Every 22 seconds, briefly in the low Earth orbit, there are two satellites moving close, less than a kilometer apart. For example, for the Starlink satellite system, there is a close approach every 11 minutes. This is going on because of the rapid expansion of satellite megaconstellations. This situation creates a constant need for collision avoidance maneuvers, where each Starlink satellite performs an average of 41 per year. However, new research indicates a possible breakdown in this precision after a serious space weather event, rendering command functions obsolete.
Sarah Thiele and her collaborators have also introduced the Collision Realization and Significant Harm Clock, which is far more drastic. As of mid-2025, calculations indicate that when operators lose the possibility of transmitting avoidance maneuvers, a catastrophic collision can be expected within 2.8 days. By 2018, before the megaconstellation rush, the window of time stood at 121 days. Losing control for just 24 hours carries a 30% probability of a collision resulting in debris that would ignite Kessler syndrome.
The threat with a worst-case scenario like this is best posed by solar storms. In fact, solar storms are the most likely cause of this kind of situation. This happens in two ways. First, solar storms heat up the upper atmosphere of the Earth, causing drag on some of the low Earth-orbit satellites. The May 2024 “Gannon Storm” prompted more than half of all low Earth orbit satellites to burn propellants during reposition maneuvers, with some science missions observing orbital altitude reductions of up to 400–600 meters. Next, solar storms may impair navigation and communication systems.
The response time is brutally short. Solar flares take eight minutes, and a coronal mass ejection, or CME, follows one to two days later. ESA’s recent Carrington-level event scenario assumed a CME that caused a 400% increase in atmospheric drag, reduced the accuracy of satellite junction, and resulted in potential collisions that shift by the hour. In such a scenario, a plan might prevent a collision while, coincidentally, increasing the risk of a different one.
Although warning systems such as the models of the Space Weather Prediction Center operated by NOAA, NASA’s Community Coordinated Modeling Center, or missions like SOHO, STEREO, and DSCOVR give warnings, it could be only two days prior to the event. This could be extended by ESA’s new Vigil mission, to be launched in 2031, with its orbit around Lagrange Point 5, where it would survey the Sun for dangerous activity prior to it appearing on Earth’s horizon.
With the megaconstellations, automation is already at the forefront of the technology. For instance, the Starlink network operated by SpaceX initiates the necessary star link maneuvers, provided the probability of collisions is greater than the Standard of 3 per 10 million. However, in the event of solar storms knocking off the automated star link systems, human control is necessary. This is impractical, since there may be as many as one million approaches for the week.
Orbital debris mitigation is another factor introduced by megaconstellations, as it complicates matters further. A study by NASA’s Large Constellation divided constellations and concluded that if 99% of a satellite constellation is made to deorbit itself in five years following mission completion, it would avoid debris generation. However, at altitudes of above 1,000 km, where mega-constellations aim to orbit their satellites, objects can stay for over a thousand years, thereby making a collision serious.
Shielding and redundancy are beneficial in mitigating single event upset damage to the electronics, but comprehensive hardening is expensive, adding to the mass. The need to weigh these considerations against the availability of fuel for collision maneuvers was illustrated by the Sentinel-1D ESA scenario simulating the operational turmoil caused by a strong storm: impaired GNSS reception, star tracker losses, battery malfunctions, and concurrent collision warnings even as the density varied erratically.
The CRASH Clock highlights the delicacy of the present-day security of orbits. In high density satellite orbits, the successful avoidance of potential collision courses on a constant basis is what has prevented major collisions thus far. A large-scale event, particularly one caused by a super-solar storm, could eliminate that security mechanism almost instantaneously. And despite Kessler syndrome taking up to several decades to fully unfurl, the initial burst of space debris following a collision in today’s highly populated region could fundamentally alter mission parameters overnight.
