The Missile Defense Agency’s towering Sea-Based X-Band Radar is expected to be visible on the horizon soon and will pull into Pearl Harbor today, officials said.

The primary purpose for its return is to make a change in contractors for some of the SBX support functions, the MDA said.

The one-of-a-kind, $1 billion SBX is a combination of an advanced X-band radar mounted on a mobile, oceangoing, semi-submersible platform that’s part of the nation’s ballistic missile defense system.

The agency said last month that it planned to sideline the missile tracker by placing it "in a limited test and contingency operations status" to save $500 million over five years.

The change was detailed as part of the Defense Department’s budget request for 2013, which set out $487 billion in cuts over the next 10 years.

It remains unclear where the agency will keep the missile-tracking platform. Pearl Harbor’s Ford Island had become its unofficial home port.

Pam Rogers, an MDA spokeswoman, said a final determination hasn’t been made as to where the SBX will be for the long term.

"For right now, it’s going to be at Pearl Harbor," she said.

It’s unclear how long the vessel will be in Hawaii. MDA said the floating radar will be available for missile tracking purposes if it is needed.