A satellite is any object that orbits or revolves around another. In addition to the Moon (a natural satellite), thousands of man-made satellites (used for communication, weather forecasting, research and surveillance) also orbit the Earth. How do they work? How are they launched? How do they communicate? This satellite tour of the Web is my contribution to Space Day.
NASA's Extreme Ultraviolet Explorer (EUVE) Satellite revolves around the Earth every ninety-six minutes in a circular orbit at an altitude of 330 miles. It was launched in 1992 to study extreme ultraviolet sources in space. How does it transmit its findings to scientists back on Earth? By sending its data to a Tracking and Data Relay Satellite System (TDRSS) which circles above the Earth in a 24-hour rotation. If you have eight friends in a room, you can simulate these rotations and revolutions by each taking a role as a satellite or a planet. To help you visualize the problem, be sure to view the http://cse.ssl.berkeley.edu/lessons/indiv/dataflow/animation.html" target="_blank">Java animation first.
Start your exploration by clicking on the large title image How Satellites Work. "Man-made satellites circle the Earth in many ways including polar and geostationary orbits." A satellite in a polar orbit travels over the North and South Poles at a height ranging from several hundred miles to several thousand miles above Earth. A satellite in a high-altitude, geostationary orbit (also known as geosynchronous) circles the earth once every twenty-four hours, the same amount of time it takes for the Earth to spin on its axis. To maintain this rotation, a geostationary satellite must travel exactly 22,237 miles above the Earth's equator.
Not only is your room filled with it, but space is also crowded with junk. "The problem is that the near-earth space environment - where most satellites, the Shuttle, Mir, and the coming International Space Station orbit the earth - is cluttered with man-made debris and naturally occurring meteoroids." These NASA scientists study space junk and analyze high-speed space collisions. They perform crash tests in their laboratory and develop shields to protect our expensive spacecraft.
Would anyone mind if I gave this site six stars? From The Tech Museum of Innovation, comes this beyond-wow introduction to satellites, suitable for all ages. After you've learned the what, why and how of man-made satellites, the don't-miss-it click is the Java-based Satellite Construction Set. First, choose a mission for your satellite. Will it be direct broadcast television, remote sensing or scientific research? Then correctly install each of five subsystems (from a list of eight) by clicking and dragging them into place.
For teens and adults, this illustrated introduction to satellites includes sections on "Launching a Satellite into Orbit", "How Many Are Up There?" and "Firsts in Satellite History." It was the Russians who launched Sputnik, the world's first satellite, on October 4, 1957. The Americans followed four months later, with their first satellite: the Explorer I. It may surprise you (as it did me) to learn the United States is NOT the country with the most satellites in orbit. Which country holds that title? I'll let you look it up.