Professor Antony Fraser-Smith

Fall 2000-2001

Date: Wednesday, June 6, 2001
Time: 4:15-5:30 PM; Refreshments at 4:00 PM
Location: Bldg. 200, Rm. 34

Study of the Anomalous Accelerations of Pioneer 10 and 11

Drs. Slava G. Turyshev and John Anderson
NASA Jet Propulsion Laboratory


Our previous analyses of radio Doppler and ranging data from distant spacecraft in the solar system indicated that an apparent anomalous acceleration is acting on Pioneer 10 and 11, with supporting data from the Galileo and Ulysses spacecraft.The data implied an anomalous, constant acceleration with a magnitude a_P ~ 8 x 10^-8 cm/s^2, directed towards the Sun.Much effort has been expended looking for possible systematic origins of the residuals.We provide a detailed investigation of effects both external to and internal to the spacecraft, as well as those due to modeling and computational techniques.Our analyses strongly suggest that it is difficult to understand how any of these mechanisms can explain the magnitude of the observed behavior of the Pioneer anomaly.

There are now further data for the Pioneer 10 orbit determination. The extended Pioneer 10 data set spans 3 January 1987 to 22 July 1998.[For Pioneer 11 the shorter span goes from 5 January 1987 to the time of loss of coherent data on 1 October 1990.]With these data sets and more detailed studies of all the systematics, we can now give a total error budget for our analysis and a result a_P = (8.76 a_P = (8.76+/-0.92)x10^8 cm/s^2.