Satellitt

Satellitt is a body that orbits a planet or another larger object. In astronomy, satellites are categorized as natural satellites, such as moons, and artificial satellites, which are spacecraft placed into orbit by humans. Natural satellites orbit planets and vary in size, often influencing their primary body through tides and illumination. The best-known natural satellite is Earth's Moon.

Artificial satellites have a wide range of purposes. Communications satellites relay telephone, television, and data signals. Weather satellites monitor climate and atmospheric conditions. Navigation satellites provide positioning services, such as GPS. Scientific and Earth-observation satellites collect data about the Earth, space weather, and other celestial bodies. Some satellites are used for military or security applications, including reconnaissance and secure communications.

Orbits and operation: satellites stay in orbit because of gravity. Orbits are described by altitude and shape. Low Earth Orbit (LEO) usually lies about 160 to 2,000 kilometers above the surface. Medium Earth Orbit (MEO) extends higher, up to roughly 35,786 kilometers, where geostationary orbits are located. A geostationary orbit (GEO) sits above the equator and appears fixed to observers on the ground, making it ideal for continuous communications. Polar and sun-synchronous orbits enable global coverage and stable lighting for imaging. Satellites are launched by rockets and rely on onboard power, propulsion, attitude control, and ground-based tracking. At end of life, operators may deorbit, move to a graveyard orbit, or dispose of the satellite in other ways.

Trends and challenges: there is growing use of small satellites and mega-constellations for broadband. This raises concerns about space debris, collision risk, and spectrum management, prompting international regulation by bodies such as the ITU and COPUOS.