After nearly 30 years at NASA supporting human spaceflight, NASA Astronaut Michael Gernhardt is leaving NASA. His last day is July 25.

Gernhardt was selected as an astronaut in March 1992. He is a four-flight veteran, logging over 43 days in space, including four spacewalks totaling 23 hours and 16 minutes. He was a mission specialist on four space shuttle missions: STS-69 in 1995, STS-83 and STS-94 in 1997, and STS-104 in 2001. In addition, he was a crewmember on the first NASA Extreme Environment Mission Operations (NEEMO) mission in an undersea habitat and led numerous subsequent NEEMO missions simulating partial gravity environments including the Moon, Mars, and near-Earth asteroids.

Prior to becoming an astronaut, Gernhardt was a professional deep-sea diver and founder of Oceaneering Space Systems, where he led the development of a variety of spacewalking tools, life support systems, and decompression procedures.

His first spaceflight was STS-69 on the Space Shuttle Endeavour in September 1995. During that mission, he performed a spacewalk to evaluate the tools, hardware, and techniques that would be used to assemble and maintain the International Space Station before construction began in 1998. This included the body restraint tether, a mechanical arm attached to the spacesuit, and the micro-conical interface that allows astronauts or robots to remove and replace station components, both of which he invented.

Gernhardt was assigned as the lead spacewalker for STS-104, when he led the installation and outfitting of the International Space Station’s airlock, Quest. He also led an international team in developing a new pre-breathing protocol that uses exercise on a bicycle ergometer while breathing oxygen to speed the elimination of nitrogen to reduce the risk of decompression sickness during spacewalks. This effort included the human research subject testing and development of the flight procedures and hardware.

“I had the great opportunity of working with Mike Gernhardt throughout his career. In my position as chief astronaut, I assigned him to lead the early assembly of the International Space Station, a role that continues to enable space station operations still decades later, and that led to an array of benefits for Earth and exploration,” said NASA Associate Administrator Bob Cabana.

On July 20, 2001, during the STS-104 mission, Gernhardt and his crewmate NASA astronaut James Reilly, were the first crew members to use the exercise pre-breathing protocol, ushering in a new era of spacewalks from the station. Gernhardt also was the principal investigator on the development and implementation of the “campout,” or sleeping overnight in the airlock at lower pressure, the in-suit light exercise pre-breathing protocol, and the exploration atmosphere that uses a lower cabin pressure with higher oxygen concentration and an associated pre-breathing protocol that will facilitate spacewalks on the Moon and Mars.

Gernhardt served as the extravehicular activity and surface operations lead of a lunar development study, where he invented the concept of a small, crewed pressurized rover with a cabin incorporating the exploration atmosphere to facilitate rapid spacewalks for exploring the surfaces of the Moon and Mars. After his flight career, he led a team across NASA in the development and testing of four generations of this rover.

“Mike has had major contributions to human spaceflight and crew safety that have had and will continue to have a tremendous impact on us and our missions”, said Chief Astronaut Reid Wiseman. “The astronaut corps will not soon forget the expertise that Gernhardt brought to NASA missions on the space station and to future missions to the Moon and Mars.”

Gernhardt was born in Mansfield, Ohio. He received a bachelor’s degree in physics from Vanderbilt University, Nashville, Tennessee, in 1978, and a master’s and a doctorate in bioengineering from University of Pennsylvania, in 1983 and 1991, respectively.

Find Gernhardt’s biography here: https://www.nasa.gov/content/michael-gernhardt