There were several objectives of this mission. The first was to bring Astronaut Nicole Stott to the International Space Station (ISS) to remain as a resident on the ISS as part of the Expedition 20 crew. She replaced Tim Kopra, who returned to Earth on the Shuttle. The second objective was using the Orbiter to carry one of the multi-purpose logistics modules, Leonardo, to and from the station. On this mission, Leonardo delivered nine racks and eight platforms. The racks are the basic structure for holding space station systems inside the laboratory. Two of the racks were set up for research in space: the Fluids Integrated Rack to study liquid in weightlessness, and the Materials Science Research Rack, which is used to conduct experiments on different materials. A second freezer for completed experiments also was carried into orbit inside Discovery, along with an air filtration system destined for the Tranquility node, which will be added to the station in 2010. Leonardo also delivered the Colbert treadmill. This treadmill is a new exercise machine that station residents will use to stay fit while in the weightlessness of space. It gained notoriety when NASA named it after Comedy Central comedian and faux newscaster Stephen Colbert following an online NASA poll to name a new station module. The exercise equipment is more advanced than the treadmill currently on the station. For example, it allows astronauts to run as fast as an Olympic sprinter. The treadmill is mounted on a system to prevent the vibrations from shaking the station as it floats through space. The third objective involved three space walks, which were primarily focused around maintenance of the station, and deployment and removal of exterior mounted experiments.
In between all the work on the exterior of the station and unloading/reloading Leonardo, the Shuttle crew found time to conduct some science experiments. The ISS now has six crewmembers on board, three laboratories and time for science. With the previous mission, the Japanese Kibo laboratory complex was completed and two experiments installed on its new porch. With the United States’ Destiny laboratory, the European Space Agency’s Columbus laboratory, and the projects attached to the station’s exterior, there are now 20 research facilities inside the space station and eight experiments going on outside. 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.
On September 8, 2009, Discovery undocked and backed away from the station. Poor weather conditions over the primary landing site at Kennedy Space Center in Florida delayed the first landing attempt and ultimately cause the mission controllers to send the astronauts to Edwards Air Force Base in California instead. Discovery’s wheels touched down at 8:53 p.m. EDT on September 11, 2009, and the shuttle rolled to a stop about a minute later to end the flight.
While the astronauts returned to their training base at NASA’s Johnson Space Center in Houston, the mission was just beginning for the team of technicians and specialists who spent the next week getting Discovery set up and mounted on a modified 747 for the ride back to Kennedy Space Center. Discovery faced more weather concerns during that flight also, but a break in the storms allowed the 747 and Discovery to land at Kennedy Space Center on September 21, 2009.