FIELD GUIDE · Tracking & Intel
What's That Satellite Overhead? How Live Satellite Tracking Works
What is that bright 'star' silently gliding across the night sky?
Look up on a clear evening shortly after sunset and, if you're patient, you'll catch one: a steady point of light, not blinking like a plane, gliding silently and purposefully across the sky. That's a satellite catching the sun — one of thousands circling overhead at this very moment. The satellites layer turns that fleeting sight into something you can identify and even predict.
You're not watching it live — you're computing it
Here's the clever part: a satellite tracker doesn't need a live video feed of each spacecraft. Every tracked object in orbit has its motion captured in a small bundle of numbers — its orbital elements — derived from radar and telescope observations and published openly.
Because orbits obey precise, well-understood physics, software can take those numbers and work out exactly where a satellite is right now, and where it will be in ten minutes or two hours. So the moving dots on the map aren't being watched in real time so much as calculated from known orbits — which, for something as predictable as an object in freefall around the Earth, is just as good.
Why they look the way they do
A satellite in low orbit is moving astonishingly fast — around 28,000 km/h, lapping the planet roughly every 90 minutes. That's why it visibly slides across the sky over a few minutes rather than hanging like a star.
And what you're actually seeing is reflected sunlight: the satellite, high up, is still lit by the sun while you stand in darkness below. That geometry is why the best passes come shortly after dusk or just before dawn — the ground is dark but the satellite is still in sunlight. It shows no blinking lights (those would be an aircraft) and doesn't twinkle (that's a star). Just a calm, steady, moving point.
The "string of pearls" mystery, solved
Every so often someone photographs an eerie line of evenly-spaced lights marching across the sky in formation, and the UFO reports roll in. It's almost always a Starlink train: a batch of internet satellites freshly released from a single launch, still clustered together before they climb to their final orbits and spread out. For a few days to weeks after a launch they fly in that striking chain, then disperse and become ordinary scattered dots.
Knowing what you're looking at
The sky overhead is genuinely crowded now — and orbit height is the best clue to what each object is:
- The ISS is among the brightest things in the night sky and crewed by astronauts; it makes spectacular bright passes.
- Starlink and other constellations provide internet from low orbit (hence the trains).
- Weather and GPS/navigation satellites quietly run the services we lean on daily.
- Geostationary satellites sit very high up and appear to hover fixed over one spot — these are the ones feeding the cloud-imagery layer.
- Plus debris and dead hardware, a growing concern as orbits get busier.
So next time you spot that silent traveller crossing the dark, you won't just wonder what it is — you can pull up the layer and find out.
Frequently asked questions
How can you track a satellite you can't see?
Every tracked object in orbit has its path described by a compact set of numbers — its orbital elements — published from radar and optical observations. Because orbits follow precise physics, software can take those numbers and calculate exactly where a satellite is at any moment, and project where it will be minutes or hours from now. So a tracker isn't watching the satellite live; it's computing its position from a known orbit, which is just as accurate for most purposes.
Why do satellites move across the sky so fast — and why don't they twinkle?
Low-orbit satellites travel at roughly 28,000 km/h, circling the Earth in about 90 minutes, so they slide noticeably across the sky in a few minutes. What you actually see is sunlight reflecting off the satellite while you're in darkness below — which is why passes happen mainly shortly after dusk or before dawn. Unlike stars, they don't twinkle, and unlike planes, they have no blinking lights: just a steady moving point.
What's the 'string of pearls' people see?
That's a Starlink 'train' — a line of recently-launched internet satellites still flying close together before they spread out to their final orbits. Right after a launch they appear as a startling chain of evenly-spaced lights gliding in formation, which regularly prompts UFO reports. Within days to weeks they disperse and stop looking like a train.
What kinds of satellites are up there?
A huge range: the crewed International Space Station (one of the brightest things in the sky), weather satellites, GPS and other navigation craft, communications and internet constellations like Starlink, Earth-observation and science missions, plus a growing amount of defunct hardware and debris. Orbit height is a big clue to purpose — low orbits for imaging and internet, very high ones for the geostationary weather and TV satellites that appear to hang fixed over one spot.
SEE IT LIVE
Everything in this guide is on one real-time map.