NASA: Astronaut rides robotic arm in successful spacewalk

Riding a robotic arm 210 miles above the Earth, NASA astronauts successfully completed their first spacewalk of the 11-day mission that launched earlier this week.

Astronauts Mike Foreman and Robert L. Satcher, Jr. spent six hours and 37 minutes outside the space shuttle Atlantis, which is docked with the International Space Station. They installed a spare S-band antenna structural assembly to the station's truss, or backbone, while also replacing a handrail, troubleshooting cable connections and lubricating one of the station's robotic arms.

Arguably the most dramatic part of the day's spacewalk was when Satcher rode the space station's robotic arm from the shuttle's payload bay to the station's truss -- all while orbiting the Earth at 17,500 miles an hour. Satcher connected his feet to the arm and carried the antenna assembly between the two crafts.

The two astronauts completed their planned tasks about two hours ahead of schedule, which allowed them to take on a job that wasn't slated until the second spacewalk. With the extra time today, Satcher and Foreman attached a system designed to hold payloads to the station's truss.

This mission was designed to move more than 27,000 pounds of equipment and spare parts to the space station before the space shuttle fleet -- NASA's heavy lifters -- are retired.

The equipment being delivered during this mission is considered critical to the operation of the space station, according to NASA. At this point, there are only six flights left for the space shuttle fleet before it's scheduled to be retired.

The equipment that needs to go up is being delivered in order of highest priority. Since this is the first mission to deliver what scientists hope will turn into a trove of spare parts, they're taking up the most important pieces.

The parts being delivered include two pump modules, two gyroscopes, two nitrogen tank assemblies, an ammonia tank assembly and a high-pressure gas tank. Parts going up for the robotic systems onboard the station include a latching end effector for the station's robotic arm and a trailing umbilical system reel assembly for the railroad cart that allows the arm to move along the station's truss system.