Satellites
What are satellites? A satellite is any object that orbits or revolves around another object. That would make the Moon a satellite of Earth, and Earth a satellite of the Sun. Artificial satellites are made by humans. They look out into space or back at Earth itself.
Uses of satellites Satellites come in many shapes and sizes and have three general uses: space science, applications, or communications. Space science satellites carry instruments to study the Sun, measure magnetic fields or to examine the universe in the different energy wavelengths of the electromagnetic spectrum, including gamma rays, X-rays, ultraviolet, visible light, infrared, microwaves and radio waves. Application satellites survey the Earth's resources and supply weather photographs and other information to forecasters. Communication satellites relay telephone calls and television signals, transmit scientific information from other satellites down to Earth, and relay voice communications between the astronauts orbiting on the Space Shuttle and mission controllers on Earth. They are used for communications, observation and monitoring, navigation, and mapping.
Different Kinds of Orbit Low Earth Orbit: When a satellite circles close to Earth it's in Low Earth Orbit (LEO). Satellites in LEO are placed 200 – 800 km high. Because they orbit so close to Earth, they must travel very fast (27,359 kilometers per hour) so gravity won't pull them back into the atmosphere. They can circle Earth in about 90 minutes. To an observer on the ground these satellites would move across the sky in a matter of minutes. Satellites that observe our planet, like Remote Sensing and Weather satellites, often travel in this orbit because from this height they can capture very detailed images of Earth's surface. Geosynchronous Orbit: Satellites that move in the same direction as Earth rotates and are 36 000 km above Earth, over the equator are in Geosynchronous Earth Orbit (GEO). They are synchronized with the rotation of Earth. To an observer on the ground these satellites would appear motionless. Radio and televisions satellites are usually in geosynchronous orbit so that you receive a continuous signal.
Communication Satellites Communications satellites act as relay stations in space. Messages are bounced from one part of the world to another. These messages can be telephone calls, TV pictures, or even Internet connections. Communications satellites allow radio, television, and telephone transmissions to be sent live anywhere in the world. Because satellites are in orbit, the signals can be sent instantaneously into space and then redirected to another satellite or directly to their destination.
Global Positioning Systems Global Positioning System (GPS) is a Satellite Navigation System. The Global Positioning System (GPS) is actually a constellation of 27 Earth-orbiting satellites (24 in operation and three extras in case one fails). Each of these 3,000- to 4,000-pound solar-powered satellites circles the globe at about 12,000 miles (19,300 km), making two complete rotations every day. The orbits are arranged so that at any time, anywhere on Earth, there are at least four satellites "visible" in the sky. A GPS receiver's job is to locate four or more of these satellites, figure out the distance to each, and use this information and the triangulation method to deduce its own location.
What Did You Find Out? Photograph A was taken by a satellite in geosynchronous orbit. Two pieces of evidence are the distance from the earth and the fact that the latitude and longitude are on the picture. Photograph A shows how the storm is progressing and which direction it is moving. Photograph B is more detailed showing exactly which part of the U.S. the storm will affect. They both could be used to show size of storms and how they affect us. For future reference of how quickly storms move or where they form above the oceans.