The so-called Pioneer Anomaly is an anomalous shift in the radio-metric trackingsignals received by Pioneer 10 and 11 spacecrafts, which can be ascribed toan approximately constant sunward acceleration acting on the probes. This anomalousacceleration has a similar magnitude for the two spacecraft, firstly reportedby Anderson and al. in 1998, to be (8.74±1.33)?10~(-10) m/s~2 (Reference 2).Since then, the existence of the anomaly has been confirmed independently byseveral groups and a large effort was devoted to find its origin providing, however,no definitive answers.The present study, carried out at the RadioScience lab of the University of Bologna in Forlì consists of two main parts:thermal modeling of the spacecraft throughout its trajectory, and orbit determinationanalysis. Based on existing documentation and recovered telemetry data,we built a finite element model of the spacecraft, whose complexity has beenconstrained to a degree allowing for sensitivity analysis.The trajectory analysis has been performed using JPL’s ODP (Orbit DeterminationProgram) available to the University of Bologna thanks to a NASA/ASI bilateralagreement. Results show that orbital solutions may be achieved that donot require any anomalous acceleration other than the one of thermal origin.
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