NASA astronauts begin solar panel upgrade on International Space Station

On a Wednesday morning in June, two astronauts prepared to float outside the International Space Station and begin work that would fundamentally reshape how the orbiting laboratory powered itself. Shane Kimbrough of NASA and Thomas Pesquet of the European Space Agency were scheduled to conduct a spacewalk starting around 8 a.m. Eastern time, their mission to install the first of six new solar arrays designed to breathe new life into aging infrastructure that had been working far longer than anyone originally planned.

The station's existing solar panels had been generating electricity for more than two decades. When they were built, engineers designed them to last fifteen years. That they had kept functioning at all was a testament to their construction, but the toll of two decades in space was becoming impossible to ignore. Thruster plumes from the station itself and from visiting spacecraft had etched away at the panels' surfaces. Micrometeorite impacts—tiny pieces of debris traveling at orbital speeds—had gradually degraded the delicate chains of solar cells that made up each array. The station's power output had begun to slip. It was time for an upgrade.

The new panels, called iROSA arrays, had arrived at the station on June 5 after launching aboard a SpaceX Dragon cargo mission. The station's robotic arm had already extracted them from the spacecraft. In their stowed configuration, each array was tightly rolled like a carpet, weighing 340 kilograms and measuring just three meters across. Once Kimbrough and Pesquet deployed them and bolted them into place, they would stretch to nineteen meters long and six meters wide—a transformation that would take about six minutes per panel. The two astronauts would install the first array on Wednesday, then return on Sunday to install the second one. These would be the 239th and 240th spacewalks conducted in support of the station's assembly, maintenance, and improvement.

The work required meticulous planning. The astronauts would be working around live electrical connectors, so ground teams had spent days calculating the plasma forecast—determining what electrical charge would surround the station during the spacewalk. Metal parts of their suits would be covered to prevent arcs that could cause dangerous electrical discharge. The timing of the spacewalk itself had been chosen so that the massive new panels would remain in darkness and unable to generate power while the astronauts worked nearby. Inside the station, NASA astronaut Megan McArthur would guide the arrays into position using the station's robotic arm.

This was not the first time Kimbrough and Pesquet had worked together in the vacuum of space. In 2017, both men had been aboard the station simultaneously and had conducted two spacewalks together to replace the station's aging nickel-hydrogen batteries with newer lithium-ion versions that would last longer. For Kimbrough, these Wednesday and Sunday walks would be his seventh and eighth spacewalks. For Pesquet, they would be his third and fourth. Pesquet would wear red stripes on his suit to mark him as extravehicular crew member one, while Kimbrough's suit would remain unmarked as crew member two.

The new arrays would be installed in front of the existing panels, which would continue generating power in parallel with the new equipment. The result would be a significant boost to the station's electrical capacity. Current power output stood at 160 kilowatts. Once all six new arrays were installed—a process that would unfold across multiple spacewalks—the station would be able to draw 215 kilowatts, a thirty-four percent increase. The new solar cells were more efficient than the originals, packing more power density into the same physical space. Even though the old panels would still be working alongside them, the new arrays alone would generate more electricity than the original panels had produced when they were brand new.

The new arrays carried an expected lifespan of fifteen years, the same design life as their predecessors. But engineers knew that the original panels had degraded faster than anticipated, so they planned to monitor the new arrays closely to understand how long they would actually last in the harsh environment of low Earth orbit. There was another reason to pay close attention: this same solar panel design would eventually power the Gateway, a lunar outpost that NASA was building as part of its Artemis program to return humans to the moon by 2024. What Kimbrough and Pesquet were about to install was not just a repair job for an aging space station. It was a test run for the technology that would support the next chapter of human spaceflight.