The ISS (International Space Station) orbits Earth about once every?
- A. 60 minutes at an altitude of about 400 km
- B. 60 minutes at an altitude of about 500 km
- C. 90 minutes at an altitude of about 400 km
- D. 90 minutes at an altitude of about 500 km
Explanation
At its roughly 400-kilometre orbit, the ISS travels fast enough to circle Earth about every 90 minutes. Its altitude varies somewhat because atmospheric drag and orbital adjustments change the orbit.