Live battery status

Satellite batteries

Small satellites, about the size of a shoebox, circle the Earth every 90 minutes. Volunteers with radio antennas hear their messages, and this page shows whether their batteries are healthy. In sunlight a battery should charge; in the Earth's shadow it drains, and that is normal.

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See the satellitesWhat is a CubeSat?

This is a CubeSat.

About 10 cm on each side, a kilogram or two. Students and small teams build them, and five of them are followed here.

It lives on sunlight.

Solar panels charge its battery for about an hour of every 90-minute trip around the Earth.

Then it goes dark.

For about half an hour of each orbit the Earth is between it and the Sun. The battery has to carry it, so draining there is normal, and the alerts know that.

And it talks to us.

Every few seconds it sends a short radio message with its battery's voltage. Volunteers on the ground hear it, and this page reads it.

Live status

Five satellites and their batteries

One row per satellite. Click a row for its last day of sunlight and shadow and its battery charts.

Behind the page

How it works

From a radio message in space to a row on this page, in four steps.

1
Listen

Volunteers around the world point small antennas at the sky and record the short radio messages each satellite sends. They share them through SatNOGS.

2
Read the numbers

Each message is a few dozen bytes. This project turns them into the battery's voltage, and its current where the satellite sends it.

3
Check against the Sun

In the Earth's shadow a battery is supposed to drain. So the orbit of each satellite is worked out, and a battery is only judged on what is normal for sunlight or shadow.

4
Warn if something is off

If a battery drains in sunlight, drops below its usual level, or a satellite goes quiet for too long, a warning goes out by Telegram and shows on this page.

The other half of this project

Five satellites are a small part of the sky.

About 17,000 active satellites circle the Earth. orbitscreen follows every one of them and checks every pair for close approaches. It shares its orbit code with this page: the same SGP4, written from scratch in Go.

5 minto screen the whole catalog 7 days ahead, on a laptop
100%of CelesTrak SOCRATES' close approaches found, on the same data
~136×faster than checking every pair
Open the live tracker How it works

Above: every active satellite in CelesTrak's catalog, 60 times faster than real time, from the tracker's own published data. Colours: cyan low orbits, violet middle, amber geostationary; the five followed here are the bright ones. A sketch from the orbit elements: the tracker itself computes exact positions with SGP4. In the tracker, click any of the five to see its battery too.