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Initial Plan and Changes
Despite a planned massive "grand tour" of the outer solar system involving dual launches to Jupiter, Saturn and Pluto from 1976 through 1977, and dual launches to Jupiter, Uranus, and Neptune in 1979, budgetary reality dictated that the program be cut back to two spacecraft only, and that each of them would only go to Jupiter and Saturn. The scaled back project cost only one-third of what the originally envisioned tour of the outer solar system would have cost. But the Voyager program has been anything but disappointing, considering that the craft were launched in 1977 and now, more than 30 years later, they continue to send valuable scientific data back to the earth.
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Each spacecraft was made of a ten-sided "bus" of 47 cm in height and 178 cm across. On top was mounted a 3.66 meter parabolic, high gain antenna. A science boom extended 2.5 m from the spacecraft, and carried most of the scientific instruments. A steerable scan platform at the end of the science boom held imaging and spectroscopic instruments. Plasma and charged particle detectors were located along the science boom as well. Magentometers were mounted on a separate boom that extended 13 m on the opposite side from the science boom. A third boom, which extended away from the scientific instrumentation carried the radioisotope thermoelectric generators to power the instrumentation and spacecraft systems. Two whip antennas extended from the craft perpendicular to each other. These were used for planetary radio astronomy and plasma wave experiments. The spacecraft was spin stabilized for selective viewing from instruments located on the scan platform.
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Jupiter, Saturn, Neptune...
Voyager 2 was actually launched before Voyager 1, on a leisurely route to Jupiter. Voyager 1 got to Jupiter first, but Voyager 2 had its closest approach to Jupiter in July 1979 and to Saturn in August 1981. It took about the same number of images of these planets as Voyager 1 (18,000 of Jupiter, and 16,000 of Saturn). Despite the fact that its primary radio receiver had failed and it was using a backup receiver, approval was granted for Voyager 2 to continue on to Uranus and Neptune. Once it reached this part of the distant solar system, engineers back home had to make changes to account for the much lower levels of sunlight at those distances, and more distant communications signals. Voyager 2 took 8,000 images of Uranus and its satellites, then 10,000 images of Neptune and its satellites. What it found was stunning.
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... Uranus ...
Uranus was found to be monochromatic, with a skewed magnetic axis to go along with a skewed rotational axis. This made Uranus' magnetosphere very peculiar. Ten more satellites and one more ring was discovered around Uranus. Neptune, on the other hand, revealed active weather systems. Two "ring arcs" were actually bright patches on one ring. Six more satellites and two other rings were discovered. It was also discovered that the moon Triton resembled a canteloupe and had geysers.
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... and Out of Here
But Voyager 2 kept on going, and in 2007 it reached a milestone by crossing the so-called termination shock, the place at the edges of the solar system where the solar wind slows down abruptly. Because Voyager 2 crossed the termination shock at a closer distance to the sun than did Voyager 1 three years earlier, it indicates that the heliosphere is asymmetrical, a phenomenon that may be due to a magnetic field that pushes farther inwards where Voyager 2 crossed the termination shock than where Voyager 1 did.
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Summary - Still Going
Today, with the help of NASA's Deep Space Network of receivers located at Goldstone, California, and near Canberra, Australia, and near Madrid, Spain, the Earth still has continuing communication with Voyager 2. As of November 1, 2009, Voyager 2 was located at 19.733 hours Right Ascension and -54.59 degrees declination. As observed from earth, it looks like it is in the constellation Telescopium. It is currently speeding away from the sun at speeds of more than 36,000 miles per hour. Even at this speed, it would take Voyager 2 18,600 years to reach a distance of one light-year. Voyager 2 went from being a quirky craft with radio problems to being part of one of the greatest space exploration missions of all time.