Geosynchronous orbit
Also called: GSO · Topic: Remote Sensing, GIS and GNSS · NCERT: Beyond NCERT
Meaning
A geosynchronous orbit (GSO) is an orbit in which a satellite takes the same time to go once around the earth as the earth takes to spin once, which is about 24 hours. It lies about 36,000 km above the earth. The satellite comes back over the same longitude (the same north-south line on the globe) at the same time every day. If the orbit is tilted, or inclined, away from the equator, the satellite does not stay still in the sky. Seen from the ground, it moves north and south each day and traces a figure-of-eight. Navigation and communication systems use this orbit because a satellite in it keeps watch over one region.
Example
India's NavIC navigation system was planned as seven satellites. Four of them are in inclined geosynchronous orbits. They swing north and south over fixed longitudes and cover India and about 1,500 km around it. The other three are in geostationary orbit.
Don't confuse with
- Geostationary orbit: This is a special kind of geosynchronous orbit. It has zero tilt and sits exactly over the equator, about 35,786 km up. A satellite there seems to stay fixed at one spot in the sky. Every geostationary orbit is geosynchronous, but not every geosynchronous orbit is geostationary.
- Sun-synchronous orbit: This is a low, near-polar orbit about 700-900 km up, with about 14 orbits a day. It is used by IRS and Landsat for detailed images, not for watching one region all the time.