Sun-synchronous polar orbit
This video illustrates the principle of Sun-synchronous orbits used by EUMETSAT's Metop satellites. The satellite's orbital plane is indicated by the red torus and the Earth's polar axis by the cyan line.
A Sun-synchronous orbit (also called a heliosynchronous orbit) is an orbit around Earth with the right combination of altitude and inclination such that the Earth's oblateness causes the orbit plane to precess once a year.
The end result is that the satellite will always cross the equator at roughly the same local time on each orbit, which means the lighting conditions are similar from one orbit to the next. This is useful for making measurements and simplifies the satellite design.
To learn more about how Metop satellites maintain their Sun-synchronous orbit, check out this post on our Science Blog: https://scienceblog.eumetsat.int/2017...
