Who causes satellites to fall from their orbits?

Who causes satellites to fall from their orbits?


Although they are in space, hundreds of kilometers from the earth’s surface, satellites that are in low orbit ‘feel’ the gravity of our planet, which pulls them towards it. Of course, it doesn’t wield the same power as it does over those of us on the ground; but, still, they notice her.

That is why engineers take this variant into account when calculating the useful life of these probes: some include thrusters to relocate in the correct area; others simply orbit until they fall into the atmosphere and disintegrate – in most cases. However, in recent months, these ships are experiencing ‘sinks’ much higher than expected, reducing their expected activity cycle.

And scientists know who is to blame: the Sun. Because it is known that the solar wind affects the drag effect and, right now, we are in the solar maximum of the cycle (which lasts about eleven years in total). One, moreover, much more intense than expected. Although we still have a lot of solar physics to understand, researchers know that during the solar maxima, the spots on our star grow in number. From them emerge solar flares Y coronal mass ejections. And the last ones are quite powerful. So much so that our upper atmosphere has been affected.


“We know that this interaction causes denser air to move to higher altitudes”explain for Anja Stromme, director of the swarm mission of the European Space Agency (ESA), a constellation of three satellites that monitor the Earth’s magnetic field but that since the end of 2021 have seen their orbits descend ten times deeper than estimated.

The explanation: denser air causes greater drag for satellites. “It’s almost like running against the wind”explains the scientist. The air exerts a resistance that reduces the speed of the satellites, which causes gravity to ‘win’ the game over inertia and is attracted towards the earth’s surface.

Specifically, the Swarm constellation fell on average about two kilometers a year; but since the end of last year, the rate has risen to 20 kilometers per year. She is not the only one who has noticed it: SpaceX reported the loss of Fourty satellites of its mega constellation Starlink by a solar storm.

Before they entered their normal orbit, at an altitude of 550 kilometers (outside the greatest danger zone), the falcon rocket He left them about 350 kilometers away. As always, after that, SpaceX raises the orbits using the boosters on board the satellites. However, this time the storm hit the group squarely, which ended up abruptly returning to the atmosphere and disintegrating with its friction.

The problems will continue

According to Anja Stromme, ships that orbit around 400 kilometers high, “surely they will have problems”including the International Space Station (ISS, for its acronym in English), which will have to carry out refloating maneuvers. It will not be the only one: the hundreds of cube sat (nanosatellites the size of a shoe box) and small satellites launched in the last decade could see their integrity endangered. “Many of these new satellites do not have propulsion systems and will re-enter the atmosphere sooner than expected”.

However, this ‘prophecy’ might not come true: astrophysicists know that every eleven years (more or less), the Sun’s magnetic field ‘flips’, and eleven years later it returns to the initial position; They also know that each one is a cycle and, also in each one, there is a solar maximum and minimum in which the activity of the star increases and decreases. But it is a guideline. At the end of 2019 we enter a new cycle, heading towards a solar maximum, which will peak in 2025.

The first calculations indicated that we were entering a quiet period, with few spots and flares. Even the most dramatic models did not predict the level of activity that our star is currently showing. But does that mean that the phenomena will grow exponentially in the coming years? It is something that scientists do not know for sure: solar activity could drop in the coming months or years, and become a more ‘relaxed’ period. There are still many unknowns to fully understand our star king.

Font: Patricia Biosca/ABC

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Written by Editor TLN

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