>NOTAM warns aircraft to avoid the north of Kwajalein Atoll's runway due to radiation hazards.
In March of 2020 the United States Space Force (USSF) declared operational acceptance and initial operational capability of the Space Fence radar on the Kwajalein Atoll in the Republic of the Marshall Islands.
https://www.lockheedmartin.com/en-us/products/space-fence.html
How Things Work: Space Fence
The new S-band phased-array radar will have tens of thousands of transmitters and hundreds of thousands of receivers, supported by structures capable of withstanding seismic activity. One of the largest S-band arrays in the world, the receiver alone measures 7,000 square feet. The transmitter is 2,000 square feet. Both will be enclosed in buildings with roofs of electronically transparent Kevlar. Within each element, gallium nitride semiconductors amplify the radar’s power. In a phased array, the elements can be pulsed separately, so the installation will be able to simultaneously search for and track individual objects.
Airspace above the array will be restricted to air travel
https://www.smithsonianmag.com/air-space-magazine/how-things-work-space-fence-180957776/