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