An orbit which takes advantage of the Earth Eric Weisstein's World of Astronomy's bulge to rotate the plane of the orbit. With the right combination of altitude and inclination, the rotation can be set to 360° y-1, keeping the orbital plane in a roughly constant relation to the earth Eric Weisstein's World of Astronomy-sun Eric Weisstein's World of Astronomy line. For low orbits, the inclination turns out to be slightly over 90°. Sun-synchronous orbits are very popular for remote sensing, weather, and spy satellites that want to view the ground at constant Sun angle.
