Two NASA astronauts aboard the International Space Station, ISS have successfully completed an emergency spacewalk to replace a failed data relay box that controls some of the key hardware on the orbital outpost. <br/><br/>Expedition 51 Commander Peggy Whitson and Flight Engineer Jack Fischer of NASA also installed a pair of antennas on the station yesterday to enhance wireless communication for future spacewalks.<br/><br/>Spacewalkers have now spent a total of 1,250 hours and 41 minutes working outside the station during 201 spacewalks in support of assembly and maintenance of the orbiting laboratory. <br/><br/>This was the 10th spacewalk for Whitson, who moves into third place all-time for cumulative spacewalking time, and the second for Fischer.