EVALUATION  of  GG
  by  the   FUNDAMENTAL  PHYSICS  ADVISORY  GROUP   (FPAG) 
of  ESA
Paris October 1996

GG has been evaluated by the Fundamental Physics Advisory Group (FPAG) of ESA on October 7 1996.  The FPAG had at its disposal the GG Pre-Phase A Report (ASI 1996) prepared by the GG Team, and a "Technical Assessment of the GALILEO GALILEI (GG) Experiment"  prepared at ESTEC by J.W. Cornelisse (on the GG spacecraft) and by Y. Jafry & M. Weinberger (on dissipation and active control in GG).   The technical work carried out by Jafry and Weinberger  was supervised by an  FPAG member (S. Vitale). The Recommendation of the FPAG is given below.

The FPAG members at the time were:
G. Busca, M. Cerdonio,  T. Damour, K. Danzman, M. Jacob (Chair), B. Shutz,  T. Sumner, S. Vitale.

A very different opinion on the GG test of the Equivalence Principle was expressed by Prof Stephen H Crandall from MIT, USA, who was consulted by ESA itself as an expert in damping and rotordynamics (click here to read).

The results reported by Jafry and Weinberger in their technical report of the GG test of the Equivalence Principle  have been published on "Classical and Quantum Gravity"  (Jafry Y.  and Weinberger  M.:  "Evaluation of a Proposed Test of the Weak Equivalence Principle  Using Earth-Orbiting Bodies in High-Speed Co-Rotation", Class. Quantum Grav.  Vol. 15,  pp. 481-500, 1998).

The response of  GG Team members, in which they clearly disproved the analysis of Jafry&Weinberge, has been published on the same Journal under the title: Evaluation of a Proposed Test of the Weak Equivalence Principle Using Earth-Orbiting Bodies in High-Speed Co-Rotation: Re-Establishing the Physical Bases  (Class. Quantum Grav.  Vol. 16,  pp. 1463-1470, 1999).

The Journal refused to publish a counter response by Jafry&Weinberger, and they did not write on the issue ever since.

anna nobili   
Last edited:  2002-02-21