Focus: the Pioneer anomaly

To date, the Pioneer 10 and 11 spacecraft are the most precisely navigated deep-space vehicles. However, as indicated by their radio-metric data, the Pioneers orbit reconstructions were limited by a small, anomalous, constant, blue-shifted, Doppler frequency drift of approximately 6 x 10^-9 Hz/s. The drift can be interpreted as due to a constant sunward acceleration of a_P = (8.74 1.33) 10^-10 m/s^2. This interpretation has become known as the Pioneer anomaly.

Although the most obvious explanation would be that there is a systematic origin to the effect, the limited set of the analyzed data does not support any of the suggested mechanisms. We assert that analysis of the entire existing Pioneer data is vital to understanding the anomaly and, hopefully, to finding its origin. Indeed, analysis of the entire existing Pioneer data record is critical in attacking the anomaly on two fronts: (i) an analysis of the early, not rigorously analyzed, data could yield a more accurate direction of the anomaly and hence might help to determine its origin; (ii) by using the entire data set, from 1972 to 2002, one could study the temporal evolution of the anomaly and determine if it is due to on-board nuclear fuel inventory and related heat radiation or other mechanism.

Goal: analysis of the entire Pioneer 10/11 data record

The limited data analyzed previously allowed the detection of the anomaly in the Pioneer data, but not a determination of its origin. With new knowledge of all on-board processes and a diverse team, we propose a two-step process in understanding the origin of the anomaly, namely: (i) analysis of the entire set of existing Pioneer 10 and 11 data, obtained from first launch to the last telemetry received from Pioneer 10, on 27 April 2002, when it was at a heliocentric distance of 80 AU. This data could yield critical new information about the anomaly. If the signal is confirmed and is not due to an on-board systematic, (ii) we will use our new knowledge to develop an instrumental package that will be capable to provide an independent confirmation of the anomaly. We will also study a design for a dedicated mission to explore the anomalous behavior of the Pioneer spacecraft.

Significance: finding the origin of the Pioneer anomaly

This ISSI investigation could lead to a determination of the origin of the anomaly and to a characterization of its physical properties. The proposed investigation is scientifically important, it is timely, and is well situated in Europe. The investigation would be an excellent example to demonstrate the value of interdisciplinary teams in addressing complex problems in fundamental physics and in application of new technologies in spacecraft and mission designs. The results of this study could find their way into many other areas of space-exploration applications in the near future. The most important outcome of this study will be the understanding of the Pioneer anomaly.