atellite From Wikipedia, the free encyclopedia Jump to navigationJump to search Part of a series on Spaceflight SpaceX Crew Dragon (More cropped).jpg History Space RaceTimeline of spaceflightSpace probesLunar missions Applications Earth observation satellitesSpy satellitesCommunications satellitesMilitary satelliteSatellite navigationSpace telescopesSpace explorationSpace tourismSpace colonization Spacecraft Robotic spacecraft SatelliteSpace probeCargo spacecraftHuman spaceflight Space capsuleSpace stationSpaceplane Space launch SpaceportLaunch padExpendable and reusable launch vehiclesEscape velocityNon-rocket spacelaunch Spaceflight types Sub-orbitalOrbitalInterplanetaryInterstellarIntergalactic Space agencies Further information: List of government space agencies Space forces China PLASSFFrance AAEIran IRGCASFRussia VKSUnited States USSF Space commands Brazil COMAECanada United States NORADFrance CDEIndia DSAIran ISCNATO NATO SCRussia KVU
nited Kingdom UKSCUnited States USSPACECOM Private spaceflight Axiom SpaceARCAspaceAstraBigelow AerospaceBlue OriginCopenhagen SuborbitalsNorthrop GrummanPerigee AerospaceRocket LabSierra Nevada CorporationSpaceXVirgin GalacticXCOR Aerospace RocketSunIcon.svg Spaceflight portal vte File:NASA Earth-observing Fleet June 2012.ogv NASA's Earth-observing fleet as of June 2019 A full-size model of the Earth observation satellite ERS 2 In the context of spaceflight, a satellite is an object that has been intentionally placed into orbit. These objects are called artificial satellites to distinguish them from natural satellites such as Earth's Moon. On 4 October 1957, the Soviet Union launched the world's first artificial satellite, Sputnik 1. Since then, about 8,900 satellites from more than 40 countries have been launched. According to a 2018 estimate, about 5,000 remained in orbit. Of those, about 1,900 were operational, while the rest had exceeded their useful lives and becom
e space debris. Approximately 63% of operational satellites are in low Earth orbit, 6% are in medium-Earth orbit (at 20,000 km), 29% are in geostationary orbit (at 36,000 km) and the remaining 2% are in various elliptical orbits. In terms of countries with the most satellites, the United States has the most with 1,897 satellites, China is second with 412, and Russia third with 176. A few large space stations, including the International Space Station, have been launched in parts and assembled in orbit. Over a dozen space probes have been placed into orbit around other bodies and become artificial satellites of the Moon, Mercury, Venus, Mars, Jupiter, Saturn, a few asteroids, a comet and the Sun. Satellites are used for many purposes. Among several other applications, they can be used to make star maps and maps of planetary surfaces, and also take pictures of planets they are launched into. Common types include military and civilian Earth observation satellites, communications satell
ites, navigation satellites, weather satellites, and space telescopes. Space stations and human spacecraft in orbit are also satellites. Satellites can operate by themselves or as part of a larger system, a satellite formation or satellite constellation. Satellite orbits vary greatly, depending on the purpose of the satellite, and are classified in a number of ways. Well-known (overlapping) classes include low Earth orbit, polar orbit, and geostationary orbit. A launch vehicle is a rocket that places a satellite into orbit. Usually, it lifts off from a launch pad on land. Some are launched at sea from a submarine or a mobile maritime platform, or aboard a plane (see air launch to orbit). Satellites are usually semi-independent computer-controlled systems. Satellite subsystems attend many tasks, such as power generation, thermal control, telemetry, attitude control, scientific instrumentation, communic
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