PRINCIPAL INVESTIGATOR (S ) : Rudolph A. Hoffman, Lawrence S. Pinsky, W. Zach 



Osborne, and J. Vernon Bailey 



EXPERIMENT TITLE/NUMBER : Visual Light Flash Observations on Skylab 4 



PROGRAM/MISSION : Skylab 4 



CLASSIFICATION : Human 



DISCIPLINE(S) : Radiobiology 



OBJECTIVES : To investigate the frequency and character of visual light 

 flashes in near Earth orbit as the Skylab trajectory passed from northern to 

 southern latitudes. Because the trajectory periodically passed through the 

 South Atlantic Anomaly (SAA), another objective was the investigation of 

 possible visual flashes during passage through this region. 



PROTOCOL : Two separate light flash observation sessions were performed on 

 mission days 74 and 81 by the pilot. The first session occurred during an 

 orbit that allowed observations from high geomagnetic latitudes. The orbit 

 for the other session passed through the center of the SAA. The pilot got into 

 his sleep restraint, set a timer for either 55 or 70 minutes, donned a 

 blindfold and recorded his observations of flashes on the voice recorder. Ten 

 minutes were allowed for dark adaptation. 



EQUIPMENT : Voice recorder, blindfold. 



RESULTS : A total of 168 flashes was reported: 24 during the first session 

 and 144 during the second. Three to nine flashes/minute were observed. The 

 frequency was related to latitude, the highest being in the SAA and the lowest 

 over the poles. 



CONCLUSIONS : There is a strong correlation of very high flash rates with 

 passage through the SAA, and from physical arguments and event descriptions it 

 appears certain that these flashes are due to trapped radiation. There is 

 evidence for the predicted latitude effect, although existing data are 

 insufficient for a thorough statistical evaluation. A greater particle flux 

 in the trajectory through the SAA probably explains the increased number of 

 flashes observed at that time, but there were also more flashes observed 

 outside the anomaly during the second period where the cosmic particle 

 environment should have been comparable. This variation remains unexplained. 

 There may be particles heavier than protons in the inner belt of trapped 

 radiation of the SAA. 



PUBLICATIONS : 276, 277, 413, 428 



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