Abstract
In this study, we propose an approach for determining the geopotential difference using high-frequency-stability microwave links between satellite and ground station based on Doppler cancellation system. Suppose a satellite and a ground station are equipped with precise optical-atomic clocks (OACs) and oscillators. The ground oscillator emits a signal with frequency f a towards the satellite and the satellite receiver (connected with the satellite oscillator) receives this signal with frequency f b which contains the gravitational frequency shift effect and other signals and noises. After receiving this signal, the satellite oscillator transmits and emits, respectively, two signals with frequencies f b and f c towards the ground station. Via Doppler cancellation technique, the geopotential difference between the satellite and the ground station can be determined based on gravitational frequency shift equation by a combination of these three frequencies. For arbitrary two stations on ground, based on similar procedures as described above, we may determine the geopotential difference between these two stations via a satellite. Our analysis shows that the accuracy can reach 1 m 2 s − 2 based on the clocks’ inaccuracy of about 10 −17 (s s −1 ) level. Since OACs with instability around 10 −18 in several hours and inaccuracy around 10 −18 level have been generated in laboratory, the proposed approach may have prospective applications in geoscience, and especially, based on this approach a unified world height system could be realized with one-centimetre level accuracy in the near future.
Highlights
One of the main objectives in geodesy is to accurately determine the geopotential as well as the orthometric height
The conventional approach of determining the geopotential by combining levelling and gravimetry has at least the following two drawbacks: (1) the error is accumulated with the increase of the length of the measurement line, and (2) it is difficult or impossible to transfer the orthometric height with high accuracy between two points located in mountainous areas or continents separated by sea
We propose an approach to extract gravitational frequency shift from the propagation of light signals between a spacecraft and a ground station based on Doppler cancelling technique (DCT; Vessot & Levine 1979) which was proposed to test the general relativity theory
Summary
One of the main objectives in geodesy is to accurately determine the geopotential as well as the orthometric height. We propose an approach to extract gravitational frequency shift from the propagation of light signals between a spacecraft (space station or satellite) and a ground station based on Doppler cancelling technique (DCT; Vessot & Levine 1979) which was proposed to test the general relativity theory. By extracting the gravitational frequency shift signals between the spacecraft and the ground station, we can determine the geopotential difference. On the right-hand side of eq (2), the first term denotes the gravitational red shift, the second term is identified as the second-order Doppler shift predicted by special relativity and the third term describes the effect of Earth’s rotation during the propagation time |rse/c| of the light signal. We will discuss the correction terms fi and ft in details
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