He was a mission specialist on the second Spacelab mission aboard the space shuttle Challenger in July–August 1985.

Henize was a senior astronomer at the Smithsonian Astrophysical Observatory 1956–9, responsible for establishing and operating a global network to track artificial satellites. In 1959 he became an associate professor of astronomy at Northwestern University, and chaired two NASA groups concerned with Spacelab telescopes 1974–80. After his flight he became a senior scientist in NASA's Space Sciences Branch.