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

TL;DR

This paper examines how the inherent assumptions of general relativity may bias satellite-based tests of the theory, especially in high-precision experiments measuring the PPN parameter gamma, potentially affecting future measurements.

Contribution

It identifies and quantifies the bias introduced by the a-priori imprint of general relativity on key solar system parameters used in tests of gravity.

Findings

Imprint of general relativity causes a bias of about 10^-6 in current experiments.

This bias is negligible for the Cassini experiment but significant for future high-precision tests.

Future experiments aiming for 10^-7 to 10^-9 accuracy need to account for this bias.

Abstract

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_{\odot}, 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.