Odd zonal harmonics in the geopotential, from analysis of 28 satellite orbits

Abstract

Abstract : The geopotential is usually expressed as an infinite series of spherical harmonics, and the odd zonal harmonics are the terms independent of longitude and antisymmetric about the equator: they define the 'pear-shape' effect. The coefficients J3, J5, J7, ... of these harmonics have been evaluated by analysing the variations in eccentricity of 28 satellite orbits from near-equatorial to polar. Most of the orbits from our previous determination in 1973 are used again, but three new orbits are added, including two at inclinations between 62 degrees and 63 degrees, which have been specially observed for more than five years by the Hewitt cameras. With the help of the new orbits and revised theory, we have obtained sets of J-coefficients with standard deviations about 40% lower than before.