# Mean Anomaly

*Anomaly* is a term for an angle. The *Mean Anomaly* is the
angle which describes the position of the satellite in its orbit, relative to
perigee. At perigee, the Mean Anomaly is zero, it increases to 180 degrees at
apogee, then back to perigee at 360 degrees.

Since the orbit is often not a circle, the measurement of the angle is
difficult, so the angle is expressed in terms of a fractional orbit (one orbit
= 360 **degrees**). This is the reason for the *mean* adjective. For
circular orbits, the Mean Anomaly is just the angle between perigee and the
current satellite position.

A special form of the Mean Anomaly is used by AMSAT controllers - instead of
360 degrees, the orbit fraction is expressed as a number in the range 0-255.
This is often referred to as "MA" and is available in the
Orbit group
of the
Info Window.

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