Mukai was selected to be an astronaut by Japanese national space agency NASDA (now called JAXA) in 1985.

In 1985, Mukai was selected as one of three Japanese Payload Specialist candidates for the First Material Processing Test (Spacelab-J) which flew aboard STS-47.

Mukai has remained a Research Instructor of the Department of Surgery, Baylor College of Medicine, Houston, Texas, since 1992.

The mission was accomplished in 236 orbits of the Earth, traveling over 6.1 million miles in 353 hours and 55 minutes.

[1] STS-95 Discovery (October 29 to November 7, 1998) was a nine-day mission during which the crew supported a variety of research payloads including deployment of the Spartan solar-observing spacecraft, the Hubble Space Telescope Orbital Systems Test Platform, and investigations on space flight and the aging process.

The mission was accomplished in 134 Earth orbits, traveling 3.6 million miles in 213 hours and 44 minutes.

In addition, she became the director of the JAXA Center for Applied Space Medicine and Human Research (J-CASMHR) in July 2012.

[4] In March 2015, Mukai became vice president of the Tokyo University of Science,[3] and is a technical counselor for JAXA.