Personal Radiation Dosimeter (PRD)
A Personal Radiation Dosimeter (PRD) was carried by each of the Apollo crewmembers. The PRD provided visual read-out of accumulated radiation dose to each crewman as the mission progressed. The PRD was approximately the size of a cigarette pack, and pockets were provided in the flight coveralls, as well as in the spacesuit, for carrying the PRD. The PRD sensor was a 7.1 cc tissue equivalent ion chamber, with a range of 0 to 1000 rads in 0.01 rad increments, and it weighed 0.4 lbs. The operational life of the PRD was 2000 hours.