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Gravity Probe B

Testing Einstein's Universe

MISSION UPDATE — September 26, 2008


Since our May 23rd status update, GP-B has continued to make significant progress--fiscal and scientific. NASA funding and sponsorship of the program ends on September 30, 2008, but GP-B has secured alternative funding that will enable our science team to continue working at least through December 2009 in order to complete the data analysis and bring GP-B to a proper close.

The GP-B science team is continuing to make large strides in the data analysis. On Friday, August 29, 2008, the 18th meeting of our external GP-B Science Advisory Committee was held at Stanford to report our progress since the previous SAC meeting in November 2007. Their ensuing report to NASA states:

“The progress reported at SAC-18 was truly extraordinary and we commend the GPB team for this achievement. This has been a heroic effort, and has brought the experiment from what seemed like a state of potential failure, to a position where the SAC now believes that they will obtain a credible test of relativity, even if the accuracy does not meet the original goal. In the opinion of the SAC Chair, this rescue warrants comparison with the mission to correct the flawed optics of the Hubble Space Telescope, only here at a miniscule fraction of the cost.” —SAC #18 Report to NASA

On October 6-10, six GP-B team members have been invited to present these dramatically improved, interim results at an International Space Science Institute (ISSI) workshop on "The Nature of Gravity: Confronting Theory and Experiment in Space" to be held in Bern, Switzerland. Following the Bern workshop, these improved interim results will undergo a thorough peer-review and vetting; then towards the end of this year, we plan to announce them publicly.

We very much appreciate your continued interest in GP-B, and we will keep you posted on our progress in future status updates.


Graphics: The photo of the GP-B launch is courtesy of photographer Bill Hartenstein ( The layered photo collage of the GP-B spacecraft in orbit was created by Gp-B Public Affairs Coordinator/Webmaster, Bob Kahn. Click on the thumbnails to view these images at full size.

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