STS-116 Pilot William Oefelein looks at the external air lock in Discovery's payload bay.

During a Crew Equipment Interface Test (CEIT) in the Orbiter Processing Facility, STS-116 Pilot William Oefelein looks at the external air lock in Discovery’s payload bay. A CEIT allows astronauts to become familiar with equipment and hardware they will use on the mission. STS-116 will be mission No. 20 to the International Space Station and construction flight 12A.1. The mission payload is the SPACEHAB module, the P5 integrated truss structure and other key components. Launch is scheduled for no earlier than Dec. 7. Photo credit: NASA/Kim Shiflett