The Thirty Meter Telescope contested case hearing will resume Monday with a field trip to the site of the planned $1.4 billion observatory near the summit of Mauna Kea.

On the tour’s agenda: the same red-balloon test that was conducted five years ago during the original contested case hearing site visit.

In 2011, a red helium balloon attached to a 187-foot rope was sent aloft to illustrate the 18-story height of the proposed cutting- edge-technology observatory that will feature one of the largest and most powerful telescopes in the world.

The state Supreme Court ordered a new contested case hearing after ruling in December that the state Board of Land and Natural Resources erred when it approved the project before conducting the 2011 contested case.

By approving the project first, the high court said, “the board put the cart before the horse” and failed to consider the evidence presented during the hearing.

As for Monday’s site visit, the parties not only will stop at the 5-acre TMT site on the mountain’s northern plateau, they will also visit the project’s batch plant staging area on Access Road below Puu Wekiu, and make a stop on Summit Loop Road near the Keck Observatory.

The tour may also include two or three other sites to be determined by hearings officer Riki May Amano as the visit proceeds, according to her latest order.

Nearly 30 hearing participants have been approved by the retired Hawaii island judge to join the mountaintop visit. The group will travel in three vans from Hilo to the top of Mauna Kea with a couple of stops to help the group acclimate to the elevation change. Hawaii’s tallest mountain rises nearly 14,000 feet.

In asking the TMT International Observatory board or the University of Hawaii at Hilo to arrange for the balloon test, Amano apparently rejected a suggestion by the Mauna Kea Hui petitioners for a more substantial demonstration.

In a filing, the group of TMT foes suggested that red balloons not only be sent 18 stories aloft to mark the dome, but be attached to poles to mark the four corners of the proposed observatory.

The group also suggested that colored tape mark the boundaries of the construction area, the dome and any support structures, as well as other sites affected by the proposed construction, including the Hale Pohaku substation, electrical boxes, batch plants and roadways.

In addition to the site visit, the replay of the formal evidentiary portion of the hearing has been scheduled to start at 10 a.m. Oct. 11 at the Hilo Naniloa Hotel on Banyan Drive.