The Orbit Period equation for Direct Orbits computes the period of a satellite's orbit around the Earth in minutes based on the input of the change in longitude of the ascending node, `DeltaL`.

Notes

The Orbit Period, P, is equal to the time during which the Earth rotates through two successive intersections of the satellite track with equator, in other words the satellite passing two successive Longitudes of the ascending node.

Orbits which move eastward are referred to as direct orbits and for direct orbits we measure the change in Longitude on successive orbits as positive to the East.

The definition of period does not apply for polar orbits.  A prograde or direct orbit has inclination i < `90^o`. A retrograde orbit has inclination i > `90^o`.  And a polar orbit has inclination i = `90^o`.