# Flight path angle (elliptic orbit)

## Description

In astrodynamics an elliptic orbit is a Kepler orbit with the eccentricity less than 1; this includes the special case of a circular orbit, with eccentricity equal to zero. In a stricter sense, it is a Kepler orbit with the eccentricity greater than 0 and less than 1 (thus excluding the circular orbit). In a wider sense it is a Kepler orbit with negative energy. This includes the radial elliptic orbit, with eccentricity equal to 1.The flight path angle is the angle between the orbiting body’s velocity vector (= the vector tangent to the instantaneous orbit) and the local horizontal.

Related formulas## Variables

ϕ | Flight path angle (radians) |

h | The specific relative angular momentum of the orbit (m^{2}/s) |

r | The radial distance of the orbiting body from the central body (m) |

v | The orbital speed of the orbiting body (m/s) |