Article

"IMPRINTING" IN GENERAL RELATIVITY TESTS?

International Journal of Modern Physics D (Impact Factor: 1.03). 09/2011; 20(10):1945-1948. DOI: 10.1142/S0218271811019980
Source: arXiv

ABSTRACT We investigate possible a priori "imprinting" of general relativity itself on spaceraft-based tests of it. We deal with some performed or proposed time-delay ranging experiments in the Sun's gravitational field. The "imprint" of general relativity on the Astronomical Unit and the solar gravitational constant GM⊙, not solved for in the spacecraft-based time-delay test performed so far, may induce an a priori bias of the order of 10-6 in typical solar system ranging experiments aimed to measuring the space curvature PPN parameter γ. It is too small by one order of magnitude to be of concern for the performed Cassini experiment, but it would affect future planned or proposed tests aiming to reach a 10-7–10-9 accuracy in determining γ.

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    ABSTRACT: Parameterised post Newtonian (PPN) parameters γ and β (which should equal unity if general relativity is valid) are estimated through the analyses of four years of LAGEOS 1 and LAGEOS 2 data. To reduce the chance of possible imprinting of general relativistic effects which could be contained in the Earth gravity model used, several low order spherical harmonic coefficients are solved in the orbit estimation and propagation process. After convergence is reached, the solved PPN parametersand γ and β are kept fixed at their solved values and scaling coefficients are introduced to explore the possibility of open parameter space in the accelerations due to the Schwarzschild field, frame dragging and de Sitter (geodesic) precession. It is found that some parameter space is available in the radial acceleration component, which could be taken up by including post-post-Newtonian components of general relativity, or it could be due to some other radial acceleration component that is not adequately modelled. The inclusion of scale coefficients in the least-squares process proves to be a valuable tool in evaluating the solutions for γ and β. A comparison with results obtained for the PPN parameters by other authors utilising different techniques such as VLBI and radar measurements to planets and probes are made.
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