Technology
LEO Satellite Constellations for Global Internet Coverage
Quick fact
The first LEO internet constellation, Iridium, launched in the 1990s with 66 satellites, but modern constellations like Starlink have over 6,000 satellites in orbit, with plans for tens of thousands more.
Why this is interesting
Imagine getting high-speed internet in the middle of the Sahara, on a cruise ship, or in a remote mountain village—no cables, no cell towers. How? A web of thousands of small satellites orbiting just above our heads is making this a reality.
Read the full explanation
Understanding LEO Satellite Constellations for Global Internet Coverage
Think of a traditional geostationary satellite as a lone lighthouse sitting 35,786 km above the equator, covering a wide area but far away. Signals to and from it take about a quarter of a second to travel, which is too slow for smooth video calls. Now imagine instead a swarm of small satellites flying much closer to Earth, at about 500–2,000 km altitude. Because they are closer, the signal travel time drops dramatically—to around 20–50 milliseconds, comparable to broadband. But because they move quickly around the planet (completing an orbit in about 90–120 minutes), a single satellite is only above your location for a few minutes. To provide continuous coverage, these satellites work together as a constellation: while one is moving out of view, another one takes over. This handover is managed by ground computers and inter-satellite links. Your internet data travels from a ground station to a satellite, then bounces from satellite to satellite (or beams straight down to your dish), and finally reaches you. The system is designed to always have a satellite overhead, giving you uninterrupted connectivity.
A deeper explanation
The key to LEO constellations is their low altitude. According to Kepler's laws, a satellite in a lower orbit moves faster and completes an orbit in a shorter time. For example, at 550 km altitude, orbital period is about 95 minutes. This low orbit also means less signal attenuation, so smaller, portable user terminals can communicate with them. The constellation design uses multiple orbital planes, each with many satellites, to ensure at least one satellite is always in view of any point on Earth. To avoid collisions and manage orbits, satellites have thrusters (often electric) that adjust their paths. Data routing within the constellation is a network problem: satellites are nodes that pass data to each other via laser or radio links. This eliminates the need for a ground station near the user. However, constellation management is complex: satellites must maintain their spacing, avoid collisions with space debris, and eventually deorbit (burn up) at end of life. This technology has profound implications for global internet access, especially for areas with no fiber infrastructure. It also introduces regulatory and environmental challenges, such as orbital congestion and light pollution. Understanding this concept reveals how the fundamentals of orbital mechanics and radio communication are applied to solve a global problem.