Experiment Operation During Apollo IVA at 0-g

Experiment: Light Flashes Experiment Package (Apollo light flash moving emulsion detector)

Apollo Flight Nos.: 11, 12, 14, 15, 16, 17
Apollo Exp't No.: NA

Discipline: Life Sciences (2500), Animal Biology/Medical - Eyes (2538), Cosmic Radiation (2900)

Weight: 3.5 kg - ALFMED
Dimensions: NA

Manufacturer: uncertain

Description/Purpose:
All crews since A-11 (and perhaps some earlier) observed light flashes when in the dark or when they closed their eyes, while in transit to and from the Moon, on the surface, and in lunar orbit. On A-14 an observational schedule was first followed to test the various theories of the origin of the flashes. Flashes could be seen with the eyes open or closed when the spacecraft was dark. They discovered that it was not necessary to be dark adapted to see the flashes. This indicates that Cerenkov radiation from energetic cosmic rays traversing the eyeball, which had been the most widely accepted explanation for the light flashes, probably did not cause all or most of the flashes because light from this source is quite faint. Some of the flashes observed in space may be caused by direct ionization interactions of cosmic rays with the retina.

The ALFMED was an electromechanical device carried on A-16 & 17 that was worn on the head somewhat like a helmet and supported cosmic-radiation-sensitive emulsions around the head of the test subject. A physical record was provided of cosmic ray particles that passed through the emulsion and, in turn, through the head. A fixed vs. moving emulsion comparison allowed time resolution to 1 sec.

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