Artificial Satellite TypesWritten by Gary Davis
Artificial Satellite Types By Gary DavisDish-Network-Satellite-TV.ws Webmasters: You may reprint this article in its entirety, providing you leave Byline and About Author sections intact, including links to Dish Network Satellite TV. A celestial body orbiting another celestial body of larger size is a satellite. An artificial satellite is a manufactured object or vehicle intended to orbit earth, moon, or another celestial body. Since October 4th, 1957 humanity is capable of putting artificial satellites in orbit around earth. The Russians were first with Sputnik; a small satellite that orbited earth for a couple of months and transmitted beeps for 21 days. The USA launched its first satellite on January 31st, 1958. This satellite was named Explorer 1, and through data transmitted back to earth by Explorer 1, scientists discovered van Allen radiation belts, zones in space around earth, and planets Jupiter and Saturn, containing high-energy protons and electrons. 50 years ago artificial satellites did not exist. Since Sputnik more than 4800 satellites have been launched by governments and private companies around world. Satellites are used for satellite TV of course, but there are many more purposes for satellites. Types of Satellites The Moon is a satellite of earth; earth is a satellite of sun. The first is called a moon, second a planet. Man made (artificial) satellites orbit any celestial body and are always called a satellite, whether they orbit earth, moon, sun or any other celestial body. We use satellites for different purposes and all satellites can be placed in one of following categories: Communications Satellites Distribution of television and audio signals, and telephone connections via satellite are done by Communications Satellites. These types of communications typically need a satellite in geostationary orbit. In 1964 US Department of Defense launched first satellite that was placed in geostationary orbit. This satellite was named Syncom 3. Today geostationary satellites are used to provide voice, audio and video communications like satellite TV by Dish Network Satellite.
| | What is HDTV?Written by Gary Davis
What is HDTV? By Gary Davis Dish-Network-Satellite-TV.wsWebmasters: You may reprint this article in its entirety, providing you leave Byline and About Author sections intact, including links to Dish Network Satellite TV. High Definition TeleVision is what HDTV literally means. But high definition compared to what? In order to answer this question, we need to know a bit about original analog TV system. Analog TV 30 images per second (in Europe 25) are shown by normal analog TV sets. It does this by writing image lines horizontally, 525 lines in one image (In Europe 625) on screen. The number of pixels on one line is about 500. This would be a definition of 500 pixels per line by 525 (or 625) lines. Compared to modern computer monitors this is really bad. Even lowest resolutions monitors have higher resolutions (640 x 480) than an analog TV. HDTV - High Definition TeleVision HDTV is high resolution Digital TeleVision (DTV) combined with Dolby Digital Surround Sound (AC-3). There are 18 different formats defined for Digital TV of which 6 are considered to be HDTV: Active Lines Per Picture | Pixels Per Line | Aspect Ratio | Frame Rate | Scanning Approach | The difference between Progressive and Interlaced is not difficult. It has to do with how one image is built up. With interlaced technology odd lines are shown first and then even lines are shown. The lines are shown in this order: 1,3,5,….521, 523, 525, 2, 4, 6,…. 522, 524, 1, 3, etc. This means that every 1/60 of a second a half image is shown. This often results in flickering, which can be tiring for eyes. Progressive technology manages to show a whole image every 1/60 of a second, resulting in a much smoother picture. How Is HDTV Better? - Normal TV has a resolution of about 210.000 pixels. An HDTV screen has a resolution of upto 2.000.000 pixels, which gives up to 10 times more picture detail.
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