How Satellites Work: Orbit Types and Everyday Uses Explained

How a satellite stays in orbit

An orbit is the path an object follows around a larger body under the pull of gravity; the European Space Agency's children's education page notes that orbits are shaped by gravity and are often elliptical, meaning oval rather than perfectly circular. A satellite placed at a given altitude is given exactly enough speed that, as it falls toward Earth, the planet's surface curves away beneath it at the same rate — so it keeps circling instead of landing.

That required speed changes with altitude. According to ESA, a satellite in low Earth orbit travels at roughly 7.8 kilometres per second to complete a circuit in about 90 minutes, while a satellite in geostationary orbit, 35,786 kilometres up, needs only about 3 kilometres per second because its orbital period matches Earth's own rotation — 23 hours, 56 minutes and 4 seconds.

Three main orbit families — and what sets them apart

Engineers group most operational satellites into three broad bands by altitude, according to ESA. Low Earth orbit (LEO) sits closest to the planet and is the most crowded; medium Earth orbit (MEO) is used mainly for navigation; and geostationary orbit (GEO) lets a single satellite watch the same patch of Earth around the clock.

ESA also lists orbit variants built for specific missions: polar and sun-synchronous orbits, which pass near both poles and cross the same spot at the same local time each day for consistent environmental monitoring; highly eccentric orbits for long dwell times far from Earth; and Lagrange points roughly 1.5 million kilometres away, used by observatories that need to stay clear of Earth's heat and light.

What satellites are actually used for

Telecommunications satellites receive a radio signal from the ground, amplify it and send it back down, according to ESA. Those placed in GEO offer a fixed, always-on link for television broadcasting, telephone and data traffic without ground antennas needing to track a moving target; ESA puts the global satellite telecommunications business at roughly €90 billion a year. Newer broadband systems instead use large LEO constellations — ESA says these can range from 48 to 288 satellites working together — to cut the signal delay and power needed compared with a single distant GEO craft.

Satellite navigation relies on MEO. The U.S. government's GPS program describes a constellation arranged in six equally spaced orbital planes, each carrying at least four satellites, so that a receiver almost anywhere on Earth can see at least four satellites at once; a device calculates its position by timing signals from several of them simultaneously. GPS satellites fly at about 20,200 kilometres altitude and complete two orbits a day; as of July 2023, according to gps.gov, the U.S. Space Force had maintained 31 operational satellites in the constellation for over a decade, above the 24-satellite minimum the government commits to maintaining 95% of the time.

Weather forecasting draws on both GEO and LEO. NOAA operates GOES satellites in geostationary orbit, about 22,236 miles above the equator, to track hurricanes and storms in near-real time with updates as often as every 30 seconds. NOAA's polar-orbiting satellites, at about 512 miles altitude, circle pole to pole 14 times a day and supply global data fed into numerical weather models used for forecasts up to seven days out, according to NOAA's National Environmental Satellite, Data, and Information Service.

Earth observation satellites serve climate and environmental monitoring, agriculture and disaster response. ESA points to missions such as Sentinel-3 and EarthCARE for tracking weather and atmospheric hazards, and to the International Charter Space and Major Disasters, which coordinates satellite imagery for emergency responders after floods, earthquakes and other disasters.

How many satellites are up there now

The number of active satellites has grown sharply in recent years, driven largely by large broadband constellations. Citing ESA's Space Debris Office annual Space Environment Report, published in September 2026 using data through 2025, the science-news outlet EarthSky reported more than 15,800 working satellites in orbit, with SpaceX's Starlink constellation accounting for over 10,000 of them — roughly 63% of all functioning satellites. The same report put the total number of tracked payloads, working and defunct combined, at more than 18,600, within a wider population of over 31,000 tracked objects in low Earth orbit.