In October 2003, satellite controllers lost track of hundreds of spacecraft for days after a large solar storm hit Earth. Experts fear that with the increasing number of satellites and debris orbiting the planet in the nearly two decades since, the next major solar storm could wreak havoc in near-Earth space for weeks.
The US Space Surveillance Network (SSN) currently tracks about 20,000 objects larger than 4 inches (10 centimeters) in low earth orbit, the region of space at altitudes below 620 miles (1,000 kilometers). Some of these objects are operational satellites, but most are defunct spacecraft, spent rocket stages, and fragments of debris created in collisions. SSN experts use radar measurements to maintain a catalog that allows them to track where these objects are in space and project their trajectories into the future. When two objects, for example a piece of space debris and a satellite, appear to be coming dangerously close to each other, the satellite operator receives a warning. In some cases, they drive evasive maneuvers to avoid an accident.
But there is a catch. The positions of these objects are not always precise and this uncertainty increases during solar stormssometimes to a point where accurate collision predictions are impossible.
“In the largest storms, the errors in the orbital trajectories become so large that the catalog of orbital objects is essentially invalidated,” Tom Berger, solar physicist and director of the Space Weather Technology Center at the University of Colorado, Boulder . he told Space.com. “Objects can be tens of kilometers from the last positions located by the radar. They are essentially lost, and the only solution is to find them again with the radar.”
Related: Wild solar weather is causing satellites to plummet from orbit. It will only get worse.
Unpredictable changes in drag
This uncertainty is the result of changes in the density of the Earth’s thermosphere, the upper layer of the atmosphere at altitudes of 60 to 370 miles (100 to 600 km). Thin gases at these altitudes interact with particles emitted by the sun coronal mass ejections (CME), large eruptions of magnetized plasma from the the sun’s upper atmosphere, the crown These interactions heat the thermosphere and cause it to swell. Denser gases from lower altitudes drift higher where the satellites suddenly experience stronger drag, which changes their speed and pulls them toward land.
Berger, who described his concerns in a paper called Flying through uncertaintypublished in 2020 in the journal Space Weather, is not alone in having concerns about the effects of a large solar storm.
“When we have a very large event and we see an intense warming of the [upper] atmosphere, the satellites won’t be where they’re supposed to be,” Bill Murtagh, program coordinator for the Space Weather Prediction Center (SWPC) at the National Oceanic and Atmospheric Administration (NOAA) told Space.com ) of the United States.
“There will be some extraordinary drag on these spacecraft and it will not be uniform at a given location at a given altitude. It will vary over time with the extraordinary dynamics of [the solar storm]. It will certainly be a challenge during one of these big events.”
A batch of Starlink satellites launched in February 2022 flew directly into a geomagnetic storm that sent the satellites hurtling back to Earth. (Image credit: SpaceX)
Satellites out of control
Fortunately, solar storms this powerful don’t happen that often. From the so-called Halloween storms as of October 2003, Earth has enjoyed a period of fairly mild space weather. In 2012, however, our planet was just nine days away of being hit by a CME that would have caused a solar storm of the century.
Still, the relatively low frequency of such events is no consolation to space security experts, who fear what would happen if we lost control of satellites’ orbital positions in today’s increasingly busy space environment. When the 2003 Halloween storms occurred, Berger said, there were only about 5,000 tracked objects in low Earth orbit, and despite the loss of control over 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 may now be spending 30 to 50 percent of their time dealing with collision alerts,” Berger said. “LEO satellite operators now get about one warning a day. About one a week is serious enough to look into in more detail, and about every few weeks they have to maneuver to reduce the probability of the collision. It was not so. in the past.”
With the huge uncertainty about the positions of satellites and debris objects after a major solar storm, spacecraft operators could “hold their hands up”, cross their fingers and hope that the Space Surveillance Network retrieves the objects piece by piece, Berger said.
Most modern satellites are equipped GPS receivers, which will allow operators to maintain some knowledge of the satellites’ position (although solar storms can cause GPS blackouts and significant inaccuracies in position readings). But debris objects do not have GPS and can only be located by radar. Even with increased investment in new tracking radars and the emergence of commercial agents in the field of debris monitoring in recent years, it could take weeks to fully restore today’s much larger catalog , Berger said.
The environment around our planet is full of space debris. (Image credit: ESA)
Kessler syndrome
During these weeks, spacecraft operators likely won’t sleep well, and it’s not just the risk of damage to any spacecraft. For several years now, the space safety community has been sounding the alarm about the growing amount of debris in low Earth orbit. These remains, along with the increase in the number of operational satellites over the past decade (as a result of the arrival of mega-constellations such as SpaceX). Starlink), threatens the sustainability of orbital operations.
Experts think that the first stages of the so-called Kessler syndromean unstoppable cascade of collisions that could render the orbital environment so unsafe as to be unusable are already underway.
A few unlucky strikes during a period of chaos in the wake of a powerful solar storm can easily tip the scales. And then? At worst, a scenario similar to the plot of the 2013 Oscar-winning film gravity it could unfold while the world watched helplessly.
“No significant improvements [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] unusable domain for decades or possibly centuries,” Berger and his colleagues wrote in their 2020 paper, adding that such a situation would have “devastating consequences for weather forecasting, space intelligence, and space commerce.”
Way out?
A solar storm with the power to cause all that is sure to come. One day. Berger hopes that if we avoid one for at least the next five years, the space weather forecasting community will be able to improve their models of the upper atmosphere to account for drag changes caused by space weather events. These models, in turn, would allow spacecraft operators (and the Space Surveillance Network) to track things in space with a sufficient level of reliability even in the midst of the most powerful geomagnetic disturbances caused by storms solar
Last year, NOAA introduced what they call the Whole Atmosphere Model, which extends the usual weather forecast model up to an altitude of about 370 miles (600 km). So far, the lack of measurements at these altitudes limits the accuracy and reliability of model output, Tzu-Wei Fang, a NOAA space weather scientist, told Space.com. in a previous interview.
Meanwhile, as the sun wakes up after a long period of sleep, it produces more sun spots, solar flares and CMEs, spacecraft operators are already feeling the pinch. In February, SpaceX lost 40 new Starlink satellites after launching into what has been described as a fairly mild geomagnetic storm. The European Space Agency reported earlier this year that its Swarm satellites, which measure Earth’s magnetic field from an altitude of about 270 miles (430 km), they have sunk ten times faster from December 2021 than in all previous years since its launch in 2013.
SpaceX, after the loss of its satellites, agreed to provide NOAA with data on the drag experienced by its satellites to help fine-tune forecast models. Such cooperation between satellite operators and agencies, according to Berger, may provide a useful way forward.
“The profusion of satellites with GPS, like Starlink, in this regard could be a benefit,” said Berger, whose team is cooperating with NOAA in developing the models. “GPS gives you accurate orbital data, which we can use to infer the density of the upper atmosphere. These data points would help us bring our model into line with actual conditions, just like normal weather models do . If we make sure that the model continuously follows the actual conditions, we hope that we can extend the predictions to six or 12 hours in the future with a decent level of accuracy.”
unpredictable
Murtagh, however, warns that a powerful solar storm can strike at any time and with little warning. The 2003 Halloween storm, during which dozens of satellites were temporarily lost, came as the 11-year activity cycle of the sun it was waning and headed for a minimum.
“The sun was really unremarkable [prior to the storms]” Murtagh said. “We had no idea what was going to happen just a week later.”
Although the sun has been showering the Earth with…