On the possibility of measuring the solar oblateness and some relativistic effects from planetary ranging

TL;DR

This paper proposes a novel method to measure the Sun's quadrupole moment and relativistic parameters using combined planetary ranging data, aiming for high precision in solar and relativistic effects detection.

Contribution

It introduces a new approach to simultaneously determine solar oblateness and PPN parameters from planetary data, improving measurement accuracy.

Findings

Potential to measure J_2 with 10^-9 precision

PPN parameters gamma and beta can be determined with 10^-4 to 10^-5 accuracy

Future missions like BepiColombo will enhance measurement precision

Abstract

In this paper we first calculate the post-Newtonian gravitoelectric secular rate of the mean anomaly of a test particle freely orbiting a spherically symmetric central mass. Then, we propose a novel approach to suitably combine the presently available planetary ranging data to Mercury, Venus and Mars in order to determine, simultaneously and independently of each other, the Sun's quadrupole mass moment J_2 and the secular advances of the perihelion and the mean anomaly. This would also allow to obtain the PPN parameters gamma and beta independently. We propose to analyze the time series of three linear combinations of the experimental residuals of the rates of the nodes, the longitudes of perihelia and mean anomalies of Mercury, Venus and Mars built up in order to absorb the secular precessions induced by the solar oblateness and the post-Newtonian gravitoelectric forces. The values of the three investigated parameters can be obtained by fitting the expected linear trends with straight lines, determining their slopes in arcseconds per century and suitably normalizing them. According to the present-day EPM2000 ephemerides accuracy, the obtainable precision would be of the order of 10^-4-10^-5 for the PPN parameters and, more interestingly, of 10^-9 for J_2. The future BepiColombo mission should improve the Mercury's orbit by one order of magnitude.