artificial satellite industry



artificial satellite Artificial Satellite - Definition and ExplanationsSource: Wikipedia licensed under CC-BY-SA 3.0.
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The GOES O meteorological satellite before its launch into geostationary orbit.
An artificial satellite is a man-made object sent into space using a launch vehicle and orbiting around a planet or a natural satellite such as the Moon. The speed imparted by the rocket to the satellite allows it to remain practically indefinitely in space by describing an orbit around the celestial body. This, defined according to the mission of the satellite, can take different forms – heliosynchronous, geostationary, elliptical, circular – and be located at more or less high altitudes classified as low, medium or high orbit.

The first artificial satellite Sputnik I was launched by the USSR in 1957. Since that time, more than 5,500 artificial satellites have been placed in orbit (2007). Satellites now play an important role on the economic (telecommunications, positioning, weather forecasting), military (intelligence) and scientific (astronomical observation, microgravity, Earth observation, oceanography, altimetry) roles. In particular, they have become essential instruments for our understanding of the physical universe, the modeling of climate change and the functioning of the information society.

An artificial satellite is made up of a payload, defined specifically for the mission it must fulfill, and an often standardized platform providing support functions such as energy supply, propulsion, thermal control, maintaining direction and communications. The satellite is tracked by a ground control center, which sends instructions and collects data collected through a network of ground stations. To fulfill its mission, the satellite must remain in a reference orbit by orienting its instruments precisely: interventions are necessary at regular intervals to correct the natural disturbances of the orbit generated, in the case of a terrestrial satellite, by the irregularities of the gravity field, the influence of the Sun and the Moon as well as the drag created by the atmosphere which remains in low orbit.

Technical progress now makes it possible to put heavier satellites into orbit (up to 6.5 tonnes for telecommunications satellites), capable of fulfilling ever more sophisticated missions (scientific satellites), with great autonomy. The lifetime of a satellite, which varies according to the type of mission, can reach 15 years. Advances in electronics also make it possible to design micro-satellites capable of carrying out elaborate missions.

The construction of satellites has given rise to a highly specialized industry, but the most complex instruments are still often made by research laboratories. The design of a satellite, which is difficult to reproduce when it is not a telecommunications satellite, is a process which can take around ten years in the case of a scientific satellite. Manufacturing costs which can amount to several hundred million euros and launch costs (around $10,000 to $20,000/kg) currently limit the development of this activity which, apart from the telecommunications sector very profitable for operators, is essentially subsidized by public budgets.

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