Pioneer effect ” : A cosmological Foucault ’ s experiment

The reported anomalous acceleration acting on the Pioneers space-crafts could be seen as a consequence of the existence of some local curvature in light geodesics when using the coordinate speed of light in an expanding space-time. We will show that, as a matter of fact, what has been detected in the experiments is just the cosmic expansion rate-the Hubble parameter H-, a feature of light signals. A relation for the reported annual term is obtained which depends on orbital parameters, leading to suggesting an analogy between the effect and Foucault's experiment. In this sense, light rays play a similar rôle in the expanding space than Foucault's Pendulum does while determining Earth's rotation. Pioneer effect. A careful analysis of orbital data from Pioneer 10/11 spacecrafts has been reported[1],[2],[3] which indicates the existence of a very weak acceleration-approximately a p ≃ 8.5 · 10 −8 cm/s 2-apparently directed toward the Sun. The most conservative (or less adventurous) hypothesis is that these sorts of effects on the Pioneers's tracking data do not entail new physics and that the detected misfit must be due to some sophisticated (technological) reason having to do with the spacecraft configuration. However , the analysis in[1]-[3] seems to have ruled out many (perhaps all) of such technical reasons and the authors even claim having taken into account the accepted values of the errors in the planetary ephemeris, Earth's orientation, precession, and nutation. Thus, in principle, a new effect seems to have unexpectedly entered the phenomenology of physics. On the other hand, if such an effect really exists (i.e., it can not be eliminated by data reanalysis) it would represent a 1 To my father's memory 2 Antequera 1-1