0020-4412/01/4405- $25.00 © 2001

A most important objective of the Sileye experi-ment, conducted on the Mir orbital station, was to determine the characteristics and types of particles which give rise to the phenomenon of light flashes (LF) observed by cosmonauts during orbital flights. This phenomenon—suddenly arising sensation of a bright light signal—was first observed during the flight of Apollo-11 to the Moon [1]. The interest in this phenom-enon has been fueled by its possible influence on the radiation safety and reliability of complicated opera-tions performed by a cosmonaut in the conditions of a space flight. The causes of LF are sought in numerous investigations, including those in space [2]. Until the present time, these experiments, mainly consisting in the statistical correlation analysis of the frequency of LF occurrence with fluxes of different cosmic-radiation particles, have failed to provide an unambiguous answer to the question of the causes of their appear-ance. The Sileye experiment is aimed at providing an answer to this question. This problem can be solved if the type and charac-teristics of cosmic-ray particles are determined during their passage through the recording system before they hit the cosmonaut’s eye (or, perhaps, his head). This scenario appears possible now, first, owing to the progress in semiconductor strip detectors engineering and, second, through the high ionizing power of the particles that are presumably responsible for this phe-nomenon. A charge-particle parameter whose value and varia-tion allows one to determine the physical characteris-tics of particles is their ionization loss. Within the zero approximation, the ionization loss d