This view of the underside of the crew cabin of the space shuttle Discovery was provided by the Expedition 23 crew during a survey as STS-131 approached the International Space Station. As part of the survey and part of every mission's activities, Discovery performed a back-flip for the rendezvous pitch maneuver (RPM). The image was photographed with a digital still camera, using a 400mm lens at a distance of about 600 feet (180 meters). Image Credit: NASA