High-accuracy open-loop velocity measurement and gravitational redshift verification design analysis based on the Chang’E-5 probe

Abstract

<p indent="0mm">The Chang’E 5 (CE-5) mission has excellent telemetry, tracking, and control resources, providing convenient conditions for verifying new ground-based radio measurement methods, engineering applications, and scientific research. This paper focuses on the open-loop velocity measurement and application of the CE-5 probe. First, an open-loop Doppler frequency extraction algorithm based on signal reconstruction cross-correlation was proposed, and the complete implementation steps from signal input and signal processing to observation output were established. Second, the CE-5 open-loop velocity measurement experiment was performed based on the China deep space station, and the CE-5 downlink signals were processed and analyzed. The results show that the open-loop Doppler measurement accuracy of the CE-5 orbiter reaches the level of <sc>2–3 MHz,</sc> which is 3–4 times better than the baseband Doppler measurement accuracy of the deep space station. Third, the high-accuracy orbit determination effectively verifies the applicability of open-loop velocity measurement. The results show that the orbit determination residual of open-loop velocity measurement is <sc>0.12 mm/s,</sc> and the orbit determination residual of baseband velocity measurement is <sc>0.46 mm/s.</sc> Finally, the gravitational redshift verification method for the multibody problem was proposed, and the potential application feasibility of gravitational redshift verification based on open-loop velocity measurement was theoretically analyzed. The verification experiment scheme was preliminarily designed. Based on the open-loop velocity measurement results of the existing CE-5 orbiter, a special experiment for gravitational redshift verification can be designed, and the gravitational redshift detection accuracy is expected to achieve the level of 10⁻⁴ to 10⁻⁵. </p>

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