Abstract
We propose to measure the gravitational constantG by putting in an orbiting laboratory a known mass of very high density and by tracking the motion of a small test mass under the gravitational influence of the primary mass. We analyse the different sources of perturbation; the consideration of the Earth's gravity gradient leads us to conclude that, if the laboratory is in a low Earth orbit, we cannot get stable satellite-like orbits of the test mass, but we must study only a process of ‘gravitational scattering’. In order to maximize the time of interaction it is proposed to use the ‘practical stability’ of a collinear equilibrium point of the system Earth-primary mass, by putting the test mass as close as possible to the stable manifold of an equilibrium point. This method will allow the determination of the value ofG within a few parts over 105, as shown by some computer simulations of the experiment taking into account also some unknown perturbation and random noise.
Two main problems are involved in this experiment: (a) refined numerical methods are needed to take into account all significant perturbations and to extract the result aboutG from the experimental data; (b) during the motion of the test mass, the primary mass must always be free-falling inside the laboratory, so that this experiment needs a drag-free satellite technique of the same type which is necessary for high-precision gravimetric measurements.
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Farinella, P., Milani, A. & Nobili, A.M. The measurement of the gravitational constant in an orbiting laboratory. Astrophys Space Sci 73, 417–433 (1980). https://doi.org/10.1007/BF00642420
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DOI: https://doi.org/10.1007/BF00642420