Mean motion

The average motion or moderate motion daily n is the average angular speed of an object on an elliptical orbit, and is often given as one of the web elements or satellite orbital elements.

Objects in the solar system and artificial satellite in Earth orbit move in an elliptical orbit around the center of gravity, for example, of the earth. During a revolution speed varies because of the conservation of angular momentum.

The mean motion is the angular velocity of a theoretical object on the auxiliary circuit of the satellite ellipse, but not corresponding to the average anomaly by Kepler, which is based on the Perizentrumsdurchgang, but refers to an observer on the equator, that is, the time of day. You will specify in d-1 or rad / d.

Derivation

To obtain the mean motion, we measure the time it takes for the satellite to orbit the earth.

The following applies:

Calculation

The unit is rad / s

Conversions

N is given, one knows T and the major axis A. Although the eccentricity ε, the following:

Example

The International Space Station has an orbital period of approximately 91 minutes.

Or

The semi-major axis of the ISS track has a length of around 6720 km ( radius of the earth orbit height ).