What particular biomedical data did NASA use to determine if an Apollo astronaut was awake or asleep?
From the APOLLO 11 MISSION COMMENTARY, page 72/1 "Our Flight Surgeon reported a short while ago that Command Module Pilot Mike Collins appeared to be sleeping soundly at this time. Biomedical data on the other two crewmen indicates that they are still awake."
If ISS astronauts' sleep is still monitored has the specific data used changed?