Earth satellite

Earth satellite

 man-made object launched into a temporary or permanent orbit around the Earth. Spacecraft of this type may be either manned or unmanned, the latter being the most common.

      The idea of an artificial satellite in orbital flight was first suggested by Sir Isaac Newton (Newton, Sir Isaac) in his book Philosophiae Naturalis Principia Mathematica (1687). He pointed out that a cannonball shot at a sufficient velocity from atop a mountain in a direction parallel to the horizon would go all the way around the Earth before falling. Although the object would tend to fall toward the Earth's surface because of gravitational force, its momentum would cause it to descend along a curved path. Greater velocity would put it into a stable orbit, like that of the Moon, or direct it away from the Earth altogether. On Oct. 4, 1957, nearly three centuries after Newton had proposed his theory, the Soviet Union launched the first Earth satellite, Sputnik I. Sputnik circled the Earth every 96 minutes, and its simple radio signal was heard by scientists and radio operators across the world. The United States orbited its first satellite, Explorer 1, three months later (Jan. 31, 1958). Explorer, though much smaller than Sputnik, was instrumented to detect radiation and discovered the innermost of the two Van Allen radiation belts, a zone of electrically charged solar particles that surrounds the Earth.

      Since these initial efforts, more than 5,000 Earth satellites have been orbited by at least 15 different nations. The satellites vary widely in size and design, ranging from a tiny sphere of several pounds equipped with only two radio transmitters to heavily instrumented space laboratories weighing many tons. They are equally diverse in function. Scientific satellites are chiefly used to collect data about the Earth's surface and atmosphere and to make astronomical observations. Weather satellites (weather satellite) transmit photographs of cloud patterns and measurements of other meteorological conditions that aid in weather forecasting, while communications satellites relay telephone calls, radio and television programs, and data communications between distant parts of the world. Navigation satellites enable the crews of oceangoing vessels and airplanes to determine the position of their craft in all kinds of weather. Some satellites have distinctly military applications, such as reconnaissance and surveillance.

      Satellites can be placed in any number of different orbits. The particular path selected is largely determined by the function of the spacecraft. Most weather and reconnaissance satellites, for example, are fired into a polar orbit in which the Earth's polar axis is a line on the orbital plane. Because the Earth rotates under polar-orbiting satellites, they pass over its entire surface within a given time period, providing full global coverage. Communications satellites, on the other hand, are generally placed into an equatorial orbit, which enables them to circle the most densely populated regions of the Earth from west to east. Moreover, communications satellites comprising a network or system are nearly always launched to a distance of 22,300 mi (35,890 km) above the Earth. At this altitude, the motion of a satellite becomes synchronized with the Earth's rotation, causing the craft to remain fixed over a single location. If properly positioned, three communications satellites travelling in such a synchronous orbit can relay signals between stations around the world. See also spacecraft.

* * *


Universalium. 2010.

Игры ⚽ Нужно сделать НИР?

Look at other dictionaries:

  • earth satellite — Any man made body, incl spacecraft, launched by rocket into space and put into orbit round the earth ● satellite * * * earth satellite, a satellite of the earth made by man, especially a metal sphere or other structure, launched by rockets into… …   Useful english dictionary

  • earth satellite — Žemės palydovas statusas T sritis radioelektronika atitikmenys: angl. earth satellite vok. Erdsatellit, m rus. спутник Земли, m pranc. satellite de la Terre, m …   Radioelektronikos terminų žodynas

  • earth satellite — /ˈɜθ sætəlaɪt/ (say erth satuhluyt) noun 1. a satellite (def. 5) which orbits the earth. 2. the moon …  

  • orbit of earth satellite — Žemės palydovo orbita statusas T sritis radioelektronika atitikmenys: angl. orbit of earth satellite vok. Erdsatellitumlaufbahn, f rus. орбита спутника Земли, f pranc. orbite d un satellite de Terre, f …   Radioelektronikos terminų žodynas

  • inclination of an orbit of an Earth satellite — Žemės palydovo orbitos posvyris statusas T sritis radioelektronika atitikmenys: angl. inclination of an orbit of an Earth satellite vok. Neigung einer Umlaufbahn eines Erdsatelliten, f rus. наклонение орбиты спутника Земли, n pranc. inclinaison d …   Radioelektronikos terminų žodynas

  • artificial earth satellite — satellite which has been manufactured and put in orbit around any heavenly body …   English contemporary dictionary

  • Satellite — This article is about artificial satellites. For natural satellites, also known as moons, see Natural satellite. For other uses, see Satellite (disambiguation). An animation depicting the orbits of GPS satellites in medium Earth orbit …   Wikipedia

  • Earth Sciences — ▪ 2009 Introduction Geology and Geochemistry       The theme of the 33rd International Geological Congress, which was held in Norway in August 2008, was “Earth System Science: Foundation for Sustainable Development.” It was attended by nearly… …   Universalium

  • satellite communication — Introduction  in telecommunication, the use of artificial satellites to provide communications links between various points on Earth (Earth satellite). Communications satellites relay voice, video, and data signals between widely separated fixed… …   Universalium

  • satellite — satellited, adj. /sat l uyt /, n. 1. Astron. a natural body that revolves around a planet; a moon. 2. a country under the domination or influence of another. 3. something, as a branch office or an off campus facility of a university, that depends …   Universalium

Share the article and excerpts

Direct link
Do a right-click on the link above
and select “Copy Link”