

When the Cassini-Huygens spacecraft arrives at Saturn, it will be traveling so fast that engineers will need to burn the spacecraft's engines for 97 minutes just to slow it down. If mission engineers don't do this, the spacecraft would keep on going, instead of entering the orbit around Saturn. A penumbral eclipse is the outer shadow in a zone where the Earth blocks part, but not all, of the Sun's rays from reaching the Moon. In contrast, the inner or umbral shadow is a region where the Earth blocks all direct sunlight from reaching the Moon. Titan is the largest of Saturn's moons. It is the second largest moon in the solar system. In fact, it is larger than both Mercury and Pluto, which are planets. Equinox literally means "equal night." On an equinox, the Sun is above the equator, so both the northern and southern hemispheres of the Earth receive about the same amount of sunlight, and day and night are the same length. Because Saturn is tilted, when its rings are facing Earth edge-on they "disappear" from our view. We now know this happens every 14 years or so, but poor Galileo questioned his sanity when they "disappeared" and then "reappeared" a few years later. Galileo, launched in 1989, was the first U.S. spacecraft to orbit Jupiter. Galileo entered Jupiter's orbit in 1995. Saturn is huge. It is the second largest planet in our Solar System. Only Jupiter is bigger. If you could line them up, more than nine Earths would fit across Saturn. Through his spyglass, in 1609 Galileo saw that there were spots on the Sun, imperfections on the Moon, and that the Milky Way was composed of millions of faint stars. His most stunning (and controversial!) discovery was of satellites orbiting Jupiter, dashing the concept that the Earth was the center of the Universe. Saturn's moon Iapetus (eye-AP-eh-tuss) is a very curious moon -- it seems to have a split personality! One hemisphere is covered with material darker than black velvet, while the other side is covered with material brighter than snow. Ganymede, one of the moons of Jupiter, is the largest moon in our Solar System. The planet Saturn is named after Saturn, the Roman god of agriculture. The day Saturday is also named after him. The Cassini spacecraft has 12 instruments capable of 27 science investigations. To operate them, the spacecraft's electronic system consists of more than 12 kilometers (almost 7.5 miles) of cabling, about 20,000 wire connections, and 1,630 interconnect circuits. On January 11, 1610, Galileo Galilei discovered Jupiter's moon Ganymede. Ganymede is the largest satellite in the solar system with a diameter of 5,268 km (3270 miles). It is larger than Mercury and Pluto and 3/4 the size of Mars. Saturn's moon Mimas has an enormous crater named Herschel that is 130 kilometers (80 miles) wide, one-third the diameter of Mimas. The impact that caused the crater probably came close to shattering Mimas. Gravity is the pulling force that keeps us on the surface of the Earth. The Huygens probe will land on Titan's surface with the same force as a skydiver lands on Earth with an open parachute. That's approximately 24 kilometers (about 15 miles) per hour! Halley's Comet makes one orbit around the Sun every 76.1 years. Because Saturn spins on its axis extremely fast and has a low-density interior, Saturn is noticeably flattened, top and bottom. Saturn is 10 percent fatter in the middle than at the poles. Did you know that there are 6 gyroscopes on the Hubble Space Telescope? The gyroscopes are used to point the telescope. The Cassini-Huygens spacecraft is about the same size as a 30-passenger school bus! It weighs roughly 5,650 kg (6 tons) -- more than half of its weight is rocket fuel. Did you know that every day the Hubble Space Telescope archives 3 to 5 gigabytes of data and delivers between 10 and 15 gigabytes to astronomers all over the world? Saturn's moon Mimas (MY-mass), one of the innermost moons of Saturn, was discovered in 1789 by William Herschel. It has a low density, meaning it probably consists mostly of ice. The Hubble Space Telescope was launched by the U.S. on April 24, 1990 and is named after Astronomer Edwin P. Hubble. It is a Low Earth Orbiting (LEO) satellite, located about 375 miles (600 km) above the surface of the Earth. Hubble completes an orbit around the Earth every 97 minutes. Saturn's main rings could cover almost the entire distance between Earth and the moon, yet they are less than a kilometer (about half-a-mile) thick. The Interplanetary Monitoring Platform (IMP) spacecraft was retired after 28 years on duty being buffeted by the solar wind and zapped by cosmic rays. Launched on October 25, 1973, IMP 8 was built and operated at NASA's Goddard Space Flight Center in Greenbelt, Maryland, and provided important space physics data as part of NASA's Sun-Earth Connection research program. Did you know that Jupiter is the largest planet in our Solar System? Did you know that the Cassini spacecraft can "see" in wavelengths of light and energy that the human eye cannot, and its onboard onboard can "feel" things about magnetic fields and tiny dust particles that no human hand could detect. NASA missions currently in development, such as Kepler and the Space Interferometry Mission, will be able to study planets more than 6,700 times farther away than Pluto, the most distant planet in our solar system. Saturn goes around the Sun very slowly, but spins on its axis extremely fast. A Saturn year lasts more than 29 Earth years, but a Saturn day lasts only 10 hours and 14 minutes. Did you know that the largest single radio telescope dish (1000 ft. wide, 305 m) is located in Arecibo, Puerto Rico? Unlike Earth, Saturn is made mostly of hydrogen and helium. While it has heavier materials in the core, Saturn has no surface on which you could stand. Saturn is the only planet in our Solar System that is less dense than water. If you could build a ridiculously large bathtub, Saturn would actually float in it. Saturn's moon Hyperion (high-PEER-ee-on) is shaped sort of like a hamburger patty and rotates chaotically because of the gravitational influence of nearby Titan, another of Saturn's many moons. One of the cameras onboard the Cassini spacecraft is so sensitive that it can see a small coin from nearly 4 kilometers (about 2.5 miles) away. Leonid meteor storms happen when Earth passes through clouds of dusty debris shed by comet 55P/Tempel-Tuttle when it comes close to the Sun every 33 years. A light-year is the distance light can travel in one year. Light moves at a velocity of about 300,000 kilometers (km) each second. So in one year, it can travel about 10 trillion km. More precisely, one light-year is equal to 9,500,000,000,000 kilometers. The Cassini-Huygens spacecraft is about 4 meters (13.1 feet) wide -- so wide that it would take about seven people with arms outstretched to encircle the spacecraft! The Mariner series of spacecraft were interplanetary probes designed to investigate Mars, Venus, and Mercury. The program included a number of firsts, including the first planetary flyby, the first planetary orbiter, and the first gravity assist. The Cassini spacecraft will fly close to Saturn 76 times and visit its moon Titan 45 times. The Huygens probe will have the closest view of Titan, and Titan will be the most distant object from Earth ever to be studied by a probe! Mars is known as the "Red Planet." During the long journey to Saturn, the Cassini spacecraft's engines will only burn for about 1 percent of the time. The other 99 percent of the trip is a long un-powered glide through space. The Mars Pathfinder landed on Mars on July 4, 1997. After landing, the lander was renamed the Sagan Memorial Station. The lander also carried the Sojourner rover. The small and rocky planet Mercury is the closest planet to the Sun. Temperatures on Mercury's surface can reach a scorching 467 degrees Celsius, but because the planet has hardly any atmosphere to keep it warm, nighttime temperatures can drop to a frigid -183 degrees Celsius. Redstone (suborbital) and Atlas (orbital) were the two launch vehicles that were used to launch the Mercury astronauts. The Cassini spacecraft will send back to Earth more than 300,000 color images of Saturn, its rings, Titan, and Saturn's other moons. Some 1,100 images of Titan will be taken by the Huygens probe during its swirling descent to Titan. A meteorite is a rock that enters Earth's atmosphere from outer space and reaches the ground. Saturn is so far away it will take almost an hour and a half for radio signals from Earth to reach the Cassini spacecraft -- between 68 and 84 minutes, depending on the position of Earth and Saturn. That's a long time, especially if you consider that radio signals travel at the speed of light! If we could shrink our solar system into the size of a U.S. quarter, the Milky Way galaxy would be the size of North America. Pan, one of Saturn's smallest moons, orbits within Saturn's A-Ring and helps clear out an area between the rings called the Encke Gap. Scientists believe that if Pan didn't exist, neither would the Encke Gap. Did you know that 842 lbs. (382 kg) of rocks were brought back from the moon during the Apollo missions? Newton's Third Law of Motion states that for every action there is an equal and opposite reaction. The three objects in the solar system known to have nitrogen-dominated atmospheres are Earth, Saturn?s moon Titan, and Neptune?s moon Triton. Saturn's density is only 0.13 that of Earth. (That's because Earth is made of rocks and stuff, and Saturn is pretty much just gas.) The Pioneer 10 spacecraft was launched on March 2, 1972. It was the first spacecraft to travel through the asteroid belt and to take close-up pictures of Jupiter. Pluto was discovered on February 18, 1930 by Clyde Tombaugh at the Lowell Observatory in Flagstaff, Arizona. The Italian Space agency built Cassini's high-gain communication antenna. The antenna can transmit in four frequencies at the same time, and it was even used as an umbrella to protect the instruments from the Sun's strong rays during the early part of the mission -- when Cassini was closer to the Sun. That's why the antenna is painted white! Remote sensing is the process of obtaining information about an object, area, or phenomenon without coming into direct contact with the object being observed. Driving at 75 miles per hour, it would take 258 days to drive around one of Saturn?s rings. A solar eclipse occurs when the Moon passes directly between the Sun and the Earth and casts a shadow on the Earth?s surface. A solar eclipse happens when the Earth passes through the Moon?s shadow. Does the Sun move? The Sun and the entire solar system revolve around the center of the Milky Way galaxy. The Sun also rotates on its own axis. If you could see as well as the Wide Field and Planetary Camera on the Hubble Space Telescope, you would be able to read the fine print on a newspaper one mile away! Did you know that the Cassini-Huygens spacecraft is one of the largest interplanetary spacecraft ever built. It's the third heaviest unmanned spacecraft ever launched into space. Most of the elements in the human body were created in the inferno of a burning star. The space between Mars and Jupiter is filled with a population of irregularly shaped chunks of rock and metal called asteroids. Scientists believe the asteroids are pieces of a planet that never formed. Throughout the Cassini mission, the spacecraft will send more than 300 gigabytes of scientific data back to Earth, which is more than 400 CD-ROMs of information! This data will be examined by more than 250 scientists around the world.



