Orbital Period

With regards to the study of satellites that currently orbit the Earth, the study of orbital mechanics becomes prevailant. Orbital mechanics, or astrodynamics, refers to the “application of ballistics and celestial mechanics to the practical problems concerning the motion of rockets and other spacecraft.”  Through orbital mechanics, which use Newton’s laws of motion and Newton’s law of universal gravitation as fundamental groundwork for celestial mapping, such elements as orbital periods can be calculated.  The orbital period of an object is the time that it takes for a given object to make one complete orbit, or free fall revolution, around the central body. For circular or elliptical orbits, the orbital period can be expressed in the following equation.

            T represents the orbital period in seconds. A (a) is the length of the orbits semi-major axis. U (u) is the standard gravitational parameter of a celestial body. It is the product of the gravitation constant G and the mass M of the central body. It is important to keep in mind that the above equation is only accurate when the masses of the two celestial bodies experiencing orbital interaction vary greatly-as in the interaction between a satellite and Earth.