While launch pad technicians were buttoning up Endeavour's payload bay on Saturday, the crew aboard the International Space Station completed a critical robotics job to vacate the port where a new module will be attached during the space shuttle mission.

The station astronauts used the Canadian-built robotic arm to remove the Pressurized Mating Adapter No. 3 from the left side of the station's Unity node and relocate the conical structure to the top side of the Harmony module.

Artist's concepts show PMA No. 3 on the side of Unity before the move (top image) and its new location on Harmony (bottom image). Credit: NASA

The PMAs are tunnel-like and serve as connectors between two large objects at the space station. PMA No 1. bridges the divide between U.S. and Russian segments of the station by connecting Unity to Zarya. PMA No. 2 is anchored on the front of Harmony and is the docking port used by space shuttles.

A successful transfer of PMA No. 3 from its storage spot on the side of Unity was seen as a major step in preparations for Endeavour's upcoming construction mission. The shuttle will deliver the new Tranquility module and attach it to the same port where the PMA had been residing.

After Tranquility is hooked up and activated during the shuttle visit, the astronauts will again use the Canadian arm to move PMA No. 3, shifting the adapter to the new module's outer berthing slot.

An artist's concept shows space station's new configuration after Endeavour's construction mission to deliver Tranquility. Credit: NASA

Down at the Kennedy Space Center, the Italian-made Tranquility has been tucked inside Endeavour's cargo hold and secured for blastoff. The shuttle's 60-foot-long payload bay doors were closed and locked for flight on Saturday.

Senior officials will gather at KSC on Wednesday for the Flight Readiness Review. The meeting will examine all aspects of mission preparations and formally schedule Endeavour's launch date.

NASA says there are no major constraints being addressed and that liftoff remains targeted for 4:39 a.m. EST on February 7.

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