Analysis of 24 Orbits to Determine Odd Zonal Harmonics in the Geopotential

Values of the odd zonal harmonics in the geopotential are best obtained by analysis of the variations in the eccentricity of satellite orbits well distributed in inclination. Previous solutions have been deficient because they have not included orbits near the critical inclination of 63.4 degrees, where the amplitude of the oscillation in eccentricity is large. Recently, accurate orbits over a cycle of the argument of perigee have been obtained for Cosmos 44 at inclination 65.1 degrees and Cosmos 248 (i = 62.2 degrees), after three years of observations with the Hewitt cameras. These orbits have now been used, together with those of Explorer 32 (i = 64.7 degrees), Geos 2, Peole and 19 other satellites to make a new determination of the odd zonal harmonic coefficients. More than 100 sets of coefficients to fit the data were studied, and it is concluded that the omission of selected coefficient offers considerable advantages.