Sun-Synchronous Orbit

"These are polar orbits which are synchronous with the Sun. A satellite in a sun synchronous orbit would usually be at an altitude of between 600 to 800 km. Generally these orbits are used for Earth observation, solar study, weather forecasting and reconnaissance, as ground observation is improved if the surface is always illuminated by the Sun at the same angle when viewed from the satellite." (ESA, 2017)