At approximately 06:30 UTC today (Wed, 28 Feb) we observed a close conjunction at 608 km between two non-maneuverable spacecraft: a derelict Russian satellite called COSMOS 2221 and an operational NASA satellite called TIMED. The miss distance was less than 20 m with a probability of collision (PC) of 3% to 8% at the time of closest approach (TCA).
Why does this event matter?
This event is notable because it is rare. In the last two years, there have been only six other events with a miss distance of less than 20 m between two intact, non-maneuverable objects. In addition, the resulting debris would have created an increased collision risk on nearby lower orbits used by large constellations and human spaceflight.
Our analysis indicates that a collision between these two objects would have resulted in approximately 2,000 to 7,000 cataloged fragments. This number is derived from analyzing the total mass, spacecraft construction, relative velocity, and encounter geometry. There are nearly 12,000 fragments in LEO as of 15 Feb. This one incident could have added 50% more debris.
The combined mass of COSMOS 2221 and TIMED is 2,530 kg. The relative velocity at TCA was ~14 km/s, well above the six km/s threshold for a hypervelocity event. If the two objects hit center-of-mass on center-of-mass, it could have created up to three times the objects’ combined mass (i.e., ~7,500 fragments). However, this was highly unlikely. The most likely event was that one of the object's solar arrays would clip the other object’s main body. In that case, one object would have been destroyed and the other would have been damaged. For instance, if TIMED clipped COSMOS 2221, the total fragment count could have been approximately 2,500.
The PC for this event was consistently high for several days. Due to this, our team initiated full response mode and we obtained more than 25 updates on both objects 24 hours prior to TCA thanks to our global sensor network.
How can this be prevented?
This event and our continuous analysis illustrate the importance of frequent, high-quality measurements from LeoLabs’ global network of independent radars. These radars are linked through a computational engine that runs on cloud services, delivering data and alerts within minutes. This is critical to maintain a 24/7, comprehensive view of objects and activities in LEO.
Events like this illustrate the critical need for collision avoidance but also debris mitigation and debris remediation to combat the growing risk from derelict objects in LEO. Active debris removal missions, like Astroscale’s ADRAS-J launched on 20 Feb, are promising steps in the right direction.
A single collision in LEO could impact thousands of other satellites for decades. That’s why we must continue to work collaboratively and strategically to ensure this domain remains safe and secure for generations to come.
