Galileo was an unmanned NASA spacecraft which studied the planet Jupiter and its moons. It was launched on October 18, 1989, by the Space Shuttle Atlantis. Galileo arrived at Jupiter on December 7, 1995, via gravitational assist flybys of Venus and Earth, becoming the first spacecraft to orbit Jupiter. Galileo Spacecraft consisted of an orbiter and probe. The probe was released into Planet Jupiter atmosphere on the 13th, July, 1995. The mission was named for the Italian Renaissance scientist Galileo Galilei, who discovered Jupiter's major moons in 1610.
- After traveling 2.4 billion miles in just over 6 years to reach Jupiter, Galileo missed its target at the Jovian moon Io by only 67 miles. That's like shooting an arrow from Los Angeles at a bull's-eye in New York and missing by only 6 inches!
- The Galileo spacecraft was made of materials that suggest it is much more like a fighter plane than a car. It used very lightweight materials such as beryllium to house the subsystems, aluminum for the structure, and carbon composites for the booms.
- On its first orbit around Jupiter, the Galileo spacecraft reached a maximum distance from Jupiter of about 20 million kilometers. This is nearly half the distance between the orbits of Earth and Venus, Earth's closest planetary neighbor.
- Galileo returned 14,387 images with the Solid State Imaging Camera, 3,762 from Jupiter’s Orbit.
- Galileo made 34 orbits of Jupiter and traveled a total Distance of 4,631,778,000 km.
- Batteries only get you so far in outer space. The Galileo orbiter carried two radioisotope thermoelectric generators (RTGs),which where used to generate electrical power on board the spacecraft. There are 7.8 kilograms (17.2 pounds) of Plutonium-238 in each RTG.
- Galileo's roots date back to an early recommendation for an atmospheric probe that would explore Jupiter's atmosphere down to pressure levels 100 times that of Earth at sea level. This proposal eventually became JOP (for Jupiter Orbiter Probe), which then eventually became Galileo.
- When the Galileo Probe entered Jupiter's atmosphere, it was traveling at a speed of 106,000 miles per hour -- the fastest impact speed ever achieved by a man- made object. At that speed, one could drive around the Earth at the equator in 14 minutes (assuming there were bridges across all the oceans) or to the Moon and back in only 5 hours!
- On its journey from Earth to Jupiter, Galileo traveled 2.4 billion miles. Along the way, about 67 gallons of fuel from the propulsion system were used to control Galileo's flight path and to keep its antenna pointed at Earth. That's equivalent to getting 36 million miles per gallon! With that kind of mileage, one would use up only 4 tablespoons of gasoline to drive to the Moon and back!
- Since being launched from Earth on October 18, 1989, Galileo has traveled 2.4 billion miles in just over 6 years to reach Jupiter. That's an average speed of 44,000 miles per hour. At that speed, one could drive around the Earth at the equator (assuming there were bridges across all the oceans) in just over half an hour, or to the Moon and back in only 11 hours!
- Jupiter has some truly high velocity winds-- they blow at speed as high as 260 miles per hour at Jupiter's cloud tops!
- Magnetic fields can be powerful entities. Jupiter's magnetosphere strips away 1 ton of material from Io a second. Io's orbital motion through Jupiter's magnetosphere generates electricity--an electric current of 3 million amps!
- Using Galileo's on board instruments to observe the asteroid Gaspra was a challenge somewhat akin to attempting to spot the Goodyear Blimp through a soda straw from five miles away, while sitting in a car going 90 mph.
- Jupiter's moon Io has some of the most dramatic-appearing volcanoes around. Geysers on Io spew out at speeds as high as 1 km/sec (2,300 mph). On Earth, Mt. Etna's ejecta erupt out at a "mere" 112 mph; terrestrial volcanoes rarely exceed 200 mph. Io's gravity is low (1/6 that of Earth), so the plumes are huge--reaching as much as 162 miles high. If you could move Old Faithful to Io, it would shoot up a plume of water and ice over 21 miles high (note, though, that we have no detection of water on Io and the most likely fluid/gas for the plume geysers is sulfur dioxide).
- Io is arguably the most volcanically active body yet known. We've seen at least 200 volcanic caldera bigger than 12 miles in diameter on its surface.
- Jupiter's tug on the Galilean moon Io causes tides, just like our own moon raises tides on the Earth's surface. A typical ocean tide on Earth is about one meter (3 feet). Io's surface tides (no water!), though, are truly something to behold: as great as 330 feet high!
- How many people have worked on Galileo? Nobody knows for sure, but it's been estimated that roughly 10,000 people have worked directly on Galileo since the Project's start in 1977. That's excluding people associated with the Space Shuttle and the Inertial Upper Stage booster.
- Because the asteroid Gaspra is so small (about 19 x 12 x 11 kilometers, or 12 x 7.5 x 7 miles), its surface gravitational force is two thousand times smaller than that of the Earth's, yielding an escape speed of only 10 meters per second (22 miles per hour); an Olympic-caliber sprinter could run himself into orbit! A 200 pound person would weigh 0.1 pounds!
- The Gaspra asteroid flyby was yet another example of outstanding navigation: at closest approach, Galileo was just 1.5 seconds and 1 kilometer (0.6 miles) from the aim point. Even so, taking the picture was a dramatic achievement. One of Galileo's scientists said "It was like taking a picture of a large house in San Francisco from Los Angeles."
- When the Galileo Photopolarimeter Radiometer detected the flashes of light caused by Comet Shoemaker-Levy 9 crashing into Jupiter in July 1994, it was using a 4 inch telescope, and it was as far away from Jupiter as Mars is from the Sun.
- Galileo's second Earth flyby brought the spacecraft within 303 kilometers (182 miles) of the Earth's surface. The gravity assist added 3.7 kilometers per second (8,300 miles per hour) to the spacecraft's speed in its solar orbit. As always, Galileo's navigation was impeccable: the spacecraft was within a kilometer of its intended path, and was just 0.1 second early.
- Jupiter's volume is about 1,400 times that of the Earth. In fact, its volume is half again bigger than all of the Solar System's other planets, moons, asteroids, and comets combined.
- Since Galileo is going into orbit around Jupiter (unlike the two Voyager spacecraft, which flew by the planet), it can fly by Jupiter and its moons at far closer distances than did Voyager, which means that Galileo's pictures will be a dramatic improvement over those from Voyager. Comparing Voyager images with those to be sent back from Galileo is like viewing a book at the base of the Empire State Building from the top story, as opposed to holding that book in your hands.
- Galileo's power sources, radioisotope thermo-electric generators, are putting out only about 520 watts on 7 December. That's not even enough to run a kitchen toaster!