“Space Fence” around earth can track objects as small as 10cm.

The Space Fence, run by the US Space Force, is now fully operational. It is a radar system used to track objects approaching earth.

https://www.upi.com/Defense-News/2020/03/30/Space-Fence-radar-operational-tracks-objects-as-small-as-10-centimeters/4311585591501/?ts_=23