The Orbital Perturbation Environment for the COBRA and COBRA Teardrop Elliptical Constellations

Abstract

Elliptical, non-geostationary satellite orbit (NGSO) satellite constellations have been proposed as a solution to the problem of the shortage of slots in the Geostationary Ring for new communications satellites. These elliptical constellations have the potential to greatly multiply the available space real estate without interfering with the existing GEO satellites. These constellations employ eight-hour “leaning” elliptical orbits, operating at approximately the critical inclination of 63.4 degrees. The three active arcs of a single satellite have a ground trace that resembles a coiled cobra, hence the acronym name COBRA. Due to the exact repeat ground-track, with three orbital revolutions for each rotation of the Earth, these COBRA orbits experience deep tesseral resonance perturbations with the 3rd, 6th, and other (multiples of three) order geopotential harmonic coefficient pairs. These resonant perturbations are dependent on the RAAN of the particular ground-track. These orbits also experience strong perturbations due to the lunar-solar point masses. The semi-analytical satellite theory DSST is used to explore both the tesseral resonance and lunar-solar point mass perturbations.