pieces of foam had broken off the external tank during lift off, including a piece that was the largest ever recorded. This was the problem that had doomed Columbia, and it had evidently not been fixed. Collins blamed herself for not pushing Michoud harder to effect changes. The STS-114 mission continued, as Discovery was already in orbit, but the Space Shuttle fleet was grounded again. Collins became the first astronaut to fly an orbiter through a complete 360-degree pitch maneuver. This was necessary so the astronauts aboard the ISS could take photographs of Discoverys belly to ensure there was no threat from debris-related damage to the orbiter upon reentry. It was a difficult maneuver, but one that she had practised many times in the simulator. She then flew under the ISS and docked with it. The inspections revealed some concerns: gap fillers were protruding between some of the tiles, which could cause them to pop out during re-entry. The three spacewalks and the transfer of supplies were carried out without problems. On the third spacewalk, Robinson rode the robotic arm to the underside of Discovery and removed the two most prominent protruding gap fillers. Discovery was supposed to land at KSC on 8 August but unfavorable weather led to a postponement until the next day, and the landing site was changed to Edwards Air Force Base. Discovery touched down after a mission lasting 13 days, 21 hours and 33 minutes. This time, Collins was unhappy with her landing, feeling that it was slightly fast. She was relieved to find that the tires were in good shape. Although she had felt well in space on this mission, her feet hurt as the bones moved back into position back on the ground, and the pain took two weeks to subside. Later life Collins retired from the USAF in January 2005 with the rank of colonel. On 1 May 2006, NASA announced that she was leaving NASA to spend more time with her family and pursue other interests. She had flown 6,751 hours in thirty different types of aircraft, and logged over 872 hours in space flights. After her retirement, Collins made occasional public appearances as an analyst covering Shuttle launches and landings for CNN. She was the commencement speaker at the 148th commencement of Syracuse University in May 2001. She addressed the 2016 Republican National Convention in Cleveland, Ohio, on 20 July