A-priori "imprinting" of General Relativity itself on some tests of it?

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We investigate the effect of possible a-priori "imprinting" effects of general relativity itself on satellite/spaceraft-based tests of it. We deal with some performed or proposed time-delay ranging experiments in the Sun's gravitational field. It turns out that the "imprint" of general relativity on the Astronomical Unit and the solar gravitational constant GM, not solved for in the so far performed spacecraft-based time-delay tests, induces an a-priori bias of the order of 10-6 in typical solar system ranging experiments aimed to measuring the space curvature PPN parameter gamma. 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 gamma.