What’s the weather like in Earth’s upper atmosphere today? Most of us only care about how the weather feels on the Earth’s surface, but understanding “space weather” is becoming increasingly important. That’s because small changes in space weather can buffet satellites around, increasing the chances of a satellite pile-up.
Currently there are nearly 5,000 satellites revolving around our planet, of which some 2,000 are operational and the remainder are space debris. With orbits between 100 and 1,000km above sea level, the upper atmosphere is now a crowded place. Both the weather down below and changes in the sun’s output influence the upper atmosphere, changing the density of the air. As satellites move through “thicker” and “thinner” air, the change in drag forces alters their orbital track, potentially putting them on a collision path.
At the moment we don’t have good forecasts of space weather, and consequently it’s hard to estimate satellite orbits accurately. This uncertainty results in large numbers of warnings being issued, like on 2 September 2019, when the European Space Agency had to raise the orbit of the Aeolus satellite to avoid collision with Starlink44. A new paper in Space Weather calls for better forecasting so that space traffic can be managed with more confidence.
