The U.S. Missile Defense Agency’s Sea-Based X-Band, or SBX, radar vessel is slowly moving east on the Strait of Juan de Fuca today.

The giant movable radar station, which normally moves around the Pacific Ocean, is headed into Admiralty Inlet and Puget Sound later today for maintenance and repair at a Seattle shipyard, according to the Missile Defense Agency.

Boeing won a $27.1 million contract to perform maintenance and upgrades on the huge system. The work is set to take about three months.

People are not allowed within 100 yards of SBX while it is in navigable U.S. waters and moored at Vigor Shipyards — the former Todd Pacific Shipyards — at Seattle’s Harbor Island.

The 280-foot tall SBX is a floating, self-propelled, mobile radar station designed to operate in high winds and heavy seas. It is part of the Defense Department’s Ballistic Missile Defense System.

The radar system is mounted on a fifth-generation, Norwegian-designed, Russian-built CS-50 semi-submersible twin-hulled oil-drilling platform.

The radar mount was built and mounted on the platform at the Kiewit yard in Ingleside, Texas, near Corpus Christi.

It is supposed to be based at Adak, Aleutian Islands, Alaska, although it’s never been there, according to the Defense Department.

Instead, it roams over the Pacific Ocean to detect incoming ballistic missiles.

The Missile Defense Agency said the radar is not operating while the giant apparatus is in port.