On a recently proposed metric linear extension of general relativity to explain the Pioneer anomaly

Recently, Jaekel and Reynaud proposed a gravitational mechanism for the Pioneer anomaly based on a metric linear extension of general relativity which would be able to explain the anomalous acceleration experienced by the Pioneer spacecraft without contradicting either the equivalence principle or what we know about the planetary motions. In this paper we perform an independent test of such an hypothesis by showing that the planets' orbits are, in fact, affected by the suggested mechanism as well and comparing the resulting effects with the latest observational determinations. It turns out that the predicted perihelion precessions, expressed in terms of an adjustable free parameter zeta_P set equal to the value used to reproduce the magnitude of the Pioneer anomalous acceleration, are quite different from the observationally determined extra-advances of such Keplerian element for the inner planets. Conversely, the values obtained for zeta_P from the determined perihelion extra-rates of the inner planets turn out to be in disagreement with the value which would be required to accommodate the Pioneer anomaly. As a consequence, the suggested explanation of gravitational origin for the Pioneer anomaly, based on the assumption that zeta_P is constant throughout the Solar System, must be rejected