Advantages of Artificial Satellite
- One can see the live coverage of various things by even sitting idle at home. And this is all due to the artificial satellite which usually takes the coverage directly. Now television is the part of almost every family and its broad casting is basically done with the help of man made/ artificial satellite.
- This satellite is alarm gong for the life of the farmers. The farmer life is directly or indirectly related to the crops. And the satellite provides early information about the chance of flood etc. which is actually an alarm gong for the farmer and is also very useful for them.
- The discoveries in other planets are all dependent upon the satellite. One can now think that life can also be possible in other planets all due to the satellite. The man has reached the mars planet; it is also because of man made satellites.
- Not only this man made satellite also provides us the detailed analysis of weather which can be useful to every one of us.
- Two persons sitting in the different part of word can contact with each other easily and this also because of the presence of man made satellites.
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This Timeline of artificial satellites and space probes includes unmanned spacecraft including technology demonstrators, observatories, lunar probes, ...
artificial satellite object constructed by humans and placed in orbit around the earth or other celestial body (see also space probe ). The satellite is lifted from the earth's surface by a rocket and, once placed in orbit, maintains its motion without further rocket propulsion. The first artificial satellite, Sputnik I, was launched on Oct. 4, 1957, by the USSR; a test payload of a radio beacon and a thermometer demonstrated the feasibility of orbiting a satellite. The first U.S. satellite, Explorer I, launched on Jan. 31, 1958, returned data that was instrumental in the discovery of the Van Allen radiation belts . During the first decade of space exploration, all of the satellites were launched from either the United States or USSR. Today, there are more than three dozen launch sites in use or under construction in more than a dozen countries. Satellite Orbits If placed in an orbit high enough to escape the frictional effects of the earth's atmosphere, the motion of the satellite is controlled by the same laws of celestial mechanics that govern the motions of natural satellites, and it will remain in orbit indefinitely. At heights less than 200 mi (320 km) the drag produced by the atmosphere will slow the satellite down, causing it to descend into the denser portion of the atmosphere where it will burn up like a meteor. To attain orbital altitude and velocity, multistage rockets are used, with each stage falling away as its fuel is exhausted; the effect of reducing the total mass of the rocket while maintaining its thrust is to increase its speed, thus allowing it to achieve the required velocity of 5 mi per sec (8 km per sec). At this speed the rocket's forward momentum exactly balances its downward gravitational acceleration, resulting in orbit. Once above the lower atmosphere, the rocket bends to a nearly horizontal flight path, until it reaches the orbital height desired for the satellite. Unless corrections are made, orbits are usually elliptical; perigee is the point on the orbit closest to the earth, and apogee is the point farthest from the earth. Besides this eccentricity an orbit of a satellite about the earth is characterized by its plane with respect to the earth. An equatorial orbit lies in the plane of the earth's orbit. A polar orbit lies in the plane passing through both the north and south poles. A satellite's period (the time to complete one revolution around the earth) is determined by its height above the earth; the higher the satellite, the longer the period. At a height of 200 mi (320 km), the period of a circular orbit is 90 min; at 500 mi (800 km), it increases to 100 min. At a height of 22,300 mi (36,000 km), a satellite has a period of exactly 24 hr, the time it takes the earth to rotate once on its axis; such an orbit is called geosynchronous. If the orbit is also equatorial, the satellite will remain stationary over one point on the earth's surface. Tracking and Telemetry Since more than 1,000 satellites are presently in orbit, identifying and maintaining contact requires precise tracking methods. Optical and radar tracking are most valuable during the launch; radio tracking is used once the satellite has achieved a stable orbit. Optical tracking uses special cameras to follow satellites illuminated either by the sun or laser beams. Radar tracking directs a pulse of microwaves at the satellite, and the reflected echo identifies both its direction and distance. Nearly all satellites carry radio transmitters that broadcast their positions to tracking antennas on the earth. In addition, the transmitters are used for telemetry, the relaying of information from the scientific instruments aboard the satellite. Types of Satellites Satellites can be divided into five principal types: research, communications, weather, navigational, and applications. Research satellites measure fundamental properties of outer space, e.g., magnetic fields, the flux of cosmic rays and micrometeorites, and properties of celestial objects that are difficult or impossible to observe from the earth. Early research satellites included a series of orbiting observatories designed to study radiation from the sun, light and radio emissions from distant stars, and the earth's atmosphere. Notable research satellites have included the Hubble Space Telescope , the Compton Gamma-Ray Observatory, the Chandra X-ray Observatory, the Infrared Space Observatory, and the Solar and Heliospheric Observatory (see observatory, orbiting ). Also contributing to scientific research were the experiments conducted by the astronauts and cosmonauts aboard the space stations launched by the United States ( Skylab ) and the Soviet Union ( Salyut and Mir ); in these stations researchers worked for months at a time on scientific or technical projects. The International Space Station, currently under construction, will continue this work. Communications satellites provide a worldwide linkup of radio, telephone, and television. The first communications satellite was Echo 1 ; launched in 1960, it was a large metallized balloon that reflected radio signals striking it. This passive mode of operation quickly gave way to the active or repeater mode, in which complex electronic equipment aboard the satellite receives a signal from the earth, amplifies it, and transmits it to another point on the earth. Relay 1 and Telstar 1, both launched in 1962, were the first active communications satellites; Telstar 1 relayed the first live television broadcast across the Atlantic Ocean. However, satellites in the Relay and Telstar program were not in geosynchronous orbits, which is the secret to continuous communications networks. Syncom 3, launched in 1964, was the first stationary earth satellite. It was used to telecast the 1964 Olympic Games in Tokyo to the United States, the first television program to cross the Pacific Ocean. In principle, three geosynchronous satellites located symmetrically in the plane of the earth's equator can provide complete coverage of the earth's surface. In practice, many more are used in order to increase the system's message-handling capacity. The first commercial geosynchronous satellite, Intelsat 1 (better known as Early Bird ), was launched by COMSAT in 1965. A network of 29 Intelsat satellites in geosynchronous orbit now provides instantaneous communications throughout the world. In addition, numerous communications satellites have been orbited by commercial organizations and individual nations for a variety of telecommunications tasks. Weather satellites , or meteorological satellites, provide continuous, up-to-date information about large-scale atmospheric conditions such as cloud cover and temperature profiles. Tiros 1, the first such satellite, was launched in 1960; it transmitted infrared television pictures of the earth's cloud cover and was able to detect the development of hurricanes and to chart their paths. The Tiros series was followed by the Nimbus series, which carried six cameras for more detailed scanning, and the Itos series, which was able to transmit night photographs. Other weather satellites include the Geostationary Operational Environmental Satellites (GOES), which send weather data and pictures that cover a section of the United States; China, Japan, India, and the European Space Agency have orbited similar craft. Current weather satellites can transmit visible or infrared photos, focus on a narrow or wide area, and maneuver in space to obtain maximum coverage. Navigation satellites were developed primarily to satisfy the need for a navigation system that nuclear submarines could use to update their inertial navigation system. This led the U.S. navy to establish the Transit program in 1958; the system was declared operational in 1962 after the launch of Transit 5A. Transit satellites provided a constant signal by which aircraft and ships could determine their positions with great accuracy. In 1967 civilians were able to enjoy the benefits of Transit technology. However, the Transit system had an inherent limitation. The combination of the small number of Transit satellites and their polar orbits meant there were some areas of
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Answers:Artificial satellites are man-made objects placed into Earth's orbit. They are currently used to aid in communications, navigation, observation (spying), and observation (astronomy and meteorlogical), and include a manned space station, and lots of old junk. The advantages of placing these objects in space is that it gives us a vantage point beyond our horizon; which lets us see and report things all around the globe in real time. Space based orbiting objects are also above most of our atmosphere, giving them a much clearer view of space then is available at the surface. Soon we will be developing spacebased storage and assembly facilities, which will allow us to work in space without having to relaunch and discard all equipment on every single mission. .
Answers:The main advantage is a somewhat "fixed" location in the sky relative to the Earth, and relative ease in repositioning them into other fixed positions. There are also some advantages to lower orbits. GPS satellites are NOT geostationary. They rely on precise on board time signals and precise knowledge of their orbital ephemerii and a large enough "constellation" such that 3 or more are above the horizon and able for your receiver to pick up at any point in time over nearly the whole planet. With a sophisticated control system you can make do with several low orbiting satellites. The advantage with a low orbit is they are cheaper to launch, and can cover a broader range of latitudes ( geostationary orbits MUST orbit over the equator to be geostationary. That means at higher latitudes they are lower on the horizon. At some point they become unusuable, so are not suitable for high bandwidth or reliable communications in places like northern Europe or Russia.) Geo satellites would make EXCELLENT relay satellites for constellations of lower orbiting spacecraft, permitting spacecraft to spacecraft communication. Instead of having to relay between several to get around the globe (*) You could go up to a geo, over to another geo and back down to the other low orbiter and get almost anywhere. You might need two hops between geos in some circumstances. (*)which would also require a much more densly populated constellation. Iridium was named that because the original plan was to have as many satellites as the element Iridium has electrons; 77!
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