In the 1950s, the world was a very different place. Radio and television signals could only be received by those who lived near the transmitters, and phone signals could only travel by wire. Weather reports were often unreliable. There were few sources of news or information.
Then the Soviet Union launched the first artificial satellite, Sputnik, in October of 1957, touching off a war of science with the United States. Within ten years humans visited the moon. Although the Race for Space has ended, space travel has not. The U.S. Space Surveillance Network currently tracks 560 active satellites. Another 7,500 objects are orbiting the earth and are either non-functional satellites or other space debris.
The modern world would not be possible without satellites. Satellites provide global communication, information about weather and the environment, entertainment, and vital navigation and rescue information. In spite of the technologyâ€™s military origins, many corporations now own satellites for communication or data-gathering purposes.
Satellites also provide an excellent observation platform. An object in orbit can see much more of the world than an observer on the ground. Orbital platforms also have a better view of things above our atmosphere, which is why the Hubble Space Telescope can see farther than anything on earth.
In February 2009, a major collision occurred between two communications satellites in the Earths€™s orbit. The collision involved one American, Iridium 33 (owned by Iridium Satellite) and the other Russian, Kosmos 2251 (owned by the Russian Space Forces). Both satellites were destroyed upon impact, propelling hundreds of pieces of satellite wreckage into orbit. Even though the American satellite was operational, it is interesting to note that the Russian satellite had been out of service since 1995. Satellite wreckage creates orbital debris. Orbital debris creates satellite pollution. Consequently, this recent collision has brought to the forefront the issue of satellite pollution and the hazards created by orbital debris. There have been other satellite collisions previously, most of them smaller in scope.
Collectively, all these collisions have left an accumulation of thousands of speeding debris in space that cannot be controlled. There are numerous satellites in orbit, including earth-tracking, weather, nuclear, or unmanned satellites owned by nations all over the world. When fragments of debris whirling through space at high speeds are added to the mix, the threat of other collisions is increased. In addition, there is the potential to trigger a chain of collisions. Fragments of debris falling into the Earth’s atmosphere unexpectedly may pose safety problems for aircraft aviation, as well as cause inclement weather conditions, possibly earthquakes. Scientists are keeping a watchful eye on the orbital debris, which could remain in orbit up to 10,000 years! US Space Surveillance Network, a division of the Department of Defense, is a space tracking network. The job of the Surveillance Network is to regularly monitor and calculate the risk of satellite collision and provide precise warnings to operators when close encounters occur. Its primary focus is the protection of priority spacecraft, which includes military satellites, the International Space Station, and space shuttle launches and their astronauts. The problem is — there is just not enough manpower or computer capabilities to provide this service for all satellites in orbit. Near-miss satellite collisions are surprising common, occurring numerous times each day. Controlling satellite pollution is a huge challenge facing space experts and scientists internationally.
Satellite Life Time
While space itself is infinite, the ideal orbits for satellites are not. Communications, weather and television satellites are typically placed in geostationary orbits above the equator, where they remain in one position over the earth. This band now contains hundreds of objects. Geostationary orbits are what allows a television satellite dish to remain in a fixed position.
Polar orbits are useful for mapping and photographing objects on the ground. The satellite stays in a single track, collecting information at the earth rotates below it. This orbit covers more area than any other type. NOAA uses polar orbits as part of its Search and Rescue Satellite program (SARSAT).
When a satellite is no longer able to function, it may continue to orbit or slowly fall into the atmosphere. Either fate can result in hazards to functional satellites, spacecraft, or even people on the ground. There is currently no practical way to collect and dispose of space junk.