Project Gemini followed on from Project Mercury. After the Mercury-Atlas 10 mission was canceled, Shepard was designated as the commander of the first crewed Gemini mission, with Thomas P. Stafford chosen as his pilot. In late 1963, Shepard began to experience episodes of extreme dizziness and nausea, accompanied by a loud, clanging noise in the left ear. He tried to keep it secret, fearing that he would lose his flight status, but was aware that if an episode occurred in the air or in space it could be fatal. Following an episode during a lecture in Houston, where he had recently moved from Virginia Beach, Virginia, Shepard was forced to confess his ailment to Slayton, who was now Director of Flight Operations, and seek help from NASA's doctors.