The astronauts helped robotic arm operators relocate the Crew Equipment Translation Aid (CETA) cart from the Port 1 to Starboard 1 truss segment, installed a new coupler on the CETA cart, lubricated snares on the "B" end of the space station's robotic arm and performed a few "get ahead" tasks. They were unable to deploy the Port 3 unpressurized cargo carrier attachment system (UCCAS) and tied it safely in place while engineers evaluate the problem. As the this issue is not yet understood, Mission Control cancelled the installation of a similar payload attachment system on the starboard side. Monday's spacewalk lasted six hours, 27 minutes and was the second spacewalk for both Acaba and Arnold and the 123rd spacewalk in support of station assembly and maintenance, totaling 775 hours. The three STS-119 spacewalks totaled 19 hours, 4 minutes. Steve Swanson has performed four spacewalks totaling 26 hours, 22 minutes. Acaba has two spacewalks totaling 12 hours, 57 minutes. Arnold has two spacewalks totaling 12 hours, 34 minutes.
(Image: Mission Specialist Joseph Acaba takes a ride on the International Space Station’s robotic arm during the mission's third spacewalk. Photo credit: NASA TV.)