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Satellites are a manmade construction which are launched into orbiting patterns in space. Since the 1960s, more than 26,000 satellites have been launched, for both military and civilian purposes. There are many different types of satellites in the sky, and they have a variety of uses, from transmissions to data gathering.
When Sputnik I, the first satellite, was launched in 1957, it carried a small radio transmitter onboard. This made it the first communications satellite, a common variety. These types of satellite were originally used for long-distance telephone transmissions, but later were adapted to carry satellite TV signals as well as serve many military purposes. Types of satellites used for communications often use a geostationary orbit, meaning that they rotate around the equator once per day, in effect turning with the Earth.
Astronomic satellites, or Space observatories, are used for gathering data from outer space. One of the most famous is the Hubble Telescope, launched by the United States National Aeronautics and Space Administration (NASA) in conjunction with the European Space Agency (ESA). The Hubble Space telescope is responsible for some of our best images of deep space objects, including far away nebula and planets.
If you look in the newspaper or flip on the TV to find a weather report, you are getting information obtained from weather satellites. One of the most common types of satellite, these objects are able to monitor Earth’s climate and weather systems from above and relay transmissions down to controllers. Weather satellites also can give data about environmental conditions, such as the ozone layer hole over Antarctica. Most types of satellites used to monitor weather either follow a geostationary orbital path or a north-south polar orbit.
One of the most storied types of satellites is the sneaky spy or reconnaissance satellite. Employed by military operations, these are used as tools for intelligence gathering, and frequently factor into fiction and conspiracy theories. In actuality, spy satellites are one of the most useful tools a military can have for preventative action, as they can provide information about sudden changes in the military positioning of hostile or threatening nations, even in remote places. These types of satellites are also used to monitor the production of nuclear materials worldwide, to give concerned nations early warnings if a country is producing nuclear weapons.
Satellites can be a useful tool, but a dangerous one. Critics suggest that spy satellites and those with Earth observation capabilities may result in a breech of privacy. Additionally, many fear that space weapons will evolve from satellite technology, turning the sky into a literal battle field. At least currently, satellites remain a tool for knowledge and information gathering and are an incredibly useful part of modern life and information technology. With only half a century gone since the launching of Sputnik and such a variety of applications, you can only guess at the new ways satellites will come to be used in the future.
Can anyone give an exact number of how many satellites are orbiting earth today and what each of those satellites do?
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