Polar Orbits

In the context of aviation and aerospace, a polar orbit is a type of orbit where a satellite passes above or nearly above both poles of the body being orbited (usually a planet such as the Earth) on each revolution. It therefore has an inclination of (or very close to) 90 degrees to the equator. A feature of polar orbits is that they provide coverage of the entire planet, as the planet rotates underneath the orbital path. This is particularly useful for satellites that carry out mapping and surveillance operations, as they can observe any point on the Earth's surface. Polar orbits are also used for meteorology, earth science and astronomy applications. The Sun-synchronous orbit is a special type of polar orbit that goes around the Earth at a rate of once per sidereal day, keeping pace with the Earth's rotation. This is useful for imaging, spy, and weather satellites, because every time that the satellite comes around to the same point in its orbit, the surface underneath it is always in the same illumination condition.