Satellites are losing altitude 10 times faster than before. According to the ESA, it threatens to get worse.
Satellites in their orbit always sink slowly towards the earth. The emphasis here is on slow. “Up to 2.5 kilometers per year are usual – at least that’s how it was for the past 5 to 6 years,” reports Anya Stromme opposite to space.com. She is Mission Manager for SWARM. The European Space Agency measures with these 3 identical satellites ESA the earth’s magnetic field.
And those same satellites are suddenly sinking much faster than they should. “Since December they have been literally descending. Between December 2021 and April 2022, the rate of descent was 20 kilometers per year.”
Stronger solar wind and solar storms
The higher sink rate goes with the increased solar activity along. The sun’s activity occurs in cycles. A cycle lasts about 11 years. Activity is currently increasing, the peak of the current cycle will be 2025 expected. Due to the increased activity, the solar wind is higher and solar flares are more frequent.
Of the solar wind is a stream of particles made up of protons and electrons that is constantly streaming out of the sun. at solar flaresmostly by sunspots go out, a particularly large number of particles are emitted. If the earth is unfavorable to the sun, it can fly directly through this stream of particles. The result is a so-called solar storm. This can cause radio connections on earth to fail and, in extreme cases, cause disruptions to the power grid, up to and including widespread blackouts.
Denser air slows satellites down
The consequences can also be felt in the vicinity of the earth, just like in orbit. “We don’t yet know exactly how solar winds interact with the upper layers of the atmosphere,” says Stromme. “But we do know that they cause the atmosphere to lift. Denser layers of air are moving upwards.”
The dense air brakes the satellites – even at a height of 400 kilometers above the earth. That’s enough to slow them down enough to sink toward Earth. Stromme likens that to headwind. “The stronger the solar wind, the slower the satellite. And if they fly slower, they sink.”
40 SpaceX satellites crashed
In May, ESA had to intervene on 2 SWARM satellites flying at an altitude of 430 kilometers. If the engines had not been ignited, they would have crashed.
February 2022 showed that this is not just a theoretical scenario. SpaceX lost 40 Starlink satellites, because they were hit by a solar storm shortly after takeoff. The denser air prevented the satellites from reaching their safe orbit – they burned up in the atmosphere.
CubeSats in particular are at risk
Satellites orbiting around 550 kilometers altitude are less affected by solar activity. Starlink satellites that reach their target orbit are also at this altitude. However, according to Stromme, the increasing solar activity will affect all satellites that are in orbit at an altitude of about 400 kilometers. This also applies to the International Space Station ISSas well as the numerous cheap ones CubeSatsthat have been launched into space in recent years.
Many of them do not have a drive system because they should be as cheap as possible. According to Stromme, they will therefore remain in space for a shorter time than their operators had intended. However, satellites with propulsion systems are also affected. If the orbit has to be corrected more frequently, more fuel is used. If you run out of fuel, the mission will soon be over. Either because the orbit can no longer be maintained and the satellite burns up, or because a targeted crash is initiated with the last remaining fuel so that the debris rains down over uninhabited areas.
Solar activity much higher than calculated
However, it is not yet clear whether there will soon be a veritable “satellite extinction”. The current solar activity does not match the calculations made previously. She is now almost as high as the maximumwhich should not actually be achieved until 2025.
Stromme: We don’t know if that means it’s going to be a particularly strong solar cycle. It could already be weakening again and become an overall very weak solar cycle. But right now, solar activity is increasing very rapidly.”
Solar winds clean up space debris
At least there seems to be a positive effect. The denser air not only slows down satellites, but also space junk out. It then falls faster towards the earth and burns up – it gets cleaner in orbit.
The disadvantage: the space junk sinks faster and in larger quantities than usual. Satellites and spaceships must dodge more oftenwhich consumes additional fuel.
A clumsy evasive maneuver could cause other satellites to evade – until at some point evasion is no longer possible. A crash could happen Trümmerfeld create, which in turn poses a greater threat to other satellites and the ISS. In the worst case, there will be one chain reactionin which more and more satellites are destroyed in the debris field and the debris field is getting bigger and bigger.