Gravity field of Jupiter and its satellite from Pioneer 10 and Pioneer 11 tracking data

Abstract

Accurate two-way Doppler tracking data were obtained from the Pioneer 10 and Pioneer 11 spacecraft during their Jupiter encounters. A comprehensive combined analysis of these data has yielded significantly improved values of the masses of the Galilean satellites and the harmonic coefficients of Jupiter, and a mass of Jupiter of comparable accuracy to the best previous determinations using asteroid motions. The ratios of the masses of the four Galilean satellites to the mass of Jupiter are (4.684 ±0.022) X 10-5 for 10, (2.523 ±0.02S) X 10-5 for Europa, (7.803 ±0.030) X 10-5 for Ganymede, and (S.661 ±0.019)X 10-5 for Callisto. (All error estimates presented in this paper are standard errors, those for Pioneer 10 and Pioneer 11 are an evaluation of real errors as distinguished from formal errors.) The ratio of the mass of the Sun to the mass of the Jupiter system is 1047.346±0.004. The second, third, fourth, and sixth zonal harmonic coefficients of Jupiter are J 2=(14733±4)X 10-6, J 3=(0.4±9)X 10-6, J 4=(-S87±7)X 10-6, and J 6=(34±SO)X 10-6 at an equatorial radius of 71 398 km. The sectorial harmonics C 22 and S 22 and the ratio of a hypothetical mass con- centration at the Red Spot to the mass of Jupiter are approximately (O±O.S)X 10-6. The instantaneous 3 December 1974 right ascension and declination of the pole of Jupiter relative to the mean Earth equator and equinox of 19S0.0 are 267'.998 ±0.016 and 64'.S04 ± 0.004, respectively. The harmonic results, which will have an important application as boundary conditions for theoretical models of Jupiter's interior, are consistent with a planet in hydrostatic equilibrium at all levels.