Measurement of the gravitational redshift effect with RadioAstron satellite

TL;DR

RadioAstron aims to test gravitational redshift with high precision, potentially surpassing previous results, but faces technical challenges that are being addressed through new techniques, with preliminary data showing promise.

Contribution

The paper presents a novel approach to measure gravitational redshift using RadioAstron, overcoming technical limitations of its communication systems.

Findings

Potential to surpass Gravity Probe A accuracy

Development of new techniques for frequency transfer

Preliminary results indicate feasibility

Abstract

RadioAstron satellite admits in principle a testing the gravitational redshift effect with an accuracy of better than $10^{-5}$. It would surpass the result of Gravity Probe A mission at least an order of magnitude. However, RadioAstron's communications and frequency transfer systems are not adapted for a direct application of the non relativistic Doppler and troposphere compensation scheme used in the Gravity Probe A experiment. This leads to degradation of the redshift test accuracy approximately to the level 0.01. We discuss the way to overcome this difficulty and present preliminary results based on data obtained during special observing sessions scheduled for testing the new techniques.