Low Earth Orbit
Low Earth orbit is the region roughly 200 to 2,000 kilometers above Earth's surface where most satellites operate. There, a satellite circles the Earth in about 90 minutes – which makes the orbit favorable for internet services and Earth observation, but also vulnerable to space debris.
Everything that orbits the Earth does so at a certain altitude. Low Earth orbit is the closest of these regions to Earth. It begins at roughly 200 kilometers in altitude and ends at about 2,000 kilometers. For comparison: a passenger aircraft flies at only about 11 kilometers. Objects at this altitude don’t fall down because they move sideways very quickly – around 28,000 kilometers per hour. This allows them to circle the Earth once in about ninety minutes.
Why almost all satellites are up there
The most important reason is proximity. A radio signal from a satellite at 550 kilometers altitude takes only a few milliseconds to reach Earth. For a satellite at 36,000 kilometers altitude, the same journey takes considerably longer. This delay is called latency. For video calls or online gaming, low latency is crucial.
The second reason is cost. A rocket needs less energy to reach a low orbit. This allows it to carry more payload, making the launch cheaper per kilogram. Companies like SpaceX therefore launch dozens of satellites at once with a single rocket.
Third, being closer allows more detail to be seen. Earth observation satellites photograph forest fires, crop areas, or troop movements from this altitude. The International Space Station ISS also orbits at about 400 kilometers altitude, right in the middle of this region.
The interplay of speed and gravity
An orbit is essentially an endless fall. Gravity constantly pulls the satellite downward. At the same time, it moves sideways so quickly that it falls past the Earth. The Earth’s surface curves away beneath it at exactly the same rate it descends. The result is a stable circle.
The closer to Earth, the faster a satellite must fly to achieve this. One disadvantage follows directly from this: because a single satellite constantly overtakes the Earth, it never stays above the same location. It is visible from a given point for only a few minutes. Continuous coverage therefore requires a great many satellites taking turns. Such groups are called constellations.
Even at this altitude, there are still minimal traces of air. This residual atmosphere gradually slows satellites down. Without occasional reacceleration, they descend after a few years and burn up. On the one hand, this is convenient, because decommissioned technology disappears on its own. On the other hand, it causes ongoing fuel costs during operation.
Starlink, satellite imagery, and the junk up there
The best known example currently is SpaceX’s Starlink, with several thousand satellites. The service provides internet in regions without cable networks. Competing projects such as Amazon's Kuiper or Europe’s IRIS² pursue the same goal. In business news, the term therefore often comes up in connection with billion-dollar investments.
Map apps and weather reports also depend on this orbit. Many satellite images seen in news coverage of wars or natural disasters come from companies like Planet Labs or Maxar. Their cameras operate from an altitude of a few hundred kilometers. A common misconception, by the way, is that GPS satellites orbit there – they actually fly much higher, at about 20,000 kilometers.
The biggest problem is space debris. Old rocket stages and broken satellites race through the same space at the same speed. Even a piece just a centimeter in size can destroy a satellite. Experts warn of the Kessler syndrome: a chain reaction of collisions that would render the orbit unusable. This is why authorities around the world are debating just how many satellites should be permitted there in the first place.