Space shuttle Endeavour is towed by a tractor into the Orbiter Processing Facility or OPF at NASA's Kennedy Space Center.

Space shuttle Endeavour is towed by a diesel-powered tractor into the Orbiter Processing Facility, or OPF, at NASA's Kennedy Space Center in Florida. Visible on Endeavour is the tail cone that covers and protects the main engines during the ferry flight. After landing in California to end the STS-126 mission, Endeavour returned to Kennedy on a piggyback flight atop a shuttle carrier aircraft. In the OPF, Endeavour will begin preparations for its next mission, STS-127, targeted for May 2009. Photo credit: NASA/Jack Pfaller