In astrodynamics or celestial mechanics a parabolic trajectory is a Kepler orbit. It eccentricity is equal to 1. When moving away from the source it is referred to as an escape orbit, otherwise a capture orbit.
The equation or formula for Parabolic orbits is,
r = the radial distance of the orbiting body from the mass center of the central body
h = specific angular momentum of the orbiting body
µ = is the standard gravitational parameter
Ɵ = the true anomaly of the orbiting body.