📘 Definition
The Space Fence is an S-band ground-based radar system located on Kwajalein Atoll in the Marshall Islands, operated by the US Space Force. It became operational in 2020 and is the most sensitive radar in the Space Surveillance Network, capable of detecting objects as small as ~5 cm in LEO. It provides an "uncued" detection capability — meaning it can detect objects passing through its beam without prior knowledge of their existence, making it particularly valuable for finding new debris. The Space Fence has significantly increased the number of tracked objects in the US catalogue.