Science Fair Project Encyclopedia
Mean anomaly
In the study of orbital dynamics the mean anomaly is a measure of time, specific to the orbiting body p, which is a multiple of 2π radians at and only at periapsis. It is the fraction of the orbital period that has elapsed since the last passage at periapsis z, expressed as an angle. In the diagram below, it is M (the angle z-c-y).
The point y is defined such that the circular sector area z-c-y is equal to the elliptic sector area z-s-p, scaled up by the ratio of the major to minor axes of the ellipse.
Calculation
In astrodynamics mean anomaly 
can be calculated as follows:
where:
is the mean anomaly at time 
,
- is the start time,
is the time of interest,
is the mean motion.
Alternatively:
where:
is orbit's eccentric anomaly,
is orbit's eccentricity.
See also
10-26-2009 08:16:03
The contents of this article is licensed from www.wikipedia.org under the GNU Free Documentation License. Click here to see the transparent copy and copyright details
The contents of this article is licensed from www.wikipedia.org under the GNU Free Documentation License. Click here to see the transparent copy and copyright details