On his first mission, Gemar served on the five-man crew of STS-38 which launched at night from the Kennedy Space Center, Florida, on November 15, 1990. During the five-day mission crew members conducted Department of Defense operations. After 80 orbits of the Earth in 117 hours, in the first Shuttle recovery in Florida since 1985, Space Shuttle Atlantis and her crew landed back at the Kennedy Space Center on November 20, 1990.
Gemar then served on the five-man crew of STS-48 aboard the Space Shuttle Discovery, which launched from the Kennedy Space Center, Florida, on September 12, 1991. During 81 orbits of the Earth, the crew successfully deployed the Upper Atmosphere Research Satellite (UARS), designed to study the Earth's upper atmosphere on a global scale thus providing scientists with their first complete data set on the upper atmosphere's chemistry, winds and energy inputs, in addition to conducting numerous secondary experiments ranging from growing protein crystals, to studying how fluids and structures react in weightlessness. This five-day mission concluded with a landing at Edwards Air Force Base, California, on September 18, 1991. Mission duration was 128 hours.
Gemar's most recent mission was STS-62 aboard the Space Shuttle Columbia, which launched from the Kennedy Space Center, Florida, on March 4, 1994. This microgravity science and technology demonstration mission carried the United States Microgravity Payload (USMP-2) and the Office of Aeronautics and Space Technology (OAST-2) payloads. Sixty experiments or investigations were conducted in many scientific and engineering disciplines including materials science, human physiology, biotechnology, protein crystal growth, robotics, structural dynamics, atmospheric ozone monitoring and spacecraft glow. During the spacecraft glow investigation, Columbia's orbital altitude was lowered to 105 nautical miles, the lowest ever flown by a Space Shuttle. STS-62, the second longest Space Shuttle mission to date, concluded after 13 days, 23 hours, and 16 minutes, following 224 orbits of the Earth with a landing at the Kennedy Space Center on March 18, 1994, after traveling 5.8 million miles.
Manned five crew. Deployed a classified payload. Orbits of Earth: 79. Landed at: Runway 33 at Kennedy Space Center, Florida. Landing Speed: 359 kph. Touchdown miss distance: 430.00 m. Landing Rollout: 2,712.00 m. Payloads: DoD Mission.
Manned five crew. Deployed UARS; conducted materials and biological research. Payloads: Upper Atmosphere Research Satellite (UARS), Ascent Particle Monitor (APM)-03, Physiological and Anatomical Rodent Experiment (PARE)-01, Protein Crystal Growth (PCG)-ll-2, Middeck Zero-Gravity Dynamics, Experiment (MODE)-01, Investigations Into Polymer Membrane Processing (IPMP)-04, Cosmic Radiation Effects and Activation Monitor (CREAM-02), Radiation Monitoring Equipment (RME)-lll-06, Shuttle Activation Monitor (SAM)-03, Air Force Maui Optical Site (AMOS) Calibration Test.
Carried USMP-2, OAST-2, SAMPIE, TES, EISG. Payloads: United States Microgravity Payload (USMP) 2, Office of Aeronautics and Space Technology (OAST) 2, Dexterous End Effector (DEE), Shuttle Solar Backscatter Ultraviolet/A (SSBUV/A), Limited-Duration Space Environment Candidate Material Exposure (LDCE), Advanced Protein Crystal Growth (APCG), Physiological Systems Experiment (PSE), Commercial Protein Crystal Growth (CPCG), Commercial Generic Bioprocessing Apparatus (CGBA), Auroral Photography Experiment Phase B (APE-B), Middeck Zero-Gravity Dynamics Experiment (MODE), Air Force Maui Optical Site (AMOS) Calibration Test, Bioreactor Demonstration System A.