The Law of Closest Approach

Abstract

In this work, we introduce the Law of Closest Approach which is derived from the properties of conic orbits and can be considered an addendum to the laws of Kepler. It states that on the closest approach, the distance between the objects is minimal and the velocity vector is perpendicular to the position vector with maximum speed. The ratio of twice the kinetic energy to the negative potential energy is equal to the eccentricity plus one. The advantage of this law is that both speed and position are at extremum making the calculation of the eccentricity more robust.