Firmly in the category of something you don't see every day in Hawai'i, a 28-story radar platform topped with what looks like a giant golf ball floated into Pearl Harbor yesterday on an even more massive semi-submersible transport ship.

The Sea-Based X-Band Radar, a component of the nation's developing ballistic missile defense program, completed a 15,000-mile trip from Corpus Christi, Texas, around South America to get to Hawai'i. The phased-array radar, atop an oil rig-like platform, whose support pylons each are as long as a Trident missile submarine, is headed for its home port of Adak, Alaska.

While in Pearl Harbor until the spring, the $815 million radar system will get a paint job and other work worth up to $5 million, officials said.

"We're very appreciative that we got the work over here," said BAE Systems Hawai'i Shipyards president Roger Kubischta. "It's mainly labor intensive getting up there and blasting" the structure with water for painting.

Honolulu high-rise dwellers who saw the behemoth sail in yesterday afternoon likened it to something out of the movie "Waterworld," Kevin Costner's sea-based adventure tale.

Pam Rogers, a spokeswoman for the Missile Defense Agency, said the 390-foot-long X-Band Radar is probably one of the more unique seagoing craft Hawai'i ever will see.

"I think the universal statement that I have heard is, 'Wow!' " Rogers said. That's followed by, "It looks like a giant golf ball on an oil rig."

The Missile Defense Agency in 2003 considered home-porting the powerful missile-tracking radar in Hawai'i three miles off Kalaeloa, the former Barbers Point, but instead picked tiny Adak, which had a population at the time of 250 and was home to a Navy base that was shuttered in 1996.

The X-Band radar yesterday sailed into Pearl Harbor on an equally impressive ship, the 736-foot semi-submersible MV Blue Marlin, which was big enough to transport on its lowlying cargo deck the destroyer USS Cole after it was attacked in Yemen by suicide bombers in 2000. The blast killed 17 U.S. sailors and injured more than 40.

The X-Band Radar will sail on its own to Alaska after getting the paint job and minor modifications. Although it will be based in Adak, the radar will be capable of moving throughout the Pacific to support testing and defensive operations.

The radar is part of the Ground-Based Midcourse Defense System, which is designed to intercept and destroy long-range ballistic missiles aimed at the United States.

Air Force Lt. Gen. Henry "Trey" Obering, director of the Missile Defense Agency, has said in the past that the radar could identify a baseball-sized object over San Francisco from as far as Chesapeake Bay.

The radar will support interceptor missiles being placed in Alaska and California to defend against a limited long-range missile attack, the Defense Department said.

The United States is pursuing a layered defense against intercontinental ballistic missiles that includes Pearl Harbor ships like the cruiser USS Lake Erie, a test bed for tracking and shooting down ICBMs.

On Nov. 17, the Lake Erie shot down a test missile fired from the Pacific Missile Range Facility on Kaua'i using an SM-3 missile. It was the sixth successful test out of seven tries.

By 2009, 18 Aegis U.S. Pacific Fleet destroyers and cruisers are expected to be able to shoot down ballistic missiles.

SEA-BASED X-BAND RADAR

This system tracks, discriminates and assesses incoming missiles.

Its radar platform is 240 feet wide and 390 feet long. It towers more than 280 feet from its keel to the top of the radar dome and displaces nearly 50,000 tons.

The radar is capable of tracking a baseball-sized object over San Francisco from as far as Chesapeake Bay.

Larger than a football field, the main deck houses living quarters, workspaces, storage, power generation, a bridge and control rooms for a crew of about 75.

Built on a semi-submersible oil-drilling platform, it is twin-hulled, self-propelled and stable in turbulent seas.

Reach William Cole at wcole@honoluluadvertiser.com.