Jupiter is the largest planet in our solar system. It is twice as large as all the other planets combined. It has 28 known satellites. The earliest discovered moons date back to 1610 and were discovered by Galileo. This is of interest because a future mission to Jupiter is named after this astronomer. Most of the remaining moons were discovered in the 20th century with advancement of technology. Some are discovered using better telescopes and others with missions directed towards Jupiter. Some of the more recently discovered moons are yet to be named. All that we know of Jupiter couldn't possibly have come form just observation. Some have come by spacecraft passing by Jupiter on their way to other missions and some of the most comprehensive by missions specifically for Jupiter. (1) (2)
Information and images of Jupiter have been from mostly fly-bys over the years. The fly-bys include; Pioneer 10, Pioneer 11, Voyager 1, Voyager 2 and Ulysses. Most of these missions were launched to investigate the outer solar system and served double duty by flying by Jupiter to gather information to send back to Earth.. The more recent Galileo mission was launched from the Space Shuttle Atlantis in 1989 to travel to Jupiter and study the planet for a period of two years and has yielded a lot more specific information about the planet. Let's look at each of the individual missions. (2)
Pioneer 10 was the first mission to the outer solar system. It was launched in March of 1972. It took approximately 21 months for Pioneer 10 to reach Jupiter.
It was the first to investigate Jupiter and then it continued out of our solar system to continue its journey to the red star Aldebaran: A journey that will take about two million years. Pioneer 10 carried out 15 experiments. It studied interplanetary and planetary magnetic fields; solar wind parameters; cosmic rays; transition region of the heliosphere; neutral hydrogen abundance; distribution, size, mass, flux, and velocity of dust particles; Jovian aurorae (a); Jovian radio waves; atmosphere of Jupiter and some of its satellites; and to photograph Jupiter and its satellites. (3)
Pioneer 11 was launched in April of 1973. It was the second to investigate Jupiter and the first to investigate Saturn. It also had a mission to continue out of our solar system. It also studied also conducted the same experiments as Pioneer 10. (3)
The Voyager missions discovered a lot more about Jupiter than was previously known. Voyager 2 was launched in August of 1977 prior to Voyager 1, which was launched in September of 1977 but arrived about 4 months later in July of 1979. Voyager 1 collected data about Jupiter until it continued on to explore Saturn. Voyager continued on to explore Saturn, Uranus and Neptune. (4)
Some of the discoveries of Voyager 1 and 2 include:
-Found 3 new satellites around Jupiter.
-One of its satellites, Io, was found to have an active volcano, the only other solar system body aside from Earth to be so.
-Over 33,000 photographs taken of Jupiter and its five major satellites.
-Auroral emissions similar to Earth's northern lights.
-Cloud-top lightning bolts, similar to superbolts in Earth's high atmosphere.
-Discovered a ring around Jupiter.
-And many other highly technical things that are not understood by the average Joe. (4)
Ulysses was launched in October of 1990. It first did a Jupiter swing by in February of 1992 and now orbits the planet once every 6 years. It is using a heliospheric orbit, which means that its orbits around the north and south pole in about a year and then completes its 6 yearlong oval orbit away from the planet. It primary mission was to investigate, as a function of solar latitude, the properties of the solar wind and the interplanetary magnetic field, of galactic cosmic rays and neutral interstellar gas, and to study energetic particle composition and acceleration. It was launched by the European Space Agency. (5)
(a) auroras or au·ro·rae: a luminous phenomenon that consists of streamers or arches of light appearing in the upper atmosphere of a planet 's magnetic polar regions and is caused by the emission of light from atoms excited by electrons accelerated along the planet 's magnetic field lines (Webster 's Dictionary)
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