Space Shuttle Endeavour Carries Out Mission Objectives

IN SPACE - JULY 24: In this photo provided by NASA, Astronauts Tom Marshburn (upper left) and Christopher Cassidy (seen just below Marshburn), mission specialists for STS-127, share duties on the fourth spacewalk of Endeavour's current mission and its crew's joint activities with the space station July 24, 2009 in Space. Eleven astronauts and cosmonauts remained inside the International Space Station and the shuttle to which it was docked, while the two continued work on the orbital outpost. The two will team up for the mission's final spacewalk on July 26. (Photo by NASA via Getty Images)