Utility Logistics Flight (ULF 1.1) is primarily an ISS crew augmentation mission (a third crewmember will arrive on this flight), with the Leonardao Multi-Purpose Logistics Module (MPLM) ferrying more than 5,000 pounds of cargo, a majority of which is food, clothing, and crew consumables. The MPLM will carry two new research facilities; Minus Eighty-degree Laboratory Freezer for ISS (MELFI) and European Modular Cultivation System (EMCS), which will be installed in the Destiny laboratory. The MELFI will provide current and future ISS crews with a critical lab freezer capability for maintaining scientific samples and experiments. The EMCS, a ½ EXPRESS rack, is a large incubator that provides control over atmosphere, lighting, and humidity of growth chambers. The MPLM will also transport the Oxygen Generation System (OGS) rack that uses water to generate breathable oxygen for crewmembers. The life-support system is considered a test initiative for future long-duration missions to the moon and Mars. The MPLM will also carry a new cycle ergometer, which will give expedition crews on station better aerobic and cardiovascular conditioning through cycling activities.
The STS-121 and Expedition Thirteen crews will work together to accomplish two spacewalks. They will focus on Shuttle thermal protection system repair techniques and space station assembly and repair tasks. A third spacewalk also will be conducted if mission managers determine the Shuttle has enough consumables for an extra day for the mission. The third spacewalk would include tests of techniques for inspecting and repairing the orbiter's heat shield, the reinforced carbon-carbon (RCC) segments that protect the orbiter's nose cone and wing leading edges.
Several Detailed Supplementary Objectives (DSOs) will also be flown during the STS-121 mission. DSOs are space and life sciences investigations. Their purpose is to determine the extent of physiological deconditioning resulting from space flight, test countermeasures to those changes, and characterize the environment of the Space Shuttle and/or space station relative to crew health. DSOs being performed during this mission are:
Space Shuttle Discovery returned to Kennedy Space Center in Florida on July 17th bringing STS-121 to an end. This flight was the orbiter's 32nd mission and the 115th in the Shuttle program's history.