Support for the thermal origin of the Pioneer anomaly

TL;DR

This paper provides strong evidence that the Pioneer anomaly can be explained by thermal recoil forces from anisotropic thermal radiation emission, eliminating the need for new physics explanations.

Contribution

The study develops a detailed thermal model of Pioneer spacecraft and independently estimates thermal recoil forces, confirming they account for the anomaly.

Findings

Thermal recoil force explains the Pioneer anomaly.

Thermal model matches observed acceleration properties.

No residual anomalous acceleration remains after accounting for thermal effects.

Abstract

We investigate the possibility that the anomalous acceleration of the Pioneer 10 and 11 spacecraft is due to the recoil force associated with an anisotropic emission of thermal radiation off the vehicles. To this end, relying on the project and spacecraft design documentation, we constructed a comprehensive finite-element thermal model of the two spacecraft. Then, we numerically solve thermal conduction and radiation equations using the actual flight telemetry as boundary conditions. We use the results of this model to evaluate the effect of the thermal recoil force on the Pioneer 10 spacecraft at various heliocentric distances. We found that the magnitude, temporal behavior, and direction of the resulting thermal acceleration are all similar to the properties of the observed anomaly. As a novel element of our investigation, we develop a parameterized model for the thermal recoil force and estimate the coefficients of this model independently from navigational Doppler data. We find no statistically significant difference between the two estimates and conclude that once the thermal recoil force is properly accounted for, no anomalous acceleration remains.