, is traveling slower than ''Voyager 1'' due to the extra speed ''Voyager 1'' gained from its flybys of Jupiter and Saturn. ''Voyager 1'' and ''Pioneer 10'' are the most widely separated human made objects anywhere, since they are traveling in roughly opposite directions from the Solar System. In December 2004, ''Voyager 1'' crossed the termination shock, where the solar wind is slowed to subsonic speed, and entered the heliosheath, where the solar wind is compressed and made turbulent due to interactions with the interstellar medium. On December 10, 2007, ''Voyager 2'' also reached the termination shock, about 1 billion miles closer to the sun than from where ''Voyager 1'' first crossed it, indicating that the Solar System is asymmetrical.〔(Voyager 2 Proves Solar System Is Squashed NASA.gov #2007-12-10 )〕 In 2010 ''Voyager 1'' reported that the outward velocity of the solar wind had dropped to zero, and scientists predicted it was nearing interstellar space. In 2011, data from the ''Voyagers'' determined that the heliosheath is not smooth, but filled with giant magnetic bubbles, theorized to form when the magnetic field of the Sun becomes warped at the edge of our Solar System. On 15 June 2012, scientists at NASA reported that ''Voyager 1'' was very close to entering interstellar space, indicated by a sharp rise in high-energy particles from outside the Solar System. In September 2013, NASA announced that ''Voyager 1'' had crossed the heliopause on August 25, 2012, making it the first spacecraft to enter interstellar space.〔(【引用サイトリンク】url=http://www.agu.org/news/press/pr_archives/2013/2013-11.shtml )〕〔(【引用サイトリンク】url=http://www.jpl.nasa.gov/news/news.php?release=2013-107&cid=release_2013-107&msource=2013107 )〕 ''Voyager 1'' and ''Voyager 2'' continue to monitor conditions in the outer expanses of the Solar System. The ''Voyager'' spacecraft are expected to be able to operate science instruments through 2020, when limited power will require instruments to be deactivated one by one. Sometime around 2025, there will no longer be sufficient power to operate any science instruments.〔(【引用サイトリンク】url=http://www.jpl.nasa.gov/interstellarvoyager/pdf/QandA-EdStone.pdf )〕 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Voyager program」の詳細全文を読む スポンサード リンク
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