The ISS orbits Earth at an average of 250 miles from the surface of Earth and completes 15.5 circles per day, once every 92 minutes. In other words, the astronauts see the sunrise and sunset 16 times every day!

The station is inhabited by astronauts conducting research in various fields, while also using it as an observatory to explore Earth and outer space. It is also intended to be a transportation center for spacecraft that are bound for the Moon, Mars and other interplanetary voyages.

The crew is not only responsible for the scientific experimentation and research being conducted onboard, but also the upkeep and maintenance of the vessel, a vessel that is continuously in motion and exposed to the worst possible elements. Such conditions are significant area of study for researchers.

The most common effect of space is the initial contact — getting used to such an alien environment. Astronauts are often seen to display anxiety or depression as they adjust to the novelty of space, according to post-psychiatric screenings of astronauts. Other causes of stress are the high pressure of work while being under frequent public observation, being away from home and family, and missing important events.

Sleep is another major factor that affects the mood and efficiency of the astronauts. Due to the irregularity in life and the constant rotation (转动) of sunrise and sunset, the circadian rhythm (生理节律) of the astronauts goes completely haywire, resulting in poor quality of sleep. The shuttle itself is noisy, with essential equipment always in operation to sustain the vessel. Half of all the astronauts onboard rely on sleeping pills to get some rest and manage to get an average 2 hours less sleep than when they’re back on Earth. Sleep is so critical for functionality that 50% of all medicines taken by astronauts in orbit is to help them sleep better. Low-Earth Orbit living is a restless endeavor, indeed.