Navy Adm. Mike Mullen, chairman of the Joint Chiefs of Staff, speaks with Defense Secretary Robert M. Gates before the U.S. Strategic Command change-of-command ceremony on Offutt Air Force Base, Neb., Jan. 28, 2011. Air Force Gen. Kevin P. Chilton was relieved by Air Force Gen. C. Robert Kehler, who retired after a 34-year career in which he was the first former astronaut to achieve the four-star general officer rank. Navy Adm. Mike Mullen, chairman of the Joint Chiefs of Staff, speaks with Defense Secretary Robert M. Gates before the U.S. Strategic Command change-of-command ceremony on Offutt Air Force Base, Neb., Jan. 28, 2011. Air Force Gen. Kevin P. Chilton was relieved by Air Force Gen. C. Robert Kehler, who retired after a 34-year career in which he was the first former astronaut to achieve the four-star general officer rank. SHARE: Download: Full Size (6.18 MB) Tags: Photo Essays Credit: VIRIN: 673258-U-ZTI63-167.jpg Photo Gallery