Method and system for determining gravitational potential using a star-space-ground optical clock time-frequency comparison system

Abstract

This invention discloses a method and system for determining gravitational potential using a star-space-ground optical clock time-frequency comparison system. The method for determining gravitational potential proposed in this invention uses a time-frequency comparison system with a frequency better than 110... ‑18 Using a high-precision optical clock as the foundation, and a free-space time-frequency comparison link based on optical frequency combs as the bridge, the optical clocks between space, air and ground are connected to achieve high-precision time-frequency transmission. By comparing the time and frequency of the remote clock, the gravity frequency shift signal is accurately extracted. Then, the gravity frequency shift equation is used to obtain the gravity potential difference at the location of the remote clock, and the gravity potential difference between the air and the ground or between any ground station is determined.

Description

Technical Field

[0001] This invention belongs to the fields of geophysics and quantum sensing technology, specifically involving a high-precision gravity potential measurement method based on time-frequency comparison of optical clocks from quantum satellites, the Chinese space station, and ground stations, as well as the system architecture for implementing this method. Background Technology

[0002] Determining gravitational potential plays a crucial role in geodesy. It is a fundamental physical field quantity required by disciplines and research areas such as seismology, geodynamics, aerospace, meteorology, oceanography, natural disasters, and global change. It is also an indispensable source of information for national defense and economic development. Traditional gravity measurements rely on equipment such as gravimeters and satellite gravity gradiometers, which suffer from low spatial resolution, insufficient dynamic monitoring capabilities, and difficulty in transferring gravitational potential across oceans and continents. Therefore, how to quickly and accurately determine the gravitational potential difference at any station has become a pressing scientific challenge for geodesists.

[0003] To address these challenges, a novel method for measuring gravitational potential using the principles of general relativity has garnered attention and research. This method primarily relies on the correlation between gravitational potential difference and the rate difference in the operation of a precision clock, determining the gravitational potential difference between two locations through time and frequency transfer. In recent years, with the maturation of clock manufacturing processes, clocks with an accuracy of 10⁻⁶ have been successfully developed internationally. -19 Clocks of this magnitude, even those in idle (or satellite) orbit, achieve an accuracy of 10. -18 This scale provides the hardware support for determining gravity potential using time-frequency signals. However, to perform time-frequency comparisons with the accuracy of optical clocks, time-frequency transmission technology of corresponding accuracy must be used to link remote clocks. Existing optical clock gravity potential measurements are mostly limited to comparisons between ground stations, failing to achieve multi-level (space-air-ground) collaborative measurements, and are limited by time-frequency transmission errors. Therefore, how to perform high-precision remote time-frequency comparisons has become an urgent problem to be solved.

[0004] The terminology mentioned in this invention specification is explained as follows:

[0005] GEOQS: Geosynchronous Orbit Quantum Satellites;

[0006] CSS: China Space Station;

[0007] GS: Ground Station. Summary of the Invention

[0008] To overcome the shortcomings of the prior art, the present invention provides a method and system for determining gravity potential using a star-space-ground optical clock time-frequency comparison system. Through star-space-ground collaborative measurement, gravity potential difference transmission at ground stations and gravity potential measurement at a single station are realized.

[0009] According to one aspect of the present invention, a method for determining gravitational potential using a star-space-ground optical clock time-frequency comparison system is provided, comprising:

[0010] A space-to-ground optical clock time-frequency comparison network is established, wherein the network is equipped with clocks with a frequency accuracy better than 1 at the quantum satellite, space station, and ground station. 10 -18 Light clocks of this magnitude;

[0011] Time and frequency synchronization is achieved based on the free space time and frequency comparison link, and the time and frequency comparison data and location coordinates of the optical clocks of each node are acquired in real time during the synchronization process;

[0012] Multi-source joint error correction is performed on the acquired time-frequency comparison data;

[0013] Based on the position coordinates of each node and the corrected time-frequency comparison data, the gravity potential difference between satellite-to-ground, air-to-ground, or ground stations is calculated, thus realizing the transfer of gravity potential difference and determining the gravity potential of unknown stations.

[0014] As a further technical solution, the time and frequency synchronization is achieved by constructing a ground-to-satellite-to-ground or air-to-satellite-to-ground optical clock time and frequency comparison link through bidirectional laser signals, using the optical clock carried by the quantum satellite as a bridge to realize optical clock time and frequency comparison between ground stations or between air and ground.

[0015] As a further technical solution, optical clocks configured at different nodes are connected through a free-space time-frequency comparison link based on an optical frequency comb, and optical clock time-frequency comparison is performed through remote time-frequency transmission.

[0016] As a further technical solution, in the space-satellite-ground optical clock time-frequency comparison link, the optical clock of the space station is connected to the optical clock of any ground station using the optical clock carried by the quantum satellite as a bridge. By comparing the time and frequency of the optical clocks of the space station and the ground station, the gravity potential of any ground station can be obtained.

[0017] As a further technical solution, in the ground-satellite-ground optical clock time-frequency comparison link, the optical clocks of the two ground stations are connected through the optical clock carried by the quantum satellite. The optical clocks of the two ground stations are compared through common observation, and the gravity frequency shift signal caused by the position difference between the two ground stations is extracted to determine the gravity potential difference between the two ground stations.

[0018] As a further technical solution, multi-source joint error correction is performed on the acquired time-frequency comparison data, including:

[0019] Based on the general relativistic model, the special relativistic frequency shift caused by the relative motion between nodes is deducted;

[0020] Compensation for optical clock frequency drift is achieved using environmental sensor data.

[0021] Redundant links are used to suppress phase noise from atmospheric turbulence on the satellite-to-ground link, and time delay in signal propagation is eliminated through common-view observation and bidirectional observation.

[0022] As a further technical solution, the method also includes:

[0023] Based on the known location coordinates of the space station or ground station, the gravity potential of the station can be obtained using a gravity field model or traditional measurement methods.

[0024] Based on the corrected time difference Or frequency difference Through formula ,in, Indicates greater than or equal to This method obtains the gravitational potential difference between any two stations A and B, realizes the transfer of gravitational potential difference, and determines the gravitational potential of unknown stations.

[0025] According to one aspect of the present invention, a system for determining gravitational potential using a star-sky-ground optical clock time-frequency comparison system is provided, comprising:

[0026] A space-to-ground optical clock time-frequency comparison network is configured with clocks with a speed better than 1 at quantum satellites, space stations, and ground stations. 10 -18 Light clocks of this magnitude;

[0027] The time-frequency comparison link is used to achieve time-frequency synchronization based on the free space time-frequency comparison link. During the synchronization process, the time-frequency comparison data and location coordinates of the optical clocks of each node are acquired in real time.

[0028] The data processing module is used to perform multi-source error joint correction on the acquired time-frequency comparison data; and to calculate the gravity potential difference between satellite-to-ground, air-to-ground, or ground stations based on the position coordinates of each node and the corrected time-frequency comparison data, so as to realize the gravity potential difference transfer and determine the gravity potential of unknown stations.

[0029] According to one aspect of the present invention, a ground station device is provided, including an optical clock, a memory, and a processor. The optical clock is used to provide a frequency reference and a time reference for the ground station. The optical clock is connected to optical clocks of other ground stations or space stations via an optical clock carried by a quantum satellite. The memory is used to store a computer program. When the processor runs the computer program stored in the memory, the processor executes the method for determining gravity potential using the satellite-space-ground optical clock time-frequency comparison system.

[0030] The method for determining gravitational potential proposed in this invention is to use a method superior to 1 10 -18 Based on a high-precision optical clock, and using a free-space time-frequency comparison link based on an optical frequency comb as a bridge, this invention connects optical clocks between space, air, and ground for high-precision time-frequency transmission. Through time-frequency comparison with remote clocks, the gravity frequency shift signal is accurately extracted. Then, the gravity potential difference at the location of the remote clock is obtained using the gravity frequency shift equation, thus determining the gravity potential difference between the space station and the ground station, or between any ground station. Compared with existing technologies, the advantages of this invention are:

[0031] 1. This invention utilizes a high-precision optical clock as a tool for measuring time and frequency, providing a high-precision time and frequency reference and significantly improving the measurement accuracy of time-frequency transmission links. In the process of determining gravitational potential using a free-space time-frequency comparison link, a high-precision time and frequency reference is crucial for accurate gravitational potential measurement. By using a high-precision frequency reference from a star-space-ground optical clock, the gravitational frequency shift caused by changes in gravitational potential can be effectively measured.

[0032] 2. This invention achieves optical clock comparison between space stations and ground stations, as well as between ground stations, through dual-frequency links or common-view comparison, eliminating various errors caused by environmental noise during the propagation of time-frequency links, accurately extracting the gravity frequency shift signal between two nodes, and measuring the gravity potential difference between stations.

[0033] In summary, the method for determining gravitational potential using the space-space-ground optical clock time-frequency comparison system proposed in this invention compares the time and frequency of optical clocks configured on quantum satellites, space stations, and ground stations by utilizing a free-space time-frequency link based on femtosecond optical combs. It makes full use of space-based platforms such as quantum satellites and the Chinese space station to achieve large-scale, long-baseline, transoceanic, and transcontinental gravitational potential difference transfer and gravitational potential measurement, providing a brand-new technical means and experimental platform for high-precision gravitational potential determination. Attached Figure Description

[0034] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the accompanying drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the accompanying drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0035] Figure 1 This is a schematic flowchart illustrating the method for determining gravitational potential using a star-space-ground optical clock time-frequency comparison system provided in an embodiment of the present invention.

[0036] Figure 2 This is a schematic diagram illustrating the principle of the star-space-ground optical clock time-frequency comparison system for determining gravity potential, as provided in an embodiment of the present invention.

[0037] Figure 3 This is a schematic diagram of gravity potential determination based on time-frequency comparison of space-satellite-ground optical clocks provided in an embodiment of the present invention.

[0038] Figure 4 This is a schematic diagram illustrating the cross-ocean gravity potential difference transfer achieved through ground-satellite-ground optical clock time-frequency comparison, as provided in an embodiment of the present invention. Detailed Implementation

[0039] With the completion of China's space station and the implementation of quantum satellite missions, China will establish a time comparison platform for high-precision optical clocks carried by both geostationary orbit satellites and the space station. This provides platform support for building an integrated space-air-ground optical clock time comparison system for determining gravity potential. By comparing spaceborne optical clocks with ground station optical clocks or between different ground stations via time-frequency comparison links, time comparison between clocks at two locations can be achieved, providing a comprehensive technical means for gravity potential measurement. Compared to fiber optic or cable time-frequency comparison technologies between ground stations, the integrated space-air-ground optical clock time-frequency comparison system offers advantages such as all-weather operation, high precision, and real-time performance, providing a research platform for gravity potential measurement globally.

[0040] Currently, in practical applications, it is rare for two ground stations to be equipped with optical clocks simultaneously. Therefore, the optical clocks on GEOQS and CSS can be used as platforms to measure the gravitational potential difference between any single station and the CSS, achieving single-site gravitational potential measurement. In the future, as the number of ground stations equipped with optical clocks increases, time-frequency comparisons between ground stations can also be implemented to determine the gravitational potential difference between the two locations. Time delays occur during the propagation of the time-frequency link in free space; eliminating errors during signal propagation and accurately extracting the gravity frequency shift signal becomes crucial for integrated space-air-ground time-frequency comparison and gravitational potential determination.

[0041] Due to the cost limitations of optical clocks, large-scale deployment at ground stations is currently difficult. However, the Chinese space station, currently in orbit, carries one... 10 -17 The light clock, which is of a certain magnitude, will also be updated in the future. 10 -18 The power of the light clock, at the same time, is equipped with 1 10 -18 A quantum satellite in geostationary orbit of this magnitude is also planned for launch in 2027, at which time my country will become the world's first country to possess such a satellite. 10 -18 A large-scale integrated space-air-ground optical clock time-frequency comparison platform provides support for this invention.

[0042] In the design of the space-air-ground integrated optical clock time-frequency comparison platform for measuring gravitational potential difference, such as Figure 2As shown, time-frequency comparisons can be performed between air-to-satellite-to-ground links and ground-to-satellite-to-ground links. Figure 2 In the diagram, A and B represent the positions of the quantum satellite in geosynchronous orbit at different times, E and D represent two ground stations, and C represents the space station. High-precision optical clocks are connected through space-satellite-ground and ground-satellite-ground time-frequency comparison links, enabling high-precision remote time-frequency comparison and accurate extraction of gravity frequency shift signals.

[0043] With current positioning and velocity measurement accuracy, it is difficult to eliminate time delay or frequency shift through models. Therefore, this invention achieves optical clock comparison between space station and ground station, as well as between ground stations, through dual-frequency link or common-view comparison, eliminating various errors caused by environmental noise during time-frequency link propagation, accurately extracting gravity frequency shift signals between two nodes, and measuring the gravity potential difference between stations.

[0044] This invention utilizes time-frequency comparison between star-space-ground optical clocks to achieve gravity potential difference transfer and gravity potential measurement at ground stations, such as... Figure 1 As shown, firstly, a star-space-ground optical clock time-frequency comparison network is established. This network is equipped with clocks with a frequency better than 1 GHz at the quantum satellite, space station, and ground station. 10 -18 A large-scale optical clock is used; next, time and frequency synchronization is achieved based on a free-space time-frequency comparison link, during which time-frequency comparison data and position coordinates of the optical clocks at each node are acquired in real time; then, multi-source error joint correction is performed on the acquired time-frequency comparison data; finally, based on the position coordinates of each node and the corrected time-frequency comparison data, the gravity potential difference between satellite-to-ground, air-to-ground, or ground stations is calculated, realizing the transfer of gravity potential difference and determining the gravity potential of unknown stations. Specifically, the following steps are included:

[0045] (1) Construction of a space-to-ground optical clock time-frequency comparison network: Long-term stability better than 1 was achieved by deploying a network on the quantum satellite, the experimental module of the Chinese space station, and the ground reference station. 10 -18 A massive optical atomic clock was established, forming an integrated space-air-ground optical clock time-frequency comparison network. Optical clocks deployed at different nodes are connected via a free-space time-frequency comparison link based on an optical frequency comb, enabling time-frequency comparison via remote time-frequency transmission. The quantum satellite / space station optical clock employs a Sr atomic optical lattice clock and is equipped with a femtosecond optical comb (the lower sideband degradation index of the optical comb is better than 2). 10 -19 (At the scale of [scale]), enabling real-time frequency conversion. The ground station optical clock is configured according to the location of different stations and the optical clock configuration conditions of the unit responsible for maintaining the stations, and is equipped with a femtosecond optical comb, which can up-convert and down-convert time and frequency signals.

[0046] (2) Dynamic time and frequency synchronization and data acquisition: Sub-femtosecond synchronization of optical clock frequencies between satellite, space station, and ground station is achieved through laser time transfer technology. During the synchronization process, the frequency deviation, clock difference, position coordinates, and environmental parameters of the optical clocks at each node are recorded in real time. Based on the real-time position coordinates, the initial gravitational potential of different nodes is calculated using a gravity field model.

[0047] (3) Multi-source error joint correction: Based on the general relativistic model, the special relativistic frequency shift (velocity difference, acceleration term) caused by the relative motion between nodes is deducted; the optical clock frequency drift is compensated by environmental sensor data (temperature, magnetic field, vibration); the phase noise of atmospheric turbulence on the satellite-to-ground link is suppressed by using redundant links (such as multi-satellite cross-comparison); the time delay in signal propagation is eliminated by common-view observation and two-way observation, and the time-frequency comparison of the remote optical clock is accurately performed to extract the gravity frequency shift signal with high precision. Among them, common-view observation is suitable for time-frequency comparison between two ground stations. Through common-view observation, the time delay caused by atmospheric turbulence can be effectively eliminated; while two-way observation can eliminate the time delay caused by the atmosphere in the signal propagation process by setting up signal transmission between two nodes.

[0048] (4) Gravity potential difference calculation: Assuming the position coordinates of a certain station (space station or ground station) are known, a high-precision gravity potential of the station can be obtained using a gravity field model or traditional measurement methods; then, based on the corrected time difference... Or frequency difference Through formula (in, Indicates greater than or equal to The method can obtain the gravitational potential difference between any two stations, thereby realizing the transfer of gravitational potential difference and determining the gravitational potential of unknown stations.

[0049] (5) Accuracy index: Gravity potential measurement accuracy reaches 1E-2 m 2 / s 2 ~10E-2 m 2 / s 2 (Equivalent elevation resolution ~1cm); the system can perform real-time data acquisition and calculation.

[0050] This invention provides a method for determining gravitational potential through star-space-ground optical clock time-frequency comparison. This method effectively eliminates frequency shifts or time delays caused by the ionosphere, troposphere, and Doppler effect, offering advantages such as high precision, high stability, and real-time performance. It overcomes the shortcomings of traditional gravitational potential measurements, including low resolution, low efficiency, and difficulty in cross-ocean and intercontinental measurements. When the stability of the high-precision optical clock used for measurement reaches 1... 10 -18At the scale of 1 cm, gravity potential can be measured, providing a brand-new technical solution for gravity potential measurement. It also makes full use of the space-air-ground integrated optical clock comparison test platform that my country is about to build, greatly improving the efficiency of gravity potential measurement.

[0051] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention. In addition, the technical features of the various embodiments or individual embodiments provided by the present invention can be arbitrarily combined to form new technical solutions. Such combinations are not bound by the order of steps and / or structural composition patterns, but must be based on the ability of those skilled in the art to implement them. When the combination of technical solutions is contradictory or cannot be implemented, it should be considered that such a combination of technical solutions does not exist and is not within the scope of protection claimed by the present invention.

[0052] Example 1

[0053] This embodiment takes the measurement of gravity potential at a mountaintop in a certain location as an example to illustrate the implementation process of the star-air-ground optical clock time-frequency comparison system for determining gravity potential. Figure 3 This diagram illustrates the application of time-frequency comparison between space-to-ground and space-to-ground optical clocks to determine gravitational potential. The diagram shows that the optical clock on the Chinese space station can be connected to ground-based optical clocks at any location via an optical clock carried by a quantum satellite. By comparing the time and frequency of the optical clocks on the space station and the ground station, the gravitational potential at any location can be obtained.

[0054] In this embodiment, a mountaintop is designated as a ground station. The gravity potential at this station location is used as the measurement object for data acquisition. The three-dimensional coordinates of the ground station are provided, and the gravity potential at the mountaintop is determined.

[0055] To achieve the application objectives, this embodiment uses a time-frequency comparison method of space-satellite-ground optical clocks to determine gravity potential, conducts a time-frequency comparison experiment, calculates the observed values, and obtains the gravity potential of the ground station.

[0056] The data acquisition process includes the following steps:

[0057] a. Atomic clock setup: Launch 1 satellite carrying 1 atomic clock. 10 -18 A quantum satellite in geosynchronous orbit with an optical clock; and a base station on the ground (e.g., at a mountaintop).

[0058] b. Data Acquisition: Set the transmission time of time and frequency signals for the space station and ground station, the time for receiving time and frequency signals for the quantum satellite, the precise orbit data of the satellite and space station, and collect and record various atmospheric-related data.

[0059] c. Data Download: Utilize broadcast messages transmitted from the space station to receive data collected by space equipment, and simultaneously download data collected by ground equipment.

[0060] d. Data processing: Using the gravity potential data of the space station, combined with a high-precision gravity field model, the gravity potential difference between the space station and the ground station is calculated using the common observation data of the space station and the ground station. The gravity potential of the ground station is measured by the real-time gravity potential calculated by the space station, and the results are compared with those of traditional methods to analyze the accuracy of the method in this embodiment of the invention.

[0061] The method of determining gravitational potential by comparing the time and frequency of space-star-ground optical clocks can yield the following results:

[0062] Absolute value of gravitational potential at a mountain peak: The absolute value of the gravitational potential at a mountain peak is obtained by comparing the time and frequency of an optical clock, with an accuracy of up to 1. 10 -18 The accuracy is on the order of centimeters (equivalent to elevation), breaking through the accuracy limitations of traditional gravity measurement methods.

[0063] Dynamic monitoring of gravity difference: Through continuous observation via the space-satellite-ground link, the changes in gravity difference between the space station and the ground station can be monitored in real time, capturing fluctuations in the microgravity environment.

[0064] Example 2

[0065] This embodiment takes the measurement of gravity difference between Qingdao and San Francisco as an example to illustrate the implementation process of cross-sea gravity difference transfer through ground-satellite-ground optical clock comparison in the technical solution of the present invention. Figure 4 This diagram illustrates the use of ground-satellite-ground optical clocks to transfer gravitational potential differences across oceans. The leveling datum located in Qingdao, China (point A) and San Francisco, USA (point B) are connected via a quantum satellite. Through shared observation between the two ground stations, the optical clocks at stations A and B can be compared to extract the gravity frequency shift signal caused by the positional difference between A and B, thus determining the gravitational potential difference between points A and B, thereby achieving the transfer of gravitational potential (altitude) across oceans and continents. The specific implementation process is as follows:

[0066] a. Ground station construction and optical clock deployment: Deploy ultra-high precision optical atomic clocks in Qingdao and San Francisco respectively, with a frequency stability of 1. 10 -18The magnitude is measured in minute frequency variations caused by sensitive gravitational potential differences. A laser transmitting / receiving system is constructed for optical link communication with the satellite. An ultra-stable environment (such as vacuum, cryogenics, and magnetic shielding) is provided for the operation of the atomic clock. A local time and frequency reference is established and synchronized with International Atomic Time (TAI).

[0067] b. Satellite Relay System Setup: A geostationary quantum satellite will be used as a relay node, ensuring that Qingdao and San Francisco can simultaneously establish optical links with the satellite. The satellite must carry a high-precision time transfer payload to support two-way time-frequency signal transmission. The effects of the satellite's orbital position, velocity, and gravitational field on the signal transmission path must be calibrated (considering the time dilation effect of general relativity). Atmospheric delays and phase noise on the optical signal from the atmosphere (ionosphere, troposphere) must be eliminated.

[0068] c. Time-frequency comparison: The Qingdao ground station transmits optical clock frequency signals to the satellite ( The satellite relayed the message to the San Francisco ground station; simultaneously, San Francisco launched... The satellite relayed the signal to Qingdao. The timestamps of signal transmission and reception were recorded (accurate to the picosecond level). The received optical clock frequencies from the other location were measured at both locations. With local optical clock frequency Differences ( According to general relativity, the frequency difference and the gravitational potential difference satisfy the following relationship: , The frequency of the time-frequency signal is represented by c, and the speed of light is represented by c.

[0069] d. Path delay and error correction: Calculate the effects of special relativistic time dilation (velocity effect) and general relativistic gravitational redshift (difference between the gravitational potential of the satellite and the ground) caused by satellite orbital motion, eliminate the influence of atmospheric turbulence using common-view comparison technology, and establish a Sagnac correction model, etc.

[0070] e. Gravity difference calculation and verification: Separate the gravity frequency shift caused by gravity difference, improve the signal-to-noise ratio through ground-satellite-ground optical clock comparison link and multiple measurements; compare the optical clock comparison results with traditional gravity measurements (such as absolute gravimeters, satellite gravity field models) to verify consistency; analyze the sources of uncertainty (such as optical clock stability, satellite positioning error), and finally output the gravity difference and its confidence interval.

[0071] The method of determining gravitational potential by comparing the time and frequency of Earth-satellite-Earth optical clocks can yield the following results:

[0072] Gravity potential difference determination at any station: Gravity potential difference between any reference points can be obtained by comparing the time and frequency of an optical clock, realizing high-precision gravity potential difference transmission and high-precision gravity potential measurement.

[0073] A new technology for unifying global elevation benchmarks: using quantum satellites as relay stations to achieve the transfer of elevation benchmarks between different countries and regions, providing a new technical means for unifying global elevation benchmarks.

[0074] Based on the same inventive concept as the foregoing embodiments, this embodiment of the invention also provides a system for determining gravitational potential using a star-space-ground optical clock time-frequency comparison system, comprising: a star-space-ground optical clock time-frequency comparison network, wherein the network is configured with a frequency comparison capability of better than 1 at the quantum satellite, space station, and ground station. 10 -18 The system includes: a large-scale optical clock; a time-frequency comparison link for achieving time-frequency synchronization based on a free-space time-frequency comparison link, during which time-frequency comparison data and position coordinates of each node's optical clock are acquired in real time; a data processing module for performing multi-source error joint correction on the acquired time-frequency comparison data; and a system for calculating the gravity potential difference between satellite-to-ground, air-to-ground, or ground stations based on the position coordinates of each node and the corrected time-frequency comparison data, thereby realizing gravity potential difference transmission and determining the gravity potential of unknown stations.

[0075] Specifically, the system described in this embodiment of the invention may include a reference optical clock module, an optical frequency comb module, a time-frequency comparison link, a ground station positioning and satellite (space station) orbit determination module, and a ground data processing center, which are equipped with quantum satellites, the Chinese space station, and ground stations, forming an integrated gravity potential measurement system that integrates data acquisition, processing, and output.

[0076] The system described in this invention compares the optical clock time and frequency signals of the GEOQS, CSS time-frequency comparison system, and GS, and uses the principles of general relativity to convert the frequency difference (or time difference) into a gravitational potential difference. Combined with multi-node collaborative observation and dynamic inversion algorithms, it achieves high-precision, high-spatial-resolution global gravity field measurement. In this embodiment, using the GEO quantum satellite as a node, it conducts optical clock time-frequency comparisons between the Chinese space station and ground stations, and between ground stations, to determine the gravitational potential. The time-frequency signals utilize uplink and downlink optical signals, and through differential analysis of the satellite-to-ground and satellite-to-space time-frequency links, various errors during signal propagation are eliminated, accurately extracting the clock difference or frequency difference of the ground station or space-to-ground clocks to determine the gravitational potential difference between the two locations.

[0077] This invention fully utilizes the high-precision optical clocks carried by space stations and quantum satellites to achieve the transmission of gravitational potential difference and the measurement of gravitational potential by constructing a time-frequency comparison link. With the help of high-precision spaceborne optical clocks, this method can measure gravitational potential with centimeter-level (equivalent height) accuracy, without being limited by terrain. It can overcome the limitations of traditional gravitational potential measurement methods that are difficult to achieve cross-sea and cross-island measurement, realize cross-sea gravitational potential transmission, and combine gravitational potential measurement with quantum physics, providing a brand-new technical solution for gravitational potential measurement.

[0078] Based on the same inventive concept as the foregoing embodiments, this embodiment of the invention also provides a ground station device, including an optical clock, a memory, and a processor. The optical clock is used to provide frequency and time references for the ground station. The optical clock is connected to optical clocks at other ground stations or space stations via an optical clock mounted on a quantum satellite. The memory is used to store computer programs. When the processor runs the computer programs stored in the memory, the processor executes the method for determining gravity potential using the aforementioned star-space-ground optical clock time-frequency comparison system, including:

[0079] A space-to-ground optical clock time-frequency comparison network is established, wherein the network is equipped with clocks with a frequency accuracy better than 1 at the quantum satellite, space station, and ground station. 10 -18 Light clocks of this magnitude;

[0080] Time and frequency synchronization is achieved based on the free space time and frequency comparison link, and the time and frequency comparison data and location coordinates of the optical clocks of each node are acquired in real time during the synchronization process;

[0081] Multi-source joint error correction is performed on the acquired time-frequency comparison data;

[0082] Based on the position coordinates of each node and the corrected time-frequency comparison data, the gravity potential difference between satellite-to-ground, air-to-ground, or ground stations is calculated, thus realizing the transfer of gravity potential difference and determining the gravity potential of unknown stations.

[0083] In summary, the gravity potential measurement method based on satellite-space-ground optical clock time-frequency comparison described in this invention constructs an optical clock time-frequency comparison network composed of a quantum satellite, the Chinese space station, and ground stations. Time-frequency synchronization is achieved through a free-space time-frequency comparison link. Time comparison data and position coordinates of the optical clocks at each node are collected synchronously. The influence of environmental noise on time transmission is eliminated. Based on the principle of gravitational redshift, centimeter-level precision gravity frequency shift signals are accurately extracted to calculate the gravity potential difference between satellite-ground, space-ground, or ground stations, thereby achieving the transmission of gravity potential difference. The time-frequency synchronization uses a laser link and utilizes adaptive optics technology to suppress atmospheric turbulence phase noise. Ground-satellite-ground and space-satellite-ground optical clock time comparison links are constructed through bidirectional laser signals. The optical clock onboard the quantum satellite serves as a "bridge" to achieve optical clock time comparison between ground stations or between space and ground. The environmental noise compensation includes: correcting the optical clock frequency drift using a frequency response model based on temperature, humidity, and pressure; and eliminating link errors in multi-node cross-transmission technology by using bidirectional time transfer and satellite common-view time comparison technology, combined with higher-precision error correction models, thereby improving the extraction accuracy of gravity frequency shift signals.

[0084] This invention configures high-precision optical clocks on a quantum satellite, a space station, and a ground station. The optical clocks on the quantum satellite are compared with those on the space station and the ground station. By observing the quantum satellite simultaneously, various time delays in signal propagation are reduced (i.e., when two stations observe the quantum satellite simultaneously, atmospheric delays in signal propagation can be reduced during inter-station differential observation). The time comparison data obtained from different nodes are processed by a data processing unit to obtain the gravitational potential difference between any two stations.

[0085] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the technical solutions of the embodiments of the present invention.

Claims

1. A method for determining gravitational potential using a star-space-ground optical clock time-frequency comparison system, characterized in that, include: A space-to-ground optical clock time-frequency comparison network was established, wherein the network was equipped with clocks with a speed better than 1x10 at the quantum satellite, space station, and ground station. -18 Light clocks of this magnitude; Time and frequency synchronization is achieved based on a free-space time and frequency comparison link. During the synchronization process, the time and frequency comparison data and location coordinates of the optical clocks at each node are acquired in real time. The time and frequency synchronization is achieved by constructing a ground-to-satellite-to-ground or space-to-satellite-to-ground optical clock time and frequency comparison link through bidirectional laser signals. The optical clock carried by the quantum satellite is used as a bridge to realize optical clock time and frequency comparison between ground stations or between space and ground. Multi-source joint error correction is performed on the acquired time-frequency comparison data, including: based on the general relativistic model, deducting the special relativistic frequency shift caused by the relative motion between nodes; Compensate for optical clock frequency drift using environmental sensor data; suppress phase noise of the satellite-to-ground link caused by atmospheric turbulence using redundant links; and eliminate time delay in signal propagation through common-view observation and bidirectional observation. Based on the position coordinates of each node and the corrected time-frequency comparison data, the gravity potential difference between satellite-to-ground, air-to-ground, or ground stations is calculated, thus realizing the transfer of gravity potential difference and determining the gravity potential of unknown stations.

2. The method for determining gravitational potential using the star-space-ground optical clock time-frequency comparison system according to claim 1, characterized in that, Optical clocks configured at different nodes are connected via a free-space time-frequency comparison link based on an optical frequency comb, and time-frequency comparison of the optical clocks is performed through remote time-frequency transmission.

3. The method for determining gravitational potential using the star-space-ground optical clock time-frequency comparison system according to claim 1, characterized in that, In the space-satellite-ground optical clock time-frequency comparison link, the optical clock of the space station is connected to the optical clock of any ground station through the optical clock carried by the quantum satellite. By comparing the time and frequency of the optical clocks of the space station and the ground station, the gravity potential of any ground station can be obtained.

4. The method for determining gravitational potential using the star-space-ground optical clock time-frequency comparison system according to claim 1, characterized in that, In the ground-satellite-ground optical clock time-frequency comparison link, the optical clocks of the two ground stations are connected through the optical clock carried by the quantum satellite. The optical clocks of the two ground stations are compared through common observation, and the gravity frequency shift signal caused by the difference in position between the two ground stations is extracted to determine the gravity potential difference between the two ground stations.

5. The method for determining gravitational potential using the star-space-ground optical clock time-frequency comparison system according to claim 1, characterized in that, The method further includes: Based on the known location coordinates of the space station or ground station, the gravity potential of the station can be obtained using a gravity field model or traditional measurement methods. Based on the corrected time difference Or frequency difference Through formula ,in, Indicates greater than or equal to This method obtains the gravitational potential difference between any two stations A and B, realizes the transfer of gravitational potential difference, and determines the gravitational potential of unknown stations.

6. A system for determining gravitational potential using a star-space-ground optical clock time-frequency comparison system, characterized in that, include: A space-to-ground optical clock time-frequency matching network is configured with clock speeds better than 1x10 on quantum satellites, space stations, and ground stations. -18 Light clocks of this magnitude; The time-frequency comparison link is used to achieve time-frequency synchronization based on the free space time-frequency comparison link. During the synchronization process, the time-frequency comparison data and location coordinates of the optical clocks of each node are acquired in real time. The time-frequency synchronization is achieved by constructing a ground-satellite-ground or air-satellite-ground optical clock time-frequency comparison link through bidirectional laser signals, using the optical clock carried by the quantum satellite as a bridge to realize optical clock time-frequency comparison between ground stations or between air and ground. The data processing module is used to perform multi-source joint error correction on the acquired time-frequency comparison data, including: based on the general relativistic model, deducting the special relativistic frequency shift caused by the relative motion between nodes; The optical clock frequency drift is compensated by environmental sensor data; the phase noise of atmospheric turbulence on the satellite-to-ground link is suppressed by redundant links; the time delay in signal propagation is eliminated by common-view observation and bidirectional observation; and the gravity potential difference between satellite-to-ground, air-to-ground, or ground stations is calculated based on the position coordinates of each node and the corrected time-frequency comparison data, so as to realize the gravity potential difference transmission and determine the gravity potential of unknown stations.

7. A ground station device, characterized in that, The system includes an optical clock, a memory, and a processor. The optical clock is used to provide frequency and time references for ground stations. The optical clock is connected to optical clocks at other ground stations or space stations via an optical clock carried by a quantum satellite. The memory is used to store computer programs. When the processor runs the computer programs stored in the memory, the processor executes the method for determining gravity potential using a star-space-ground optical clock time-frequency comparison system as described in any one of claims 1 to 5.

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