The International Space Station [Images] grew further on Tuesday when two astronauts floated outside to connect a new 15.9 tonne truss that will increase the power capability of the ISS.

James Reilly and John 'Danny' Olivas made up for a delayed start on Monday, working quickly to put themselves an hour ahead of schedule. They firmly locked the 15.9-tonne segment to the ISS and removed temporary covers, as well as bolts and restraints used to hold the solar array in place during the launch of the space shuttle Atlantis.

They also checked whether a new radiator was ready to be deployed, and installed two of five lock assemblies meant to help the solar array rotate to catch the sun's rays.

The new truss was attached at 2:28 p.m. EDT. The S3/S4, which is 45 feet long and weighs 35,678 pounds, was attached to the end of the Starboard 1 truss segment by crew members using the station's robotic arm.

The S3/S4 contains a new set of solar arrays that will increase the station's power-generation capabilities. The STS-117 crew will conduct three spacewalks to activate the S3/S4. The first spacewalk began at 4:02 pm on Tuesday and will last about 6.5 hours.

The new solar arrays are slated to be deployed Tuesday.      

Late Sunday, NASA [Images] Astronaut [Images] Clayton Anderson joined the Expedition 15 crew, replacing Indian-American astronaut Sunita Williams. He arrived at the station as a member of Space Shuttle [Images] Atlantis' crew.

He and Williams officially changed crews when his custom-made seat liner was swapped out in the Soyuz spacecraft docked to the station. Williams is wrapping up a six-month stay aboard the station. She will return to Earth on Atlantis, which is slated to undock June 17.