2007 Asimov Debate: The Pioneer Anomaly main content.

2007 Isaac Asimov Memorial Debate: The Pioneer Anomaly

Monday, March 26, 2007

The Pioneer spacecraft, two identical unmanned planetary probes, were launched in the early 1970s on trajectories that would send them past the outer planets and onward with enough speed to leave the Solar System entirely—a first in space exploration. While attempting to account for all known forces that act on these craft, scientists analyzed the telemetry signals from the craft and found an inconsistency. The positions of the craft do not match the scientists' predictions. There seems to be an extra force at work, not included in the analysis, which has affected the motion of these craft across decades of monitoring their signals, from launch until their last contact.

The big questions are: What is this force? Is it an unforeseen glitch of spacecraft design? Is it a sign of the discovery of new physics or a new understanding of gravity? Or simply of something in our present knowledge of physics that has been overlooked?


  • John D. Anderson—Senior Research Scientist, Global Aerospace Corporation, formerly of NASA's Jet Propulsion Laboratory; led the team in 1998 that discovered the Pioneer Anomaly
  • Ed Belbruno—Visiting Research Collaborator in the Department of Astrophysical Sciences, Princeton University; President and Founder of Innovative Orbital Design, Inc.
  • Gary M. Kinsella—Group Supervisor, Spacecraft Thermal Engineering and Flight Operations at NASA's Jet Propulsion Laboratory; engineer who specializes in the thermal design development of spacecraft and science instruments
  • Irwin Shapiro—Timken University Professor at Harvard and a Senior Scientist at the Smithsonian Institution; research has mainly involved tests of general relativity
  • Slava G. Turyshev—Astrophysicist at NASA's Jet Propulsion Laboratory; specialist in gravitational physics and leader of the Pioneer Anomaly Team working to solve this great mystery


Host & Moderator

  • Neil deGrasse Tyson—Astrophysicist and The Frederick P. Rose Director of the Hayden Planetarium.