Astronauts on the STS-130 mission have installed the two major pieces of European-built hardware they delivered to the International Space Station on space shuttle Endeavour, edging the station ever closer to its long-awaited completion. The shuttle lifted off February 8 from Kennedy Space Center in Florida.

The cylindrical Node 3, also known as Tranquility, was transferred from Endeavour and placed on the station February 12, and the node's panoramic observatory, or cupola, was secured early Monday. The shuttle astronauts used the station's robotic arm to shift the cupola, which will provide astronauts a view of Earth and of the station's exterior, from its flight-stowage location into its permanent position on Tranquility at 1:31 A.M. (Eastern Standard Time).

Tranquility is a seven-meter-long cylindrical node that will house exercise and life-support equipment, including a urine-to-water processor and a system that removes carbon dioxide from the station's air. It will also serve as a workstation—Tranquility's cupola can be used as a control tower for the station's robotic arm or to observe spacewalks.

The mission's final spacewalk, scheduled for Tuesday, will finish prepping the new components for use, removing the cupola's window covers and setting up Tranquility's climate-control system. NASA estimates that the station will be 90 percent complete once the new node and cupola are integrated.

Four flights of the space shuttle remain, all to the International Space Station, before NASA loses its ability to launch manned missions for an indefinite amount of time. The planned replacement for the shuttle, Ares 1, is targeted for readiness in 2015, but President Obama has requested that the program be canceled and that NASA instead rely on private operators for future manned launches.

Photo of cupola on ISS robotic arm: NASA TV