Low Earth Orbit

Low Earth Orbit is an orbit close above the Earth. A satellite there flies at roughly 200 to 2,000 kilometers altitude. For comparison: a passenger jet stays at around 10 kilometers. The distance between Berlin and Rome is about 1,200 kilometers. Such satellites are thus surprisingly close. In exchange, they move very fast, at roughly 28,000 kilometers per hour. A full orbit of the Earth takes only about 90 minutes. Seen from a fixed point on the ground, such a satellite crosses the sky within a few minutes and disappears again. The English abbreviation LEO is also common in German.

Why it matters

The proximity to Earth determines two things: latency and cost. Radio signals need time to travel up and back. From an altitude of 550 kilometers, this latency is barely noticeable, about 20 to 50 milliseconds. Classic television satellites, by contrast, sit almost 36,000 kilometers high. There, the latency adds up to half a second or more. For video calls or online gaming, that is disruptive.

Moreover, satellites close to Earth are smaller and cheaper. They can be mass-produced and launched by the dozen on a single rocket. Exactly this has triggered a boom: companies like SpaceX, Amazon, or the European provider Eutelsat OneWeb are sending thousands of satellites into orbit. For investors, LEO has therefore become its own investment theme.

How it works

A satellite is actually constantly falling toward Earth. But at the same time it flies sideways so fast that it keeps “missing” the Earth’s curvature. This eternal falling-past is the orbit. The lower the orbit, the faster it has to be for this to work.

A single LEO satellite is useless for internet service because it moves on after a few minutes. That’s why constellations are built: hundreds or thousands of satellites that take turns. As soon as one leaves the horizon, the next one takes over, similar to how a phone switches from one cell tower to the next. Many of these satellites also relay data to each other via laser, instead of routing everything through a ground station each time.

At this altitude there are still traces of air. These slowly slow the satellite down. Without occasional boosts from a small thruster, it sinks after a few years and burns up. This is convenient on the one hand, since no permanent debris is created. On the other hand, operators must constantly replace their fleet.

Where you encounter the term

The best known example is Starlink, SpaceX’s satellite internet service. It provides connectivity to places without cables: farms, ships, aircraft, crisis regions. The International Space Station ISS also orbits in Low Earth Orbit, as does the EU’s Earth observation program Copernicus. Its images underpin weather services and climate studies.

In business news, LEO comes up in connection with billion-dollar investments and regulation. A persistent topic is space debris: the more crowded the orbits, the higher the risk of collisions. Astronomers also criticize that the satellites leave bright streaks across telescope images. The AI industry, too, is interested in LEO. There are early plans to place data centers in orbit, since sunlight is continuously available there and cooling works differently. Whether this will pay off remains an open question.