The expansion of the International Space Station continued today with the installation of the 13 1/2 ton S0 (S-Zero) truss segment on the orbital outpost. Assisted by Expedition Four Flight Engineer Dan Bursch, Atlantis Mission Specialist Ellen Ochoa gently lifted the truss out of the shuttle's payload bay at 5:30 a.m. Central time through the use of the station’s robotic arm and maneuvered it onto a clamp at the top of the station's Destiny Laboratory. It took just under four hours to complete the delicate procedure.
During the S-Zero installation, Atlantis Commander Mike Bloomfield and Pilot Steve Frick operated the shuttle's robotic arm to provide additional camera views to Ochoa and Bursch, who were working in the Destiny Lab at one of the robotic workstations. The truss will serve as the backbone for future station expansion to the length of a football field. S-Zero contains navigational devices, computers, cooling and power systems necessary to attach additional laboratories to the complex.
Within minutes after the new truss was temporarily latched to the Destiny Lab, mission specialists Rex Walheim and Steve Smith left the station's Quest Airlock at 9:36 a.m. Central time to begin the first of four spacewalks of the mission to electrically and structurally mate S-Zero to the station.
Smith and Walheim first unfurled and firmly attached two of four mounting struts on the truss to Destiny before deploying trays of avionics equipment and cables on the truss which include power, data and fluid lines connecting Destiny to the S-Zero. They also attached an umbilical system from the truss to the Mobile Transporter housed on the forward face of the huge girder. The umbilical will enable the Transporter, which is the first railcar in space, to move up and down the length of the station to position the ISS robotic arm for future assembly work. Two other struts on the truss will be mated to Destiny Saturday during the second spacewalk, permanently bolting the truss to the Laboratory.
Working deliberately to connect all of the critical power connections, Walheim spent the day working at the end of the station’s Canadarm2, the first time the large arm has been used as a form of cherry picker to maneuver astronauts during assembly work at the ISS. Smith operated as a so-called “free-floater”, tethered to the station and to various work sites around the truss itself. Atlantis astronaut Jerry Ross and ISS Flight Engineer Carl Walz took turns choreographing the spacewalk from the aft flight deck of the shuttle.
With all but two tasks successfully completed, Smith and Walheim returned to Quest late this afternoon and ended their spacewalk at 5:24 p.m. Central time, completing a 7 hour, 48 minute excursion. It was the 35th spacewalk devoted to station assembly and the 10th staged from the station itself. As Smith and Walheim wrapped up their work, flight controllers reported that the activation of the S-Zero Truss had begun and that all of the initial systems appear to be in excellent shape.
Time ran out before Smith and Walheim could install two circuit breakers on the truss, but that task will be picked up on a subsequent spacewalk.
After a long and tedious day, the shuttle and station crew members were scheduled to begin an eight-hour sleep period at 7:44 p.m. Central time and will be awakened just before 4 a.m. Friday.
The next STS-110 mission status report will be issued Friday morning, or earlier if events warrant.
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