Sun-Synchronous Orbit (SSO)
Sun-synchronous orbit is a specific type of polar orbit in which a satellite’s orbital plane precesses (rotates) around the Earth at the same rate as the Earth orbits around the Sun. This synchronisation between the satellite’s orbital plane and the Sun’s position ensures that the satellite passes over a specific location on Earth at the same local solar time during each orbit.
To achieve a sun-synchronous orbit, the satellite’s orbital inclination and altitude are carefully selected. The inclination is set such that the satellite’s orbital plane is nearly perpendicular to the Earth’s equator. Typically, the inclination is around 98 to 99 degrees. The altitude is then adjusted to ensure that the satellite’s orbital period matches the Earth’s rotational period around the Sun, which is approximately one year.
The specific combination of inclination and altitude allows the satellite to maintain a consistent relationship with the Sun and the Earth as they move in their respective orbits. As the Earth orbits the Sun, the satellite’s orbital plane precesses in such a way that it always maintains the same orientation relative to the Sun. This means that the satellite will pass over a particular point on the Earth’s surface at approximately the same local solar time during each orbit.