Light Flashes Experiment

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

Acronym: None (ALFMED) 

Interior view of ALFMED device (S-71-39590).

The ALFMED device as worn during light flashes investigation (S-71-39591).

PI/Engineer: Richard E. Benson/JSC
Other Contacts: Lawrence S. Pinsky/JSC, W. Zachary Osborn/Univ. of Houston, J. Vernon Bailey/JSC

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

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.

Unloading from the LM: NA

Transporting by foot or MET: NA

Loading/unloading tools/exp’ts on LRV: NA

Site Selection:
In the CM during coast periods. Casual observations from the LM were made, too.

Deploying experiment:
The ALFMED unit was donned like a helmet with a face shield.

Check-out of experiment: NA

Operation of experiment:
The A-15 crew had observing sessions with eye shades on during the trans-lunar and trans-Earth coasts. They reported the flashes to MCC real-time. Also, the CMP had an observing session in lunar orbit and the crew on the surface reported that they saw flashes while in the LM. The LMP reported that the frequency of flashes was lower when he was lying on his stomach in his hammock than when he was on his back. On A-16 & 17 two one-hour sessions were conducted, one each during trans-lunar and trans-Earth coasts. ALFMED was worn in the 1st session only, eye shades were used for the second. The observa-tion of flashes was reported to MCC and was correlated with ALFMED results. The event rate was higher during trans-lunar than trans-Earth coast. Photography of the fundus of the eye before and after flight revealed no detectable changes. The CMP never saw any flashes for the entire flight of A-16, but it is worth noting that he has poor night vision.

Repairs to experiment: NA

Recovery/take-down of experiment: NA

Stowing experiment for return: NA

Loading/unloading samples on LRV: NA

Loading of exp’t/samples into the LM: NA

Stowing of package once in the LM: NA

Sampling operations – soil, rocks: NA

Trenching: NA

Raking: NA

Drilling: NA

Navigating/recognizing landmarks: NA

Were there any hazards in the experiment?
i.e. hazardous materials (explosive, radioactive, toxic), sharp objects, high voltages, massive, bulky, tripping hazards, temperatures?

Was lighting a problem? Dark adaptation may have affected the results.

Were the results visible to the crew?
Yes, by definition.

Would you recommend any design changes?
No comments by crew.

Were any special tools required?
A-11, 12, and 13 merely reported light flash observations during crew debriefings. A-14 and 15 had a special 1 hour observation period and reported the flashes to Mission Control as they occurred. A-15 was the first to have special light-tight eye shades to provide a uniform and reproducible degree of darkness. A-16 & 17 wore a special headgear designed to document the passage of cosmic rays, called ALFMED (Apollo light flash moving emulsion detector.)

Was the orientation of the experiment (i.e. horizontal/vertical) important? Difficult?

Was the experiment successful? Yes

Were there related experiments on other flights?
Lab studies with humans exposed to X-rays and several types of particulate radiation have been done and show that similar light-flash sensations are observed.

Where was it stored during flight?
CM aft bulkhead locker A8 (for A-16.).

Were there any problems photographing the experiment?
The emulsions recorded the passage of the cosmic rays through the film. Since one moved relative to another, coincidence of two tracks by alignment of the plates defined the time of passage. This was correlated with the times of the observations of the crew to Mission Control.

What pre-launch and cruise req’ts were there?

What was different between training and actual EVA?
No comments by crew.

What problems were due to the suit rather than the experiment?

Any experiences inside the CM of interest from the experiment/operations viewpoint?


Preliminary Science Reports

Apollo light flash investigations, in “Biomedical Results of Apollo”, pp 355 – 365, NASA, Osborne, W. Z., Pinsky, L. S., Bailey, J. V.

Apollo Program Summary Report, section Visual light flash phenomenon, JCS-09423, April, 1975.

Apollo 16 Technical Crew Debriefing, 5 May 1972, in JSC History Office.

Apollo Stowage List – Apollo 16, MSC, 18 April 1972

Memorandum to Manager, Apollo Spacecraft Program, from Director of Medical Research and Operations, re Visual Light Flash Phenomenon – Apollo 15 DTO Assessment Report, 18 October 1971, in JSC History Office.

Luna Spacey

Luna Spacey

Luna Spacey, a distinguished space researcher, earned her Ph.D. in Astrophysics from MIT, specializing in exotic matter near black holes. Joining NASA post-graduation, she significantly contributed to the discovery of gravitational waves, enriching cosmic understanding.With a 15-year stellar career, Luna has numerous published papers and is currently spearheading a dark matter research project. Beyond her profession, she’s an avid stargazer, dedicated to community science education through local school workshops.Luna also cherishes hiking and astrophotography, hobbies that harmoniously blend her admiration for nature and the cosmos, making her a revered figure in both the scientific and local communities.

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