In orbital mechanics, the speed required to maintain a particular orbit depends on the balance between the gravitational force pulling the satellite inward and the centrifugal force pushing it outward.
To understand why a satellite in geostationary orbit moves slower than a satellite in a low Earth orbit, let's consider the following factors:
Orbital Radius: The radius of an orbit determines the distance between the satellite and the center of the Earth. In general, the farther away a satellite is from the Earth, the longer its orbital period (the time it takes to complete one orbit) will be.
Centripetal Force: The centripetal force acting on a satellite is responsible for keeping it in orbit. For a satellite in a circular orbit, this force is provided by the gravitational attraction between the satellite and the Earth. The centripetal force is proportional to the square of the satellite's velocity.
In a geostationary orbit, the satellite is positioned at an altitude of approximately 35,786 kilometers (22,236 miles) above the Earth's equator. At this specific altitude, the satellite's orbital period matches the Earth's rotational period, causing it to appear stationary from the ground. To achieve this, the satellite must move at the same angular velocity as the Earth's rotation.
In comparison, satellites in low Earth orbit (LEO) are much closer to the Earth's surface and have smaller orbital radii. To maintain their orbits, they need to travel at higher velocities to generate enough centripetal force to counterbalance the gravitational force. LEO satellites typically orbit at altitudes ranging from a few hundred kilometers to a few thousand kilometers, and they complete their orbits in significantly less time than geostationary satellites.
In summary, the orbital speed required to maintain an orbit is determined by the balance between the gravitational force and the centrifugal force. The specific speed needed for a particular orbit depends on the radius of that orbit. A satellite in geostationary orbit moves slower than a satellite in a low Earth orbit because the geostationary orbit has a larger radius, requiring a lower orbital speed to maintain the balance of forces.