The Pioneer Anomaly: an inconvenient reality or NASA's 12 year misconception?

Abstract

This paper discusses the likelihood of whether the Pioneer anomaly is due to 'mundane' systematic errors/effects or indicative of new or unappreciated physics. The main aim of this paper is to argue that recent publications suggesting that the anomaly is previously overlooked thermal recoil forces, which is in stark contrast to the earlier consensus (1998-2010), are open to questioning. Both direct and circumstantial evidence are examined, and the uncertainty or inaccuracy associated with observations of such a small magnitude effect is recognised. Whilst a non-systematic based anomaly appears to be very unlikely, by way of the awkwardness of the observational characteristics that would need to be modelled, the existence of other peripheral anomalous phenomena makes an outright dismissal of the anomaly unwise. Issues from the philosophy of science (and physics) are also tabled. In the interests of having a contingency plan, should future experiments provide support for a Pioneer-like anomaly, the type of unappreciated physics that could conceivably satisfy the awkward observational evidence is alluded to, albeit in a non-rigorous and cursory manner.