Satelitti

Satelitti is a body that orbits another body in space. The term covers both natural satellites, such as moons, and artificial satellites—human-made objects placed into orbit to perform a range of tasks. In many languages the word is a cognate of the Latin satelles; in Finnish the common form is satelliitti and in English the usual form is satellite.

Most artificial satelitti consist of a satellite bus, which provides structure, power, propulsion, and attitude control, and a payload, the mission-specific equipment such as cameras, sensors, or communications transponders.

Orbits vary by altitude and purpose. Low Earth orbit (LEO) ranges roughly from 160 to 2,000 kilometers above the planet, used for imaging and many communications satellites. Geostationary orbit (GEO) sits at about 35,786 kilometers and maintains a fixed position relative to Earth, ideal for communications and weather monitoring. Medium Earth orbit (MEO) lies between these, and polar or sun-synchronous orbits provide global coverage and regular overpasses.

Functions include telecommunications, broadcasting, navigation and timing, Earth observation for weather and science, space science, and military applications. Together, satelitti enable modern services such as internet access, GPS, weather forecasting, and remote sensing.

History and outlook: The first artificial satelitti, Sputnik 1, was launched in 1957 by the Soviet Union, initiating the space era. Since then thousands have been deployed. Challenges include space debris and end-of-life disposal. The current trend emphasizes small satellites and mega-constellations, advances in propulsion and manufacturing, and in-space servicing concepts.