Spacewalker Steven Swanson works on the removal of the keel pin and drag line from the S3 truss, in this view from NASA TV, June 17, 2007.  (Xinhua/Reuters Photo) Photo Gallery>>>

    WASHINGTON, June 17 (Xinhua) -- Two astronauts finished the fourth spacewalk of Atlantis mission, safely re-entering the International Space Station at 6:54 p.m. EDT (2254 GMT) on Sunday, according to NASA TV.

    Mission Specialists Patrick Forrester and Steven Swanson began the excursion at 12: 25 p.m. EDT (1625 GMT) and quickly went to work preparing the new truss segment for operation. The new component was installed onto the station on June 11. Most of the truss work centered on activating the Solar Alpha Rotary Joint (SARJ), which will allow the new truss solar arrays to track the Sun.

    Early in the spacewalk, Forrester verified the installation of a mechanism that will drive rotation of the SARJ, and Swanson installed a TV camera. Then, the duo removed the final launch restraints on the SARJ before removing a keel pin and drag link to clear the path for the station's mobile transporter.

    They also installed a computer network cable onto the Unity module and removed a Global Positioning System antenna. Finally, the orbital duo completed the installation of a piece of debris shielding on the Destiny laboratory.

    The two spacewalkers wished their fathers well for Father's Day before closing the outer hatch of Quest airlock.

    "Absolutely, a lot of fathers on this flight and we're all enjoying a great Father's Day," added astronaut James Reilly inside the station.

    Forrester and Swanson conducted Atlantis mission's second spacewalk. Mission Specialist James Reilly and John Olivas conducted the other two.

    Sunday's excursion is the 88th spacewalk devoted to station assembly and maintenance.