Another Look at the Pioneer Anomaly

The unexpected frequency shift observed by the Pioneer team, usually described as an anomalous acceleration, is discussed from the perspective of two alternative assumptions on the origin of cosmological redshift (Hubble effect). One is the standard assumption of an “expanding space”, the other is the assumption of an energy loss of photons without expanding space sections (“downscaling photons”). We find that the Pioneer frequency shift is an anomaly from the point of view of the expanding space hypothesis only. If one assumes a downscaling photon hypothesis for the Hubble effect, the anomaly dissolves and can be identified with a direct manifestation of the Hubble law inside