Both spacecraft are still sending scientific information about their surroundings through the Deep Space Network, or DSN. The primary mission was the exploration of Jupiter and Saturn. After making a string of discoveries there — such as active volcanoes on Jupiter's moon Io and intricacies of Saturn's rings — the mission was extended. Voyager 2 went on to explore Uranus and Neptune, and is still the only spacecraft to have visited those outer planets. Voyagers 1 and 2 are identical spacecraft.
Each is equipped with instruments to conduct 10 different experiments. The instruments include television cameras, infrared and ultraviolet sensors, magnetometers, plasma detectors, and cosmic-ray and charged-particle sensors.
In addition, the spacecraft radio is used to conduct experiments. The Voyagers travel too far from the Sun to use solar panels; instead, they were equipped with power sources called radioisotope thermoelectric generators RTGs. These devices, used on other deep space missions, convert the heat produced from the natural radioactive decay of plutonium into electricity to power the spacecraft instruments, computers, radio and other systems. Textor of JPL.
The Voyager project scientist is Dr. Edward C. Stone of the California Institute of Technology. The assistant project scientist for the Jupiter flyby was Dr. Arthur L. Lane, followed by Dr.
Ellis D. Miner for the Saturn, Uranus and Neptune encounters. Both are with JPL. The first spacecraft flew within , kilometers , miles of the planet's cloud tops, and Voyager 2 came within , kilometers , miles. Jupiter is the largest planet in the solar system, composed mainly of hydrogen and helium, with small amounts of methane, ammonia, water vapor, traces of other compounds and a core of melted rock and ice. Colorful latitudinal bands and atmospheric clouds and storms illustrate Jupiter's dynamic weather system.
The giant planet is now known to possess 16 moons. The planet completes one orbit of the Sun each Although astronomers had studied Jupiter through telescopes on Earth for centuries, scientists were surprised by many of the Voyager findings. The Great Red Spot was revealed as a complex storm moving in a counterclockwise direction.
An array of other smaller storms and eddies were found throughout the banded clouds. Discovery of active volcanism on the satellite Io was easily the greatest unexpected discovery at Jupiter. It was the first time active volcanoes had been seen on another body in the solar system.
Together, the Voyagers observed the eruption of nine volcanoes on Io, and there is evidence that other eruptions occurred between the Voyager encounters. Plumes from the volcanoes extend to more than kilometers miles above the surface.
The Voyagers observed material ejected at velocities up to a kilometer per second. Io's volcanoes are apparently due to heating of the satellite by tidal pumping. Io is perturbed in its orbit by Europa and Ganymede, two other large satellites nearby, then pulled back again into its regular orbit by Jupiter.
This tug-of-war results in tidal bulging as great as meters feet on Io's surface, compared with typical tidal bulges on Earth of one meter three feet. It appears that volcanism on Io affects the entire jovian system, in that it is the primary source of matter that pervades Jupiter's magnetosphere -- the region of space surrounding the planet influenced by the jovian magnetic field.
Sulfur, oxygen and sodium, apparently erupted by Io's many volcanoes and sputtered off the surface by impact of high-energy particles, were detected as far away as the outer edge of the magnetosphere millions of miles from the planet itself. Europa displayed a large number of intersecting linear features in the low-resolution photos from Voyager 1.
At first, scientists believed the features might be deep cracks, caused by crustal rifting or tectonic processes. The closer high-resolution photos from Voyager 2, however, left scientists puzzled: The features were so lacking in topographic relief that as one scientist described them, they "might have been painted on with a felt marker.
Europa is thought to have a thin crust less than 30 kilometers or 18 miles thick of water ice, possibly floating on a kilometer-deep mile ocean. Ganymede turned out to be the largest moon in the solar system, with a diameter measuring 5, kilometers 3, miles. It showed two distinct types of terrain -- cratered and grooved -- suggesting to scientists that Ganymede's entire icy crust has been under tension from global tectonic processes.
Callisto has a very old, heavily cratered crust showing remnant rings of enormous impact craters. The largest craters have apparently been erased by the flow of the icy crust over geologic time.
Almost no topographic relief is apparent in the ghost remnants of the immense impact basins, identifiable only by their light color and the surrounding subdued rings of concentric ridges. A faint, dusty ring of material was found around Jupiter. Its outer edge is , kilometers 80, miles from the center of the planet, and it extends inward about 30, kilometers 18, miles. Two new, small satellites, Adrastea and Metis, were found orbiting just outside the ring. A third new satellite, Thebe, was discovered between the orbits of Amalthea and Io.
Between them, the two spacecraft have explored all the giant outer planets of our solar system — Jupiter , Saturn , Uranus and Neptune — as well as 49 moons, and the systems of rings and magnetic fields those planets possess. On Aug. These are some of the Voyager program's achievements while the spacecraft were still flying past the planets, according to NASA:. The current mission, the Voyager Interstellar Mission, was planned to explore the outermost edge of our solar system and eventually leave our sun's sphere of influence to enter interstellar space — the space between the stars.
Since passing the boundary of interstellar space in , Voyager 1 is examining the intensity of cosmic radiation , and also looking at how the sun's charged particles are interacting with particles from other stars, according to Voyager project scientist Ed Stone.
Voyager 2 is still traveling within the solar system, but is expected to breach interstellar space in the next few years. Both Voyager spacecraft carry recorded messages from Earth on golden phonograph records — inch, gold-plated copper disks.
The "Golden Records," as these records are called, are cultural time capsules that the Voyagers bear with them to other star systems. They contain images and natural sounds, spoken greetings in 55 languages and musical selections from different cultures and eras. The program's observations of Jupiter, Saturn, Uranus and Neptune also provide valuable touchstones for current observations of these planets. NASA sent follow-on probes to Jupiter Galileo, and Saturn Cassini, to examine these giant planets up close for several years, following the quick glimpses provided by Voyager.
Galileo and Cassini each gathered data about the icy moons at their respective planets, as well as information about the structure and composition of the giant planets themselves, among other activities. The Voyager mission was designed to take advantage of a rare geometric arrangement of the outer planets in the late s and the s which allowed for a four-planet tour for a minimum of propellant and trip time.
This layout of Jupiter, Saturn, Uranus and Neptune, which occurs about every years, allows a spacecraft on a particular flight path to swing from one planet to the next without the need for large onboard propulsion systems. The flyby of each planet bends the spacecraft's flight path and increases its velocity enough to deliver it to the next destination. While the four-planet mission was known to be possible, it was deemed to be too expensive to build a spacecraft that could go the distance, carry the instruments needed and last long enough to accomplish such a long mission.
Thus, the Voyagers were funded to conduct intensive flyby studies of Jupiter and Saturn only. More than 10, trajectories were studied before choosing the two that would allow close flybys of Jupiter and its large moon Io, and Saturn and its large moon Titan; the chosen flight path for Voyager 2 also preserved the option to continue on to Uranus and Neptune.
Both spacecraft were delivered to space aboard Titan-Centaur expendable rockets.
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