Artificial satellite
From Halbeeg, the open encyclopedia · Af-Soomaali
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An artificial satellite is a technological instrument built by humans and launched from Earth to orbit a planet or other celestial body. The term "artificial" distinguishes it from natural satellites that naturally orbit Earth.
An artificial satellite remains in its orbit through the balance between the gravitational pull of the body it orbits and its own velocity. If the velocity is sufficient, the satellite continues to orbit steadily. The altitude of the orbit determines the period of one revolution: satellites in low Earth orbit complete a full orbit in hours, while those at higher altitudes take longer.
History
The first artificial satellite to achieve orbit was Sputnik 1, launched by the Soviet Union in 1957. This event triggered a space race between the Soviet Union and the United States. Since then, many countries and private companies have launched artificial satellites, with the total number reaching into the tens of thousands.
Types and applications
Artificial satellites are classified by their use. Communications satellites transmit television, telephone, and internet signals. Earth observation and remote sensing satellites capture images for weather monitoring, night vision, and environmental mapping. Navigation satellites such as those in the GPS system provide users with their geographic location. There are also research satellites and military satellites.
Commonly used orbits
Low Earth orbit (LEO) is suited for imaging and communication networks with multiple satellites. Geostationary orbit lies above the equator, where a satellite orbits at the same speed as Earth's rotation, appearing stationary when viewed from the ground—an arrangement that facilitates ground-based communication networks.
Space debris
Defunct satellites, defunct rocket stages, and debris from collisions continue to orbit in many orbital regions. This debris poses a hazard to functioning satellites, as velocities are extremely high. Space agencies attempt to track large objects, and regulations have been developed to require satellites to be deorbited into the atmosphere or moved to uninhabited orbits.