This is different from the natural satellites, or moons, that orbit planets, dwarf planets and even asteroids. Artificial satellites are used to study the Earth, other planets, to help us communicate, and even to observe the distant Universe. The first artificial satellite was the Soviet Sputnik 1 mission, launched in
The Columbia Encyclopedia, 6th ed. Copyright The Columbia University Press artificial satelliteobject constructed by humans and placed in orbit around the earth or other celestial body see also space probe.
The first artificial satelliteSputnik I, was launched on Oct. During the first decade of space explorationall 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.
At heights less than mi 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 Artificial satellites, 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.
Once above the lower atmosphere, the rocket bends to Artificial satellites 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. A polar orbit lies in the plane passing through both the north and south poles.
At a height of mi kmthe period of a circular orbit is 90 min; at mi kmit increases to min. At a height of 22, mi 36, kma 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. Tracking and Telemetry Since more than 1, 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 satellites measure fundamental properties of outer space, e. 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 Stationwhose first permanent crew boarded incontinues this work.
Communications satellites provide a worldwide linkup of radio, telephone, and television. The first communications satellite was Echo 1; launched init 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.This timeline of artificial satellites and space probes includes unmanned spacecraft including technology demonstrators, observatories, lunar probes, and interplanetary probes.
First satellites from each country are included.
Not included are most earth science satellites, commercial satellites or manned missions.. Key: Year – Origin – . Related WordsSynonymsLegend: Switch to new thesaurus Noun 1. artificial satellite - man-made equipment that orbits around the earth or the moon orbiter, satellite astronomy satellite - a satellite equipped with a telescope to observe infrared radiation communications satellite - an artificial satellite that relays signals back to earth; .
Nov 14, · Artificial satellites are human-made, orbital objects sent into space. (There are several thousand of these in orbit around Earth.) Our moon is the only natural satellite that.
satellite 1. a celestial body orbiting around a planet or star 2. a man-made device orbiting around the earth, moon, or another planet transmitting to earth scientific information or used for communication 3. a country or political unit under the domination of a foreign power 4.
a subordinate area or community that is dependent upon a larger adjacent.
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The uses of Artificial satellites are: They are used for communication purpose. Carry instrument or passengers to perform experiments in space. For Weather Forecasting System.