It’s coming down to the wire for the Thirty Meter Telescope, whose board of directors aims to decide by April whether to build in Hawaii or the Canary Islands.

The Hawaii Supreme Court this week set a March 15 date for oral arguments over the question of whether the state must hold yet another TMT contested case hearing — this time on the project’s sublease.

In addition, opening briefs are due at the high court Feb. 15 for anti-TMT forces who are appealing the construction permit that was awarded following the lengthy contested case hearing do-over in Hilo last year.

Answering briefs by permit applicants University of Hawaii and state Board of Land and Natural Resources are due March 27, with the appellants having 14 days to reply after that.

Despite the recent legal progress, it seems unlikely the clouds of uncertainty hovering over the $1.4 billion project will be totally clear by April.

The TMT International Observatory board is putting on a brave face.

“TMT is pleased that the legal process is moving forward and we remain respectful of that process,” TMT spokesman Scott Ishikawa said in a statement Friday. “Mauna Kea is still our preferred site for the Thirty Meter Telescope, and we continue to assess the ongoing situation.”

Meanwhile the California nonprofit is continuing to lay the groundwork for a possible exit to the Canary Islands, a Spanish archipelago off the coast of northwestern Africa.

A demarcation certificate identifying a 24-acre site where the cutting-edge telescope would be built high on a La Palma island mountain is expected to be signed next week, according to a report on TMT’s new Spanish-language website, tmtlapalma.org.

On Dec. 18 the La Palma island council signed the land over to the Institute of Astrophysics of the Canary Islands for a period of 75 years, the website reported this week.

“The TMT team continues to work to make La Palma a real alternative when the board of directors of the TMT International Observatory makes a decision this year regarding the construction site,” according to a translation.

Mauna Kea astronomer Thayne Currie said he remains skeptical about whether TMT will choose to abandon Hawaii. He said he’s heard TMT is behind schedule in planning for La Palma, and it will be even longer with any legal challenge.

Currie, a leader with a group known as Yes2TMT, said studies have shown that La Palma doesn’t compare to Mauna Kea for many forms of astronomy.

“A few months or even a year head start for TMT’s construction is not worth getting saddled with a mediocre site for the next 50-plus years,” he said. “TMT should let the legal process in Hawaii run its course first before making any decisions.”

TMT’s timeline could be blown if the Hawaii Supreme Court doesn’t move relatively quickly. It will certainly take a hit if it decides that another contested case hearing is necessary on the sublease issue.

In his order last year, Hawaii island Circuit Judge Greg Nakamura said the Land Board violated the constitutional rights of plaintiff E. Kalani Flores of Hilo in denying his request for a contested case hearing in 2014, prior to allowing the university to issue a 6-acre sublease to TMT.

UH’s 1967 lease of more than 11,000 acres at the summit of Mauna Kea requires the board’s consent to sublease.

Flores appealed the board’s denial, and Nakamura ruled that, based upon the Supreme Court’s opinion overturning the TMT construction permit, the Land Board infringed upon Flores’ constitutional right to due process. Nakamura vacated the board’s sublease.

For the TMT to move forward quickly, the Supreme Court would have to reinstate the sublease.

The university declined to comment for this story.