Geostationary Orbit

Geostationary orbit (GEO) is a circular orbit in Earth's equatorial plane at an altitude of approximately 35,786 km, where a satellite's orbital period matches Earth's rotation period of 23 hours, 56 minutes, and 4 seconds. This synchrony causes the satellite to remain stationary above a fixed point on the equator as seen from the ground. GEO is the preferred orbit for most SBSP designs because a satellite at this altitude receives sunlight for approximately 99% of the year (briefly eclipsed during equinox periods) and can illuminate a fixed ground receiving station continuously. The altitude means that the satellite must transmit power over a very long distance, requiring large aperture transmitting and receiving arrays. Launching mass to GEO is significantly more expensive per kilogram than launching to low Earth orbit, making launch economics a central constraint for GEO-based SBSP systems.