The Missile Defense Agency’s giant floating radar left its Ford Island dock yesterday after $7 million in maintenance was completed faster than expected, officials said.

When it will return to Hawaii is unclear. Missile Defense Agency officials said it will resume operations at sea.

The $1 billion ballistic missile tracker, known as the Sea-Based X-Band Radar, or SBX, arrived back at Pearl Harbor on July 13.

The Missile Defense Agency said the SBX would be in port in Hawaii for "periodic maintenance" and to conduct American Bureau of Shipping surveys leading to renewal of a U.S. Coast Guard certificate of inspection.

The work included checks of the vessel hull and machinery operating condition and safety, as well as checking all safety programs aboard SBX.

The distinctive radar was expected to be in Hawaii until the fall.

Missile Defense Agency officials last month said they also were looking at three deepwater ports on the West Coast for additional maintenance.

Those shipyards were Naval Station Everett, Wash.; Todd Pacific Shipyard in Seattle; and Naval Air Station North Island, San Diego, said Pam Rogers, an agency spokeswoman. Pearl Harbor is not deep enough, she said.

The powerful radar has 45,000 radiating elements within its white pressurized dome to track targets. Designed to discriminate nuclear warheads from decoys, the radar is so powerful it can detect a baseball flying through the air on the East Coast when the SBX itself is on the West Coast.

Adak, Alaska, was the radar’s intended home port, but the SBX has spent scant time there. It has never pulled into port in Adak, officials said.

The radar platform is large enough to fit 18 basketball courts.

In 2003, Pearl Harbor and Kalaeloa were considered as home port possibilities for the SBX, along with anchorages in California, Washington state, the Marshall Islands and two sites in Alaska, before Adak was selected.

Since the "golf ball" arrived here in 2006 from Corpus Christi, Texas, for a temporary stay, it has returned periodically to Hawaii for millions of dollars in maintenance and repairs.

The SBX last left Pearl Harbor on June 16, 2009.

According to the Missile Defense Agency, the vessel traveled around the central Pacific within a thousand miles of Hawaii, and was in the northern Pacific near Adak, and the Bering Sea north of Dutch Harbor. But the SBX did not dock in Adak.