Review of Gravity Probe B


Preface


In response to a request by the NASA Administrator, the National Research Council (NRC) has conducted an accelerated scientific review of NASA's Gravity Probe B (GP-B) mission. The review was carried out by the Task Group on Gravity Probe B, under the auspices of the NRC's Space Studies Board and Board on Physics and Astronomy. The specific charge to the task group was to review the GP-B mission with respect to the following terms of reference:

  1. Scientific importance—including a current assessment of the value of the project in the context of recent progress in gravitational physics and relevant technology.
  2. Technical feasibility—the technical approach will be evaluated for likelihood of success, both in terms of achievement of flight mission objectives but also in terms of scientific conclusiveness of the various possible outcomes for the measurements to be made.
  3. Competitive value—if possible, GP-B science will be assessed qualitatively against the objectives and accomplishments of one or more fundamental physics projects of similar cost (e.g., the Cosmic Background Explorer, COBE).

The task group was assembled by December 1994. It included experimental physicists with considerable experience in the conception, design, and successful execution of complicated experiments, engineers who have played pivotal roles in the space program, and theoretical physicists whose specialty has been gravitational theory, as well as a distinguished theorist from outside this particular subfield.

During the course of the study the task group met three times. The first meeting, held at Stanford, California, on January 10-12, 1995, was an extensive on-site review of the relativity mission, including tours of both the Stanford and Lockheed GP-B facilities. During this review the Stanford team addressed the scientific importance of GP-B, discussed the resolved and unresolved scientific and technological challenges, and described various spin-offs of the 30-year-old project. The second and third meetings were held on February 10-11 and March 3-4, 1995, in Washington, D.C. At these meetings some invited guests presented alternative views on GP-B as well as other NASA missions such as the Stratospheric Observatory for Infrared Astronomy (SOFIA) and the Space Infrared Telescope Facility (SIRTF).

As part of the assessment process the task group solicited input from the astrophysics and general relativity communities. Solicitation letters were sent to approximately 15 leaders in the field requesting their input on the issues raised in the charge. In addition, general solicitation notices were placed in the newsletters of the American Astronomical Society and the Astrophysics Division of the American Physical Society. A notice to the worldwide general relativity community was placed on an Internet bulletin board maintained at Queen Mary College in London. In its deliberations the task group considered the diversity of opinions expressed in responses to these public notices.




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