Satellites Undergo “Mass Migrations” Due to Geomagnetic Storms

This year, two significant geomagnetic storms caused hundreds of satellites in low Earth orbit to undergo unusual “mass migrations,” raising new questions regarding the coordination of space traffic.

The Gannon storm, a May solar occurrence, was the first to be observed, causing auroral displays in the northern hemisphere at latitudes slightly further south than usual.

Recent Storms' Impact

William Parker of the Massachusetts Institute of Technology highlighted that a recent storm significantly increased air density at low Earth orbit altitudes, causing additional drag on satellite orbits, as he spoke at the American Geophysical Union's annual conference.

The first issue was the lack of precision in forecasting the storm's timing, severity, and length. “As a result of this low skill in our forecasts, SpaceX saw 20 kilometres of position error in their one-day computations” of the orbits of Starlink satellites, he explained. “If we're uncertain about where our spacecraft are by 20 kilometres, then you can throw collision avoidance out the window.”

Remarkably, the issue was made worse by the earlier projections' inaccuracy, resulting in ignorance of their precision and having a big influence on the decision-making process for spacecraft manoeuvres.

The second issue occurred after the storm's peak, with increased drag causing satellites' orbits to decay, leading to automated maneuvers to raise them to pre-storm altitudes.

In the previous geomagnetic storm of the same scale as the Gannon storm, in 2003, there was a two-to-threefold increase from the baseline of around 10 satellites per day performing orbit-raising manoeuvres.

A Spark for Unprecedented Satellite Manoeuvres

Following the Gannon storm, nearly 5,000 Starlink satellites, performed orbit-raising maneuvers in one day, significantly outpacing the daily average of 300. This marks the largest mass migration in history, with half of all active satellites deciding to maneuver simultaneously.

Moreover, the record was broken in October due to a geomagnetic storm, with slightly more satellites moving in one day, despite the addition of hundreds of Starlink satellites launched between the two events.

Mass maneuvers complicate collision avoidance efforts, exacerbated by storm position errors, causing uncertainty in collision timing, a capability lost for days at a time, according to Parker.

Additionally, satellite operators were unaware of position errors and mass-migration phenomena at the time, leading to pointless maneuvers that did not represent reality, as many continued to manoeuvre as if nothing was wrong.

He concluded that improved space weather models and predictions are required. “This is a significant impact,” he stated. “This is critical infrastructure to all of our space operations moving forward, and it will only become more important as time goes on.”

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