What is a satellite?
A satellite is basically any object that revolves around a planet in a circular or elliptical path. The moon is Earth's original, natural satellite, and there are many artificial satellites as well, usually closer to Earth.
Although anything that is in orbit around Earth is technically a satellite, the term "satellite" is typically used to describe a useful object placed in orbit purposely to perform some specific mission or task. We commonly hear about weather satellites, communication satellites and scientific satellites.
Not so long ago, satellites were exotic, top-secret devices. They were used primarily in a military capacity, for activities such as navigation and espionage. Now they are an essential part of our daily lives. We see and recognize their use in weather reports, television transmission by DIRECTV and the DISH Network, and everyday telephone calls. In many other instances, satellites play a background role that escapes our notice:
Original information courtesy of HowStuffWorks.com
- The path a satellite follows is an orbit. In the orbit, the farthest point from Earth is the apogee, and the nearest point is the perigee.
- Artificial satellites generally are not mass-produced. Most satellites are custom built to perform their intended functions. Exceptions include the GPS satellites (with over 20 copies in orbit) and the Iridium satellites (with over 60 copies in orbit).
- Approximately 23,000 items of space junk -- objects large enough to track with radar that were inadvertently placed in orbit or have outlived their usefulness -- are floating above Earth. The actual number varies depending on which agency is counting. Payloads that go into the wrong orbit, satellites with run-down batteries, and leftover rocket boosters all contribute to the count. This online catalog of satellites has almost 26,000 entries!
Although anything that is in orbit around Earth is technically a satellite, the term "satellite" is typically used to describe a useful object placed in orbit purposely to perform some specific mission or task. We commonly hear about weather satellites, communication satellites and scientific satellites.
Not so long ago, satellites were exotic, top-secret devices. They were used primarily in a military capacity, for activities such as navigation and espionage. Now they are an essential part of our daily lives. We see and recognize their use in weather reports, television transmission by DIRECTV and the DISH Network, and everyday telephone calls. In many other instances, satellites play a background role that escapes our notice:
- Some newspapers and magazines are more timely because they transmit their text and images to multiple printing sites via satellite to speed local distribution.
- Before sending signals down the wire into our houses, cable television depends on satellites to distribute its transmissions.
- The most reliable taxi and limousine drivers are sometimes using the satellite-based Global Positioning System (GPS) to take us to the proper destination.
- The goods we buy often reach distributors and retailers more efficiently and safely because trucking firms track the progress of their vehicles with the same GPS. Sometimes firms will even tell their drivers that they are driving too fast.
- Emergency radio beacons from downed aircraft and distressed ships may reach search-and-rescue teams when satellites relay the signal.
Original information courtesy of HowStuffWorks.com