Satellite
From Halbeeg, the open encyclopedia · Af-Soomaali
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A satellite is an object built by humans and launched into the upper atmosphere, usually to orbit the Earth or another body in space. The Somali term "dayax gacmeed" literally means "satellite made by hand," referring to an artificial satellite distinct from natural celestial bodies orbiting the Earth.
Satellites are placed in the atmosphere by rockets with sufficient thrust to overcome Earth's gravity. Once the proper velocity and altitude are achieved, the device enters an orbit where it continues in motion without requiring continuous fuel consumption.
How orbital motion works
Orbital motion depends on the balance between Earth's gravitational pull and the satellite's forward velocity. The satellite is constantly falling toward Earth, but its forward motion causes it to "miss" the planet. The altitude of the orbit determines the time required to complete one pass: lower orbits near the surface take only hours, while higher orbits known as geostationary remain fixed above a single point on Earth and take one day to complete.
Types and applications
Satellites exist for communications (telephone, television, internet), weather and climate monitoring, Earth observation and imaging, navigation such as GPS systems, and scientific research including space-based telescopes. Some are crewed spacecraft carrying astronauts, such as space stations.
Components
Most satellites have a structural frame (bus) holding equipment, typically including power systems using solar panels and batteries, a thermal control system, an attitude control system directing the satellite's orientation, and radio communication with ground stations. A failure in any critical subsystem can disable the entire satellite, since repair in orbit is usually not feasible.
History and current issues
The first satellite launched by humans was Sputnik 1, sent by the Soviet Union in 1957, marking the beginning of the space race. Since then, tens of thousands of objects have been placed in orbit. A significant current concern is space debris (space debris): fragments and defunct equipment remaining in orbit, which pose collision hazards to operational satellites.