GNSS-r wide-swath ionospheric vertical total electron content measurement method, device, equipment and medium

Abstract

The application provides a GNSS-R wide-swath ionospheric vertical total electron content measurement method, device, equipment and medium, and the method comprises the following steps: measuring the propagation time delay difference of direct signal and reflected signal from the same navigation satellite through a space-borne GNSS-R dual-frequency receiver; calculating a first VTEC value below the satellite orbit at the mirror reflection point according to the propagation time delay difference; calculating a second VTEC value and a third VTEC value below the satellite orbit at the incident piercing point and the reflection piercing point according to a two-dimensional ionospheric model and the first VTEC value; for each target point in the mirror reflection point, the incident piercing point and the reflection piercing point, calculating the total VTEC value of the vertical path based on a three-dimensional ionospheric model and the VTEC value below the satellite orbit at the target point, as the VTEC observation result of a single navigation satellite; and fusing the VTEC observation results of multiple navigation satellites to generate wide-swath ionospheric VTEC observation data.

Description

Technical Field

[0001] This application relates to the field of satellite remote sensing technology, and in particular to a method, apparatus, equipment and medium for measuring the vertical total electron content of the ionosphere using GNSS-R (Global Navigation Satellite System - Reflectometry). Background Technology

[0002] The ionosphere is the region of Earth's upper atmosphere ionized by solar radiation. Vertical Total Electron Content (VTEC) is a key parameter characterizing the vertical integral of ionospheric electron density and is crucial for satellite navigation, communication, and space weather monitoring. Currently, VTEC monitoring primarily relies on ground-based dual-frequency GNSS observation stations. However, the global distribution of ground-based GNSS stations is uneven, with a severe shortage of stations in the ocean region, which covers approximately 71% of the Earth's surface, resulting in insufficient real-time VTEC observation data for this region.

[0003] Due to insufficient observational data in ocean regions, traditional ionospheric modeling methods based on spherical harmonic functions or Kriging interpolation struggle to accurately fit the electron content distribution in these areas. This is particularly problematic in vast ocean areas and the Southern Hemisphere, often resulting in large fitting residuals and even negative VTEC values ​​that do not conform to physical reality. This severely limits the accuracy and reliability of global ionospheric models and hinders the development of spaceborne applications requiring high-precision ionospheric corrections. Therefore, overcoming the limitations of ocean regional observations and achieving efficient and high-precision wide-swath VTEC monitoring has become an urgent technical challenge. Summary of the Invention

[0004] The purpose of this application is to provide a GNSS-R wide-span ionospheric vertical total electron content measurement method, device, equipment, and medium, which can solve the problem of missing ionospheric monitoring data in areas such as the ocean where there are no ground observation stations, and realize wide-area and efficient detection of the ionospheric vertical total electron content.

[0005] To solve the above-mentioned technical problems, this application is implemented as follows:

[0006] A first aspect of this application discloses a method for measuring the vertical total electron content of the ionosphere using a GNSS-R wide-swath ionosphere, the method comprising:

[0007] The propagation delay difference between direct signals from the same navigation satellite and reflected signals reflected from the ground is measured using a spaceborne GNSS-R dual-frequency receiver. The propagation delay difference includes a first propagation delay difference corresponding to the high-frequency signal and a second propagation delay difference corresponding to the low-frequency signal.

[0008] Based on the dual-frequency combined observation principle, the first VTEC value below the satellite orbit at the specular reflection point is calculated according to the propagation time delay difference.

[0009] Based on the two-dimensional ionospheric model and the first vertical total electron content VTEC value, the second VTEC value below the satellite orbit at the incident puncture point and the third VTEC value below the satellite orbit at the reflection puncture point are calculated respectively.

[0010] For each target point among the specular reflection point, the incident puncture point, and the reflection puncture point, based on the three-dimensional ionospheric model and the VTEC value below the satellite orbit at the target point, the total VTEC value covering the vertical path from the Earth's surface to the top of the ionosphere is calculated as the VTEC observation result of a single navigation satellite.

[0011] By fusing VTEC observations from multiple navigation satellites, wide-swath ionospheric VTEC observation data is generated.

[0012] Optionally, the propagation delay difference between the direct signal from the same navigation satellite and the reflected signal after reflection from the ground is measured using a spaceborne GNSS-R dual-frequency receiver, including:

[0013] The onboard GNSS-R dual-frequency receiver receives direct signals from the same navigation satellite and reflected signals reflected from the ground. The direct signals include high-frequency direct signals and low-frequency direct signals, and the reflected signals include high-frequency reflected signals and low-frequency reflected signals.

[0014] Based on the direct signal and the reflected signal, the first propagation delay difference corresponding to the high-frequency signal and the second propagation delay difference corresponding to the low-frequency signal are extracted respectively.

[0015] Optionally, when the spaceborne GNSS-R dual-frequency receiver is an interferometric receiver, the first propagation delay difference corresponding to the high-frequency signal and the second propagation delay difference corresponding to the low-frequency signal are extracted based on the direct signal and the reflected signal, respectively, including:

[0016] Based on the high-frequency direct signal and the high-frequency reflected signal, obtain the first interference waveform corresponding to the high-frequency signal, and extract the first propagation delay difference from the first interference waveform;

[0017] Based on the low-frequency direct signal and the low-frequency reflected signal, a second interference waveform corresponding to the low-frequency signal is obtained, and the second propagation delay difference is extracted from the second interference waveform.

[0018] Optionally, when the spaceborne GNSS-R dual-frequency receiver is a local code correlation type receiver, the first propagation delay difference corresponding to the high-frequency signal and the second propagation delay difference corresponding to the low-frequency signal are extracted based on the direct signal and the reflected signal, respectively, including:

[0019] The first propagation delay of the high-frequency direct signal and the second propagation delay of the high-frequency reflected signal are measured respectively, and the difference between the first propagation delay and the second propagation delay is obtained to obtain the first propagation delay difference;

[0020] The third propagation delay of the low-frequency direct signal and the fourth propagation delay of the low-frequency reflected signal are measured respectively, and the difference between the third propagation delay and the fourth propagation delay is obtained to obtain the second propagation delay difference.

[0021] Optionally, the method further includes:

[0022] The propagation delay difference is subjected to receiver hardware delay correction processing to obtain the corrected propagation delay difference;

[0023] Based on the principle of dual-frequency combined observation, the first VTEC value below the satellite orbit at the specular reflection point is calculated according to the propagation time delay difference, including:

[0024] Based on the principle of dual-frequency combined observation, the first VTEC value below the satellite orbit at the specular reflection point is calculated according to the corrected propagation delay difference.

[0025] Optionally, based on the principle of dual-frequency combined observation, the first VTEC value below the satellite orbit at the specular reflection point is calculated according to the propagation time delay difference, including:

[0026] Based on the difference between the first propagation delay difference and the second propagation delay difference, the amount of dual-frequency differential delay caused by the ionosphere is determined;

[0027] Calculate the projection factor of the ionospheric puncture point at the specular reflection point based on the signal reflection angle, Earth radius, and ionospheric puncture point height at the specular reflection point.

[0028] The first VTEC value is calculated based on the dual-frequency differential delay, the projection factor of the ionospheric puncture point, the frequency of the high-frequency signal, and the frequency of the low-frequency signal.

[0029] Optionally, the first VTEC value is calculated using the following formula:

[0030] ,

[0031] in, The first VTEC value, The frequency of the high-frequency signal. The frequency of the low-frequency signal. For the first propagation delay difference, This is the second propagation delay difference. For the Earth's radius, Height of the ionospheric puncture point. The angle of signal reflection at the point of mirror reflection.

[0032] Optionally, the method further includes:

[0033] The first VTEC value is spatially filtered to obtain the filtered first VTEC value.

[0034] Based on the two-dimensional ionospheric model and the first VTEC value, the second VTEC value below the satellite orbit at the incident puncture point and the third VTEC value below the satellite orbit at the reflection puncture point are calculated, including:

[0035] Based on the two-dimensional ionospheric model and the filtered first VTEC value, the second VTEC value below the satellite orbit at the incident puncture point and the third VTEC value below the satellite orbit at the reflection puncture point are calculated respectively.

[0036] Optionally, the spatial filtering process employs a quadratic polynomial fitting method.

[0037] Optionally, based on the two-dimensional ionospheric model and the first VTEC value, the second VTEC value below the satellite orbit at the incident puncture point and the third VTEC value below the satellite orbit at the reflection puncture point are calculated, including:

[0038] From the two-dimensional ionospheric model, obtain the ratio between the VTEC at the incident puncture point and the VTEC at the reflected puncture point;

[0039] Based on the ratio, the first VTEC value is proportionally allocated to the incident puncture point and the reflected puncture point to obtain the second VTEC value and the third VTEC value, respectively.

[0040] Optionally, the second VTEC value and the third VTEC value are calculated using the following formulas respectively:

[0041] ,

[0042] ,

[0043] in, Indicates the second VTEC value. Indicates the third VTEC value. R This represents the ratio between the VTEC at the incident puncture point and the VTEC at the reflected puncture point. This indicates the first VTEC value.

[0044] Optionally, based on the three-dimensional ionospheric model and the VTEC value below the satellite orbit at the target point, the total VTEC value covering the vertical path from the Earth's surface to the top of the ionosphere is calculated, including:

[0045] Based on the three-dimensional ionospheric model, the VTEC ratio of the upper and lower parts of the satellite orbital altitude is obtained;

[0046] The total VTEC value of the vertical path corresponding to the target point is calculated by combining the VTEC value below the satellite orbit at the target point with the VTEC ratio.

[0047] Alternatively, the total VTEC value of the vertical path can be calculated using the following formula:

[0048] ,

[0049] in, The total VTEC value for the vertical path. This represents the VTEC value below the satellite's orbit at the target point. k This represents the VTEC ratio for the upper and lower portions of the satellite's orbital altitude.

[0050] Optionally, VTEC observations from multiple navigation satellites are fused to generate wide-swath ionospheric VTEC observation data, including:

[0051] The VTEC observation results from multiple navigation satellites are assimilated or interpolated to generate the wide-swath ionospheric VTEC observation data.

[0052] Optionally, the locations of the incident puncture point and the reflected puncture point are determined by combining satellite orbital parameters, the location of the onboard GNSS-R dual-frequency receiver, and the geometric relationships of the ionospheric monolayer model.

[0053] A second aspect of this application discloses a GNSS-R wide-swath ionospheric vertical total electron content measurement device, the device comprising:

[0054] The time delay difference measurement module is used to measure the propagation time delay difference between a direct signal from the same navigation satellite and a reflected signal reflected from the ground using a spaceborne GNSS-R dual-frequency receiver. The propagation time delay difference includes a first propagation time delay difference corresponding to the high-frequency signal and a second propagation time delay difference corresponding to the low-frequency signal.

[0055] The first calculation module is used to calculate the first VTEC value below the satellite orbit at the specular reflection point based on the dual-frequency combined observation principle and the propagation time delay difference.

[0056] The second calculation module is used to calculate the second VTEC value below the satellite orbit at the incident puncture point and the third VTEC value below the satellite orbit at the reflection puncture point, respectively, based on the two-dimensional ionospheric model and the first VTEC value.

[0057] The third calculation module is used to calculate the total VTEC value covering the vertical path from the Earth's surface to the top of the ionosphere for each target point among the specular reflection point, the incident puncture point and the reflection puncture point, based on the three-dimensional ionospheric model and the VTEC value below the satellite orbit at the target point, as the VTEC observation result of a single navigation satellite.

[0058] The results fusion module is used to fuse VTEC observations from multiple navigation satellites to generate wide-swath ionospheric VTEC observation data.

[0059] A third aspect of this application discloses an electronic device, including a memory, a processor, and a computer program stored in the memory and executable on the processor. When the processor executes the computer program, it implements the steps of the GNSS-R wide-span ionospheric vertical total electron content measurement method described in the first aspect of this application.

[0060] A fourth aspect of this application discloses a readable storage medium storing a computer program thereon, which, when executed by a processor, implements the steps of the GNSS-R wide-span ionospheric vertical total electron content measurement method described in the first aspect of this application.

[0061] The embodiments of this application have the following advantages:

[0062] In this embodiment, by using a spaceborne GNSS-R dual-frequency receiver to measure the propagation delay difference between the direct signal from the same navigation satellite and the reflected signal reflected from the ground, direct observation of vast areas such as the ocean without ground observation stations is achieved, solving the problem of missing VTEC data in marine areas due to the scarcity of observation stations in related technologies.

[0063] Furthermore, based on the principle of dual-frequency combined observation, the VTEC value at the specular reflection point is calculated according to the propagation time delay difference. By utilizing the difference in ionospheric delay between the dual-frequency signals, measurement noise can be effectively suppressed, thereby improving the inversion accuracy of the single-point VTEC value.

[0064] By combining a two-dimensional ionospheric model, the VTEC values ​​of the specular reflection point are rationally allocated to the incident puncture point and the reflection puncture point. This enables the simultaneous acquisition of VTEC values ​​at three locations—the incident puncture point, the reflection puncture point, and the specular reflection point—with a single observation from a single satellite (i.e., "one satellite, three points"), thereby improving the information acquisition efficiency and spatial coverage density of single-satellite observations.

[0065] By further introducing a three-dimensional ionospheric model, the VTEC value below the satellite orbit is reconstructed into the total VTEC value covering the complete vertical path from the Earth's surface to the top of the ionosphere. This makes the observation results more consistent with the actual vertical structure of the ionosphere, providing a more reliable data foundation for high-precision navigation, remote sensing and other applications that require full-path ionospheric delay correction.

[0066] Ultimately, by fusing VTEC observations from multiple navigation satellites, the discrete point observations from a single satellite can be expanded into continuous, wide-swath ionospheric VTEC observation data products, thereby improving the spatiotemporal resolution and coverage of ionospheric monitoring.

[0067] Thus, this method enables wide-swath, high-precision VTEC ionospheric detection based on spaceborne GNSS-R technology, providing important data support for applications such as global space environment monitoring and satellite navigation enhancement. Attached Figure Description

[0068] To more clearly illustrate the technical solutions of the embodiments of this application, the drawings used in the description of the embodiments of this application will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0069] Figure 1 This is a flowchart illustrating the steps of a GNSS-R wide-span ionospheric vertical total electron content measurement method provided in this application embodiment;

[0070] Figure 2 This is a schematic diagram of a geometric model for a "one-star three-point method" GNSS-R wide-span ionospheric VTEC measurement provided in an embodiment of this application;

[0071] Figure 3 This is a schematic diagram of a local area of ​​the Pacific Ocean using GNSS-R wide-swath VTEC monorail observation data of the ionosphere, provided in an embodiment of this application.

[0072] Figure 4 This is a schematic diagram of the structure of a GNSS-R wide-span ionospheric vertical total electron content measurement device provided in an embodiment of this application;

[0073] Figure 5This is a schematic diagram of the structure of an electronic device provided in an embodiment of this application. Detailed Implementation

[0074] To make the above-mentioned objectives, features, and advantages of this application more apparent and understandable, the technical solutions in the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, not all embodiments. Based on the embodiments in this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0075] Reference Figure 1 As shown, Figure 1 This is a flowchart illustrating the steps of a GNSS-R wide-swath ionospheric vertical total electron content measurement method provided in an embodiment of this application. Figure 1 As shown in the embodiments of this application, a method for measuring the vertical total electron content of the ionosphere using a wide-span GNSS-R swathe array may include steps S110 to S150:

[0076] Step S110: Measure the propagation delay difference between the direct signal from the same navigation satellite and the reflected signal reflected from the ground using a spaceborne GNSS-R dual-frequency receiver. The propagation delay difference includes a first propagation delay difference corresponding to the high-frequency signal and a second propagation delay difference corresponding to the low-frequency signal.

[0077] Direct signals refer to signals directly emitted by navigation satellites (without ground reflection), including high-frequency and low-frequency direct signals. Reflected signals refer to signals obtained after direct signals are reflected off the ground, including high-frequency and low-frequency reflected signals. Navigation satellites can be China's BeiDou Navigation Satellite System, the US GPS (Global Positioning System) navigation satellites, Europe's Galileo navigation satellites, etc.

[0078] The propagation delay difference refers to the additional time delay that a reflected signal experiences relative to a direct signal on its propagation path. It includes information such as the geometric path difference caused by the longer reflection path and the ionospheric delay difference caused by the different regions the reflection path traverses in the ionosphere.

[0079] Specifically, by using a satellite-borne GNSS-R dual-frequency receiver (e.g., an interferometric receiver or a local code correlation receiver) mounted on a satellite platform, the direct signal transmitted by the same navigation satellite and the reflected signal after the signal is reflected by the ground are simultaneously acquired. The propagation delay difference between the reflected signal and the direct signal at two different operating frequencies (high frequency and low frequency), namely the first propagation delay difference and the second propagation delay difference, are measured to obtain raw observation data reflecting the differences in signal propagation paths (especially the differences in ionospheric delay).

[0080] Step S120: Based on the dual-frequency combined observation principle, calculate the first vertical total electron content (VTEC) value below the satellite orbit at the specular reflection point according to the propagation time delay difference.

[0081] Specifically, the propagation delay difference obtained in step S110 is processed using the principle of dual-frequency combined observation (ionospheric dispersion effect, i.e., the characteristic that the ionospheric delay of dual-frequency signals is inversely proportional to the square of the frequency). By combining the geometric information of signal propagation, the total vertical electron content of the ionosphere above the specular reflection point (i.e., the position where the signal is reflected from the ground) and below the satellite orbit is calculated, which is the first VTEC value below the satellite orbit at the specular reflection point. This step completes the first conversion from raw observation data to key physical quantities of the ionosphere, eliminating the influence of the satellite elevation angle and directly obtaining the electron content in the vertical direction.

[0082] Step S130: Based on the two-dimensional ionospheric model and the first VTEC value, calculate the second VTEC value below the satellite orbit at the incident puncture point and the third VTEC value below the satellite orbit at the reflection puncture point.

[0083] The two-dimensional ionospheric model is used to describe the two-dimensional prior information of the horizontal distribution of electron content in the ionosphere. In an optional embodiment, the two-dimensional ionospheric model is a global ionospheric map model.

[0084] The incident puncture point is the intersection of the direct signal path and the thin ionospheric layer, i.e., the point where the direct signal penetrates the ionosphere; the reflection puncture point is the intersection of the reflected signal path and the thin ionospheric layer, i.e., the point where the reflected signal exits the ionosphere. Specifically, the locations of the incident puncture point and the reflection puncture point are determined by combining the satellite orbital parameters, the location of the onboard GNSS-R dual-frequency receiver, and the geometric relationships of the ionospheric single-layer model.

[0085] This step utilizes a two-dimensional ionospheric model, combined with the first VTEC value obtained from step S120, to infer and allocate the VTEC values ​​(second and third VTEC values) at two additional key locations along the signal propagation path: the incident puncture point and the reflection puncture point, below the satellite orbit. This step expands the single-point observation information to three related spatial points (i.e., one satellite, three points), thereby increasing the density of observational information.

[0086] For example, the "one star, three points" geometric model is as follows: Figure 2 As shown, Figure 2 This is a schematic diagram of a geometric model for "one-star three-point method" GNSS-R wide-span ionospheric VTEC measurement provided in an embodiment of this application. Specifically, in Figure 2 The diagram illustrates the spatial location of each puncture point (target point) and its corresponding VTEC measurement area below the track.

[0087] Step S140: For each target point among the specular reflection point, the incident puncture point, and the reflection puncture point, calculate the total VTEC value covering the vertical path from the Earth's surface to the top of the ionosphere based on the three-dimensional ionospheric model and the VTEC value below the satellite orbit at the target point, and use this as the VTEC observation result of a single navigation satellite.

[0088] The three-dimensional ionospheric model is used to describe the three-dimensional prior information of the vertical distribution of electron density in the ionosphere. This model can describe the variation of electron density with height. In an optional embodiment, the three-dimensional ionospheric model is the NeQuick model.

[0089] Specifically, for the three target points (specular reflection point, incident puncture point, and reflected puncture point) obtained in step S130, three-dimensional ionospheric models describing the vertical distribution of ionospheric electron density are introduced. Using the vertical structure information provided by these models, the VTEC values ​​at each target point, representing only the portion below the satellite orbit, are corrected and synthesized into a total VTEC value covering the entire vertical path from the Earth's surface to the top of the ionosphere. Thus, a single observation from a single navigation satellite can provide complete vertical total ionospheric electron content for three spatial locations, forming a set of discrete but complete VTEC observation results from a single navigation satellite.

[0090] Step S150: Integrate VTEC observation results from multiple navigation satellites to generate wide-swath ionospheric VTEC observation data.

[0091] Specifically, a spaceborne GNSS-R dual-frequency receiver can typically track multiple navigation satellites simultaneously (e.g., N). Each navigation satellite can provide the total VTEC value of the complete vertical path at three target points (specular reflection point, incident puncture point, and reflection puncture point) through steps S110 to S140. Therefore, a single pass of a spaceborne GNSS-R dual-frequency receiver can obtain 3N (N being the number of navigation satellites) discrete VTEC observations. These observation points, projected onto the ground, form an observation band (strip) thousands of kilometers wide, which can be referenced... Figure 3 As shown, Figure 3 This is a schematic diagram of a local area of ​​the Pacific Ocean using GNSS-R wide-swath VTEC single-track observation data provided in this application embodiment. By performing data fusion processing on the VTEC observation results of multiple navigation satellites acquired by a single spaceborne GNSS-R dual-frequency receiver, a spatially continuous ionospheric VTEC distribution map or data product (i.e., wide-swath ionospheric VTEC observation data) covering the wide-swath area can be generated.

[0092] The technical solution of this application utilizes a spaceborne GNSS-R dual-frequency receiver to measure the propagation delay difference between the direct signal from the same navigation satellite and the reflected signal reflected from the ground. This enables direct observation of vast areas, such as oceans, where there are no ground observation stations, solving the problem of missing VTEC data in ocean areas due to the scarcity of observation stations in related technologies. Furthermore, based on the principle of dual-frequency combined observation, the VTEC value at the specular reflection point is calculated according to the propagation delay difference. By utilizing the difference in ionospheric delay between the two-frequency signals, measurement noise can be effectively suppressed, thereby improving the inversion accuracy of the single-point VTEC value. By combining a two-dimensional ionospheric model to rationally allocate the VTEC value of the specular reflection point to the incident puncture point and the reflection puncture point, the VTEC values ​​at three locations—the incident puncture point, the reflection puncture point, and the specular reflection point—can be simultaneously acquired in a single observation using a single satellite (i.e., "one satellite, three points"), improving the information acquisition efficiency and spatial coverage density of single-satellite observations. Furthermore, a three-dimensional ionospheric model is introduced to reconstruct the VTEC values ​​below the satellite orbit into total VTEC values ​​covering the entire vertical path from the Earth's surface to the top of the ionosphere. This makes the observation results more consistent with the actual vertical structure of the ionosphere, providing a more reliable data foundation for high-precision navigation, remote sensing, and other applications requiring full-path ionospheric delay correction. Finally, by fusing VTEC observations from multiple navigation satellites, discrete point observations from a single satellite can be expanded into continuous, wide-swath ionospheric VTEC observation data products, improving the spatiotemporal resolution and coverage of ionospheric monitoring. Thus, this method achieves wide-swath, high-precision ionospheric VTEC detection based on spaceborne GNSS-R technology, providing crucial data support for global space environment monitoring, satellite navigation enhancement, and other applications.

[0093] The GNSS-R wide-span ionospheric vertical total electron content measurement method implemented in this application will be described in detail in sections 1.1, 1.2, 1.3, 1.4, and 1.5 respectively.

[0094] 1.1 Obtaining the propagation delay difference:

[0095] In an optional implementation, step S110 above, "measuring the propagation delay difference between the direct signal from the same navigation satellite and the reflected signal reflected from the ground using a spaceborne GNSS-R dual-frequency receiver," may include steps S110-1 to S110-2:

[0096] Step S110-1: Receive direct signals from the same navigation satellite and reflected signals reflected from the ground using the onboard GNSS-R dual-frequency receiver. The direct signals include high-frequency direct signals and low-frequency direct signals, and the reflected signals include high-frequency reflected signals and low-frequency reflected signals.

[0097] The spaceborne GNSS-R dual-frequency receiver is mounted on space platforms such as low Earth orbit (LEO) satellites. Its antenna system typically includes an antenna pointing towards the zenith to receive direct signals from navigation satellites (such as GPS, BeiDou, and Galileo systems), and an antenna pointing towards the ground to receive reflected signals from the ground (specular reflection point). By simultaneously receiving direct signals from the same navigation satellite and reflected signals from the ground, the spaceborne GNSS-R dual-frequency receiver ensures signal source consistency in subsequent processing.

[0098] Step S110-2: Based on the direct signal and the reflected signal, extract the first propagation delay difference corresponding to the high-frequency signal and the second propagation delay difference corresponding to the low-frequency signal, respectively.

[0099] Specifically, depending on the type of spaceborne GNSS-R dual-frequency receiver, different delay difference extraction methods can be used to extract the first propagation delay difference corresponding to the high-frequency signal and the second propagation delay difference corresponding to the low-frequency signal. For example, for an interferometric receiver, the direct signal and the reflected signal are interfered with to directly form an interference waveform, which can be directly obtained from the interference waveform; for a local code correlation receiver, the propagation delays of the direct signal and the reflected signal need to be measured separately and then subtracted to obtain the delay difference.

[0100] In an optional implementation, when the spaceborne GNSS-R dual-frequency receiver is an interferometric receiver, the step S110-2 above, "extracting the first propagation delay difference corresponding to the high-frequency signal and the second propagation delay difference corresponding to the low-frequency signal based on the direct signal and the reflected signal respectively," may include steps A1 and A2:

[0101] Step A1: Based on the high-frequency direct signal and the high-frequency reflected signal, obtain the first interference waveform corresponding to the high-frequency signal, and extract the first propagation delay difference from the first interference waveform.

[0102] Step A2: Based on the low-frequency direct signal and the low-frequency reflected signal, obtain the second interference waveform corresponding to the low-frequency signal, and extract the second propagation delay difference from the second interference waveform.

[0103] Specifically, step A1 targets high frequencies (such as...) The signal is processed in a frequency band. The interferometric receiver coherently mixes and processes the received high-frequency direct signal and high-frequency reflected signal (for example, after preprocessing the high-frequency direct signal and high-frequency reflected signal by down-conversion, filtering, and delay, the direct and reflected baseband signals are directly correlated and integrated to generate a first interference waveform. The first interference waveform is a function of time delay (or equivalent path difference), and its amplitude (or power) characterizes the coherence of the two signals under different relative time delays. The leading edge of the first interference waveform can be calculated by interferometric waveform matching to obtain the position of the specular reflection point, which directly corresponds to the total propagation time delay difference of the high-frequency reflected signal relative to the high-frequency direct signal. By detecting the time delay coordinates corresponding to the specular reflection point of the first interference waveform, the first propagation time delay difference can be directly and accurately read and extracted. This method does not require independent code tracking loop locking for the direct and reflected signals, simplifying the processing flow. At the same time, it can also utilize non-public high-bandwidth ranging codes in the signal to achieve high-precision time delay difference measurement.

[0104] Step A2 targets low frequencies (such as...) The signal (in the specified frequency band) is processed in the same way as in step A1. The interferometric receiver coherently mixes and processes the low-frequency direct signal and the low-frequency reflected signal to generate a second interference waveform. Similarly, by detecting the position of the specular reflection point of the second interference waveform, the total propagation delay of the low-frequency reflected signal relative to the low-frequency direct signal, i.e., the second propagation delay difference, can be determined.

[0105] Thus, this implementation utilizes the characteristics of an interferometric receiver to directly obtain the propagation delay difference by generating and analyzing the interference waveform. This method has the advantages of direct processing, relatively simple structure, and high measurement accuracy. Furthermore, since the interferometric processing itself has a certain ability to suppress common errors of the two-frequency signals, it helps to obtain a high-quality propagation delay difference, laying a reliable data foundation for subsequent high-precision VTEC inversion.

[0106] In an optional implementation, when the spaceborne GNSS-R dual-frequency receiver is a local code correlated receiver, the step S110-2 above, "extracting the first propagation delay difference corresponding to the high-frequency signal and the second propagation delay difference corresponding to the low-frequency signal based on the direct signal and the reflected signal respectively," may include steps B1 and B2:

[0107] Step B1: Measure the first propagation delay of the high-frequency direct signal and the second propagation delay of the high-frequency reflected signal respectively, and calculate the difference between the first propagation delay and the second propagation delay to obtain the first propagation delay difference.

[0108] Step B2: Measure the third propagation delay of the low-frequency direct signal and the fourth propagation delay of the low-frequency reflected signal respectively, and calculate the difference between the third propagation delay and the fourth propagation delay to obtain the second propagation delay difference.

[0109] The local code correlation receiver contains independent signal channels for processing direct and reflected signals. For high-frequency signals, in the direct channel, the local code correlation receiver generates a local copy code and performs correlation calculations with the received high-frequency direct signal. By adjusting the phase of the local code, the correlation peak is maximized, thereby accurately locking and measuring the direct path propagation time from the navigation satellite to the receiver, i.e., the first propagation delay. In the reflection channel, the local code correlation receiver performs open-loop tracking of the high-frequency reflected signal, outputting a local code correlation power waveform. After local code correlation waveform matching calculations, the position of the specular reflection point at the leading edge of the waveform can be obtained, and the total propagation time of the reflection path from the navigation satellite, after reflection on the ground, to the receiver can be measured, i.e., the second propagation delay. Since the high-frequency direct signal and the high-frequency reflected signal originate from the same transmission time, the difference between the first and second propagation delays is the difference in the first propagation delay caused only by factors such as the additional geometric path of the reflection path and differential ionospheric delay.

[0110] Similarly, for low-frequency signals, in the corresponding direct and reflected channels, the local code correlation receiver performs open-loop tracking of the low-frequency direct signal and the low-frequency reflected signal respectively, accurately measuring their respective absolute propagation times, which are denoted as the third propagation delay and the fourth propagation delay, respectively. The second propagation delay difference is then obtained from the third propagation delay and the fourth propagation delay.

[0111] Thus, this implementation method obtains the absolute propagation delays of both direct and reflected signals, providing more comprehensive data. By calculating the time delay difference, common-mode errors such as satellite clock bias and receiver clock bias can be effectively offset, and observations mainly composed of path geometric differences and ionospheric differential delays can be extracted, thereby achieving high-precision time delay difference measurement.

[0112] In an optional implementation, in addition to the steps described above, the method may further include: performing receiver hardware delay correction processing on the propagation delay difference to obtain a corrected propagation delay difference.

[0113] Receiver hardware delay refers to the fixed signal delay introduced by the receiver's (spaceborne GNSS-R dual-frequency receiver) own RF front-end, filters, cables, and other hardware components in the signal reception and processing link. The hardware delay difference between the receiver and high-frequency signals can be accurately measured in advance through ground calibration or on-orbit calibration. This difference is then subtracted from the propagation delay (first propagation delay difference and second propagation delay difference) to obtain an observed value that reflects only the actual time delay difference during signal propagation in space; this is the corrected propagation delay difference.

[0114] Furthermore, the step S120 above, "calculating the first VTEC value below the satellite orbit at the specular reflection point based on the dual-frequency combined observation principle and the propagation delay difference", specifically includes: calculating the first VTEC value below the satellite orbit at the specular reflection point based on the corrected propagation delay difference, according to the dual-frequency combined observation principle.

[0115] Thus, this implementation method can effectively separate and eliminate the systematic errors of the equipment itself and suppress the random noise of the observation, thereby improving the calculation accuracy and stability of the first VTEC value from the data source and ensuring the accuracy and reliability of the final VTEC inversion result.

[0116] 1.2 Calculate the VTEC value at the reflecting mirror surface point:

[0117] In an optional implementation, step S120 above, "calculating the first VTEC value below the satellite orbit at the specular reflection point based on the dual-frequency combined observation principle and the propagation time delay difference," may include steps S120-1 to S120-3:

[0118] Step S120-1: Based on the difference between the first propagation delay difference and the second propagation delay difference, determine the amount of dual-frequency differential delay caused by the ionosphere.

[0119] This step is the core operation applying the dual-frequency combined observation principle. The ionosphere has different effects on the propagation delay of signals at different frequencies, and the delay is inversely proportional to the square of the signal frequency. The measured first propagation delay difference (corresponding to high frequency) and second propagation delay difference (corresponding to low frequency) include both the common geometric path difference and the ionospheric delay difference caused by the different frequencies. The first propagation delay difference is calculated... Difference between the second propagation time delay The difference can accurately eliminate common errors such as shared geometric path delay and receiver clock bias. This difference reflects the differential delay caused by the ionosphere on high-frequency and low-frequency signals, that is, the amount of dual-frequency differential delay caused by the ionosphere. .

[0120] Step S120-2: Calculate the projection factor of the ionospheric puncture point at the specular reflection point based on the signal reflection angle, Earth radius, and ionospheric puncture point height at the specular reflection point.

[0121] This step establishes the geometric transformation relationship between oblique path observations and vertical parameters. The signal propagation path from the navigation satellite to the ground reflection point is oblique through the ionosphere. To obtain the total electron content (VTEC) in the vertical direction, the observation effects along the oblique path need to be projected and transformed.

[0122] Specifically, the electron content of the entire ionosphere is approximately concentrated at an average height (i.e., the height of the ionospheric puncture point). On the spherical shell, combined with the known Earth's radius and the signal reflection angle at the mirror reflection point The projection factor of the ionospheric puncture point at the specular reflection point was calculated using spherical geometry. ), used to convert the estimated electron content on the slant path into an equivalent value in the zenith direction, is a geometric correction parameter for obtaining the total vertical VTEC.

[0123] Step S120-3: Calculate the first VTEC value based on the dual-frequency differential delay, the projection factor of the ionospheric puncture point, the frequency of the high-frequency signal, and the frequency of the low-frequency signal.

[0124] Specifically, the dual-frequency differential delay obtained in step S120-1, the ionospheric puncture point projection factor calculated in step S120-2, and the known high-frequency and low-frequency signal frequencies are substituted into the inversion formula derived from physical principles to calculate the first VTEC value.

[0125] Optionally, the first VTEC value is calculated using the following formula:

[0126] (Formula 1)

[0127] in, The first VTEC value, The frequency of the high-frequency signal. The frequency of the low-frequency signal. For the first propagation delay difference, This is the second propagation delay difference. It is the Earth's radius (approximately 6371 km). The height of the ionospheric puncture point (usually taken as 450–507 km). This represents the signal reflection angle at the specular reflection point. The constant 40.28 in the formula is related to the theoretical expression for the ionospheric refractive index.

[0128] Thus, this implementation method achieves the detailed process of inverting the vertical electron content from the original dual-frequency time delay difference observations. Step S120-1 effectively extracts the ionospheric signal through dual-frequency differential analysis; step S120-2 achieves accurate conversion from the oblique path to the vertical path using a precise geometric model; and step S120-3 integrates all information to complete the quantitative calculation. This process ensures the scientific validity and accuracy of the first VTEC value inversion.

[0129] In an optional implementation, in addition to the steps described above, the method may further include: performing spatial filtering on the first VTEC value to obtain a filtered first VTEC value.

[0130] This step performs spatial filtering on the series of first VTEC values ​​(distributed along the satellite trajectory) calculated in step S120. Specifically, by performing statistical analysis or fitting on a series of VTEC values ​​within a certain spatial window, a more robust and smoother VTEC value at the center of the window is estimated, thereby effectively suppressing random noise and high-frequency spatial fluctuations and highlighting the large-scale spatial variation trend of ionospheric electron content. The data obtained after filtering is called the filtered first VTEC value, whose signal-to-noise ratio and spatial consistency are improved.

[0131] Optionally, the spatial filtering process employs a quadratic polynomial fitting method.

[0132] The process of spatial filtering using a quadratic polynomial fitting method is as follows: For each point to be filtered on the satellite trajectory, all first VTEC values ​​within a given filtering scale (e.g., 250 km) centered on that point are selected as a data window. Within this window, a quadratic polynomial function (i.e., ...) is used... The least-squares fit is performed on the discrete first VTEC values ​​(where x is the spatial coordinate, y is the first VTEC value, and a, b, and c are fitting coefficients). The resulting smooth curve represents the spatial variation trend of VTEC in the region. Finally, the value calculated by the fitting polynomial corresponding to the location of the point to be filtered is taken as the filtered first VTEC value for that point. This method can effectively smooth noise while preserving the spatial curvature characteristics of the data.

[0133] Furthermore, in step S130 above, "calculating the second VTEC value below the satellite orbit at the incident puncture point and the third VTEC value below the satellite orbit at the reflection puncture point based on the two-dimensional ionospheric model and the first VTEC value" specifically includes: calculating the second VTEC value below the satellite orbit at the incident puncture point and the third VTEC value below the satellite orbit at the reflection puncture point based on the two-dimensional ionospheric model and the filtered first VTEC value.

[0134] Thus, this implementation improves the quality of the original inversion data by spatially filtering the first VTEC value. The filtering process removes unreliable high-frequency fluctuations, making the reference values ​​used for subsequent scaling and expansion smoother and more reliable. This enhances the spatial continuity and physical plausibility of the final second and third VTEC values, reduces the risk of single-point observation noise being amplified through model allocation, and thereby improves the overall accuracy and usability of the "one satellite, three points" VTEC observation results.

[0135] 1.3 Calculate the VTEC values ​​at the incident puncture point and the reflected puncture point:

[0136] In an optional implementation, step S130 above, "calculating the second VTEC value below the satellite orbit at the incident puncture point and the third VTEC value below the satellite orbit at the reflection puncture point based on the two-dimensional ionospheric model and the first VTEC value," may include steps S130-1 to S130-2:

[0137] Step S130-1: Obtain the ratio between the VTEC at the incident puncture point and the VTEC at the reflected puncture point from the two-dimensional ionosphere model.

[0138] Two-dimensional ionospheric models (such as global ionospheric maps) can provide information on the distribution of VTECs in the ionosphere on a horizontal plane over a global scale. The large-scale horizontal gradients and relative spatial distribution characteristics of the ionosphere captured by these models are generally highly reliable. This step uses the two-dimensional ionospheric model as a scale reference source to determine the ratio between the VTECs at the incident puncture point and the VTECs at the reflected puncture point.

[0139] Specifically, based on satellite orbital parameters, the location of the onboard GNSS-R dual-frequency receiver, and the geometric relationships of the ionospheric monolayer model, the locations of the incident puncture point (the intersection of the direct signal path and the thin ionospheric layer) and the reflected puncture point (the intersection of the reflected signal path and the thin ionospheric layer) are determined. Then, based on the two-dimensional ionospheric model, the model VTEC values ​​at these two puncture point locations are interpolated or read. Finally, the ratio of the two model VTEC values ​​is calculated. R This ratio RThe relative strength of the VTEC in the ionosphere between the incident and reflection points was quantitatively described at the observation time and region.

[0140] Step S130-2: Based on the ratio, the first VTEC value is proportionally allocated to the incident puncture point and the reflection puncture point to obtain the second VTEC value and the third VTEC value respectively.

[0141] The first VTEC value is the sum of electron content along the path below the satellite orbit at the specular reflection point, approximately equal to half the sum of the VTEC values ​​along the corresponding paths at the incident and reflection puncture points. Therefore, based on the relative proportion defined by the ratio R and the constraint that the sum is the first VTEC, the first VTEC is allocated to the incident and reflection puncture points to obtain the second VTEC value below the satellite orbit at the incident puncture point and the third VTEC value below the satellite orbit at the reflection puncture point.

[0142] Optionally, the second VTEC value and the third VTEC value are calculated using the following formulas respectively:

[0143] (Formula 2)

[0144] (Formula 3)

[0145] in, Indicates the second VTEC value. Indicates the third VTEC value. R This represents the ratio between the VTEC at the incident puncture point and the VTEC at the reflected puncture point. This represents the first VTEC value. In other words, using formulas 2 and 3 above, the first VTEC value can be proportionally allocated to the incident puncture point and the reflected puncture point.

[0146] Thus, this implementation method, by combining a two-dimensional ionospheric model, rationally allocates the VTEC values ​​of the specular reflection point to the incident puncture point and the reflection puncture point, enabling the simultaneous acquisition of VTEC values ​​at three locations—the incident puncture point, the reflection puncture point, and the specular reflection point—with a single observation from a single satellite (i.e., "one satellite, three points"), significantly improving the spatial coverage density and efficiency of single-satellite observations. When the onboard GNSS-R dual-frequency receiver simultaneously tracks N navigation satellites, it can measure the VTEC values ​​below 3N orbits, forming an observation swath thousands of kilometers wide, providing ionospheric correction data for payloads on the same platform.

[0147] 1.4 Calculate the total VTEC value for the vertical path:

[0148] In an optional implementation, step S140 above, "calculating the total VTEC value covering the vertical path from the Earth's surface to the top of the ionosphere based on the three-dimensional ionospheric model and the VTEC value below the satellite orbit at the target point," may include sub-steps S140-1 to S140-2:

[0149] Step S140-1: Based on the three-dimensional ionospheric model, obtain the VTEC ratio of the upper and lower parts of the satellite orbital altitude.

[0150] Among them, three-dimensional ionospheric models (such as the NeQuick model) can describe the three-dimensional variation of electron density with geographical location, time, and altitude.

[0151] Specifically, the geographic coordinates of the target point (specular reflection point, incident puncture point, or reflection puncture point), the current time, and the known satellite orbital altitude are used as input conditions to invoke the three-dimensional ionospheric model; thereby, based on the ionospheric physics and empirical parameters built into the three-dimensional ionospheric model, the electron content along the vertical path from the Earth's surface to the satellite orbital altitude at that target point and time is calculated, i.e., the VTEC content below the orbital altitude. Simultaneously, the electron content along the vertical path from the satellite's orbital altitude to the top of the ionosphere was calculated, i.e., the VTEC content above the orbital altitude. Finally, by calculating the ratio of the two VTEC components mentioned above... k (Right now, The VTEC ratio describes the proportion of the total ionospheric electron content above the satellite observation path to the portion below the path at the target point.

[0152] Step S140-2: Combine the VTEC value below the satellite orbit at the target point with the VTEC ratio to calculate the total VTEC value of the vertical path corresponding to the target point.

[0153] This step uses the VTEC ratio obtained in the previous step to vertically extend the actual observations. For each target point, the VTEC value below the satellite orbit at that point (i.e., ...) is obtained through the aforementioned steps. This can be the first VTEC value, the second VTEC value, or the third VTEC value. According to the definition of the VTEC ratio ( From the VTEC value below the satellite orbit, the VTEC value above the satellite orbit can be determined, further determining the total VTEC value of the vertical path. This total VTEC value of the vertical path is the sum of the VTEC values ​​below and above the satellite orbit (i.e., ).

[0154] Alternatively, the total VTEC value of the vertical path can be calculated using the following formula:

[0155] (Formula 4)

[0156] in, The total VTEC value for the vertical path. This represents the VTEC value below the satellite's orbit at the target point. k This represents the VTEC ratio for the upper and lower portions of the satellite's orbital altitude.

[0157] Thus, by incorporating vertical structure information (VTEC ratio) provided by a three-dimensional ionospheric model, this implementation can cover the total VTEC value along the vertical path from the Earth's surface to the top of the ionosphere. This ensures that the final output VTEC observation results contain complete information across the entire vertical range of the ionosphere, enhancing the practical value and physical consistency of the observation data for applications requiring full-path ionospheric delay correction (such as precise point positioning, synthetic aperture radar atmospheric correction, etc.).

[0158] 1.5 Fusion Observation Results:

[0159] In an optional implementation, step S150 above, "fusing VTEC observation results from multiple navigation satellites to generate wide-swath ionospheric VTEC observation data", specifically includes: performing data assimilation or interpolation processing on the VTEC observation results from multiple navigation satellites to generate the wide-swath ionospheric VTEC observation data.

[0160] Each navigation satellite's VTEC observation results contain three discrete VTEC observations. In order to generate a spatially continuous, intuitive, and easy-to-use ionospheric state map (i.e., wide-swath ionospheric VTEC observation data), these discrete observations need to be spatially reconstructed.

[0161] Specifically, one approach involves data assimilation of VTEC observations from multiple navigation satellites. This involves inputting the VTEC observations from multiple navigation satellites (multiple discrete VTEC observations) as actual observations into the assimilation system. The system then fuses these observations with the predicted field from the background ionospheric model, ultimately outputting an updated, spatially continuous, and physically consistent two-dimensional VTEC analysis field—i.e., wide-swath ionospheric VTEC observation data. This method not only generates a continuous distribution but also effectively utilizes observational information to improve the model, enhancing the reconstruction accuracy of the entire region.

[0162] One approach involves interpolating VTEC observations from multiple navigation satellites, using all puncture point locations (latitude and longitude) and their corresponding total VTEC values ​​as a known dataset. A suitable spatial interpolation algorithm (such as spherical interpolation or two-dimensional interpolation that considers the spatial variations of the ionosphere) is selected to estimate VTEC values ​​at regular grid points (e.g., 1 degree × 1 degree) within the target area (i.e., the area covered by the observation swath). Finally, a two-dimensional VTEC distribution map (i.e., wide-swath ionospheric VTEC observation data) is generated, composed of regular grid point values.

[0163] In this way, sparse puncture point observations can be synthesized into a continuous image or data grid that can fully reflect the spatial variation characteristics of the ionosphere within the observation swath. The final VTEC observation data spatially covers a strip-shaped area hundreds to thousands of kilometers wide below the satellite when it passes over, truly realizing wide swath observation.

[0164] This application also provides a GNSS-R wide-span ionospheric vertical total electron content measurement device, referring to... Figure 4 As shown, Figure 4 This is a schematic diagram of a GNSS-R wide-span ionospheric vertical total electron content measurement device provided in an embodiment of this application. The device includes:

[0165] The time delay difference measurement module 410 is used to measure the propagation time delay difference between a direct signal from the same navigation satellite and a reflected signal reflected from the ground via a spaceborne GNSS-R dual-frequency receiver. The propagation time delay difference includes a first propagation time delay difference corresponding to the high-frequency signal and a second propagation time delay difference corresponding to the low-frequency signal.

[0166] The first calculation module 420 is used to calculate the first VTEC value below the satellite orbit at the specular reflection point based on the dual-frequency combined observation principle and the propagation time delay difference.

[0167] The second calculation module 430 is used to calculate the second VTEC value below the satellite orbit at the incident puncture point and the third VTEC value below the satellite orbit at the reflection puncture point, respectively, based on the two-dimensional ionospheric model and the first VTEC value.

[0168] The third calculation module 440 is used to calculate the total VTEC value covering the vertical path from the Earth's surface to the top of the ionosphere for each target point among the specular reflection point, the incident puncture point and the reflection puncture point, based on the three-dimensional ionospheric model and the VTEC value below the satellite orbit at the target point, as the VTEC observation result of a single navigation satellite.

[0169] The result fusion module 450 is used to fuse VTEC observation results from multiple navigation satellites to generate wide-swath ionospheric VTEC observation data.

[0170] In one optional implementation, the time delay difference measurement module includes:

[0171] The receiving module is used to receive direct signals from the same navigation satellite and reflected signals reflected from the ground via the onboard GNSS-R dual-frequency receiver, wherein the direct signals include high-frequency direct signals and low-frequency direct signals, and the reflected signals include high-frequency reflected signals and low-frequency reflected signals;

[0172] The extraction module is used to extract the first propagation delay difference corresponding to the high-frequency signal and the second propagation delay difference corresponding to the low-frequency signal based on the direct signal and the reflected signal, respectively.

[0173] In an optional implementation, when the spaceborne GNSS-R dual-frequency receiver is an interferometric receiver, the extraction module is specifically used for:

[0174] Based on the high-frequency direct signal and the high-frequency reflected signal, obtain the first interference waveform corresponding to the high-frequency signal, and extract the first propagation delay difference from the first interference waveform;

[0175] Based on the low-frequency direct signal and the low-frequency reflected signal, a second interference waveform corresponding to the low-frequency signal is obtained, and the second propagation delay difference is extracted from the second interference waveform.

[0176] In an optional implementation, when the spaceborne GNSS-R dual-frequency receiver is a local code correlated receiver, the extraction module is specifically used for:

[0177] The first propagation delay of the high-frequency direct signal and the second propagation delay of the high-frequency reflected signal are measured respectively, and the difference between the first propagation delay and the second propagation delay is obtained to obtain the first propagation delay difference;

[0178] The third propagation delay of the low-frequency direct signal and the fourth propagation delay of the low-frequency reflected signal are measured respectively, and the difference between the third propagation delay and the fourth propagation delay is obtained to obtain the second propagation delay difference.

[0179] In one alternative embodiment, the device further includes:

[0180] The correction module is used to perform receiver hardware delay correction on the propagation delay difference to obtain the corrected propagation delay difference;

[0181] The first calculation module is also used to calculate the first VTEC value below the satellite orbit at the specular reflection point based on the dual-frequency combined observation principle and the corrected propagation delay difference.

[0182] In one optional implementation, the first computing module is specifically used for:

[0183] Based on the difference between the first propagation delay difference and the second propagation delay difference, the amount of dual-frequency differential delay caused by the ionosphere is determined;

[0184] Calculate the projection factor of the ionospheric puncture point at the specular reflection point based on the signal reflection angle, Earth radius, and ionospheric puncture point height at the specular reflection point.

[0185] The first VTEC value is calculated based on the dual-frequency differential delay, the projection factor of the ionospheric puncture point, the frequency of the high-frequency signal, and the frequency of the low-frequency signal.

[0186] In one alternative embodiment, the device further includes:

[0187] The filtering module is used to perform spatial filtering on the first VTEC value to obtain the filtered first VTEC value.

[0188] The second calculation module is further configured to calculate, based on the two-dimensional ionospheric model and the filtered first VTEC value, the second VTEC value below the satellite orbit at the incident puncture point and the third VTEC value below the satellite orbit at the reflection puncture point.

[0189] In one alternative implementation, the spatial filtering process employs a quadratic polynomial fitting method.

[0190] In one optional implementation, the second computing module is specifically used for:

[0191] From the two-dimensional ionospheric model, obtain the ratio between the VTEC at the incident puncture point and the VTEC at the reflected puncture point;

[0192] Based on the ratio, the first VTEC value is proportionally allocated to the incident puncture point and the reflected puncture point to obtain the second VTEC value and the third VTEC value, respectively.

[0193] In one optional implementation, the third computing module is specifically used for:

[0194] Based on the three-dimensional ionospheric model, the VTEC ratio of the upper and lower parts of the satellite orbital altitude is obtained;

[0195] The total VTEC value of the vertical path corresponding to the target point is calculated by combining the VTEC value below the satellite orbit at the target point with the VTEC ratio.

[0196] In one optional implementation, the result fusion module is specifically used to: perform data assimilation or interpolation processing on the VTEC observation results of multiple navigation satellites to generate the wide-swath ionospheric VTEC observation data.

[0197] In one alternative implementation, the locations of the incident puncture point and the reflected puncture point are determined by combining satellite orbital parameters, the location of the onboard GNSS-R dual-frequency receiver, and the geometric relationships of the ionospheric monolayer model.

[0198] This application also provides an electronic device, see embodiments thereof. Figure 5 , Figure 5 This is a schematic diagram of the structure of an electronic device provided in an embodiment of this application. Figure 5 As shown, the electronic device 500 includes a memory 510 and a processor 520. The memory 510 and the processor 520 are connected via a bus for communication. The memory 510 stores a computer program that can run on the processor 520 to implement the steps of the GNSS-R wide-span ionospheric vertical total electron content measurement method described in this application embodiment.

[0199] This application also provides a computer-readable storage medium storing a computer program thereon, which, when executed by a processor, implements the steps of the GNSS-R wide-span ionospheric vertical total electron content measurement method described in this application.

[0200] The various embodiments in this specification are described in a progressive manner, with each embodiment focusing on the differences from other embodiments. The same or similar parts between the various embodiments can be referred to each other.

[0201] This application describes embodiments of methods and apparatus according to flowchart illustrations and / or block diagrams. It should be understood that each block of the flowchart illustrations and / or block diagrams, and combinations of blocks in the flowchart illustrations and / or block diagrams, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, special-purpose computer, embedded processor, or other programmable data processing terminal device to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing terminal device, generate instructions for implementing the flowchart illustrations and / or block diagrams. Figure 1 One or more processes and / or boxes Figure 1 A device that provides the functions specified in one or more boxes.

[0202] Although preferred embodiments of the present application have been described, those skilled in the art, upon learning the basic inventive concept, can make other changes and modifications to these embodiments. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments as well as all changes and modifications falling within the scope of the embodiments of the present application.

[0203] Finally, it should be noted that in this document, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or terminal device that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or terminal device. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or terminal device that includes said element.

[0204] The foregoing has provided a detailed description of a GNSS-R wide-span ionospheric vertical total electron content measurement method, apparatus, equipment, and medium. Specific examples have been used to illustrate the principles and implementation methods of this application. The descriptions of the above embodiments are only for the purpose of helping to understand the method and core ideas of this application. At the same time, for those skilled in the art, there will be changes in the specific implementation methods and application scope based on the ideas of this application. Therefore, the content of this specification should not be construed as a limitation of this application.

Claims

1. A method for measuring the vertical total electron content of the ionosphere using a GNSS-R wide-swath ionosphere, characterized in that, include: The propagation delay difference between direct signals from the same navigation satellite and reflected signals reflected from the ground is measured using a spaceborne GNSS-R dual-frequency receiver. The propagation delay difference includes a first propagation delay difference corresponding to the high-frequency signal and a second propagation delay difference corresponding to the low-frequency signal. Based on the dual-frequency combined observation principle, the first vertical total electron content (VTEC) value below the satellite orbit at the specular reflection point is calculated according to the propagation time delay difference. Based on the two-dimensional ionospheric model and the first VTEC value, the second VTEC value below the satellite orbit at the incident puncture point and the third VTEC value below the satellite orbit at the reflection puncture point are calculated respectively. For each target point among the specular reflection point, the incident puncture point, and the reflection puncture point, based on the three-dimensional ionospheric model and the VTEC value below the satellite orbit at the target point, the total VTEC value covering the vertical path from the Earth's surface to the top of the ionosphere is calculated as the VTEC observation result of a single navigation satellite. By fusing VTEC observations from multiple navigation satellites, wide-swath ionospheric VTEC observation data is generated.

2. The GNSS-R wide-span ionospheric vertical total electron content measurement method according to claim 1, characterized in that, The propagation delay difference between direct signals from the same navigation satellite and reflected signals from the ground is measured using a spaceborne GNSS-R dual-frequency receiver, including: The onboard GNSS-R dual-frequency receiver receives direct signals from the same navigation satellite and reflected signals reflected from the ground. The direct signals include high-frequency direct signals and low-frequency direct signals, and the reflected signals include high-frequency reflected signals and low-frequency reflected signals. Based on the direct signal and the reflected signal, the first propagation delay difference corresponding to the high-frequency signal and the second propagation delay difference corresponding to the low-frequency signal are extracted respectively.

3. The GNSS-R wide-span ionospheric vertical total electron content measurement method according to claim 2, characterized in that, When the onboard GNSS-R dual-frequency receiver is an interferometric receiver, based on the direct signal and the reflected signal, the first propagation delay difference corresponding to the high-frequency signal and the second propagation delay difference corresponding to the low-frequency signal are extracted, including: Based on the high-frequency direct signal and the high-frequency reflected signal, obtain the first interference waveform corresponding to the high-frequency signal, and extract the first propagation delay difference from the first interference waveform; Based on the low-frequency direct signal and the low-frequency reflected signal, a second interference waveform corresponding to the low-frequency signal is obtained, and the second propagation delay difference is extracted from the second interference waveform.

4. The GNSS-R wide-swath ionospheric vertical total electron content measurement method according to claim 2, characterized in that, When the spaceborne GNSS-R dual-frequency receiver is a local code correlation type receiver, the first propagation delay difference corresponding to the high-frequency signal and the second propagation delay difference corresponding to the low-frequency signal are extracted based on the direct signal and the reflected signal, respectively, including: The first propagation delay of the high-frequency direct signal and the second propagation delay of the high-frequency reflected signal are measured respectively, and the difference between the first propagation delay and the second propagation delay is obtained to obtain the first propagation delay difference; The third propagation delay of the low-frequency direct signal and the fourth propagation delay of the low-frequency reflected signal are measured respectively, and the difference between the third propagation delay and the fourth propagation delay is obtained to obtain the second propagation delay difference.

5. The GNSS-R wide-swath ionospheric vertical total electron content measurement method according to any one of claims 1-4, characterized in that, The method further includes: The propagation delay difference is subjected to receiver hardware delay correction processing to obtain the corrected propagation delay difference; Based on the principle of dual-frequency combined observation, the first VTEC value below the satellite orbit at the specular reflection point is calculated according to the propagation time delay difference, including: Based on the principle of dual-frequency combined observation, the first VTEC value below the satellite orbit at the specular reflection point is calculated according to the corrected propagation delay difference.

6. The GNSS-R wide-swath ionospheric vertical total electron content measurement method according to claim 1, characterized in that, Based on the principle of dual-frequency combined observation, the first VTEC value below the satellite orbit at the specular reflection point is calculated according to the propagation time delay difference, including: Based on the difference between the first propagation delay difference and the second propagation delay difference, the amount of dual-frequency differential delay caused by the ionosphere is determined; Calculate the projection factor of the ionospheric puncture point at the specular reflection point based on the signal reflection angle, Earth radius, and ionospheric puncture point height at the specular reflection point. The first VTEC value is calculated based on the dual-frequency differential delay, the projection factor of the ionospheric puncture point, the frequency of the high-frequency signal, and the frequency of the low-frequency signal.

7. The GNSS-R wide-swath ionospheric vertical total electron content measurement method according to claim 6, characterized in that, The first VTEC value is calculated using the following formula: ， in, The first VTEC value, The frequency of the high-frequency signal. The frequency of the low-frequency signal. For the first propagation delay difference, This is the second propagation delay difference. For the Earth's radius, Height of the ionospheric puncture point. The angle of signal reflection at the point of mirror reflection.

8. The GNSS-R wide-span ionospheric vertical total electron content measurement method according to claim 6 or 7, characterized in that, The method further includes: The first VTEC value is spatially filtered to obtain the filtered first VTEC value. Based on the two-dimensional ionospheric model and the first VTEC value, the second VTEC value below the satellite orbit at the incident puncture point and the third VTEC value below the satellite orbit at the reflection puncture point are calculated, including: Based on the two-dimensional ionospheric model and the filtered first VTEC value, the second VTEC value below the satellite orbit at the incident puncture point and the third VTEC value below the satellite orbit at the reflection puncture point are calculated respectively.

9. The GNSS-R wide-span ionospheric vertical total electron content measurement method according to claim 8, characterized in that, The spatial filtering process employs a quadratic polynomial fitting method.

10. The GNSS-R wide-span ionospheric vertical total electron content measurement method according to claim 1, characterized in that, Based on the two-dimensional ionospheric model and the first VTEC value, the second VTEC value below the satellite orbit at the incident puncture point and the third VTEC value below the satellite orbit at the reflection puncture point are calculated, including: From the two-dimensional ionospheric model, obtain the ratio between the VTEC at the incident puncture point and the VTEC at the reflected puncture point; Based on the ratio, the first VTEC value is proportionally allocated to the incident puncture point and the reflected puncture point to obtain the second VTEC value and the third VTEC value, respectively.

11. The GNSS-R wide-span ionospheric vertical total electron content measurement method according to claim 10, characterized in that, The second VTEC value and the third VTEC value are calculated using the following formulas respectively: ， ， in, Indicates the second VTEC value. Indicates the third VTEC value. R This represents the ratio between the VTEC at the incident puncture point and the VTEC at the reflected puncture point. This indicates the first VTEC value.

12. The GNSS-R wide-span ionospheric vertical total electron content measurement method according to claim 1, characterized in that, Based on the three-dimensional ionospheric model and the VTEC value below the satellite orbit at the target point, the total VTEC value covering the vertical path from the Earth's surface to the top of the ionosphere is calculated, including: Based on the three-dimensional ionospheric model, the VTEC ratio of the upper and lower parts of the satellite orbital altitude is obtained; The total VTEC value of the vertical path corresponding to the target point is calculated by combining the VTEC value below the satellite orbit at the target point with the VTEC ratio.

13. The GNSS-R wide-span ionospheric vertical total electron content measurement method according to claim 12, characterized in that, The total VTEC value of the vertical path is calculated using the following formula: ， in, The total VTEC value for the vertical path. This represents the VTEC value below the satellite's orbit at the target point. k This represents the VTEC ratio for the upper and lower portions of the satellite's orbital altitude.

14. The GNSS-R wide-swath ionospheric vertical total electron content measurement method according to claim 1, characterized in that, By fusing VTEC observations from multiple navigation satellites, wide-swath ionospheric VTEC observation data is generated, including: The VTEC observation results from multiple navigation satellites are assimilated or interpolated to generate the wide-swath ionospheric VTEC observation data.

15. The GNSS-R wide-span ionospheric vertical total electron content measurement method according to claim 1, characterized in that, The locations of the incident puncture point and the reflected puncture point are determined by combining the satellite orbital parameters, the location of the onboard GNSS-R dual-frequency receiver, and the geometric relationships of the ionospheric single-layer model.

16. A GNSS-R wide-span ionospheric vertical total electron content measurement device, characterized in that, include: The time delay difference measurement module is used to measure the propagation time delay difference between a direct signal from the same navigation satellite and a reflected signal reflected from the ground using a spaceborne GNSS-R dual-frequency receiver. The propagation time delay difference includes a first propagation time delay difference corresponding to the high-frequency signal and a second propagation time delay difference corresponding to the low-frequency signal. The first calculation module is used to calculate the first VTEC value below the satellite orbit at the specular reflection point based on the dual-frequency combined observation principle and the propagation time delay difference. The second calculation module is used to calculate the second VTEC value below the satellite orbit at the incident puncture point and the third VTEC value below the satellite orbit at the reflection puncture point, respectively, based on the two-dimensional ionospheric model and the first VTEC value. The third calculation module is used to calculate the total VTEC value covering the vertical path from the Earth's surface to the top of the ionosphere for each target point among the specular reflection point, the incident puncture point and the reflection puncture point, based on the three-dimensional ionospheric model and the VTEC value below the satellite orbit at the target point, as the VTEC observation result of a single navigation satellite. The results fusion module is used to fuse VTEC observations from multiple navigation satellites to generate wide-swath ionospheric VTEC observation data.

17. An electronic device comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, characterized in that, When the processor executes the computer program, it implements the steps of the GNSS-R wide-span ionospheric vertical total electron content measurement method according to any one of claims 1-15.

18. A readable storage medium having a computer program stored thereon, characterized in that, When executed by a processor, the computer program implements the steps of the GNSS-R wide-span ionospheric vertical total electron content measurement method according to any one of claims 1-15.

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