Spacewalkers Prep Space Station For Final Roll Out Solar Arrays

NASA astronaut Nicole “Duke” Mann and Japan Aerospace Exploration Agency astronaut Koichi Wakata conduct a spacewalk outside the International Space Station on Jan. 20.

HOUSTON—U.S. and Japanese astronauts carried out preparations for the installation of a third and final pair of Roll Out Solar Arrays (iROSAs) on the International Space Station’s (ISS) long solar power truss with a more than 7-hr. spacewalk on Jan. 20.

The excursion took NASA astronaut Nicole “Duke” Mann and Japan Aerospace Exploration Agency (JAXA) astronaut Koichi Wakata to the starboard end of the nearly 360-ft.-long truss to complete the installation of an iROSA mounting platform at the IB power channel. They also mostly installed a mounting platform at the nearby 1A power channel. The iROSA work was started on a previous NASA spacewalk.

They were not able to secure a left middle strut on the overall triangular support structure for the 1A power channel. The astronauts were instructed by NASA’s Mission Control to return the strut to the ISS U.S. segment Quest airlock to await another attempt on a future spacewalk.

The iROSAs assigned for installation at the 1B and 1A sites are planned for launch to the seven-person ISS in June aboard the 28th NASA-contracted SpaceX Cargo Dragon resupply mission.

The ISS is host to eight pairs of original solar arrays installed between December 2000 and March 2009 as part of the orbital laboratory’s overall assembly. Working with Boeing, NASA’s ISS operations contractor, and Redwire, the space agency began the augmentation of six of the original eight solar array pairs with iROSA’s in June 2021. The third and fourth iROSAs were installed with NASA spacewalks in December 2022.

So far, the 2B, 4A and 4B power channels on the port side of the truss and the 3A power channel on the starboard side have been equipped with iROSAs.

Last year Congress authorized NASA to extend ISS operations from 2024 through 2030. The orbital science lab has been continuously staffed by astronauts and cosmonauts since November 2000. The number of scientific research and technology development activities underway at any one time now exceeds 300. As the ISS ages, the original solar arrays gradually degrade.

“I think the hardware has been extremely impressive. When you see the arrays unfurl, they tend to do so perfectly and then provide power right away,” Dina Contella, NASA’s ISS operations integration manager, told a Jan. 17 pre-spacewalk news briefing. “This is serving a good technology. They are lightweight and flexible and easy to launch. This particular technology is proving to be a good technology for us,” she said of the iROSAs.

EAch iROSA is launched in a rolled-up configuration that when deployed unfurls out on its own to a length of 60 ft. and width of 20 ft. When installation of the six 20-kW iROSAs is completed over the summer, the ISS solar power generation will reach an estimated 215 kWs.

In addition to supporting ISS operations, the iROSA solar panel technology is to be part of the lunar-orbiting, human-tended  Gateway station. The internationally supported outpost is part of NASA’s Artemis initiative to establish a sustained human presence at the Moon to prepare for human expeditions to Mars.

The iROSA technology also provided solar power for NASA’s Double Asteroid Redirection Test mission, which last September demonstrated a kinetic impact strategy for diverting an asteroid or comet headed toward an impact with Earth.

The latest NASA iROSA installation spacewalk was the first for Mann, a U.S. Marine Corps colonel and test pilot on her first trip to space, and Wakata, who is on his fifth trip to space and recently surpassed the 400-day mark for total time in space.

Wakata, who led the hand-intensive excursion, focused initially on completing the installation of an iROSA mounting platform on the IB power channel that began during December spacewalks. But it required the driving of more fasteners to finish.

Wakata then joined Mann to fully assemble and mostly complete the installation of the mounting platform support structure at the neighboring 1A power channel, link up associated power cables and resecure protective thermal insulation.

“It’s a lot like an erector set. We have to drive a lot of bolts, put linkages together,” said Keith Johnson, the lead spacewalk officer in NASA’s Mission Control Center. “It all goes together so beautifully that it’s fun and gives the crew a chance to go out and drive a lot of bolts like a construction engineer. It’s a lot of fun. You will never see two people work together more carefully and concisely.”

The spacewalkers fell nearly an hour behind their timeline at one point in the excursion. But they managed to catch up until they could not “soft dock” the left middle strut so that it could be bolted firmly into place to help stabilize its future iROSA.

The two iROSA spacewalk installations completed in December were carried out by NASA astronauts Josh Cassada and Frank Rubio, the other two crewmembers currently living and working aboard the ISS’s U.S. segment.

The spacewalk began at 8:14 a.m. EST and concluded at 3:35 p.m. EST for a total elapsed time of 7 hr., 21 min.

Mark Carreau

Mark is based in Houston, where he has written on aerospace for more than 25 years. While at the Houston Chronicle, he was recognized by the Rotary National Award for Space Achievement Foundation in 2006 for his professional contributions to the public understanding of America's space program through news reporting.