SOLAR SYSTEM

Detailed explanation-1: -The flight path angle is the angle that the velocity vector makes with the normal to the position vector, as shown in Fig. 35. The normal to the position vector points in the same direction as by definition, so the flight path angle is zero at periapsis and apoapsis.

Detailed explanation-2: -Flight Path Angle: If you are flying in a level flight your Flight Path Angle will be zero (over the horizon), regardless of the Pitch Angle. During the descent, the Flight Path Angle will be negative (below the horizon) thus when climbing the Flight Path Angle will be positive (over the horizon).

Detailed explanation-3: -In astrodynamics or celestial mechanics, an elliptic orbit or elliptical orbit is a Kepler orbit with an eccentricity of less than 1; this includes the special case of a circular orbit, with eccentricity equal to 0.

Detailed explanation-4: -Orbits are eliptical because of Newtons Law of Gravity (bodies attract each other in proportion to their mass and inversly proportional to the square of the distance between them).