Feb 16, 2022
Will Geomagnetic Storms Complicate Low Earth Orbit Constellations?
SpaceX’s Starlink constellation lost 40 satellites last week due to unanticipated effects of a geomagnetic storm. As we enter a new 11-year solar cycle, many of these constellations will experience previously untested conditions. We asked our space weather expert about what this will mean for future LEO constellations.
SpaceX’s Starlink provides high-speed, low-latency broadband internet across the globe using a fleet of satellites in Low Earth Orbit. More than 2,000 Starlink satellites have been launched by SpaceX as of January, 2022.
On February 8, 2022, SpaceX announced that 40 of the 49 Starlink satellites launched five days earlier were lost to a geomagnetic storm. These satellites were deployed around 210km (130 miles) above the Earth’s surface, according to SpaceX updates. While atmospheric density falls off exponentially with altitude, there is still enough of the sparse atmosphere at this altitude to slow satellites. This phenomenon, known as drag, can cause small satellites to lose altitude and reenter relatively quickly if they cannot use thrusters to raise their orbits. SpaceX reported each satellite achieved controlled flight after launch, however, geomagnetic storming resulted in increased atmospheric drag of roughly 50% shortly after insertion.
We talked with Bob Rutledge, director of Aerospace’s Space Sciences Department, to learn about future implications of geomagnetic storms. Prior to joining Aerospace, Bob was the Lead of the Space Weather Forecast Office at NOAA’s Space Weather Prediction Center.
What happened to the Starlink satellites when the geomagnetic storm hit?
While geomagnetic storming can cause substantial changes in atmospheric density, this geomagnetic storm was relatively small, particularly compared to what is typically observed in larger storms. In this orbital regime, however, the margins for error are likely quite small.
SpaceX attempted to put the satellites into a low drag configuration “safe mode,” flying them edge-on, but all but nine of satellites were lost as they could not be recovered from this safe mode and had to safely reenter.
Was this a predictable event? How much warning time did SpaceX have?
While the prediction of geomagnetic storms remains challenging, with the larger uncertainties associated with events originating from eruptions on the sun, this low-level storm was reasonably well-predicted. In fact, NOAA predicted a slightly higher storm intensity for this event than what actually occurred.
Storms of this intensity are common, occurring nearly one in every four days when averaged over an 11-year solar cycle. This event would be on the very low end of what would be considered a storm. While the storms associated with eruptive events can occur less than 24 hours after an event was observed on the Sun, some of these storms are caused by features on the sun that can be predicted with days or even weeks of lead time.
What kind of precautions are taken before launch to address space weather events?
Space weather is considered as a launch constraint, but historically more focus has been on the energetic radiation environment. As satellites are launched to very low insertion orbits, like this Starlink mission, the margins for error and sensitivities to drag become more pronounced. While this is a defensible posture in that satellites that do not function will quickly deorbit, there are sensitivities and variations that increase risk in mission success.
Is the frequency of Space Weather incidents increasing? If so, will this endanger existing Low Earth Orbit SmallSat constellations?
Space weather is a broad term that captures a variety of phenomena including geomagnetic storms, solar flares, and changes in the near-Earth radiation environment. Some of this activity trends with the roughly 11-year solar cycle and some of it is less well correlated. While overall solar activity is on the rise, big space weather events can occur at any time and throughout the solar cycle. There has been a rapid expansion in Low Earth Orbit (LEO) satellite constellations in recent years, during a time in which space weather has been generally quiet. A severe space weather event may reveal satellite vulnerabilities not yet seen.
Was the event detected by ECP-lite or other Aerospace-developed space weather sensors?
While the ECP-lite sensors inform situational awareness of the radiation environment, there are no indications or reasons to believe this was radiation-induced or related to radiation effects on microelectronics. While Energetic Charged Particle (ECP) sensors would have shown some variation as a result of this low-level activity, the overall radiation environment remained benign, particularly at this low insertion altitude. Initial indications are that this is purely drag-related and not a result of any other part or system failure.
Were there widespread impacts to other satellites during this event?
As this event was not associated with an increase in the energetic radiation environment, either from an eruption on the sun or as a result of the dynamics of Earth’s trapped radiation, impacts to satellites would not be expected. The ever-present trapped radiation environment constantly challenges satellites systems and can drive satellite anomalies at any time. Careful satellite design is required to mitigate and reduce these anomalies. With respect to increased drag on other satellites, satellites at higher altitudes would not be affected by these small changes that are well within the normal variability of the environment.
What challenges does the loss of these satellites underscore?
Aerospace continuously engages in research in the upper atmosphere, its changes in density, and the subsequent impacts on satellite systems. We develop LEO missions, sensors, and models to better understand these changes and the underlying science. This research keeps Aerospace at the cutting edge of the expanding space enterprise, particularly in the proliferated LEO domain. With the growing utilization of these orbits and the rapid development and deployment of systems, understanding and predicting the overall satellite environment is increasingly important. The margins between success and failure can be small and can only be fully understood and mitigated through the best of science and application of technology in this area.
Bob Rutledge is currently the director of Aerospace’s Space Sciences Department. Prior to joining Aerospace, Bob was the Lead of the Space Weather Forecast Office at NOAA’s Space Weather Prediction Center, the Nation’s official source for civil space weather watches, warnings, and alerts. Prior to joining SWPC, Bob worked at NASA’s Johnson Space Center as the International Space Station (ISS) Radiation System Manager, responsible for oversight of the development and sustaining engineering of NASA’s operational radiation measurement hardware on board ISS. Bob began his career at NASA with the Space Radiation Analysis Group with responsibilities spanning planning, modeling, measurement, and operational management of astronaut radiation exposures.
