In the third spacewalk of the year outside the International Space Station, NASA astronauts Kate Rubins and Victor Glover concluded their spacewalk after 7 hours and 4 minutes.The two NASA astronauts began work on Monday to install modification kits required for the upcoming solar array upgrades, the US space agency said in a blog post.The duo worked near the farthest set of existing solar arrays on the station's left side, known as P6.Glover built a bracket structure and worked with Rubins to attach the bracket and support struts to the mast canister, the base, of one of the P6 solar arrays, known as 2B.One of the bolts did not fully engage on the first attempt, so Rubins used a power drill to back it out and reseat it, then used a ratchet wrench to tighten the bolt, reaching a safe configuration.The bolt likely will need to be secured further before installing one of the new solar arrays that will be delivered to the space station later this year aboard SpaceX's 22nd commercial resupply services mission, NASA said.Rubins and Glover then moved to begin identical assembly work for the bracket for the second of the P6 solar array pair, known as 4B.They completed the construction of upper support hardware and secured it to the space station's exterior structure until work can be completed on the next spacewalk on March 5.During the spacewalk on March 5, Rubins and Japan Aerospace Exploration Agency (JAXA) astronaut Soichi Noguchi will venture outside the orbiting outpost to complete the installation of the 4B array modification kit and are expected to tackle additional work, NASA said.