KENNEDY SPACE CENTER, FLA. In the Space Station Processing Facility at NASA Kennedy Space Center, workers get ready to move a supply rack into the multi-purpose logistics module Leonardo (at right). The module is being prepared for the second return-to-flight mission, STS-121, on space shuttle Discovery, carrying more than two tons of equipment and supplies to the International Space Station. This will be the fourth trip to the station for Leonardo, the first of three Italian-built logistic modules. Equipment and supplies no longer needed on the station will be moved to Leonardo before it is unberthed on Flight Day 10 and put back into Discovery's cargo bay for return to Earth. This second return-to-flight test mission is to carry on analysis of safety improvements that debuted on the first return-to-flight mission, STS-114, and build upon those tests. The launch is targeted for a date no earlier than May.