Voyager 1 and 2

The Voyager space probes are probably two of the most famous space probes in history, for they provided us with our first detailed close-up views and scans of the outer planets: Jupiter, Saturn, Uranus, and Neptune (they did not fly by Pluto). Because of the two Voyager probes, we have gained much knowledge on the outer planets, their moons, and their rings.

Mission Highlights:

Courtesy of http://pds.jpl.nasa.gov (see Bibliography)

Voyager 1:

Voyager 1 was launched on September 5, 1977, after Voyager 2. Voyager 1 flew by Jupiter and Saturn only, but could have visited Neptune and Uranus, but NASA didn't want to pass up the opportunity to view Saturn's moon Titan more closely. Voyager 1 passed Jupiter on March 5, 1979, and passed by Saturn on November 13, 1980.

Voyager 1 has passed Pioneer 10, so has become the most distant human-made object.

Voyager 2:

Voyager 2 was launched on top of a Titan 3-E/Centaur rocket on August 20, 1977, before Voyager 1. Only eight months into the journey though, Voyager 2's primary radio stopped working, and its backup radio receiver developed a short circuit. Functioning weakly, it was still able to relay all of its scientific discoveries. Voyager 2 flew by Jupiter, Saturn, Uranus, and Neptune. It flew by Jupiter on August 7, 1979, Saturn on August 26, 1981, Uranus on January 24, 1986, and Neptune on August 8, 1989.

Voyager 2 took advantage of a once-in-189-years alignment of the outer planets to "slingshot" its way from planet to planet.

Voyager 2 found Uranus to be solidly-colored. It showed that Uranus's magnetic axis was far off (thirty degrees) from its already ninety degree off rotational axis, and that the magnetic axis doesn't even pass through the center of the planet. Voyager 2 also identified Uranus as a radio source. It found ice patches on Ariel. It found strange collages of different types of terrains. Voyager 2 also found ten more moons and one more ring.

Courtesy of http://vraptor.jpl.nasa.gov/voyager/images/neptune.gif (see Bibliography)

Voyager 2 found Neptune to have interesting weather patterns, which include clouds. Neptune was found to have an internal heat source, and, like Uranus, Neptune's magnetic axis is inclined greatly off of its rotational axis. Neptune's ring arcs were discovered to be bright patches on one ring. Voyager 2 discovered two more rings, and six more moons. Neptune's magnetic axis was also far off of its rotational axis. Triton, a moon, was found to be cantaloupe-shaped and to have geysers. Triton was also found to have pink nitrogen snow at its poles.

Both Voyager 1 and 2 Found:

Jupiter:

Jupiter has complicated atmospheric dynamics, lightning, and auroras.

Three new moons.

Jupiter has rings.

Io has active sulfur volcanoes, and these volcanoes have major effects on Jupiter's magnetosphere.

The Great Red Spot rotates once every six days, an it can survive almost indefinitely because it pulls in smaller eddies and adds their spin to its own.

Saturn:

Saturn has over 1000 ringlets.
Saturn's rings have braids, kinks, and spokes which have not yet been explained.
Seven new moons, including shepherd moons which keep the rings stable.
Massive jet streams which change rarely.
Saturn's magnetic poles lie exactly on its true north and south poles.
Titan, a moon, has a smoggy atmosphere, mostly composed of nitrogen, and at the surface has a density about 1.5 times Earth's at sea level.
Mimas, a moon, has a crater in it that covers about twenty-five per cent of the surface.

Ongoing Mission:

If nothing happens to them, NASA should be able to remain in contact with the two Voyager space probes until about 2030. Both crafts have enough hydrazine fuel (Voyager 1 should last until 2040 and Voyager 2 until 2034).

Courtesy of http://www.nasa.gov/projects.html (see Bibliography)

The only problem is that the crafts' Radio-isotope Thermal Generators (RTG's) are slowly diminishing their power output. By 2000, there will not be enough power to run the UltraViolet Spectrometer (UVS). By 2010, power output will be so low that not all of the instruments can be in operation at the same time. When that occurs, NASA will initiate a plan of taking different instruments on and off line at different times. This should keep the Voyagers in operation until 2020, and then power will be too low to maintain the crafts.

The Voyagers have not detected any evidence of planets beyond Pluto.

Voyager 1 is traveling above the plane that the planets are in at about 35 degrees at a rate of about 320 million miles (520 million kilometers) a year. Voyager 2 is traveling below the plane at an angle of about 48 degrees and a rate of about 290 million miles (470 million kilometers) a year.

The distance of the Voyagers has given scientists a new vantage point to study objects that emit ultraviolet light. After the year 2000, though, scientists aren't sure weather or not there will be enough power to keep the instrument warm enough to operate. Other instruments that are currently operational are the cosmic ray subsystem, the low-energy charge particle instrument, the magnetometer, the plasma subsystem, the plasma wave subsystem, and the planetary radio astronomy instrument.

The Voyagers are now studying the Heliopause. Low-frequency radio emissions which are believed to originate at the heliopause have been detected between 90 and 120 A.U.* from the Sun. The Voyagers use their ultraviolet spectrometers to map the heliopause. They use their cosmic ray detectors to study the energy spectra of interstellar cosmic rays which are coming from the outer heliopause.

The cost of the Voyager 1 and 2 missions, including launch, mission operations from launch through the Neptune encounter and the spacecraft's nuclear batteries (provided by the Department of Energy), was $865 million. NASA budgeted an additional $30 million to fund the Voyager Interstellar Mission for two years following the Neptune encounter.

*A.U. stands for Astronomical Unit, and is equal to the average distance between the Earth and the Sun (about 93 million miles (150 million km)).