Global Positioning System (GPS)

The space segment (SS) comprises the orbiting GPS satellites or Space Vehicles (SV) in GPS terms. Originally, the GPS is design for 24SV. Firstly it contains three circular orbital planes with eight satellites per plane. But later on, this is modified to four satellites each in six orbital planes. The orbital planes are center on the earth.

Their orbits are nominally circular with an inclination of about 55 degrees and have a period of 12 hours. The six planes have approximately 55° inclination (tilt relative to Earth’s equator) and are separated by 60° right ascension of the ascending (angle along the equator from a reference point to the orbit’s intersection). The orbits are arranged so that at least six satellites are always within line of sight from almost everywhere on Earth’s surface.

The SV orbiting at an altitude of approximately 20200 km (12600 miles) with orbital radius of 26600 km (16500 miles). Each SV makes two complete orbits each day (MEO satellite).