Joseph P. Kerwin is photographed strapped into the sleep restraint in the crew quarters of the Orbital Workshop of the Skylab 1 & 2 space station cluster in Earth orbit.

Scientist-astronaut Joseph P. Kerwin, Skylab 2 science pilot, is photographed strapped into the sleep restraint in the crew quarters of the Orbital Workshop of the Skylab 1 & 2 space station cluster in Earth orbit. Kerwin is wearing the special cap which contains biomedical instrumentation for the M133 Sleep Monitoring Experiment. The purpose of the M133 experiment is to evaluate quantity and quality of sleep during prolonged space flight by the analysis of electroencephalographic (EEG) and electrooculographic (EOG) activity. Photo credit: NASA