Abstract
Current least squares fits to solar system data, including transit circle observations of the terrestrial and giant planets, radar observations of the terrestrial planets, Mariner 9 range fixes to Mars, and Pioneer 10 11 range fixes to Jupiter, have yielded some new results of interest to experimental relativity. Solutions have been obtained for the PPN parameters β and γ, the solar gravitational quadrupole moment J 2, a time variation in the gravitational constant G, and four Nordtvedt parameters. The existing planetary data provide no significant result on the Nordtvedt effect. Under the assumption that the precession of the perihelion of Mercury is caused exclusively by planetary perturbations, general relativity, and the gravitational quadrupole moment, a value of (2.5 ± 1.6) × 10 −6 is obtained for J 2. There are various combinations of the PPN parameters β, γ, α 1, and α 3 that will also yield the observed precession of the perihelion, but there is no real empirical evidence for PPN values which disagree with general relativity. A positive upper bound of 1.4 × 10 −10 yr −1 is indicated for G ̇ G from existing data. A few months of Viking data are needed to refine this result, and at least 2.5 yr of Viking data are needed to determine the Nordtvedt effect to the same accuracy as the current lunar laser result.
Published Version
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