Table of Contents

Orbital Mechanics

Geostationary and Geosynchronous Orbits

Long Period Satellites

Geosynchronous

Geosynchronous orbits are those which have a period of twenty-four hours. Geosynchronous orbits which are at an angle to the equatorial plane do not allow a satellite to hover over a single geographical location. If the orbit is not exactly in the plane of the Equator the satellite will have a ground track in the form of a figure eight, with the centre of the eight crossing the Earth's equator as shown in the illustration below.

Geosynchronous orbits are very useful for satellites which are designed for continual monitoring of a single hemisphere of the Earth.

Omnidirectional communication satellites are examples of satellites which are in geosynchronous orbits. A fleet of such satellites can form a small swarm of relay stations high above the Earth for long range telecommunication such as those used in long range hand-held telephone units.

 

Geostationary

A geostationary orbit is a special case of geosynchronous orbits. Geostationary orbits lie in the plane of the Earth's equator and have an orbital period of twenty-four hours.

Geostationary orbits are configured so that a satellite in such an orbit will appear to remain over a single geographical location on the Earth's equator creating the illusion that the satellite is stationary.

Commercial television broadcast satellites are examples of satellites which are in geostationary orbits. It is because these satellites are geostationary that you do not need to keep moving your receiver dish to follow the motion of the satellite.

GOES

The National Oceanic and Atmospheric Administration (NOAA) maintains a fleet of active geostationary satellites called the GOES series (Geostationary Operational Environmental Satellite) that allows constant monitoring of a single part of the Earth.

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