Precision Measurement of Gravitational Frequency Shift of Electromagnetic Signals in the RadioAstron Mission#

The space radio telescope RadioAstron is a unique instrument for studying extremely weak radio signals in the centimeter and decimeter wavelength ranges 1. Acting as the space-based baseline of an interferometer, the spacecraft has achieved a record-breaking angular resolution, opening new possibilities for investigating black holes, pulsars and the structure of the interstellar medium. A key feature of its onboard system is the use of a hydrogen frequency standard synchronized with a ground-based tracking station. The difference in gravitational potentials between the spacecraft and the ground station leads to a relativistic frequency shift 2 (RedShift effect), providing experimental confirmation of general relativity and Einstein’s equivalence principle. This study proposes methods for a high-precision measurement of this effect, based on an original Doppler shift compensation scheme 3 and statistical analysis of gravitational observation sessions. The results allow for an estimation of the cumulative violation parameter, contributing to further verification of the fundamental principles of general relativity. The paper also discusses prospects for new high-precision experiments.