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Most satellites are considered to be in space, but within Earth’s atmosphere they occupy the thermosphere and exosphere. The specific layer depends on the satellite’s mission and orbit type. Since the launch of Sputnik, thousands of satellites have been deployed, serving roles from the International Space Station to global positioning systems.
The thermosphere spans from about 85 km to 640 km above the surface. Temperatures can reach 1,500 °C (2,732 °F), yet the extremely low pressure means satellites are not exposed to significant heat damage.
Above the thermosphere lies the exosphere, extending up to roughly 10,000 km. Its upper boundary is not fixed; molecules drift into space under the influence of solar wind. The exosphere marks the outermost atmospheric layer before interplanetary space.
LEO includes any orbit below 2,000 km. Satellites here circle the Earth rapidly, experiencing atmospheric drag that gradually lowers their orbit unless they are periodically boosted. The International Space Station resides in LEO, primarily within the thermosphere, though the highest LEO satellites approach the exosphere. Scientific missions often choose LEO to monitor Earth closely.
Satellites above LEO travel through the exosphere and can maintain stable orbits for decades with minimal station‑keeping. Weather and communication satellites are placed in higher orbits to achieve broader coverage. The pinnacle of High Earth Orbit is the geosynchronous orbit, where a satellite’s orbital period matches Earth’s rotation. A special case, the geostationary orbit, lies along the equator, keeping the satellite fixed over a single point on Earth’s surface.
Understanding these atmospheric layers helps engineers design orbits that balance coverage, lifespan, and fuel consumption.
