Science

Satellites can get lost during strong solar storms and it can take weeks to find them.

In October 2003, satellite controllers lost sight of hundreds of spacecraft for several days after a powerful solar storm hit Earth. Experts fear that with the increase in the number of satellites and debris circling the planet over the past twenty years, the next big solar storm could plunge near-Earth space into chaos for several weeks.

The US Space Surveillance Network (SSN) currently tracks about 20,000 objects larger than 4 inches (10 centimeters) in low Earth orbit, in the region of space below 620 miles (1,000 kilometers). Some of these objects are active satellites, but most are failed spacecraft, spent rocket stages, and fragments of debris from collisions. SSN experts use radar measurements to maintain a catalog that allows them to track where these objects are in space and predict their future trajectories. When two objects, such as a piece of space debris and a satellite, come dangerously close to each other, the satellite operator is alerted. In some cases, they perform evasive maneuvers to prevent an accident.

But there is one catch. The positions of these objects are not always accurate, and this uncertainty increases during solar storms, sometimes to the point where accurate collision predictions are not possible.

“During the strongest storms, errors in orbital trajectories become so large that, in fact, the catalog of orbiting objects becomes invalid,” says Tom Berger, solar physicist and director of the Space Weather Technology Center at the University of Colorado at Boulder. told Space.com. “Objects can be tens of kilometers from the positions last detected by the radar. They are practically lost, and the only solution is to find them again with the help of radar.”

On the subject: Wild sunny weather causes satellites to fall out of orbit. It will only get worse.

Unpredictable changes in resistance

This uncertainty is the result of density changes in the Earth’s thermosphere, the upper atmosphere, at altitudes of 60 to 370 miles (100 to 600 km). The rarefied gases at these altitudes interact with particles emitted by the Sun in coronal mass ejections (CMEs), large ejections of magnetized plasma from the Sun’s upper atmosphere, the corona. These interactions heat the thermosphere and cause it to swell. Dense gases from lower altitudes move higher, where the satellites suddenly experience stronger drag that changes their speed and pulls them toward Earth.

Berger, who described his concerns in a 2020 article titled “Flight Through Uncertainty” in the journal Space Weather, is not alone in his worries about the effects of a major solar storm.

“When we receive a very big event and see a strong incandescence [upper] atmosphere, the satellites won’t be where they should be,” Bill Murtagh, program coordinator for the National Oceanic and Atmospheric Administration’s (NOAA) Space Weather Prediction Center (SWPC), told Space.com.

“These spaceships will have some extraordinary resistance, and it will not be the same in a given place at a given height. It will change over time with extraordinary dynamics. [the solar storm]. It will certainly be a challenge during one of these big events.”

A batch of Starlink satellites launched in February 2022 got right into a geomagnetic storm that sent the satellites back to Earth. (Image credit: SpaceX)

satellites out of control

Fortunately, such powerful solar storms do not happen very often. After the so-called Halloween storms in October 2003, the Earth experienced a period of fairly mild space weather. In 2012, however, our planet was just nine days away from a CME impact that would have triggered the solar storm of the century.

However, the relatively low frequency of these events is no comfort to space security professionals who fear what will happen if we lose control of the orbital positions of satellites in today’s increasingly busy space environment. When the 2003 Halloween storms hit, Berger said there were only about 5,000 tracked objects in low Earth orbit, and despite losing control of the situation, no collisions were reported. But the number of objects in this vulnerable region of space has quadrupled since 2003, and with it the risk of orbital accidents.

“A typical satellite operator can now spend 30 to 50 percent of their time on collision alerts,” Berger said. “Currently, LEO satellite operators receive about one warning per day. About one warning a week is serious enough to be analyzed in more detail, and about every few weeks they have to maneuver to reduce the chance of a collision. It wasn’t like that. in the past.”

With huge uncertainty about the position of satellites and debris objects following a major solar storm, spacecraft operators can simply raise their hands, cross their fingers, and wait for the Space Surveillance Network to trace the objects piece by piece. Berger said.

Most modern satellites are equipped with GPS receivers, allowing operators to store some satellite position information (although solar storms can cause GPS outages and significant position inaccuracies). But debris objects do not have GPS and can only be detected using radar. Even with increased investment in new tracking radars and the emergence of commercial players in debris monitoring in recent years, Berger said it could take weeks to fully rebuild today’s much larger catalog.

The environment around our planet is full of space debris. (Image credit: ESA)

Kessler syndrome

During these weeks, spacecraft operators are unlikely to sleep well, and it’s not just the risk of damage to any individual spacecraft. For several years now, space security experts have been sounding the alarm about the growing amount of debris in low Earth orbit. This debris, together with the increase in the number of operational satellites over the past decade (the result of the emergence of megaconstellations such as SpaceX’s Starlink), threatens the sustainability of orbital operations.

Experts believe that the early stages of the so-called Kessler syndrome, an unstoppable cascade of collisions that can render the orbital environment so unsafe that it cannot be used, are already underway.

A few bad strikes in a period of chaos following a massive solar storm can easily tip the balance. And then? At worst, a scenario similar to that of the 2013 Oscar-winning film Gravity could unfold, with the world watching helplessly.

“Without significant improvement in [space traffic management] and space weather forecasting technology, there is a real risk that we will reach exponentially increasing levels of cascading collisions that could lead to [low Earth orbit] the domain will be unusable for decades or possibly centuries,” Berger and colleagues wrote in their 2020 paper, adding that such a situation would have “devastating consequences for weather forecasting, space exploration and space trade.”

Exit?

A solar storm capable of causing anything that is bound to happen. One day. Berger hopes that if we avoid this for at least the next five years, the space weather community can improve their upper atmospheric models to account for changes in drag caused by space weather events. Such models, in turn, would allow spacecraft operators (and the Space Observation Network) to track what is happening in space with a reasonable degree of certainty even in the midst of the most powerful geomagnetic shocks caused by solar storms.

Last year, NOAA introduced what they call the All Atmosphere Model, which extends a conventional weather forecasting model to an altitude of about 370 miles (600 km). So far, the lack of measurements at these altitudes limits the accuracy and reliability of the model’s results, Zu-Wei Fang, a NOAA space weather specialist, admitted in an earlier interview with Space.com.

Meanwhile, as the sun wakes up from a long sleep period and produces more sunspots, solar flares and CMEs, spacecraft operators are starting to feel out of sorts. In February, SpaceX lost 40 brand new Starlink satellites after a launch that was described as a fairly weak geomagnetic storm. Earlier this year, the European Space Agency reported that its Swarm satellites, which measure the Earth’s magnetic field from an altitude of about 270 miles (430 km), have been sinking ten times faster since December 2021 than in all previous years since their launch in 2013. year. .

SpaceX, after losing its satellites, agreed to provide NOAA with data on the drag experienced by their satellites to help fine-tune their prediction models. Such cooperation between satellite operators and agencies, according to Berger, can be a useful step forward.

“A large number of GPS satellites, such as Starlink, can be an advantage in this sense,” said Berger, whose team is collaborating with NOAA on model development. “GPS gives you accurate orbital data that we can use to determine the density of the upper atmosphere. These data points will help us adjust our model to real world conditions, just like we do with regular weather models. make sure the model keeps track of actual conditions at all times, we hope to extend forecasts up to six to twelve hours in the future with a decent level of accuracy.”

Unpredictable

Murtha, however, warns that a massive solar storm could come at any time and without prior warning. The Halloween storm of 2003, during which dozens of satellites were temporarily lost, began as the Sun’s 11-year activity cycle was waning and approaching a minimum.

“The sun was really unremarkable [prior to the storms]Murtagh said. “We had no idea what would happen in just a week.”

Although the Sun has regularly brought down CMEs on Earth since time immemorial, it is only very recently that mankind has become dependent on technologies vulnerable to such flares.

The two largest solar storms in known history occurred before the start of the era of space exploration. The so-called Carrington Event of 1859 is known to have caused auroras that were visible all the way to the Caribbean and knocked out telegraph networks throughout Europe and America.

The so-called New York railroad storm in May 1921 set fire to several telegraph hubs around the world, including one at New York’s Grand Central Station.

Both of these storms were an order of magnitude more powerful than the 2003 Halloween storm.

“If something like the 1921 storm happened today, it could have a very serious impact on orbital operations for weeks, not just hours or days,” Berger said. “And since we know that we’re going to be hit by a big storm at some point, we need to do research to improve the models and make sure they can predict the changes happening in these geomagnetic storms better than they can. currently.”

Follow Tereza Pultarova on Twitter @TerezaPultarova. Follow us on Twitter @Spacedotcom and on Facebook.

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