Exploration with space probes
Main article: Exploration of Jupiter
Since 1973 a number of automated spacecraft have visited Jupiter. Flights to other planets within the Solar System are accomplished at a cost in energy, which is described by the net change in velocity of the spacecraft, or delta-v. Reaching Jupiter from Earth requires a delta-v of 9.2 km/s,[71] which is comparable to the 9.7 km/s delta-v needed to reach low Earth orbit.[72] Fortunately, gravity assists through planetary flybys can be used to reduce the energy required to reach Jupiter, albeit at the cost of a significantly longer flight duration.[71]
Main article: Exploration of Jupiter
Since 1973 a number of automated spacecraft have visited Jupiter. Flights to other planets within the Solar System are accomplished at a cost in energy, which is described by the net change in velocity of the spacecraft, or delta-v. Reaching Jupiter from Earth requires a delta-v of 9.2 km/s,[71] which is comparable to the 9.7 km/s delta-v needed to reach low Earth orbit.[72] Fortunately, gravity assists through planetary flybys can be used to reduce the energy required to reach Jupiter, albeit at the cost of a significantly longer flight duration.[71]
FLYBY MISSIONS
Beginning in 1973, several spacecraft have performed planetary flyby maneuvers that brought them within observation range of Jupiter. The Pioneer missions obtained the first close-up images of Jupiter's atmosphere and several of its moons. They discovered that the radiation fields in the vicinity of the planet were much stronger than expected, but both spacecraft managed to survive in that environment. The trajectories of these spacecraft were used to refine the mass estimates of the Jovian system. Occultations of the radio signals by the planet resulted in better measurements of Jupiter's diameter and the amount of polar flattening.[20][73]
Six years later, the Voyager missions vastly improved the understanding of the Galilean moons and discovered Jupiter's rings. They also confirmed that the Great Red Spot was anticyclonic. Comparison of images showed that the Red Spot had changed hue since the Pioneer missions, turning from orange to dark brown. A torus of ionized atoms was discovered along Io's orbital path, and volcanoes were found on the moon's surface, some in the process of erupting. As the spacecraft passed behind the planet, it observed flashes of lightning in the night side atmosphere.[13][20]
The next mission to encounter Jupiter, the Ulysses solar probe, performed a flyby maneuver in order to attain a polar orbit around the Sun. During this pass the spacecraft conducted studies on Jupiter's magnetosphere. However, since Ulysses has no cameras, no images were taken. A second flyby six years later was at a much greater distance.[74]
In 2000, the Cassini probe, en route to Saturn, flew by Jupiter and provided some of the highest-resolution images ever made of the planet. On December 19, 2000, the spacecraft captured an image of the moon Himalia, but the resolution was too low to show surface details.[75]
The New Horizons probe, en route to Pluto, flew by Jupiter for gravity assist. Closest approach was on February 28, 2007.[76] The probe's cameras measured plasma output from volcanoes on Io and studied all four Galilean moons in detail, as well as making long-distance observations of the outer moons Himalia and Elara.[77] Imaging of the Jovian system began September 4, 2006.[78][79]
Six years later, the Voyager missions vastly improved the understanding of the Galilean moons and discovered Jupiter's rings. They also confirmed that the Great Red Spot was anticyclonic. Comparison of images showed that the Red Spot had changed hue since the Pioneer missions, turning from orange to dark brown. A torus of ionized atoms was discovered along Io's orbital path, and volcanoes were found on the moon's surface, some in the process of erupting. As the spacecraft passed behind the planet, it observed flashes of lightning in the night side atmosphere.[13][20]
The next mission to encounter Jupiter, the Ulysses solar probe, performed a flyby maneuver in order to attain a polar orbit around the Sun. During this pass the spacecraft conducted studies on Jupiter's magnetosphere. However, since Ulysses has no cameras, no images were taken. A second flyby six years later was at a much greater distance.[74]
In 2000, the Cassini probe, en route to Saturn, flew by Jupiter and provided some of the highest-resolution images ever made of the planet. On December 19, 2000, the spacecraft captured an image of the moon Himalia, but the resolution was too low to show surface details.[75]
The New Horizons probe, en route to Pluto, flew by Jupiter for gravity assist. Closest approach was on February 28, 2007.[76] The probe's cameras measured plasma output from volcanoes on Io and studied all four Galilean moons in detail, as well as making long-distance observations of the outer moons Himalia and Elara.[77] Imaging of the Jovian system began September 4, 2006.[78][79]
Flyby missions
Spacecraft
Closestapproach
Distance
Pioneer 10
December 3, 1973
130,000 km
Pioneer 11
December 4, 1974
34,000 km
Voyager 1
March 5, 1979
349,000 km
Voyager 2
July 9, 1979
570,000 km
Ulysses
February 1992
409,000 km
February 2004
240,000,000 km
Cassini
December 30, 2000
10,000,000 km
New Horizons
February 28, 2007
2,304,535 km
GALILEO MISSION
So far the only spacecraft to orbit Jupiter is the Galileo orbiter, which went into orbit around Jupiter on December 7, 1995. It orbited the planet for over seven years, conducting multiple flybys of all of the Galilean moons and Amalthea. The spacecraft also witnessed the impact of Comet Shoemaker-Levy 9 as it approached Jupiter in 1994, giving a unique vantage point for 
the event. However, while the information gained about the Jovian system from Galileo was extensive, its originally designed capacity was limited by the failed deployment of its high-gain radio transmitting antenna.[80]
An atmospheric probe was released from the spacecraft in July 1995, entering the planet's atmosphere on December 7. It parachuted through 150 km of the atmosphere, collecting data for 57.6 minutes, before being crushed by the pressure to which it was subjected by that time (about 22 times Earth normal, at a temperature of 153 °C).[81] It would have melted thereafter, and possibly vaporized. The Galileo orbiter itself experienced a more rapid version of the same fate when it was deliberately steered into the planet on September 21, 2003 at a speed of over 50 km/s, in order to avoid any possibility of it crashing into and possibly contaminating Europa—a moon which has been hypothesized to have the possibility of harboring life.[80]
the event. However, while the information gained about the Jovian system from Galileo was extensive, its originally designed capacity was limited by the failed deployment of its high-gain radio transmitting antenna.[80]An atmospheric probe was released from the spacecraft in July 1995, entering the planet's atmosphere on December 7. It parachuted through 150 km of the atmosphere, collecting data for 57.6 minutes, before being crushed by the pressure to which it was subjected by that time (about 22 times Earth normal, at a temperature of 153 °C).[81] It would have melted thereafter, and possibly vaporized. The Galileo orbiter itself experienced a more rapid version of the same fate when it was deliberately steered into the planet on September 21, 2003 at a speed of over 50 km/s, in order to avoid any possibility of it crashing into and possibly contaminating Europa—a moon which has been hypothesized to have the possibility of harboring life.[80]
Future probes
NASA is planning a mission to study Jupiter in detail from a polar orbit. Named Juno, the spacecraft is planned to launch by 2011.[82]
Because of the possibility of subsurface liquid oceans on Jupiter's moons Europa, Ganymede and Callisto, there has been great interest in studying the icy moons in detail. Funding difficulties have delayed progress. NASA's JIMO (Jupiter Icy Moons Orbiter) was cancelled in 2005.[83] A European Jovian Europa Orbiter mission was also studied.[84] Both of these missions were superseded by the Europa Jupiter System Mission (EJSM) which is a joint NASA/ESA proposal for exploration of Jupiter and its moons. In February 2009 it was announced that ESA/NASA had given this mission priority ahead of the Titan Saturn System Mission.[85][86] ESA's contribution will still face funding competition from other ESA projects.[87] Launch date will be around 2020. EJSM consists of the NASA-led Jupiter Europa Orbiter, and the ESA-led Jupiter Ganymede Orbiter.[88]
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