2 00 6 The Pioneer Anomaly : seeking an explanation in newly recovered data

The Pioneer 10/11 spacecraft yielded a very accurate navigation in deep space that was, however, limited by a small, anomalous frequency drift of their carrier signals received by the radio-tracking stations of the NASA Deep Space Network (DSN). This drift signifies a discrepancy between the frequency of the Doppler signals observed by the DSN and that frequency modeled using modern-day deep space navigational codes. This discrepancy, evident in the data for both spacecraft, was interpreted as an approximately constant acceleration. This acceleration has become known as the Pioneer anomaly. The origin of this anomaly is as of yet unknown. Recent efforts to explain the effect included a search for independent confirmation, analyses of conventional mechanisms, even ideas rooted in new physics and proposals for a dedicated mission. We assert that in order to determine the origin of the Pioneer anomaly, and especially before any discussion of new physics and/or a dedicated mission can take place, one must analyze the entire set of radiometric Doppler data received from Pioneers 10 and 11. In this paper we report on our efforts to recover and utilize the complete set of radio Doppler and telemetry records of the Pioneer 10/11 spacecraft. The collection of radio Doppler data for both missions is now complete; we are ready to begin its evaluation. We also made progress utilizing the recently recovered Pioneer telemetry data in the development of a complete engineering profile of the spacecraft. We present a strategy for studying the effect of on-board generated small forces with this newly recovered information on the performance of thermal, electrical, power, communication and other subsystems, in conjunction with the analysis of the entire set of the Pioneer Doppler data. We report on the preparations for the upcoming analysis of the newly recovered data with the ultimate goal of determining the origin of the Pioneer anomaly. Finally, we discuss implications of our on-going research of the Pioneer anomaly for other missions, most notably for New Horizons, NASA’s recently launched mission to Pluto.