Artificial Satellite TypesWritten by Gary Davis
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Navigation Satellites These satellites were of enormous help to transportation companies, especially transportation over water and through air. The US GPS satellites are in Low Earth Orbit (LEO) and can determine position with a precision of 1 cm (0.4 inch). However, that very precise positioning is available for military purposes only. For commercial use precision is less accurate. Navigation satellites are also used for distance measurements for instance between buildings. Weather Satellites Observing earth is task for weather satellites, and then especially what happens in atmosphere. Different kinds of cameras, like infrared and normal cameras are used to observe either same part of earth, from a geostationary orbit, or more closely from polar orbits to get more detailed pictures. These low orbit weather satellites focus more on study of atmosphere than on current weather it self. Military Satellites Very similar to weather satellites, military satellites are also used for observing earth. Generally with higher resolution cameras and instead of normal communications equipment, they use encryption as well. Sometimes these types of satellites have very different types of orbits. For instance a very elliptical orbit which brings satellite as far away from earth as moon and as close to earth that it shortly enters atmosphere, to get as close as possible to earth surface without falling back to earth. Probably many more tactics are used, but for obvious reasons, these are unknown. Scientific Satellites Observing earth for scientific purposes is also very good possible with satellites. Making maps with low polar orbits satellites for instance, but also measuring exact shape of earth, geological research, etc can all benefit greatly from scientific satellites. But scientific satellites are not just used for observing earth. The research of space benefits also from scientific satellites. For instance Hubble Satellite which actually is a huge telescope that orbits earth. Because Hubble telescope doesn’t have to “see” through atmosphere it can produce much clearer and detailed images than earth based telescopes.
Gary Davis is owner of Dish Network Satellite TV, has several years experience in the Satellite TV Industry and has written several articles on satellite TV.
| | What is HDTV?Written by Gary Davis
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The aspect ration of normal TV is 4 x 3 (4/3 times wider than high). An HDTV screen has an aspect ration of 16 x 9, which is also known as wide screen. Higher sound quality using Dolby Surround. The Future of HDTV The FCC (Federal Communications Committee) has mandated that all TV stations in USA have to be able to broadcast HDTV programs by year 2006. The mandates of FCC do not have an impact on just broadcast companies, but also on cable companies and consumers. - Broadcast companies have to invest on new equipment like cameras, editing equipment, etc.
- Cable companies have to convert all of their equipment, including receivers at homes of their clients.
- Consumers may have to buy new equipment, like a top-box to convert digital signals back to analog signals, or even buy a whole new TV set.
HDTV is future, and a really big step forward. We once started with simple black and white TV, then moved to color TV, and wide screen TV. But all those systems were still based on same signals as original black and white TV used. When color TV was introduced it was not possible to force complete population to throw away their black and white TV-sets and buy a color TV set. Therefore a color TV signal still needed to be understandable for a black and white TV. This prohibited improvement of picture quality until age of Digital TV. The need to satisfy older TV sets no longer exists and much higher quality HDTV is available via Satellite TV Systems.
Gary Davis is owner of Dish Network Satellite TV, has several years experience in the Satellite TV Industry and has written several articles on satellite TV.
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