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Unexpected solar weather is accelerating satellites' orbital decay


This is simply part of the solar cycle. And it's a standard part of satellite planning when it comes to operational quality and reliability to account for solar cycle radiation effects.

This is an ignorant fear article and/or an article written by someone who knows NOTHING about space launch and design.

(I used to be a military rocket scientist specializing in radiation effects on space electronics many moons ago).


The article could be much clearer about this but no, this isn’t just about the standard solar cycle. The issue is that the sun has been more active in this portion of the solar cycle than predicted, resulting in greater atmospheric mass in LEO than anticipated. Planners knew that the cycle was ramping up, but may have underestimated its intensity.

Check out the NOAA solar cycle data:

You are right that operators plan for variations in solar activity. But it remains to be seen how many can cope with a significantly more active cycle than predicted.


The article at length describes how this solar cycle is different from prior cycles and forecasts.

> This drag also helps clean up the near-Earth environment from space junk. Scientists know that the intensity of this drag depends on solar activity — the amount of solar wind spewed by the sun, which varies depending on the 11-year solar cycle. The last cycle, which officially ended in December 2019, was rather sleepy, with a below-average number of monthly sunspots and a prolonged minimum of barely any activity. But since last fall, the star has been waking up, spewing more and more solar wind and generating sunspots, solar flares and coronal mass ejections at a growing rate. And the Earth's upper atmosphere has felt the effects.

> In late 2021, operators of the European Space Agency's (ESA) Swarm constellation noticed something worrying: The satellites, which measure the magnetic field around Earth, started sinking toward the atmosphere at an unusually fast rate — up to 10 times faster than before.

> By coincidence (or beginner's luck), the onset of the new space revolution came during that sleepy solar cycle. These new operators are now facing their first solar maximum. But not only that. The sun's activity in the past year turned out to be much more intense than solar weather forecasters predicted, with more sunspots, more coronal mass ejections and more solar wind hitting our planet.

> "The solar activity is a lot higher than the official forecast suggested," Hugh Lewis, a professor of engineering and physical sciences at the University of Southampton in the U.K. who studies the behavior of satellites in low Earth orbit, told "In fact, the current activity is already quite close to the peak level that was forecasted for this solar cycle, and we are still two to three years away from the solar maximum."

> Stromme confirmed those observations. "The solar cycle 25 that we are entering now is currently increasing very steeply," she said. "We do not know if this means that it will be a very tough solar cycle. It could slow down, and it could become a very weak solar cycle. But right now, it's increasing fast."


I concur with this, and also, one possible solution to this from a technical perspective is to increase the amount of fuel carried for ion/hall effect and similar thrusters (high specific impulse, low thrust) for periodic orbit raising maneuvers to extend lifetime.

Theoretically, as $ per kg launch costs come down with things like reusable falcon 9, it makes it much less costly to equip medium sized LEO satellite with more fuel than it might have costed 10 or 15 years ago.

Or if you have something that needs to orbit really low and minimize drag/maximize lifespan, you could design it to be particularly aerodynamic and shaped like this:


>(I used to be a military rocket scientist specializing in radiation effects on space electronics many moons ago).

Great, and I'm sure literal rocket scientists are not's target audience.

I read the article, and I didn't receive it as fear mongering at all. You might not be aware that people outside of rocket science are probably pretty ignorant of space weather and its direct affect on the Earth and its inhabitants. Putting a bit of explanation out there in a fairly easy way to understand is not a bad thing. As easy as this was to grasp, there will still be people that are confused after reading.


>By coincidence (or beginner's luck), the onset of the new space revolution came during that sleepy solar cycle.

Apparently not simply part of the solar cycle when new types of spacecraft (lacking typical propulsion systems) haven’t been in orbit during a high activity solar peak.

There are some points that are alarmist. “Plummet” isn’t something that seems to happen.


Exactly. The issue is you cannot easy say “unexpected”. Whilst we cannot account for everything and there could be something new like mercury orbit is “unexpected” and not due to Vulcan (as suspected in one stage there is another planet inside its orbit).

Really what is unexpected.


As people are pointing out, the rate of orbital decay does matter (even if it's not a "plummet"!) -- because everyone concerned knows that solar activity should be increasing to some extent in 2022 as a new solar cycle takes hold.

This plot of sunspot activity, and the (highly correlated) 10.7cm radio flux, indicates that the current cycle (cycle #25) is rising much faster than typical:

As you can see, cycle #24, which ended in 2019, was quieter than expected (annoying to solar physicists who only see a few cycles within their whole career) -- so it's actually very interesting that Cycle #25 is starting out with a bang.

NOAA is the main US government agency tasked with monitoring/predicting solar activity for the protection of ground and space systems. The main facility is the Space Weather Prediction Center which is in Boulder, CO -- that's the data source of the above plots. The SWPC centerpiece used to be a control room with a bunch of people looking at computer monitors filled with various real-time and historical time series.

We don't know why some cycles are less intense, and the last few cycles have generally been on a downward trend (e.g., So again, it is indeed quite interesting to see this high activity - if it holds up.


(December 19, 2020) "The consensus view of an international panel of 12 scientists calls for the new cycle, Solar Cycle 25, to be small to average, much like its predecessor, Solar Cycle 24.

But a prominent astrophysicist at the National Center for Atmospheric Research, Scott McIntosh, foresees the sun going gangbusters. The cycle is already off to a fast start, coinciding with the recent publication of McIntosh’s paper in Solar Physics. The study, with contributions from several of his colleagues, forecasts the nascent sunspot cycle to become one of the strongest ever recorded."



Update on the prediction:

(Feb. 26, 2022) "“We have finalized our forecast of SC25’s amplitude,” says McIntosh. “It will be just above the historical average with a monthly smoothed sunspot number of 190 ± 20.”

"“Above average” may not sound exciting, but this is in fact a sharp departure from NOAA’s official forecast of a weak solar cycle"



There were some space tech startups planning to provide a kind of tug-service to satellites on the low orbit. Not sure if any viability for this is on the near-future horizon.

Space tugs as a service:


Sure hope that Jello Biafra doesn't have his facts straight in his 1991 song The Sky Is Falling And I Want My Mummy (Falling Space Junk) with NoMeansNo. The part of the song about US orbital satellites carrrying plutonium waste with them. Please be just a little bidenism from this also so priestly character that JB is. The pitfall of the priestly archetypical character so many a time is just being out to to get the good old Holy Spirit emotional response from the churchgoers and not so much alawys concerned with getting the facts straight.

Increased solar flare EMP risk during the next years ain't a picnic either. Yo this all sucks. Bummer vibes. But don't shoot the messenger.

The song:


I am thinking about a commercial data product to address the situational awareness need here. It feels daunting though, because customers would be the likes of SpaceX and other intimidating entities. If anyone has thoughts, or is interested, please send me an email. (Contact info in profile!) Thanks.


Commercial SSA is getting to be a busy... space. Have you seen what others are doing in that area? How does your idea differ?


With NASA and related space weather data products and internal tracking of satellites being a core competence of companies like SpaceX, I don't necessarily see where a commercial data product would fit or provide value. Unless you're actually going to launch orbital assets and have some significant scientific work, I'm just not sure.

Some competition:


So this effect is caused by more solar wind slamming into the atmosphere at 100’s of km/hr and is so powerful that it’s CAUSING THE ATMOSPHERE TO HEAT UP AND EXPAND?

Does the global warming models take this into effect? This seems like an unfathomable amount of energy.


Solar irradiance variations amount to a bit less than 0.1% over the solar cycle. It used to be thought solar-cycle variations (the 11-year period) could be a significant contributor to climate change.

This turned out not to be the case...that was pretty much known by the early 2000s.

Other irradiance variations, due to orbital variations called Milankovich cycles, happening in the 10,000's of year range, do appear to influence climate. Of course, the extremes we're seeing now are not on the 10,000-year time scale.


It's causing the uppermost layers of atmosphere to expand. That's less than an unfathomable amount of energy because the uppermost layers of atmosphere are extremely rarefied, to the extent they don't even behave like gases.


Unexpected or failed theory or failed engineering or … . What is expected in the real world? Or just an excuse.

You always have unknown unknown but is this sort of expected as the sun is not yours. The solar wind model is the problem?




"[Solar] climate is what you expect, [solar] weather is what you get." - Mark Twain


I wonder what this means for Starlink. I know that Elon put them into a slightly lower orbit accidentally than what they originally intended. Which probably had the positive side effect of better latency. But, now that solar weather is accelerating orbital decay, this perhaps affects Starlink more adversely than it would have otherwise.


That wouldn't affect latency in any noticable way.


Maybe this will help clean up the debris from Russia's ASAT missile test last year?