A Sun-synchronous orbit (SSO, also called a heliosynchronous orbit) is a geocentric orbit that combines altitude and inclination in such a way that the satellite passes over any given point of the planet's surface at the same local solar time. Such an orbit can place a satellite in constant sunlight and is useful for imaging, spy, and weather satellites. More technically, it is an orbit arranged in such a way that it precesses once a year. The surface illumination angle will be nearly the same every time that the satellite is overhead. This consistent lighting is a useful characteristic for satellites that image the Earth's surface in visible or infrared wavelengths (e.g. weather and spy satellites) and for other remote sensing satellites (e.g. those carrying ocean and atmospheric remote s