After graduating from The Ohio State University College of Veterinary Medicine in June 1985, Dr. Linnehan entered private veterinary practice and was later accepted to a 2-year joint internship in Zoo Animal Medicine and Comparative Pathology at the Baltimore Zoo and The Johns Hopkins University. After completing his internship, Dr. Linnehan was commissioned as a Captain in the U.S. Army Veterinary Corps and reported for duty in early 1989 at the Naval Ocean Systems Centre, San Diego, California, as chief clinical veterinarian for the U.S. Navy’s Marine Mammal Program. During his assignment at the Naval Ocean Systems Centre, Dr. Linnehan initiated and supervised research in the areas of cetacean and pinniped anaesthesia, orthopaedics, drug pharmacokinetics and reproduction in direct support of U.S. Navy mobile marine mammal systems stationed in California, Florida, and Hawaii.
Selected by NASA in March 1992, Dr. Linnehan reported to the Johnson Space Centre in August 1992 where he completed one year of Astronaut Candidate training qualifying him for space shuttle flight assignments as a Mission Specialist. Dr. Linnehan was initially assigned to flight software verification in the Shuttle Avionics Integration Laboratory (SAIL). He was subsequently assigned to the Astronaut Office Mission Development Branch, working on payload development and mission development flight support for future space shuttle missions. He first flew as a Mission Specialist in 1996 on STS-78, the Life Sciences and Microgravity Spacelab (LMS) mission. In 1998, he served as the payload commander on the STS-90 Neurolab mission. In 2002, he was a member of the four-man spacewalk (EVA) crew on STS-109, the fourth servicing mission to the Hubble Space Telescope. In 2008, he was lead EVA crewmember on the STS-123/1JA mission to the International Space Station. A veteran of four space flights, Dr. Linnehan has logged more than 58 days in space, including six spacewalks – totalling 42 hours and 11 minutes. In August 2009, Linnehan returned to Houston, TX and the Astronaut Office after completing a Master’s Degree in Public Administration at the Harvard Kennedy School of Government in Boston, MA and was subsequently assigned as JSC representative to the Texas A&M University’s Office of Strategic Initiatives, College Station, TX on a NASA Interagency Personnel Agreement (IPA). Dr. Linnehan’s IPA activities targeted collaborative, advanced biomedical research projects as well as K-12 Science, Technology, Engineering and Mathematics (STEM) educational initiatives in direct support of NASA/JSC and the Texas A&M University System.
Presently, Dr. Linnehan is jointly assigned to both the JSC Astronaut Office Exploration and Integration branches as well as The NASA Human Research Program (HRP). He continues to work on advanced initiatives in space suit design, physiological modelling/research while also directly supporting development of next generation space flight resistive exercise hardware and on-orbit exercise methodologies, as well as radiation and nutritional countermeasures protocols, in preparation for future long-duration manned exploration Orion Class space missions.