There are three major types of Earth orbits

    High Earth Orbit -                                                                               Lagrange Points
    As the name suggests these orbits are very far away from the surface of the Earth. 
    These orbits are useful for weather satellites because they can be geosynchronous which means they are constantly over the same geographical location. 

    There are five special 'sweet spots' in this orbit range called Lagrange Points. 
    L4 and L5 are the most stable, and they lead and follow the Earth at a sixty degree angles.  L1 and L2 are the closest to Earth and take a lot of calculations and monitoring to keep in stable orbit.  L3 is on the other side of the sun, making it very difficult to communicate with anything orbiting there. 
                                                                                                                                                                                                                                                                                                                                                                                                                                  Molniya Orbit
    Medium Earth Orbit-

    These orbits are closer to the surface of the Earth.

    There are two notable orbits in this range: The semi-synchronous orbit which takes only 12 hours to complete, and the Molniya orbit which also only takes 12 hours to complete a single trip, but it is very eccentric-meaning it does not follow a  circular path. 

    The semi-synchronous orbit passes over the same geographical location twice every day which makes it ideal for Global Positioning System satellites. 
    The Molniya orbit is elliptical so it passes earth really close on one side, and far away from the other.  This orbit is best for observing the poles which are difficult to see otherwise. 

    Low Earth Orbit

                                                                                                                                                                                              Sun-synchronous Orbit 

    This orbit range is the closest to the surface of the Earth.  This is where the majority of the science satellites aimed at monitoring the Earth itself are located.  The absolute coolest orbit in this range is the polar orbits that passes each pole.  Because the orbit is so close to Earth the satellite will actually stay in the same zone with each pass.  It can always be five 'o clock on that satellite!  This orbit is also sun-synchronous which means that the area it is observing is always in daylight.   

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