A geosynchronous orbit is when a satellite or other device’s orbit matches the Earth’s rotation so that the satellite travels around the Earth in a straight line and stays at the same point in the sky relative to the Earth. This means that as the Earth rotates, the satellites rotates  around the Earth at the same speed so that its relative position never changes. Geosynchronous orbits are used for a number of purposes, including monitoring a specific region and communicating with Earth-based systems. Geosynchronous orbits include geostationary orbits, super-synchronous orbits, sub-synchronous orbits, and graveyard orbits.

How a Geosynchronous Orbit Works
A geosynchronous orbit is relatively common and many communication and surveillance satellites currently travelling around the Earth use it. Geosynchronous orbits often occur in nature with moons, asteroids, or other natural satellites and chemical rocket thrusters that keep the satellite from floating off into space or crashing into the Earth can artificially produce them. Computer systems and ground-based controllers that activate the thrusters at a highly calculated time and position control these chemical rocket thrusters in order to keep the satellite in the same position throughout its orbit.

Applications
Geosynchronous orbits are used for communication, surveillance, and data transfers. For example, a satellite with a geosynchronous orbit provides Internet access and phone service to users in rural areas that do not have local service providers. Geosynchronous satellites can also be used to survey a landmass for map-making, spy on military forces on the ground, and listen in on communication broadcasts from all over the world.

Advantages
Geosynchronous orbits have several advantages over other types of orbits. For example, geosynchronous orbits allow ground systems to stay in communication with satellites and prevent the satellite from wandering away from where it is expected to be. Geosynchronous orbits allow two-way communication with ground stations on a daily basis and allow the satellite to cover a much larger area than a geostationary orbit.

Disadvantages
Although geosynchronous orbits are advantageous, they also have several disadvantages. For example, geosynchronous orbits cause a slight delay in the time it takes for radio signals to reach the satellite and return to a ground station on the Earth. This delay causes a significant loss of data and lack of real-time communication, especially for Internet and telephone services. Another disadvantage is that they do not cover all areas of the Earth, especially in the Northern hemisphere, where land masses and curvature of the Earth tend to block radio signals.