Method and system for measuring gravitational potential and altitude through air-ground double-frequency combined frequency transmission

Abstract

The invention discloses a method and a system for measuring gravitational potential and altitude through air-ground double-frequency combined frequency transmission. The method comprises the following steps: acquiring a ground observation value and a space observation value of an air-ground microwave signal transmitted by adopting an air-ground double-frequency combined microwave frequency transmission model; extracting a gravity frequency shift signal based on the ground observation value and the space observation value; calculating a gravity potential difference between the space and the ground based on the extracted gravity frequency shift signal, and calculating a gravity potential of a space carrier in combination with a gravity field model; and determining the gravitational potential and altitude of any ground station based on the gravitational potential of the space carrier in combination with the gravitational potential difference between the space and the ground. According to the invention, the gravity frequency shift signal is accurately extracted and the gravitational potential and the altitude are measured by using the air-ground dual-frequency combined microwave frequency transmission.

Description

Technical Field

[0001] The present invention belongs to the fields of geodesy, geophysics and time-frequency science, and particularly relates to a method for extracting gravity frequency shift by transmitting microwave frequency signals between air and ground and accurately measuring gravity potential and altitude, and specifically relates to a method and system for measuring gravity potential and altitude by transmitting microwave frequency signals between air and ground and a dual-frequency combination. Background Art

[0002] The determination of gravity potential occupies a very important position in the field of geodesy. It is a basic physical field quantity required by disciplines and research fields such as seismology, geodynamics, aerospace, meteorology, oceanography, natural disasters and global change. It is also an important information source that is indispensable for national defense construction and national economic development. The determination of altitude is closely related to the unification of global elevation datum and gravity potential. It is the vertical spatial information necessary for national economic construction. Since the end of the last century, determining the global geoid and unifying the global elevation datum with an accuracy level better than 1 cm has become the strategic goal of the future development of the International Association of Geodesy. The traditional method of determining gravity potential requires the method of gravity combined with leveling measurement, which has the defects of low efficiency and high cost; the high-precision gravity field model has only a resolution of 5′×5′, which provides the average result instead of the specific value of the point; although satellite gravity detection technology can restore the global gravity potential field with higher accuracy, the resolution is generally low (about 1°×1°). Therefore, how to quickly and accurately determine the gravity potential and altitude of any station has become the first problem that geodesists need to solve.

[0003] In order to solve these problems, a new method of measuring gravitational potential using the principle of general relativity has attracted attention and research. This method is mainly based on the correspondence between the gravitational potential difference and the speed difference of the precision clock, and determines the gravitational potential difference between two places by means of time and frequency transmission. In recent years, with the maturity of clock manufacturing technology, the world has successfully developed a precision of 10 -19 The precision of space-borne clocks has reached 10 -18This provides hardware guarantee for the implementation of using time-frequency signals to determine gravity potential. However, in order to perform time-frequency comparison at the accuracy of optical clocks, time-frequency transmission technology with corresponding accuracy must be used to connect remote clocks. Therefore, how to perform high-precision remote time-frequency comparison has become an urgent problem to be solved. Using optical fiber or cable to connect atomic clocks in two places for time-frequency comparison to determine gravity potential difference is not affected by the external environment and does not produce errors during signal propagation, which can meet the needs of high-precision time-frequency comparison. However, due to geographical factors and the cost of laying optical fiber or cable, this method is difficult to apply in long baselines and across the sea. Comparing airborne (satellite) optical clocks through microwave links to achieve time and frequency comparison of clocks in two places has become a research hotspot. Compared with optical fiber and cable comparison technology, airborne (satellite) atomic clocks have the advantages of all-weather, low cost and no baseline length restrictions, providing a platform for the global implementation of airborne dual-frequency combined microwave frequency signal transmission to determine gravity potential and altitude.

[0004] Determining the gravity position and altitude with centimeter-level accuracy requires an air-to-ground (satellite) time-frequency transmission link with an accuracy of 10 -18 In practical applications, it is difficult to eliminate various errors in the signal propagation process through a single microwave link. Therefore, how to eliminate the errors in the signal propagation process and accurately extract the gravity frequency shift signal has become the key to the time-frequency transmission measurement of gravity position and altitude. Summary of the invention

[0005] To overcome the deficiencies of the prior art, the present invention provides a method and system for measuring gravity position and altitude by using air-to-ground dual-frequency combined frequency transmission, which accurately extracts gravity frequency shift signals and measures gravity position and altitude by using air-to-ground dual-frequency combined microwave frequency transmission.

[0006] According to one aspect of the present invention, there is provided a method for measuring gravity position and altitude by air-to-ground dual-frequency combined frequency transmission, comprising:

[0007] Obtain ground observation values ​​and space observation values ​​of air-to-ground microwave signals transmitted using an air-to-ground dual-frequency combined microwave frequency transmission model;

[0008] Extracting gravity frequency shift signals based on the ground observation values ​​and the space observation values;

[0009] Based on the extracted gravity frequency shift signal, the gravity potential difference between the open space and the ground is calculated, and the gravity potential of the space carrier is calculated in combination with the gravity field model;

[0010] Based on the gravity potential of the space carrier and the gravity potential difference between the air and the ground, the gravity potential and altitude of any ground station are determined.

[0011] As a further technical solution, before adopting the air-to-ground dual-frequency combined microwave frequency transmission model for air-to-ground microwave signal transmission, the method further includes:

[0012] Set the transmission time of ground and space microwave signals, and ensure that the microwave signals transmitted by the uplink and downlink microwave links have the same frequency and opposite polarization directions. Both the ground station and the space station are equipped with high-precision clocks.

[0013] Simultaneously receive microwave signals transmitted from the ground and space.

[0014] As a further technical solution, the method further includes:

[0015] Utilize the broadcast messages sent by the space carrier to receive the observation values ​​collected by the space station equipment, and download the observation values ​​collected by the ground station equipment at the same time.

[0016] As a further technical solution, the method further includes:

[0017] A tidal model is constructed to eliminate the frequency shift of microwave signals caused by tidal effects.

[0018] As a further technical solution, the method further includes:

[0019] A second-order Doppler frequency shift model is constructed to eliminate the frequency shift of microwave signals caused by the second-order Doppler frequency shift.

[0020] As a further technical solution, after calculating the gravity potential of the space carrier, it also includes:

[0021] Based on the gravity potential difference between the space carrier and the open ground, the gravity potential of any ground station is obtained;

[0022] Combined with the coordinates of the ground station, the gravity potential at the ground station is converted to the global geoid to determine the altitude of the ground station.

[0023] According to one aspect of the present invention, there is provided a system for measuring gravity position and altitude by air-to-ground dual-frequency combined frequency transmission, comprising:

[0024] The first main module is used to obtain ground observation values ​​and space observation values ​​of air-to-ground microwave signals transmitted using an air-to-ground dual-frequency combined microwave frequency transmission model;

[0025] A second main module is used to extract a gravity frequency shift signal based on the ground observation value and the space observation value;

[0026] The third main module is used to calculate the gravity potential difference between the open space and the ground based on the extracted gravity frequency shift signal, and at the same time calculate the gravity potential of the space carrier in combination with the gravity field model;

[0027] The fourth main module is used to determine the gravity position and altitude of any ground station based on the gravity position of the space carrier and the gravity potential difference between the air and the ground.

[0028] As a further technical solution, the first main module is further used to execute the following instructions:

[0029] Set the transmission time of ground and space microwave signals, and ensure that the microwave signals transmitted by the uplink and downlink microwave links have the same frequency and opposite polarization directions. Both the ground station and the space station are equipped with high-precision clocks.

[0030] Simultaneously receive microwave signals transmitted from the ground and space.

[0031] According to one aspect of the present invention specification, there is provided a ground station device, comprising a high-precision clock, a memory and a processor, wherein the high-precision clock is used to provide a frequency reference and a time reference for the ground station, and 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 position and altitude by air-to-ground dual-frequency combined frequency transfer.

[0032] According to one aspect of the present specification, a non-transitory computer-readable storage medium is provided, wherein the non-transitory computer-readable storage medium stores computer instructions, wherein the computer instructions enable the computer to execute the method for determining gravity position and altitude by air-to-ground dual-frequency combined frequency transmission.

[0033] Compared with the prior art, the present invention has the following beneficial effects:

[0034] The method for measuring gravity potential and altitude proposed in the present invention is to use a high-precision optical clock as a basis, use a microwave signal link as a bridge, connect the optical clocks between space (star) and the ground, and perform high-precision microwave frequency transmission. The frequency shift caused by various errors in the microwave signal propagation process is effectively eliminated through the space-ground dual-frequency combined microwave frequency transmission model, and 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 and altitude of any ground station are determined. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, a brief introduction is given below to the drawings used in the embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0036] Figure 1 A flow chart of a method for measuring gravity potential and altitude by air-to-ground dual-frequency combined frequency transmission provided in an embodiment of the present invention.

[0037] Figure 2 A schematic diagram of the principle of measuring gravity potential and altitude by air-to-ground dual-frequency combined frequency transmission provided in an embodiment of the present invention.

[0038] Figure 3 This is a schematic diagram of the application of the air-to-ground dual-frequency combined frequency transmission to measure gravity potential and altitude provided by an embodiment of the present invention.

[0039] Figure 4 A schematic diagram of a system for measuring gravity position and altitude by air-to-ground dual-frequency combined frequency transmission provided in an embodiment of the present invention. DETAILED DESCRIPTION

[0040] The present invention utilizes a high-performance optical clock carried in space (satellite), performs space (satellite)-ground frequency comparison through microwave links with the same frequency but different polarization directions, implements high-precision microwave frequency transmission, effectively extracts gravity frequency shift signals, and measures space (satellite)-ground gravity potential difference. The present invention proposes to use microwave links with the same frequency but different polarization directions for uplink and downlink frequency transmission. During the propagation process of the uplink and downlink microwave links, the first-order Doppler frequency shift, the first-order ionospheric frequency shift, the tropospheric frequency shift, etc. are equal in magnitude and have the same sign. The influence of related errors can be eliminated by differentiating the uplink and downlink same-frequency links. In addition, the present invention also takes into account the influence of high-order ionospheric frequency shift, tidal effect, and Shapiro effect. Through error modeling, various errors are effectively eliminated, and gravity frequency shift signals are extracted at the centimeter-level accuracy level to achieve remote frequency comparison. According to the principle of general relativity, the gravity potential difference between space (satellite) and the ground is calculated using the gravity frequency shift equation. Then, the gravity potential and altitude of the space-borne (satellite) atomic clock are calculated through the gravity field model EGM2008. Combined with the gravity potential difference measured by the airborne dual-frequency combined microwave frequency signal transmission method, the gravity potential of any ground station is obtained, and the gravity potential at the measuring station is converted back to the global (regional) geoid to determine the altitude of the measuring station.

[0041] The terms "including" and "having" and any variations thereof in the specification and claims of the present invention and the above-mentioned drawings are intended to cover non-exclusive inclusions, for example, a process, method, system, product or apparatus comprising a series of steps or units is not necessarily limited to the steps or units explicitly listed, but may include other steps or units not explicitly listed or inherent to these processes, methods, products or apparatuses.

[0042] The block diagrams shown in the accompanying drawings are merely functional entities and do not necessarily correspond to physically independent entities. That is, these functional entities may be implemented in software, or in one or more hardware modules or integrated circuits, or in different networks and / or processor devices and / or microcontroller devices. The flowcharts shown in the accompanying drawings are merely exemplary and do not necessarily include all the contents and operations / steps, nor do they necessarily have to be executed in the order described. For example, some operations / steps may be further decomposed, while some operations / steps may be combined or partially combined, so the actual execution order may change according to the actual situation.

[0043] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments in the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention. In addition, the technical features in the various embodiments or single embodiments provided by the present invention are arbitrarily combined with each other to form a new technical solution. This combination is not restricted by the sequence of steps and / or the structural composition mode, but must be based on the ability of ordinary technicians in this field to achieve. When the combination of technical solutions is contradictory or cannot be achieved, it should be considered that this combination of technical solutions does not exist and is not within the scope of protection required by the present invention.

[0044] The embodiment of the present invention provides a method for measuring gravity position and altitude by air-ground dual-frequency combined frequency transmission, such as Figure 1 As shown, it includes: obtaining ground observation values ​​and space observation values ​​of air-to-ground microwave signals transmitted by adopting an air-to-ground dual-frequency combined microwave frequency transmission model; extracting gravity frequency shift signals based on the ground observation values ​​and space observation values; calculating the gravity potential difference between air and ground based on the extracted gravity frequency shift signals, and calculating the gravity potential of the space carrier in combination with the gravity field model; determining the gravity potential and altitude of any ground station based on the gravity potential of the space carrier and the gravity potential difference between air and ground.

[0045] The embodiment of the present invention uses a high-precision airborne optical clock to measure the gravity potential and altitude of any ground point. The high-precision optical clock is used as the basis, and the microwave signal link is used as a bridge to connect the optical clocks between the air (satellite) and the ground, and high-precision microwave frequency transmission is performed. The frequency shift caused by various errors in the microwave signal propagation process is effectively eliminated through the air-ground dual-frequency combined microwave frequency transmission model, and 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 and altitude of any ground station are determined.

[0046] The principle of using air-ground dual-frequency combination frequency transmission to measure gravity potential and altitude is as follows Figure 2 As shown in the figure, E represents the position of the ground station, S represents the space station or satellite, the blue line and the red line represent the uplink and downlink microwave links respectively, which are respectively connected to the high-precision atomic clock, and high-precision microwave frequency measurement can be performed; the frequencies of the microwave signals are f1 and f2 respectively. When applying the present invention, f1=f2 is set, and the polarization directions are opposite. The method can be used to eliminate various errors and accurately extract the gravity frequency shift signal.

[0047] As a preferred embodiment, the embodiment of the present invention sets a ground station at an arbitrary point, collects data with the gravity position and altitude of the point as the measurement object, and gives the three-dimensional coordinates and gravity position of the ground station.

[0048] In order to achieve the application goal, the embodiment of the present invention uses an airborne dual-frequency combined microwave frequency signal transmission method to determine the gravity potential and altitude to carry out air-to-ground microwave frequency transmission, calculate the observed values, and obtain the gravity potential and altitude of the ground station.

[0049] Figure 3 This is a schematic diagram of an example application of the present invention. In the figure, the space station can compare frequencies with ground clocks at any location. By comparing microwave frequencies, the gravity potential of any station can be obtained. Combining the gravity potential difference between different points and the geoid, the altitude of any ground point can be determined.

[0050] The data collection process includes the following steps:

[0051] a. Atomic clock settings: The atomic clocks on the ground and in space are high-precision optical clocks with a long-term stability of 10 -18 Magnitude.

[0052] b. Data collection: Set the transmission time of space and ground microwave signals, and make sure that the transmitted microwave signals have the same frequency and opposite polarization directions. At the same time, receive the microwave signals transmitted from space and the ground, and collect and record various types of data.

[0053] c. Data download: Receive data collected by space equipment using broadcast messages sent by space carriers, and download data collected by ground equipment at the same time.

[0054] d. Data processing: The gravity potential is measured by using an unloaded dual-frequency combined microwave frequency signal transmission method to measure the gravity potential and the altitude, and the gravity potential of any ground station is calculated. The results are compared with those of the traditional method to analyze the accuracy of the method of the present invention.

[0055] The following results can be obtained by using the method of measuring gravity position and altitude through the transmission of unloaded dual-frequency combined microwave frequency signals:

[0056] Determine gravity potential: It is possible to determine the gravity potential of any ground station with centimeter-level accuracy.

[0057] Determine altitude: Measure the altitude of any point without leveling, and realize cross-sea elevation transmission.

[0058] The embodiment of the present invention utilizes the microwave frequency signals (microwave signals of equal frequency and opposite polarization directions) simultaneously transmitted by the uplink and downlink of the airborne (satellite) equipment. By setting the working frequency point, the uplink and downlink microwave frequencies are differentiated, which can effectively eliminate the influence of various errors in the signal propagation process and improve the accuracy of gravity frequency shift signal extraction. Furthermore, the air (satellite)-ground microwave frequency comparison is performed through a ground station equipped with a high-performance optical clock. Due to the high measurement accuracy of the optical clock, it is necessary to eliminate the influence of the troposphere and ionosphere in the signal propagation process at a higher accuracy level. By setting microwave links with the same frequency but different polarization directions, the influence of high-order ionospheric frequency shift can be effectively eliminated, and the accuracy of time-frequency transmission can be improved.

[0059] The details are as follows:

[0060] 1) The target station sets up a ground observation station and a high-precision optical clock to provide a high-precision and high-stability frequency reference and time reference for the ground station. When the optical clock reaches a certain accuracy, how to eliminate various errors in the signal propagation process and accurately extract the gravity frequency shift signal becomes the key. Assume that the microwave frequency emitted by point A is f A , the microwave frequency received at point B is f B , considering that the relative frequency deviations of the atomic clocks at points A and B are y A and B , then the one-way microwave frequency transmission model in free space is:

[0061]

[0062] In the model is the Doppler frequency shift caused by the mutual motion between the space station and the ground station, is the frequency shift caused by the gravitational potential, and The terms represent the impact of the ionosphere, troposphere and other hardware equipment on the microwave frequency.

[0063] The main errors in the term come from the first-order and second-order Doppler shifts:

[0064]

[0065] In the formula and represents the correction model of the first-order and second-order Doppler frequency shift, f represents the frequency of microwaves, v I and vJ represents the velocity at points I and J, N IJ Represents the unit vector from I to J. From the above model, it can be seen that when the uplink and downlink have the same frequency, the first-order Doppler frequency shift can be eliminated by differentially eliminating the uplink and downlink.

[0066] 2) Analyze the influence of ionosphere and troposphere in microwave transmission. When microwave signals propagate in the atmosphere, the frequency shift caused by atmospheric influence is divided into ionosphere frequency shift and troposphere frequency shift. Among them, ionosphere frequency shift is:

[0067]

[0068] It can be seen from the formula that the magnitude of the first-order and second-order ionospheric frequency shifts is only related to the frequency of the microwave signal. The second-order ionospheric frequency shift is not only related to the signal frequency, but also to the polarization direction of the microwave signal and the angle between the geomagnetic field and the signal propagation direction. When the upper and lower microwave links have the same frequency but different polarization directions, the first-order, second-order and third-order ionospheric frequency shifts are equal in magnitude and have the same sign, and can be eliminated by differentially combining the upper and lower links.

[0069] The effect of tropospheric frequency shift is:

[0070]

[0071] Where, ΔL d and ΔL w are the dry and wet delay components of the troposphere, respectively. From equation (5), we can see that the tropospheric frequency shift has nothing to do with the frequency of the microwave signal, and any frequency uplink and downlink difference can eliminate it.

[0072] Optionally, the embodiment of the present invention also eliminates errors based on tidal model correction. By utilizing the high-performance tidal model shown in formula (6), the tidal effects of the space carrier and the ground station are calculated in real time, and the influence of the tidal effect on the microwave frequency is modeled and analyzed. Through model correction, the frequency shift of the microwave signal caused by the tidal effect is effectively eliminated.

[0073] The tidal potential ΔV(r,φ,λ) at any station can be obtained by spherical harmonic expansion to the Nth order:

[0074]

[0075] Where n is the order, m is the degree, (r, φ, λ) is the geocentric radius, latitude and longitude at any point; GM is the gravitational constant of the Earth, R e represents the radius of the Earth's equator, represents the fully normalized associated Legendre polynomials, represents the spherical harmonic coefficients.

[0076] Optionally, the embodiment of the present invention further eliminates the second-order Doppler frequency shift of the microwave signal based on the model shown in formula (3) to improve the extraction accuracy of the gravity frequency shift signal.

[0077] 3) Set up the microwave transmitting devices of the ground station and the space station (satellite), set the frequencies of the uplink and downlink microwave links to be equal, and the polarization directions to be the same, use the airborne dual-frequency combined microwave frequency signal transmission model to transmit air (satellite)-ground microwave signals, and use the dual-frequency combined frequency transmission method to measure the gravity potential to measure the gravity potential difference between the ground station and the space station. The basic method is as follows:

[0078] Dividing the difference of the upper and lower frequency links by 2 can effectively eliminate the first-order Doppler shift, ionospheric shift, tropospheric shift and other frequency shifts, extract the gravity shift, and the dual-frequency dual-link (dual-frequency combination) combination model is:

[0079]

[0080] Among them, f r Indicates the frequency of the received microwave signal, f Dop2 represents the second-order Doppler frequency shift, the subscripts AB and BA represent transmission from A to B and from B to A, respectively, Δf other Represents the sum of other errors. Through the microwave links with the same frequency and different polarization directions, the ionospheric frequency shift, tropospheric frequency shift, first-order Doppler frequency shift, etc. can be effectively eliminated.

[0081] 4) According to the observation value of the airborne dual-frequency combined microwave frequency signal transmission, the gravity potential difference between any two points is obtained. Since the main error of the airborne dual-frequency combined microwave frequency signal transmission comes from the clock error of the airborne (satellite) atomic clock, the accuracy of the atomic clock directly determines the measurement accuracy of the gravity potential and altitude. According to this model, when the accuracy of the atomic clock reaches 10 -18 At this level, the gravity potential and altitude can be measured with centimeter-level accuracy.

[0082] The implementation basis of each embodiment of the present invention is to implement programmed processing through a device with a processor function. Therefore, in engineering practice, the technical solutions and functions of each embodiment of the present invention are encapsulated into various modules. Based on this reality, on the basis of the above embodiments, an embodiment of the present invention provides a system for measuring gravity level and altitude by air-to-ground dual-frequency combined frequency transmission, which is used to execute the method for measuring gravity level and altitude by air-to-ground dual-frequency combined frequency transmission in the above method embodiment.

[0083] See also Figure 4The device includes: a first main module, which is used to obtain the ground observation value and the space observation value of the air-to-ground microwave signal transmitted by the air-to-ground dual-frequency combined microwave frequency transmission model; a second main module, which is used to extract the gravity frequency shift signal based on the ground observation value and the space observation value; a third main module, which is used to calculate the gravity potential difference between the air and the ground based on the extracted gravity frequency shift signal, and at the same time calculate the gravity potential of the space carrier in combination with the gravity field model; a fourth main module, which is used to determine the gravity potential and altitude of any ground station based on the gravity potential of the space carrier and the gravity potential difference between the air and the ground

[0084] The system for measuring gravity position and altitude by transmitting unloaded dual-frequency combined microwave frequency signals provided by the embodiment of the present invention adopts Figure 4 Several modules in the system can effectively eliminate the frequency shift caused by the ionosphere, troposphere and Doppler effect, and have the advantages of high precision, high stability and real-time performance, which can overcome the shortcomings of low efficiency, high cost and poor accuracy of traditional gravity position and high altitude measurement. When the stability of the high-precision atomic clock used for measurement reaches 10 -18 At this level, it can meet the application requirements of measuring gravity potential with centimeter-level accuracy, greatly improving the efficiency of gravity potential measurement and reducing the cost of gravity potential measurement.

[0085] It should be noted that the system embodiment provided by the present invention is used to implement the methods in the above method embodiment as well as the methods in other method embodiments provided by the present invention. The only difference is that the corresponding functional modules are set. The principle is basically the same as the principle of the above system embodiment provided by the present invention. As long as the technical personnel in this field refer to the specific technical solutions in other method embodiments on the basis of the above system embodiment, obtain the corresponding technical means and the technical solutions composed of these technical means by combining the technical features, and on the premise of ensuring the practicality of the technical solutions, improve the modules in the above system embodiment to obtain the corresponding system class embodiments, which are used to implement the methods in other method class embodiments. For example:

[0086] Based on the contents of the above system embodiment, as a preferred embodiment, in the system for measuring gravity position and altitude by air-to-ground dual-frequency combined frequency transmission provided in the embodiment of the present invention, the first main module is also used to execute the following instructions:

[0087] Set the transmission time of ground and space microwave signals, and ensure that the microwave signals transmitted by the uplink and downlink microwave links have the same frequency and opposite polarization directions. Both the ground station and the space station are equipped with high-precision clocks.

[0088] Simultaneously receive microwave signals transmitted from the ground and space.

[0089] An embodiment of the present invention further provides an electronic device, including a memory and a processor, wherein a computer program is stored in the memory, and when the processor runs the computer program stored in the memory, the processor executes the above-mentioned various possible methods.

[0090] The memory is connected to the processor, the memory may be a flash memory or a read-only memory or other memory, and the processor may be a central processing unit or a single-chip microcomputer.

[0091] In addition, an embodiment of the present disclosure further provides a computer-readable storage medium, on which a computer program is stored, and the computer program is executed by a processor to perform the above-mentioned various possible methods.

[0092] The computer-readable storage medium includes volatile or non-volatile, removable or non-removable media implemented in any method or technology for storing information (such as computer-readable instructions, data structures, computer program modules or other data). Computer-readable storage media include, but are not limited to, RAM (Random Access Memory), ROM (Read-Only Memory), EEPROM (Electrically Erasable Programmable read only memory), flash memory or other memory technology, CD-ROM (Compact Disc Read-Only Memory), Digital Versatile Disk (DVD) or other optical disk storage, magnetic cassettes, magnetic tapes, magnetic disk storage or other magnetic storage devices, or any other medium that can be used to store the desired information and can be accessed by a computer.

[0093] In summary, the method for measuring gravity position and altitude by using unloaded dual-frequency combined microwave frequency signal transmission proposed in the present invention has the following advantages:

[0094] (1) The present invention can effectively measure the gravitational frequency shift of microwave signals caused by changes in gravitational potential through the high-precision frequency reference of space (satellite) optical clocks and ground optical clocks. Specifically, using a high-precision optical clock as a tool for measuring frequency can provide a high-precision time and frequency reference, significantly improving the measurement accuracy of microwave links; and in the process of measuring gravitational potential using microwave time-frequency signal transmission, a high-precision time and frequency reference is crucial for accurately measuring gravitational potential.

[0095] (2) The present invention adopts the uplink and downlink frequency combination transmission to effectively eliminate the first-order Doppler frequency shift. The reason is that in the process of one-way microwave frequency transmission, the microwave signal is affected by the Doppler effect and produces Doppler frequency shift, among which the influence of the first-order Doppler frequency shift reaches 10 -5 ~10 -6 With the current positioning and speed measurement accuracy, it is difficult to eliminate this frequency shift through the model.

[0096] (3) When the present invention uses a microwave link with the same frequency but different polarization directions for uplink and downlink, the tropospheric frequency shift, the first-order ionospheric frequency shift and the second-order ionospheric frequency shift can be effectively eliminated. The reason is that during the propagation of microwave signals in the atmosphere, they are affected by the ionosphere and troposphere. Through research, it is found that the frequency shift caused by the troposphere has nothing to do with the frequency of the microwave signal, the frequency shift caused by the ionosphere is related to the frequency of the microwave signal, and the second-order ionospheric frequency shift is also related to the polarization direction of the microwave signal.

[0097] (4) The present invention eliminates the frequency shift caused by the second-order Doppler frequency shift and the tidal effect by adding a second-order Doppler frequency shift model and a tidal correction model, thereby improving the extraction accuracy of the gravity frequency shift signal.

[0098] (5) The present invention uses high-precision gravity frequency shift signals to determine the gravity potential difference between space (satellite) and the ground. Using the existing gravity field model, the gravity potential of the space atomic clock can be accurately determined. Combined with the gravity potential query data, the gravity potential of the ground point can be obtained. Furthermore, using the conversion relationship between gravity potential and altitude, a conversion model for the entire region is established to determine the altitude of any point.

[0099] In summary, the method for measuring gravity position and altitude by unloaded dual-frequency combined microwave frequency signal transmission proposed by the present invention realizes high-precision microwave signal frequency measurement by using a high-precision optical clock. The proposed dual-frequency combined frequency transmission method can effectively eliminate errors in the signal propagation process, and correct the frequency shift caused by the second-order Doppler frequency shift and the tidal effect, thereby improving the extraction accuracy of the gravity frequency shift signal, and providing a new idea for high-precision gravity position and altitude measurement. This method can provide important technical support and innovative solutions for the measurement of gravity position and altitude.

[0100] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the technical solutions of the embodiments of the present invention.

Claims

1. A method for measuring gravity potential and altitude by air-ground dual-frequency combined frequency transmission, characterized in that: include: Obtain ground observation values ​​and space observation values ​​of air-to-ground microwave signals transmitted using an air-to-ground dual-frequency combined microwave frequency transmission model; Extracting gravity frequency shift signals based on the ground observation values ​​and the space observation values; Based on the extracted gravity frequency shift signal, the gravity potential difference between the open space and the ground is calculated, and the gravity potential of the space carrier is calculated in combination with the gravity field model; Based on the gravity potential of the space carrier and the gravity potential difference between the air and the ground, the gravity potential and altitude of any ground station are determined.

2. The method for measuring gravity potential and altitude by air-to-ground dual-frequency combined frequency transmission according to claim 1 is characterized in that: Before using the air-to-ground dual-frequency combined microwave frequency transmission model to perform air-to-ground microwave signal transmission, the method further includes: Set the transmission time of ground and space microwave signals, and ensure that the microwave signals transmitted by the uplink and downlink microwave links have the same frequency and opposite polarization directions. Both the ground station and the space station are equipped with high-precision clocks. Simultaneously receive microwave signals transmitted from the ground and space.

3. The method for measuring gravity potential and altitude by air-to-ground dual-frequency combined frequency transmission according to claim 2 is characterized in that: The method further comprises: Utilize the broadcast messages sent by the space carrier to receive the observation values ​​collected by the space station equipment and download the observation values ​​collected by the ground station equipment at the same time.

4. The method for measuring gravity potential and altitude by air-to-ground dual-frequency combined frequency transmission according to claim 1 is characterized in that: The method further comprises: A tidal model is constructed to eliminate the frequency shift of microwave signals caused by tidal effects.

5. The method for measuring gravity potential and altitude by air-to-ground dual-frequency combined frequency transmission according to claim 1 is characterized in that: The method further comprises: A second-order Doppler frequency shift model is constructed to eliminate the frequency shift of microwave signals caused by the second-order Doppler frequency shift.

6. The method for measuring gravity potential and altitude by air-to-ground dual-frequency combined frequency transmission according to claim 1 is characterized in that: After calculating the gravity potential of the space carrier, it also includes: Based on the gravity potential difference between the space carrier and the open ground, the gravity potential of any ground station is obtained; Combined with the coordinates of the ground station, the gravity potential at the ground station is converted to the global geoid to determine the altitude of the ground station.

7. A system for measuring gravity position and altitude by air-ground dual-frequency combined frequency transmission, characterized in that: include: The first main module is used to obtain ground observation values ​​and space observation values ​​of air-to-ground microwave signals transmitted using an air-to-ground dual-frequency combined microwave frequency transmission model; A second main module is used to extract a gravity frequency shift signal based on the ground observation value and the space observation value; The third main module is used to calculate the gravity potential difference between the open space and the ground based on the extracted gravity frequency shift signal, and at the same time calculate the gravity potential of the space carrier in combination with the gravity field model; The fourth main module is used to determine the gravity position and altitude of any ground station based on the gravity position of the space carrier and the gravity potential difference between the air and the ground.

8. The system for measuring gravity position and altitude by air-to-ground dual-frequency combined frequency transmission according to claim 7 is characterized in that: The first main module is also used to execute the following instructions: Set the transmission time of ground and space microwave signals, and ensure that the microwave signals transmitted by the uplink and downlink microwave links have the same frequency and opposite polarization directions. Both the ground station and the space station are equipped with high-precision clocks. Simultaneously receive microwave signals transmitted from the ground and space.

9. A ground station device, characterized in that: The method comprises a high-precision clock, a memory and a processor, wherein the high-precision clock is used to provide a frequency reference and a time reference for a ground station, and 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 position and altitude by air-to-ground dual-frequency combined frequency transfer as described in any one of claims 1 to 6.

10. A non-transitory computer readable storage medium, characterized in that: The non-transitory computer-readable storage medium stores computer instructions, and the computer instructions enable the computer to execute the method for determining gravity potential and altitude by air-to-ground dual-frequency combined frequency transmission as described in any one of claims 1 to 6.

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