Two astronauts exited the International Space Station airlock on Tuesday on a nearly 7-hour spacewalk to continue the years-long process of upgrading the orbiting laboratory’s power grid.

NASA Astronauts Raja Chari and Kayla Barron exited the airlock at 8:12 a.m. ET to assemble and install modifications kits to support solar array upgrades on the station. The kits will support the second pair of six ISS Roll-Out Solar Arrays (iROSA). The iROSAs are part of the plan to upgrade the ISS power system over the next year and a half.

During a spacewalk in June, NASA astronaut Shane Kimbrough and ESA European Space Agency astronaut Thomas Pesquet unfurled the first two iROSAs outside the space station. The solar arrays roll up like a carpet for launch and then unroll when released in space. 

Barron and Chari spent about 6 hours and 54 minutes outside the ISS for the installation on Tuesday. Barron could be identified on NASA TV because she was wearing a suit with red stripes. Chari’s suit did not have stripes. 

The duo finished their work in the vacuum of space at 3:06 p.m. 

Barron and Chari are part of the 2017 NASA astronaut class, nicknamed the turtles. Barron posted to Instagram Monday, saying after “4.5 years training and working alongside one another [Chari] and I are feeling ready and excited for the first all-turtle spacewalk!”

The spacewalk was Barron’s second and Chari’s first.

Tuesday’s spacewalk is one of two planned this month, and a second will be conducted on March 23.

Next week astronauts will install hoses outside the ISS to keep the station’s systems at the proper temperature as well as install a power and data cable on the Columbus module’s science platform and replace a camera on the station’s truss.

For the March 23 spacewalk, NASA managers said the astronauts would be assigned after Tuesday’s EVA is complete.