“For some of the [low Earth orbit] science missions, we saw a lowering of the [satellite’s] orbit of anywhere from dozens of meters to hundreds of meters,” recalled NASA’s DeHart following the May 2024 solar storm, “as much as 400 to 600 meters for some of our spacecraft.” That one incident, fueled by the Sun’s frenetic activity, provides a glimpse into the deep and occasionally contradictory impact of solar maximum on the busy freeways of low-Earth orbit (LEO).
The Sun’s 11-year cycle peaked in late 2024, releasing a flood of coronal mass ejections and geomagnetic storms that have remade the upper atmosphere and with it, the destiny of thousands of satellites. The outcome: an abrupt spike in atmospheric drag, trimming satellites’ altitude at a rate seldom observed during the age of mega-constellations.
Starlink’s constellation, now in the thousands, is the bellwether for this new world. NASA’s Goddard Space Flight Center monitored 523 Starlink reentries from 2020 to 2024, which showed a stark trend: under low geomagnetic activity, satellites at a reference altitude of 280 km generally reentered after 16 days; under moderate activity, that period decreased to 12 days; under extreme storms, satellites fell from orbit within 7 days. The May 2024 “Gannon” superstorm itself initiated the biggest en masse satellite maneuver in history, with almost half of all operational LEO satellites largely Starlink carrying out emergency orbit-raising burns.
This spike in atmospheric density is not a faint signal. In geomagnetic storms, the thermosphere can get hot and bloated, doubling or tripling mass density at altitude 400 km within hours. The physics is uncomplicated but merciless: drag acceleration varies in direct proportion to atmospheric density, and as satellites decapitate, they plummet downward, puncturing increasingly dense air and amplifying the process. “During an extreme magnetic storm event, a satellite could drop nearly a third of a mile in elevation in one day,” said Denny Oliveira of NASA Goddard, “as much as a satellite would typically lose in a year.”
For satellite operators, it is a two-edged sword. While added drag serves as a natural mechanism for removing debris by accelerating the deorbit of dead satellites and pieces that could otherwise remain in LEO for decades a fleeting respite from the fight against the Kessler Syndrome, where uncontrolled collisions would make LEO unusable the same forces endanger operational satellites, particularly those without propulsion or with low fuel reserves. The destruction of 39 Starlink satellites in February 2022, during a moderate geomagnetic storm, was an omen of the threat: low-altitude deployed satellites could not overcome the abrupt increase in drag and disintegrated before entering operational orbit.
The operational stakes are immense. Automatic collision avoidance and stationkeeping algorithms now vital for mega-constellations are no better than the models and forecasts on which they are based. But as recent storms have demonstrated, space weather forecasting is still a crude art. The ap and Dst indices that monitor geomagnetic activity are famously hard to forecast more than a day or two ahead of time. At the beginning of the May 2024 event, the initial rise in ap was underestimated by as much as 300 units, and predictions trailed behind actual events. This uncertainty directly maps to satellite position errors errors of several kilometers over the course of a day, making conjunction analysis and collision avoidance difficult.
Satellite drag models, including NRLMSISE-00 and DTM2020, have become more accurate in the past few years, with storm-time biases typically now a few percent when calibrated with in-situ measurements. But model accuracy varies with altitude, and multi-peaked storms such as those now more frequently occurring in the ongoing solar cycle are more difficult to simulate accurately. It is further complicated by variation in satellite design: later-generation Starlinks, for instance, have quadrupled in mass and area over previous designs, changing their ballistic coefficients and therefore their response to drag.
Operators are now presented with a world where fuel margins are nibbled away by unforecasted storms, removing years of mission lifetime. For close-altitude or phasing mission requirements, including Earth observation and inter-satellite link constellations, the expense of repeated maneuvers can be steep not only in propellant but in mission continuity and data integrity. And for non-propulsive satellites, the danger is existential.
Space weather mitigation strategies are evolving. NASA’s CARA team and the U.S. Space Force’s tracking networks now issue real-time conjunction alerts and coordinate maneuver planning. Automated systems can place satellites in safe mode or reorient solar panels to minimize drag during predicted storms.
The solar maximum paradox is evident: the very storms that come with the potential to reduce satellite lifetimes and make collision avoidance more difficult are also responsible for purging the orbital environment of its debris. As operators learn to adjust, the dynamic interplay between solar activity, atmospheric physics, and satellite engineering is creating a new space traffic management era in which the Sun’s moods are as important as any human choice.
