PRINCIPAL INVESTIGATOR ( S ) : T. F. Budinger, Cornelius A. Tobias, E. 



Schopper, J. U. Schott, R. H. Huesman, F. 

 T.Upham, and T. F. Weiskamp 



EXPERIMENT TITLE/NUMBER : Light Flash Observations, MA- 106 



PROGRAM/MISSION : Apollo-Soyuz Test Project 



CLASSIFICATION : Human 



DISCIPLINE(S) : Radiobiology 



OBJECTIVES : To ascertain quantitatively the frequency, character, latitudinal 

 dependence, and identity of cosmic particles that cause light flash phenomena. 

 The ultimate objective was the assessment of radiation hazards for long-term 

 Earth-orbiting and interplanetary missions. 



PROTOCOL : Two revolutions were devoted to this experiment. During revolution 

 110, the silicon telescope-spectrometer was deployed for the measurement of 

 the trajectory, atomic charge Z, and velocity of cosmic particles with a 

 stopping power of 10 keV/micrometer or greater. During revolution 111, the 

 Apollo commander and the Command Module pilot made continuous observations of 

 visual sensations while dark adapted. The Docking Module pilot operated the 

 experiment control unit, which received data from the silicon detectors as 

 well as from silver chloride crystals that were used to register particle 

 tracks in four sectors of the orbit corresponding to northern latitudes, 

 equatorial latitudes, the South Atlantic Anomaly (SAA), and southern 

 latitudes. 



EQUIPMENT : Two dark adaptation masks, two pushbuttons, two cosmic-particle 

 detector boxes, and a control and power unit that housed a data tape. 



RESULTS : A total of 82 events was reported by the two astronauts. No 

 increased activity in the SAA and no graying of the darkened visual fields 

 occurred. The abundance of ions that caused the light flash phenomena is 

 minimal between latitudes 30 degrees N and 30 degrees S. The frequency of 

 light flash events between latitudes 30 degrees N and 50 degrees N and 30 

 degrees S and 50 degrees S is 25 times that noted in equatorial latitudes. 

 This distribution of flashes is correlated with the distribution of cosmic 

 particles with stopping power greater than 15 keV/micrometer in the eye. 



CONCLUSIONS : The frequency of reported light flash events is strongly 

 dependent on latitude. There was an increased rate of visual events near the 

 south geomagnetic pole which can be explained by dark adaptation of the 

 crewmembers . There were no reports of high frequency throughout the SAA as 

 was expected from a previous Skylab 4 report. The flux of protons was 23 

 times greater for Skylab at a 443 km altitude than for Apollo-Soyuz at 225 km. 

 The Apollo Command Module had greater radiation shielding than Skylab which 

 allowed fewer events. 



PUBLICATIONS : 108, 109, 110, 111, 112 



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