Skylab. NASA Skylab space station

This 1970 photograph shows equipment for the Skylab's Sleep Monitoring Experiment (M133), a medical evaluation designed to objectively determine the amount and quality of crewmembers' inflight sleep. The experiment monitored and recorded electroencephalographic (EEG) and electrooculographic (EOG) activity during astronauts' sleep periods. One of the astronauts was selected for this experiment and wore a fitted cap during his sleep periods. The Marshall Space Flight Center had program management responsibility for the development of Skylab hardware and experiments.