Henize applied for the first scientist-astronaut group, but was denied because the age limit was 35 and he was 37. In 1967, NASA abolished the age limit, and Henize was selected as a scientist-astronaut by NASA in August. Astronauts that did not already know how to fly had to complete a 53-week jet pilot training program at
Vance Air Force Base, Oklahoma. They also completed initial education there. He was a member of the astronaut support crew and CAPCOM for the
Apollo 15 mission. The entire support crew consisted of scientist-astronauts, as the prime crew of the mission thought they would need more help with the science aspects of the mission rather than the piloting. He was also a member of the astronaut support crew for the
Skylab 2,
3, and
4 missions. He was mission specialist for the ASSESS-2 spacelab simulation mission in 1977. He logged 2,300 hours flying time in
jet aircraft. Henize was a mission specialist on the
Spacelab-2 mission (
STS-51-F) which launched from
Kennedy Space Center, Florida, on July 29, 1985. He was accompanied by Col.
Gordon Fullerton (spacecraft commander), Col.
Roy D. Bridges (pilot), fellow mission specialists Dr.
Anthony W. England and Dr.
F. Story Musgrave, as well as two payload specialists, Dr.
Loren Acton and Dr.
John-David Bartoe. This mission was the first pallet-only Spacelab mission and the first mission to operate the Spacelab
Instrument Pointing System (IPS). It carried 13 major experiments, of which seven were in the field of astronomy and solar physics, three were for studies of the Earth's
ionosphere, two were life science experiments, and one studied the properties of
superfluid helium. Henize's responsibilities included testing and operating the IPS, operating the
Remote Manipulator System (RMS), maintaining the Spacelab systems, and operating several of the experiments. After 126 orbits of the Earth, STS 51-F
Challenger landed at Edwards Air Force Base, California, on August 6, 1985. With the completion of this flight Henize logged 190 hours in space. In 1986, he retired as an astronaut and accepted a position as senior scientist in the Space Sciences Branch. He studied space debris and hazards to the space station. In the 1998 miniseries
From the Earth to the Moon, Henize was played by
Marc Macaulay. ==Death==