STS-121 Mission Specialist Piers Sellers practices working with the replacement trailing umbilical system reel assembly that will be installed on the International Space Station.

In the Space Station Processing Facility at NASA Kennedy Space Center, STS-121 Mission Specialist Piers Sellers practices working with the replacement trailing umbilical system reel assembly that will be installed on the International Space Station. He and other crew members -- Commander Steven Lindsey, Pilot Mark Kelly and Mission Specialists Lisa Nowak, Stephanie Wilson and Michael Fossum -- are at Kennedy to take part in the crew equipment interface test (CEIT). The CEIT provides hands-on experiences with equipment used on-orbit. Mission STS-121 is the second in the Return to Flight sequence and will carry on improvements that debuted during last year's STS-114 mission and build upon those tests. Launch is scheduled in May. Photo credit: NASA/Kim Shiflett