By Jacinta Bowler for ABC
The Aurora Australis, also known as the Southern Lights, glow on the horizon over waters of Lake Ellesmere on the outskirts of Christchurch on 11 May, 2024. Photo: Sanka Vidanagama / AFP
While stargazers around the world were trying to catch a glimpse of the widespread auroras in May, satellites were bearing the brunt of the worst geomagnetic storm in 20 years.
US researchers used open-access US data to analyse how satellites fared over the mid-May storm.
Their study, which has been accepted for publication in the Journal of Spacecraft and Rockets, found many satellites lost significant altitude and had to quickly manoeuvre back to the correct position.
The researchers suggested a combination of poor forecasting and satellites having to raise themselves back up to the correct altitude "en masse", provided an unreasonable risk of satellite collisions.
William Parker, an aeronautical researcher at the Massachusetts Institute of Technology (MIT) and one of the authors of the new paper, believes this risk will only increase over time as satellite constellations like Elon Musk's Starlink launch hundreds of new satellites each month.
"A single collision in orbit … can generate thousands of pieces of orbital debris or space junk that can persist for decades, centuries, or longer," Parker said.
"This debris inevitably leads to more collisions, perpetuating a dangerous cycle."
The age of satellites
Geomagnetic storms are nothing new. Every few years, the Sun releases a huge amount of energy and plasma aimed at the Earth.
As well as producing widespread auroras, this blast of energy and plasma can indirectly mess with planes, communications and GPS systems, satellites, and even power lines or undersea cables.
None of these recent storms have caused the widespread damage to technology that scientists have feared, but since the last major storm in 2003, the number of active satellites in space has increased eight-fold.
"More satellites have been launched in the past five years than in the previous 60 years combined," Parker said.
"The current number of satellites in orbit is so high that many satellites must manoeuvre daily to avoid collisions."
This surge in satellites has taken place during solar minimum, when solar activity is significantly lower.
But with the solar maximum getting close, and more sunspots already appearing, these technology-damaging solar storms become more likely.
These storms can drop satellites' altitude significantly, as well as damaging sensitive electronics inside them due to increases in radiation.
The May solar storm was a perfect opportunity to test if the new wave of satellites could handle the solar event.
What did the research find?
Before this new research paper no-one had reported any satellite collisions due to the storm, but Starlink had warned of "degraded service" during the event.
Brett Carter, a researcher in space physics and space weather at the Royal Melbourne Institute of Technology (RMIT) notes that SpaceX owned Starlink and other commercial satellite companies aren't keen to release proprietary information about the satellites to scientists.
The new study bypassed these companies to get their data, instead taking publicly available information called two-line element data collected from the US Space Force, which tracks satellite positioning to avoid collisions.
Carter thought the researchers could have provided more information about the methodology, but said the team handled the data in a way that was "rather clever".
"These authors have gone ahead and utilised this openly accessible data set to investigate what happened," he said.
"[And] I'm not surprised by the results."
More than 85 percent of active satellites, and almost all new satellites sit in low-Earth orbit.
This region of space, which encompasses orbits less than 2,000 kilometres above sea level, is also home to the International Space Station and the Hubble Space Telescope.
The researchers found one satellite called SATCAT 43180 lost altitude four times faster than normal. This meant the satellite lost on average 180 metres of altitude a day.
The paper notes that partially due to the solar storm being poorly forecast, satellites had to "manoeuvre en masse" to avoid this drop in altitude.
The vast majority of these manoeuvres were done by Starlink satellites, which currently make up around 60 per cent of active satellites in low-Earth orbit.
"The fact that SpaceX in particular were actively looking after their satellites and manoeuvring them to try and recover during the storm - this is all positive," Carter said.
"The problem … was that it's not controlled, it's not openly communicated, and it's not transparent."
Without this communication, other satellites have a higher risk of colliding.
"If everybody is free to manoeuvre however they like, then what's to say that objects aren't being manoeuvred into a collision course with something else?" he said.
After the storm, Starlink posted on X (formally Twitter) that all its satellites "weathered the geomagnetic storm and remain healthy", but they did not respond to ABC's request for comment about the new study.
Both Carter and Parker want open communication between the satellite companies and researchers.
"Space is a shared resource that requires international consensus and cooperation," Parker said.
"The only way to ensure long-term sustainable access to space is through common-sense regulation and oversight."
A silver lining
In an interesting twist, the May solar storm would have helped tackle a different issue for satellites: space debris.
The drop in altitude doesn't just affect active satellites, but also anything that is orbiting in the low-Earth environment.
This means that debris - junk objects in Earth orbit such as rockets, rocket parts or inactive satellites - also drop closer to Earth. Eventually the debris reaches a threshold to burn up in the atmosphere, producing a type of "self-cleansing" effect.
The paper notes that some debris dropped a staggering 10 kms during the storm.
Space debris is another thing that satellites can collide with, so less space debris means less potential for collisions.
Another silver lining for Carter was the lack of satellite and technological issues reported during the May storm.
A solar storm that big can pose a "really big challenge for satellites," but with very little damage reported, it shows the precautions put in place worked.
While he noted that GPS was minimally affected, other technologies also seemed to get through relatively unscathed.
"Power grids were fine. Aircraft seemed to still be able to do their thing," he said.
But he stressed that being able to better predict and forecast this solar weather would provide a larger safety net for the next big storm.
"Right now we can't predict what's going to happen in three hours time, let alone what's going to happen in three days time," he said.
"This might sound pretty cliche coming from an academic, but we need more research funding on this."
- ABC