Assigned as a payload specialist John H. Glenn, Jr. was also a subject for basic research on how weightlessness affects the body of an older person. Glenn was a test subject for what is an expanded effort by NASA and the National Institute on Aging (NIA) to study the aging process in older persons.
At 77 years of age, Glenn was the oldest astronaut to fly in space, nearly twice the age of the average astronaut. He was assigned several areas of personal basic research, with monitoring to occur pre-flight, in-flight, and post-flight, along with other bio-research projects involving all crew members. John H. Glenn, Jr. was involved in two age-related experiments, as both a researcher and a guinea pig. One studied the way certain proteins are processed during weightlessness, in the hope that researchers will gain hints about what causes muscle weakening in space. The other looked into sleep patterns by comparing the circadian rhythm, or biological clock that governs alertness and sleepiness, between Glenn and the others in the crew. Glenn was also in charge of the flight's still and video photography.
This mission also supported a variety of research payloads, including deployment of the Spartan solar-observing spacecraft, the Hubble Space Telescope Orbital Systems Test Platform, as well as investigations on space flight and aging. The highly successful mission concluded with the landing on Saturday, November 7, 1998 at 12:04 p.m. EST at KSC.