An improved approach for testing gravitational redshift via satellite-based three frequency links combination

We propose a novel approach for testing the gravitational redshift based on frequency signals transmitted between a spacecraft and a ground station. The main idea is integrating one uplink signal from ground to spacecraft and two downlink signals from spacecraft to ground. Based on the integration and certain correction models, the gravitational shift of the signals between spacecraft and ground station can be detected at high precision level. The gravitational redshift effect can be used to validate the Einstein equivalence principle (EEP), which can be tested at about 10(-6) similar to 10(-8) levels in different cases for a short period (less than a month) if the stability of onboard atomic clock reach 10(-17) /day. Compared to the scheme of Gravity Probe-A (GP-A) experiment conducted in 1976, in the new approach, any on-board signal transponders is not required, and the frequency values of the three links can be arbitrary. Since the hardware requirement is decreased, a number of spacecrafts can be candidates for a gravitational redshift experiment provided that they are able to emit two different frequency signals and receive a frequency signal from the ground. (C) 2021 COSPAR. Published by Elsevier B.V.