Recently we reported that radio Doppler data generated by NASA's Deep Space Network (DSN) from the Pioneer 10 and 11 spacecraft indicate an apparent anomalous, constant, spacecraft acceleration with a magnitude $\sim 8.5\times 10^{-8}$ cm s$^{-2}$, directed towards the Sun (gr-qc/9808081). Analysis of similar Doppler and ranging data from the Galileo and Ulysses spacecraft yielded ambiguous results for the anomalous acceleration, but it was useful in that it ruled out the possibility of a systematic error in the DSN Doppler system that could easily have been mistaken as a spacecraft acceleration. Here we present some new results, including a critique suggestions that the anomalous acceleration could be caused by collimated thermal emission. Based partially on a further data for the Pioneer 10 orbit determination, the data now spans January 1987 to July 1998, our best estimate of the average Pioneer 10 acceleration directed towards the Sun is $\sim 7.5 \times 10^{-8}$ cm s$^{-2}$. (Refer to PDF file for exact formulas.)

Date of creation, presentation, or exhibit



"The Apparent Anomalous, Weak, Long-Range Acceleration of Pioneer 10 and 11," Proceedings of the 34th Recontres de Moriond Meeting on Gravitational Waves and Experimental Gravity. Held at Les Arcs: Savoi, France: 23-30 January 1999. AND also archived at: arXiv:gr-qc/9903024 v2 9 Mar 1999 This work was supported by the Pioneer Project, NASA/Ames Research Center, and was performed at the Jet Propulsion Laboratory, California Institute of Technology, under contract with NASA. P.A.L. and A.S.L. acknowledge support by a grant from NASA through the Ultraviolet, Visible, and Gravitational Astrophysics Program. M.M.N. acknowledges support by the U.S. DOE.Note: imported from RIT’s Digital Media Library running on DSpace to RIT Scholar Works in February 2014.

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Conference Proceeding

Department, Program, or Center

School of Physics and Astronomy (COS)


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