"We catch a glimpse of a huge swirl of clouds out the window over the middle of the Pacific Ocean, or the boot of Italy jutting down into the Mediterranean, or the brilliant blue coral reefs of the Caribbean strutting their beauty before the stars. And...we experienced those uniquely human qualities: awe, curiosity, wonder, joy, amazement." (Russell L. Schweickart, Apollo Astronaut ("The Home Planet")
Space Station Orbit Tutorial
Cynthia A. Evans and Julie A. Robinson, Earth Sciences and Image Analysis, NASA Johnson Space Center
FACT 2: With each orbit taking 90-93 minutes, there are approximately 16 orbits per day (24 hours). The exact number of
orbits per day is usually less than 16 (generally 15.5 to 15.9 orbits/day) depending on the altitude of the ISS. Each orbit
shifts to the west by approximately 22.9° of longitude (measured as the position where the orbit crosses the equator).
Figure 2. Example of two consecutive orbits (daylight only shown) the first orbit is in red and the second in yellow. Arrows
show the travel direction of the spacecraft.
Figure 3. Daylight tracks for 16 consecutive orbits (about one day). The part of orbit 16 overlaps into the next day is during
darkness and is not shown here. The first daylight orbit of the next day, number 17, is shown in red.