The Sea-Based X-Band Radar recently did yeoman duty in the Pacific watching for North Korean missiles and participating in testing as the Pentagon develops a web of new land-based radars and space-based sensors that are expected to make the seagoing vessel less necessary.

The towering “golf ball” radar spent more than a year and a half at sea, returning to its unofficial home port at Pearl Harbor’s Ford Island on May 31, according to the Missile Defense Agency.

“As of now SBX has been at sea for more than 500 days without a port visit,” Michelle Atkinson, the agency’s acting director of operations, said at a Pentagon briefing in mid-March. “The (fiscal 2020) program continues to provide extended SBX sea time to maintain its important contribution to homeland defense.”

The Missile Defense Agency was not able to say how much of the time the more than $2 billion radar spent at sea on defense of the homeland versus missile- defense testing or other missions such as space observation.

But what is clear is that the operating gaps created by the SBX needing to travel to and from the vicinity of Midway Atoll to watch for North Korean missiles will be filled by a series of planned land-based sensors, including the $1 billion Homeland Defense Radar-Hawaii, which is expected to have initial operating capability in late 2023.

That, in turn, could mean a departure of the SBX from Hawaii, experts say.

“With the addition of the long-range discriminating radar in Alaska, the homeland defense radar in Hawaii and the future Pacific radar, we will have in place a diverse sensor architecture in the Pacific to provide an improved and persistent” missile-tracking capability, former Missile Defense Agency Director Lt. Gen. Sam Greaves testified in April.

The Pacific radar, eyed for Japan, would be part of what the military calls a “birth-to-death” tracking custody chain for missiles heading toward Hawaii and the mainland and is tied into the 44 ground-based interceptors in Alaska and California that theoretically would shoot them down.

All told, the three powerful radars will cost more than $3 billion, an expenditure being made to tackle a proliferation of increasingly sophisticated long-range ballistic missiles.

“Nearly all of our adversaries are concerned with U.S. missile defenses and have devised various means to complicate missile defense operations,” the Missile Defense Agency said as part of its fiscal 2020 budget estimates. “Many foreign ballistic and cruise missile systems are progressively incorporating advanced countermeasures, including maneuverable re-entry vehicles and electromagnetic jamming.”

Thomas Karako, director of the Missile Defense Project at the Center for Strategic and International Studies, said the planned new systems amount to a “radar renaissance.”

“There’s really cool stuff coming out,” he said. “The capabilities of various solid-state radars are significantly greater than the radars of the past or the radars that are deployed today.”

Among the advances is the Navy’s new SPY-6 Air and Missile Defense Radar for new destroyers, which is 100 times more sensitive and has a much greater range than the current SPY-1 system on ships.

The radar, tested at the Pacific Missile Range Facility on Kauai, has tracked ballistic missile targets possibly as far as Kwajalein Atoll, a distance of about 2,500 miles.

Riki Ellison, chairman of the Missile Defense Advocacy Alliance, suggested that Hawaii could be better protected from North Korean missiles in times of emergency by operating Kauai’s SPY-6 radar in conjunction with ship- or shore based SM-3 Block IIA missiles.

The new radar developments leave the future of the SBX radar, which is limited by a narrow field of view, up in the air.

The SBX spent 250 days at sea and traveled over 5,800 nautical miles in calendar year 2017, according to the Pentagon.

To “address the continued missile test activity in North Korea,” the Missile Defense Agency said it is seeking 305 days at sea and 60 days for in-port maintenance for SBX in fiscal 2020, and 330 days at sea annually from 2021 to 2024.

The radar is back in Hawaii for regular maintenance and installation of system upgrades. Shore personnel will conduct inspections and surveys, and crew members will conduct training, said Maria Njoku, a Missile Defense Agency spokeswoman.

“Something like SBX will remain an important asset in the near term, to have a defense-and-defeat dominant posture toward North Korea,” Karako said. “In the longer term, however, adapting to Russia and China will require a much different solution set than a chain of surface-based radars, capable as they are.”

The United States might need to “consider accepting greater risk with North Korea and moving with all deliberate haste toward a robust space sensor layer capable of tracking both ballistic missiles and hypersonic gliders,” he said.

Supporting that could potentially involve canceling the Pacific radar, parking the SBX in its place or moving its radar ashore, and transferring the funds to space sensors, he said.

Ellison, meanwhile, said if tensions continue to heat up with Iran, and with other radars being built in the Pacific, the SBX could at some point be moved to the Atlantic.