Fig. 2From: On-orbit sleep problems of astronauts and countermeasuresFrame diagram of on-orbit sleep problems of astronauts and countermeasures. In human space flight, sleep time and quality on orbit are apparently decreased. This figure presents six kinds of causes, some effects of sleep deficiency on performance and mental and physical health, and seven kinds of countermeasures for sleep disturbance in spaceflight. The symbol of ‘↓’ means decreased or impairedBack to article page