The Missile Defense Agency is back seeking public comment on two possible locations for a powerful ballistic missile defense radar on either the North Shore of Oahu or the west side of Kauai — both looking toward North Korea — with Congress most recently pumping $133 million into the plan.

Whether the $1.9 billion Homeland Defense Radar- Hawaii, first discussed publicly in 2018, will ever get built remains a question mark, with not enough missile defense dollars chasing too many very costly missile defense efforts.

The equation in recent years became far more complicated with the arrival of Chinese and Russian hypersonic maneuvering and low-flying cruise missiles that can evade ground-based radars and as the Pentagon looks to space to solve part of the problem.

Hawaii’s congressional delegation has sought to put money in the budget for the Hawaii tracking radar, while the Pentagon has previously taken it out.

“Unfortunately, without consulting with Congress and contrary to the Missile Defense Agency’s position, former President Donald Trump’s Secretary of Defense Mark Esper zeroed out funding in the fiscal year 2021 budget request,” said U.S. Sen. Mazie Hirono, a Hawaii Democrat and member of the Senate Armed Services Committee.

Esper last year noted local opposition to Oahu sites for the radar and said development of the system “is one thing, but if I develop a system and can’t put it somewhere, it has no effect. It’s wasted money.”

Hirono said in an email to the Honolulu Star-Advertiser that she “worked to restore the authorization and funding so the Missile Defense Agency can move forward with the environmental analysis and community outreach for siting HDR-H.”

Details of the latest Hawaii radar plan can be found here: https://www.mda.mil/system/hdrh/. Public comment for the current phase of the “environmental impact statement” will be taken through April 12.

Three possible sites on Oahu for the radar, expected to have a single face up to 85 feet tall, have been whittled down to one at the Army’s Kahuku Training Area above the Kahuku Motocross Park. Also being considered is a site at the southern end of the Navy’s Pacific Missile Range Facility on Kauai. Restricted airspace arcs would fan out over the ocean to a distance of 9 miles.

But even as the the Missile Defense Agency was refining those candidate sites, the Pentagon zeroed out funding for the Hawaii radar and a Pacific radar that might have been placed in Japan, in favor of a review of sensor needs.

“Due to a shift in Department of Defense priorities, the department has postponed pursuing the development and fielding of a Homeland Defense Radar-­Hawaii beginning in FY2021,” budget documentation from last year states. “In light of the postponement of the program, MDA is evaluating contract termination and other open commitments.”

Testifying a year ago before a House Armed Services subcommittee, Missile Defense Agency Director Vice Adm. Jon Hill said the United States was at an “inflection point” that was complicating missile defense.

“Ballistic, hypersonic and cruise missiles are becoming more capable of carrying conventional and mass destruction payloads farther, faster and with greater accuracy,” he said in prepared remarks.

Russia and China continue to develop advanced missiles designed to overfly air defense sensors and fly below ballistic missile sensors, he said.

Missile defense will “continue to leverage space-based, ground-based and maneuverable sea-based sensors,” Hill said. “Yet there will never be enough terrestrial-based sensors to track maneuvering missiles in large numbers. If we are to outpace the threat, we need a persistent space-based global sensor capability.”

In January, Northrop Grumman and L3Harris received contracts for satellite prototypes to track hypersonic and ballistic missiles.

In the meantime, Hawaii relies on a network of smaller radars as well as the Sea-Based X-Band Radar should a North Korea threat become imminent.

Lest anyone reject that possibility, Gen. John Hyten, vice chairman of the Joint Chiefs of Staff, said last month that “I would challenge anybody that lived through” heightened tensions with North Korea in 2017 “to look at that problem and not realize (there) was a real possibility that Kim Jong-Un would actually use a ballistic missile, possibly with a nuclear warhead, in anger at the United States.”

Sensors cue defensive missiles, and the Missile Defense Agency also continues to develop the SM-3 Block IIA missile, which was fired from a Navy destroyer in November and destroyed a mock intercontinental ballistic missile in a “defense of Hawaii” test.

Hawaii is expected to receive such “regional” protection in the near future against North Korean threats using SM-3 IIA missiles that are either ship- or shore-based at the Aegis Ashore test complex at the Pacific Missile Range Facility.

Amid all of the flux, the Missile Defense Agency says it is “engaged in advance planning studies and preparing an environmental impact statement for the siting and development of the (Hawaii radar) should a deployment decision be made and is funded.”

Congress in December passed an appropriations bill that included $133 million for the Hawaii radar. Riki Ellison, chairman of the nonprofit Missile Defense Advocacy Alliance, said at the time that “the Hawaii delegation came strong” with the radar.

But it’s still been left out of the Pentagon’s five-year planning known as the Future Years Defense Program.

“There’s always a demand for more sensors to track and better discriminate the threat,” said Tom Karako, director of the Missile Defense Project at the Center for Strategic and International Studies. “The path forward will depend upon restoring the longer term budget wedge; balancing the benefits of a Hawaii radar with global sensor needs, including space sensors; and resolving local objections.”

Bradley Bowman, senior director of the Center on Military and Political Power at the Foundation for Defense of Democracies, said there is “no doubt that we need to improve missile defense sensing and discrimination capabilities in Hawaii — and the HDR-H would help do that.”

“The problem is that Washington has consistently underfunded missile defense, increasing risk and forcing tough choices. The United States should deploy HDR-H if sufficient resources are available,” he said.

Hirono noted that while the Missile Defense Agency chalked up a successful ICBM intercept in the SM-3 IIA missile test, “that system is but a part of the layered missile defense system MDA is currently fielding to defend Hawaii against threats in the region — including (the Hawaii radar) upon its completion. I am committed to protecting the safety and security of Hawaii residents and all Americans.”