A satellite is an object that orbits around something else. For example, the moon orbits around the earth, and it is a satellite. However, when most people think about satellites, they usually think of the man-made machines that send radio waves down to Earth and are used for communication.
The first artificial (man-made satellite) was a Soviet satellite named Sputnik. It was launched in the fall of 1958. It was a metal ball the size of a basketball that weighed 184 pounds. It doesnít seem so great now, but it was amazing at the time! It was only up in space for nine months. It fell through the atmosphere and burned up. Soon the United States launched its first satellite, Explorer I in January of 1958. Explorer I was called a research satellite. It helped scientists study rays and radiation in space. Like Explorer I, most early satellites were used for science research only.
Types of Satellites
There are several more types of satellites other than the research satellite. There are navigation, communication, weather, earth observing, and military satellites.
Weather satellites help scientists study forecasts and weather patterns. Most weather satellites orbit on the polar orbit. The satellite shown in the photograph on the left is the Vanguard 2. It was designed to measure cloud-cover over the daylight part of its orbit.
The next type of satellite is used for communication. This kind of satellite receives messages and sends them back to another place. They do this with thousands of calls all at the same time. These machines never rest. Cell phones, satellite television systems, and governments use this type of satellite. The photograph on the right is of the Military Strategic and Tactical Relay satellite (MILSTAR). It is a United States government satellite communications system. It is used to provide secure, worldwide communications during wartime for United States military users.
Navigation satellites are relied upon by aircraft and ships to tell them where they are located. Global positioning systems (GPS) use this type of satellite too.
Earth observation satellites are another type of satellite. Earth observing satellites help to keep track of the weather and the environment. They are also used for mapping. Scientists know what the earth is recently like with the help of these satellites. The satellites take photos of the earth which can be applied to maps. To view images of Earth taken by a satellite visit the Space Imaging website.
The last type of satellite is for the military. Military satellites are like all the other types, but they are specially designed and used for military purposes. Some military satellites are called spy satellites. They might be used to find out about missile launches, the courses of ships at sea, and to track the movement of military equipment.
Types of Orbit
There are about 9,000 satellites in orbit around the earth, and there are different types of satellite orbits. The first is the Low Earth Orbit, or L.E.O. L.E.O. is 248 to 621 miles high from earth. L.E.O. is good for weather, survey and scientific satellites.
Next is the G.E.O. which stands for Geostationary Orbit. The G.E.O. orbit is about 22,300 miles above the equator. G.E.O. is good for communication and surveying satellites.
The E.O. (Elliptical Orbit) is from 24,855 to only 124 miles high. It changes from high to low distance. E.O. is good for military and surveillance satellites.
There is also the P.O. which is the Polar Orbit. Polar Orbit is another low earth orbit used for mapping, navigation and surveillance.
is the H.E.O. or High Earth Orbit. H.E.O. varies from 6,214 to 12,428 miles from
Earth, and it is good for navigation.
A satellite is often launched from the inside of a rocket. The satellite may be folded up in the rocketís nosecone. The engines fire, and the rocket blasts off. Then, the first stage of the rocket falls away from the rest of the rocket. The first stage includes the main rockets. Next, the satellite is launched. Its thrusters blast it into orbit. The satellite parts, including solar energy panels and antennas, unfold. Now the satellite is in its orbit and is tested and starts its working time in space.
know what you are thinking now. You probably want to know what happens to
old worn out satellites. Guess!
Parker, Steve. Satellites now and Future. Austin, Texas: Dillon Press, 1998.
"Types of artificial satellites." World book online. December 10, 2004 <http://www.worldbookonline.com/wb/article?id=ar492220&st=satellite&sc=2>.
Photograph of Sutnik 1, Vanguard 2 weather satellite, and MILSTAR communications satellite have been released into the public domain under the terms of the GNU Free Documentation License from Wikipedia, the Free Encyclopedia. <http://en.wikipedia.org/wiki/Main_Page>.
Copyrighted animations of satellites from "Microsoft Office Online" <http://office.microsoft.com/clipart/default.aspx?lc=en-us&cag=1> (October-March, 2004-2005). Clip art available only to licensed users for non-commercial purposes.