Even small solar outbursts can have massive consequences for the environment around Earth, space weather experts have learned after SpaceX lost 40 brand-new satellites in February after launching them into a "mild" geomagnetic storm. In a new study, a team of researchers outlines how to fix space weather forecasts in the future, to prevent companies from sending their craft into such "treacherous waters."
In late January of this year, an eruption of hot magnetized plasma burst from the sun toward Earth, prompting space weather forecasters at the U.S. National Oceanic and Atmospheric Administration's (NOAA) Space Weather Prediction Center (SWPC) to issue a warning for a mild geomagnetic storm.
At the same time, SpaceX engineers were readying a batch of 50 Starlink internet satellites for launch on the company's Falcon 9 rocket. They saw the space weather alert and ran the data through a model of Earth's upper atmosphere, into which they were about to place their spacecraft. The analysis suggested the environment was safe, but when the rocket discharged the payload at an altitude of 217 miles (350 kilometers), all hell broke loose. The thin air around the spacecraft behaved differently than what the ground controllers had expected, and 38 of the new satellites quickly headed back to Earth instead of climbing to their operational orbit 340 miles (550 km) above the planet.
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The geomagnetic storm was soon identified as the culprit of the mishap, and a new study by SpaceX and NOAA experts has now revealed that had SpaceX followed NOAA's additional resources, the company may have changed its mind about that fateful launch.
Last year, NOAA launched what it calls the Whole Atmosphere Model (WAM), which models processes in Earth's atmosphere all the way to the altitude of 370 miles (600 km), way above the troposphere where terrestrial weather occurs. The model includes the thermosphere, the second-highest layer of Earth's atmosphere, where thin, diffuse gases cause drag that slows satellites down.
When space weather hits, the thermosphere swells up, the density of its thin air temporarily increasing. The study showed that during that geomagnetic storm, the air density at altitudes between 125 and 250 miles (200 and 400 km) increased by 50% to 125%. For satellites orbiting Earth at speeds of nearly 20,000 mph (28,000 kph), such an increase in density would feel like suddenly running against a very strong wind.
Since the mishap, SpaceX has been working with NOAA to help improve space weather forecasts for satellite operators, Tzu-Wei Fang, a space scientist at the SPWC and lead author of the new study, told Space.com in an earlier interview.
The company even started providing data about its low Earth-orbiting satellites to the agency to improve the model, as NOAA currently struggles with a lack of measurements from the critical region, according to Fang.
"This study demonstrates the benefits that can come from collaborative work between government and industry," Fang said in a statement. "The free exchange of model and satellite data and close interaction between SWPC and the Starlink team have enabled us to identify the quantitative impact of space weather events on these satellites, which help us to quickly prioritize our tasks to improve our space weather models and design the operational products that will better meet the needs of modern space commerce."
SpaceX is not the only satellite operator to have experienced problems due to space weather. Earlier this year, the European Space Agency said its Swarm satellites, which monitor Earth's magnetic field, had been sinking 10 times faster since December 2021 than in other years since their 2013 launch. The reason for that is increasing solar activity as the sun moves toward the peak of its current solar cycle, the 11-year cycle of ebb and flow in the generation of sunspots and eruptions. Moreover, the current solar cycle is turning out to be much more active than space weather forecasters predicted, and it comes after a prolonged quiet period.
Experts warn that the current period of disturbed space weather comes at a time when a much higher number of small satellites is being launched into low Earth orbit than during previous solar cycle peaks. Many of these new satellites are simple cubesats without onboard propulsion. Increased atmospheric drag due to space weather may therefore considerably reduce the time the spacecraft can stay in orbit performing their missions.
The study concluded that it is "crucial for SWPC to establish suitable alerts and warnings based on [air] density predictions to provide users guidance for preventing satellite losses due to drag and to aid in collision avoidance calculations."
Other teams have warned that, in cases of very severe solar storms, the changes in drag could be so substantial that the speeds and altitudes of orbiting satellites would change so much that computer algorithms that generate warnings when two objects, satellites or space debris, get too close to each other would become completely inaccurate.
It would take several weeks to retrace all of the junk and cubesats and sync the catalog with reality. During that time, operators would not be receiving accurate collision avoidance notices, and the risks of devastating in-orbit collisions would substantially increase.
Severe solar storms can also cause havoc on Earth, triggering power blackouts and disrupting GPS and radio signals. Although such powerful solar storms are not common, they can sometimes appear with little warning.
The study, published in AGU's journal Space Weather, was published on Nov. 2.
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