Commentary regarding "on-orbit sleep problems of astronauts and countermeasures".

This commentary addresses the article by Wu et al. entitled "On-orbit sleep problems of astronauts and countermeasures". In this article, the authors discussed the sleep problems of astronauts. Despite its challenging topic, the paper authored by Wu et al. has at least one major shortcoming. This issue is related to the observation that the sleep pattern of astronauts can be disturbed by light flash phenomenon. Since the first report by astronaut E.E. Aldrin in 1969, many astronauts have reported light flashes. These visually perceived flashes of light occurred in different shapes but they apparently moved across the visual field of astronauts and possibly caused, at least to some extent, sleep problems. Moreover, the countermeasures proposed by the authors may improve astronauts' sleep pattern, but they do not address the root cause of the light flashes (i.e., heavy ion interactions outside the shielding provided by the Earth's magnetosphere). A possible approach to reducing light flashes is available using the fact that much of the galactic cosmic radiation (GCR) spectrum is composed of ions that can be diverted from the spacecraft using electromagnetic fields. Possible design parameters and the requisite electric and magnetic field strengths to successfully deflect GCR radiation are outlined.