Each day, the senator and Mukai will be tested for alertness, reaction time, and job performance. One test involves solving math problems. The results of such tests can be compared with how well they slept on previous nights. The radio broadcasts body-temperature readings to a small, wearable receiver until it is passed from the astronaut's body. Then another pill must be swallowed.
Body temperatures reveal what time it is according to a person's natural, or biological, clock.
The power source of this clock is an area deep in the brain that regulates body temperature, natural melatonin levels, sleep and wakefulness. When biological and clock times get out of synchronization, people have difficulty sleeping, staying awake, or both. Jet lag is a good example. Whenever Glenn discusses the flight with reporters, someone asks whether his sleeping and other medical experiments are merely a public relations stunt designed by NASA to revive flagging interest in the space program. Glenn was the first American to orbit Earth, circling the planet three times on Feb. 20, 1962.