On 2026-09-09 02:56 UTC, RU COSMOS 1233 and US USA 121 reached a closest approach (TCA) of 5.74 km, with a relative velocity of 3.71 km/s. This is a cross-border encounter between objects of different nations, the kind of event closely watched for space-security implications. Miss distance and time of closest approach are computed by propagating the latest published orbital elements for both objects, and values update as new element sets are published. See the Satellite Maneuver Tracker for the live picture and space situational awareness for context.
The Two Objects
Where This Happens
At 1434 km this pass sits in low Earth orbit. Objects here stay up for decades: there is too little atmospheric drag to clean the band naturally. Why crowded bands matter →
History Between This Pair
Repeat encounters are common for objects in near-intersecting orbital planes; each pass is re-screened as fresh element sets arrive.
These Objects Elsewhere
How These Numbers Are Computed
Miss distance and TCA come from propagating the latest published orbital elements for both objects and searching for the minimum separation over the screening window. Element sets carry kilometre-scale uncertainty, so figures here describe a close pass, not a collision prediction; a change in either object's published elements re-computes the pass automatically. What is a conjunction? → How conjunction assessment works →