A space-based ultra-long baseline interferometric SAR system and implementation method

Abstract

The present invention provides a design method and device for a space-based ultra-long baseline interferometric SAR system, belonging to the field of radar measurement, including: for bistatic interferometry, analyzing the relationship between elevation accuracy, phase error, and coherence, thereby deriving the relationship between elevation accuracy and the vertical baseline; for bistatic interferometry, combining the critical baseline, analyzing the relationship between coherence, the vertical baseline, and the critical baseline; obtaining the relationship between the ratio of the vertical baseline to the critical baseline and elevation accuracy; performing an analysis of the deformation rate error in the interferometric SAR time series, thereby deriving the relationship between the deformation rate accuracy and each error source; deriving the influence of decorrelation noise on the deformation rate accuracy; obtaining the relationship between the ratio of the coherence time baseline to the revisit period and the deformation rate accuracy. The present invention meets the requirements of high-precision terrain and deformation measurement tasks for space-based SAR technology.

Description

Technical Field

[0001] The present invention belongs to the field of radar measurement, and particularly relates to a design method and device for a space-based ultra-long baseline interferometric SAR system. Background Art

[0002] Interferometric Synthetic Aperture Radar (InSAR) technology can achieve two core functions of surface elevation measurement and deformation monitoring by utilizing the phase difference of radar signals, and has become a key technical means in the fields of topographic mapping, geological disaster warning, and infrastructure safety assessment. The realization of this technology depends on two typical observation modes:

[0003] 1. Single-pass mode: By synchronously observing the same area with two satellites or dual antennas to form a spatial baseline, and extracting high-precision surface elevation information based on the differential interferometry principle. Typical applications of this mode include the construction of digital elevation models (DEMs), glacier topographic mapping, etc.

[0004] 2. Repeat-pass mode: By a single satellite or multiple satellites revisiting the same area multiple times to form a temporal baseline, and using repeat-pass interferometric SAR technology to monitor slow surface deformations, such as fault creep, urban ground subsidence monitoring, etc.

[0005] However, facing the increasing demand for terrain and deformation measurement accuracy, there are still problems of mutual restriction between system design and measurement accuracy in the existing interferometric SAR systems, and the analytical relationship between the spatial baseline, temporal baseline and the measurement performance of interferometric SAR is still unclear; the elongation of the spatial baseline is beneficial to elevation measurement, and the elongation of the temporal baseline is beneficial to time-series deformation measurement, but the existing research has not given clear definitions and quantitative analyses for ultra-long spatial baselines and ultra-long temporal baselines.

[0006] For spatial baseline and elevation measurement, interferometric SAR obtains elevation information through the spatial baseline, and its sensitivity is proportional to the length of the spatial baseline. The spatial baseline is defined as the component perpendicular to the radar beam line-of-sight direction in the baseline of the cross-track plane (paying attention to the vertical baseline). Increasing the baseline length can improve the elevation measurement accuracy, but at the same time, it will cause decoherence phenomena, which will in turn affect the elevation measurement accuracy, and the spatial baseline cannot be increased infinitely. Therefore, it is urgent to construct the constraint relationship between the baseline length and the elevation measurement accuracy and find the longest interferometric baseline.

[0007] For time baseline and deformation measurement, InSAR can measure surface deformation by observing the ground periodically at different times. The time baseline is defined as the time difference between two images of the interferogram. The coherence time baseline is defined as the time required for the temporal decorrelation to decay from the initial value to 1 / e (approximately equal to 0.36) of the original value. Generally, increasing the coherence time baseline can improve the measurement accuracy of the deformation rate, but the coherence will decrease with the increase of the time span, and the coherence time baseline cannot be increased infinitely. Therefore, it is urgent to propose a spaceborne ultra-long baseline interferometric SAR system to clarify the definition of the ultra-long time baseline and guide the design and development of the spaceborne interferometric SAR system.

[0008] In summary, the existing InSAR technology faces double constraints of baseline length and system design in elevation and deformation measurement, and there is no definition method for ultra-long space baselines and ultra-long time baselines. How to define the highly robust observation of interferometric SAR under ultra-long baselines through innovative error analysis has become a technical problem that urgently needs to be solved in the field of spaceborne radar remote sensing. Summary of the Invention

[0009] To solve the above technical problems, the present invention proposes a design method and device for a spaceborne ultra-long baseline interferometric SAR system. First, taking bistatic interferometry as an example, the relationship between elevation accuracy, phase error, and coherence is analyzed, mainly considering volume scattering decorrelation and spatial baseline decorrelation. Combining the critical baseline, the relationship between the ratio of the vertical baseline to the critical baseline and the elevation accuracy is constructed, and the optimal vertical baseline length is analyzed, thereby defining the ultra-long space baseline. Considering the relationship between the measurement accuracy of the deformation rate and atmospheric delay, decorrelation noise, system phase noise, orbit error, and DEM error, the time series covariance matrix of the decorrelation noise is mainly analyzed. Using spatial baseline decorrelation and temporal decorrelation, comprehensively considering the coherence time baseline, revisit period, and long-term coherence, the relationship between the ratio of the coherence time baseline to the revisit period and the deformation rate accuracy is obtained, thereby defining the ultra-long time baseline. The present invention can guide the design of a spaceborne ultra-long baseline interferometric SAR system, so as to meet the requirements of high-precision terrain and deformation measurement tasks of spaceborne SAR technology.

[0010] The principle relied on by the present invention is: taking the ratio of the vertical baseline to the critical baseline as the definition basis of the ultra-long space baseline, classifying the influencing factors of elevation accuracy, and determining the mutual relationship between the two; taking the ratio of the coherence time baseline to the revisit period as the definition basis of the ultra-long time baseline, classifying the influencing factors of the deformation rate accuracy, and determining the mutual relationship between the two.

[0011] To achieve the above object, the technical solution of the present invention is:

[0012] A design method for a spaceborne ultra-long baseline interferometric SAR system includes the following steps:

[0013] Step 101: For bistatic interferometry, analyze the relationship among elevation accuracy, phase error, and coherence, so as to derive the relationship between elevation accuracy and vertical baseline.

[0014] Step 102: For bistatic interferometry, combined with the critical baseline, analyze the relationship among coherence, vertical baseline, and critical baseline.

[0015] Step 103: Combine Step 101 and Step 102 to obtain the relationship between the ratio of vertical baseline to critical baseline and elevation accuracy.

[0016] Step 104: Conduct error analysis on the deformation rate of the interferometric SAR time series, so as to derive the relationship between deformation rate accuracy and each error source.

[0017] Step 105: Deduce the influence of decorrelation noise on deformation rate accuracy; combined with the relationship derived in Step 104, obtain the relationship between the ratio of coherence time baseline to revisit period and deformation rate accuracy.

[0018] The present invention also provides a space-based ultra-long baseline interferometric SAR system design device, including the following modules:

[0019] Derivation module: For bistatic interferometry, analyze the relationship among elevation accuracy, phase error, and coherence, so as to derive the relationship between elevation accuracy and vertical baseline.

[0020] Analysis module: For bistatic interferometry, combined with the critical baseline, analyze the relationship among coherence, vertical baseline, and critical baseline.

[0021] Ratio and elevation accuracy acquisition module: Combine the relationship derived by the derivation module and the relationship analyzed by the analysis module to obtain the relationship between the ratio of vertical baseline to critical baseline and elevation accuracy.

[0022] Error analysis module: Conduct error analysis on the deformation rate of the interferometric SAR time series, so as to derive the relationship between deformation rate accuracy and each error source.

[0023] Relationship acquisition module: Deduce the influence of decorrelation noise on deformation rate accuracy; combined with the relationship derived by the error analysis module, obtain the relationship between the ratio of coherence time baseline to revisit period and deformation rate accuracy.

[0024] The present invention also provides an electronic device, including a memory, a processor, and a computer program stored on the memory and executable on the processor. When the processor executes the program, the steps of the above-mentioned space-based ultra-long baseline interferometric SAR system design method are implemented.

[0025] The present invention also provides a non-transitory computer-readable storage medium, on which a computer program is stored. When the computer program is executed by a processor, the steps of the above-mentioned design method for a space-based ultra-long baseline interferometric SAR system are implemented.

[0026] Beneficial effects:

[0027] The present invention takes into account various error sources, focuses on the influence of decorrelation noise on elevation and deformation accuracy, balances the restrictive relationships between various factors, and gives the definitions of ultra-long space baselines and ultra-long time baselines, which can provide an important reference for designers of space-based interferometric SAR systems to design system parameters. Description of the drawings

[0028] Figure 1 is a flowchart of a design method for a space-based ultra-long baseline interferometric SAR system according to an embodiment of the present invention;

[0029] Figure 2a , Figure 2b , Figure 2c , Figure 2d , Figure 2e is a relationship diagram between the ratio of the vertical baseline to the critical baseline and the elevation accuracy; wherein, Figure 2a is the case of a slope of -20°, Figure 2b is the case of a slope of -10°, Figure 2c is the case of a slope of 0°, Figure 2d is the case of a slope of 10°, Figure 2e is the case of a slope of 20°;

[0030] Figure 3 is a relationship diagram between atmospheric delay, decorrelation noise, system noise and total error on the measurement accuracy of deformation rate;

[0031] Figure 4a , Figure 4b , Figure 4c is an influence diagram of the relationship between decorrelation noise and coherence time baseline, revisit period, and long-term coherence on the deformation measurement accuracy; wherein, Figure 4a is the influence of the coherence time baseline on the deformation measurement accuracy, Figure 4b is the influence of the revisit period on the deformation measurement accuracy, Figure 4c is the influence of long-term coherence on the deformation measurement accuracy;

[0032] Figure 5a , Figure 5b is a relationship diagram between the ratio of the coherence time baseline to the revisit period and the deformation rate accuracy; wherein, Figure 5a is the two-dimensional relationship between the coherence time baseline, the revisit period and the deformation rate accuracy, Figure 5b The relationship between the ratio of the coherence time baseline to the revisit period and the deformation rate accuracy. Detailed Implementation Manner

[0033] Next, with the help of the schematic diagrams in the embodiments of the present invention, the technical solutions in the present invention will be described more clearly and completely. It should be noted that all embodiments based on the present invention, as long as they can be understood and implemented by those of ordinary skill in the art without additional creative labor, should be regarded as falling within the protection scope of the present invention.

[0034] As Figure 1 shown, an embodiment of the present invention discloses a design method for a space-based ultra-long baseline interferometric SAR system, including the following steps:

[0035] Step 101: Taking bistatic interference as an example, analyze the relationship between phase error, elevation accuracy, and coherence, so as to derive the relationship between elevation accuracy and vertical baseline, including:

[0036] The relationship between the elevation accuracy of bistatic interference and the phase error is:

[0037] (1)

[0038] Wherein, is the standard deviation of elevation accuracy, is the standard deviation of phase error, is the wavelength, is the slant range of the main satellite, is the incident angle, is the vertical baseline.

[0039] The relationship between phase error and coherence is:

[0040] (2)

[0041] Wherein, is the standard deviation of the phase error caused by decoherence, is the standard deviation of the phase error caused by other factors, is the number of looks, is the coherence.

[0042] From formula (1) - formula (2), the relationship between elevation accuracy and vertical baseline can be obtained as:

[0043] (3)

[0044] Step 102: Taking bistatic interference as an example, combine the critical baseline and analyze the relationship between coherence, vertical baseline, and critical baseline, including:

[0045] The critical baseline The expression is:

[0046] (4)

[0047] Among them, is the range bandwidth, is the wavelength, is the slant range of the main satellite, is the incident angle, is the local slope angle, is the speed of light.

[0048] Coherence The expression is:

[0049] (5)

[0050] Among them, is the quantization noise de - coherence coefficient, is the Doppler de - coherence coefficient, is the sidelobe de - coherence coefficient, is the registration error de - coherence coefficient, is the ambiguity de - coherence coefficient, is the thermal noise de - coherence coefficient, is the volume scattering de - coherence coefficient, is the spatial baseline de - coherence coefficient. Among the above coherence coefficients, the volume scattering de - coherence coefficient and the spatial baseline de - coherence coefficient are related to the vertical baseline and the critical baseline.

[0051] Volume scattering de - coherence coefficient The expression is:

[0052] (6)

[0053] Among them, is the integration independent variable, is the vegetation height, is the exponential function, is the imaginary unit, is the attenuation function of the vegetation to the electromagnetic wave, expressed as:

[0054] (7)

[0055] Among them, is the one - way extinction coefficient of the electromagnetic wave in the vegetation.

[0056] Spatial baseline de - coherence coefficient The expression is:

[0057] (8)

[0058] From formulas (4) to (8), the relationship between coherence and vertical baseline and critical baseline can be obtained as follows:

[0059] (9)

[0060] Among them, the intermediate parameter , is a constant with a value of , represents a function with the independent variable . .

[0061] Step 103: Combining Step 101 and Step 102, obtain the relationship between the ratio of the vertical baseline to the critical baseline and the elevation accuracy, including:

[0062] From formulas (3), (4), and (9), the relationship between the ratio of the vertical baseline to the critical baseline and the elevation accuracy can be obtained as follows:

[0063] (10)

[0064] Step 104: Conduct an analysis of the deformation rate error of the InSAR time series, and thus derive the relationship between the deformation rate accuracy and each error source, including:

[0065] The standard deviation of the deformation rate measurement accuracy is related to atmospheric delay, decorrelation noise, system phase noise, orbit error, and DEM (Digital Elevation Model) error. Specifically:

[0066] (11)

[0067] (12)

[0068] (13)

[0069] (14)

[0070] Among them, is the design matrix of the linear deformation model, such as , is the 1st, 2nd,..., Nth time, is the covariance matrix of the deformation time series, is the covariance matrix of the atmospheric delay, is the covariance matrix of the decorrelation noise, is the covariance matrix of the system phase noise, is the covariance matrix of the orbit error, is the covariance matrix of the DEM error, is the generalized inverse of the matrix, and the superscript T represents the transpose of the matrix. is a diagonal matrix. is the phase standard deviation of the residual atmospheric delay error. is the standard deviation of the system phase noise error. is the number of time instances.

[0071] Step 105: Deduce the influence of decoherence noise on the accuracy of deformation rate; combined with Step 104, obtain the relationship between the ratio of the coherence time baseline to the revisit period and the accuracy of the deformation rate, including:

[0072] The decoherence noise covariance matrix (based on the small baseline subset method) is:

[0073] (15)

[0074] (16)

[0075] where is the design matrix of the phase estimation of the small baseline subset method with size ; is the number of interferograms, e.g.,

[0076] ;

[0077] is the covariance matrix of the interferometric stack of the decoherence noise, is the standard deviation of the decoherence noise, and the superscript represents the inverse of the matrix. Among them, the standard deviation of the decoherence noise and the expression of the coherence of the time series decoherence noise is:

[0078] (17)

[0079] where is the number of looks, is the coherence, and the spatial baseline decoherence coefficient is calculated by formula (8), is the temporal decoherence coefficient, is the thermal noise decoherence coefficient, is the signal-to-noise ratio, is the coherence time baseline, is the length of the time series, is the revisit period, is the number of time instances, is the long-term coherence coefficient.

[0080] The technical solution of the present invention will be further described in detail below with specific embodiments.

[0081] Example 1

[0082] Perform simulation analysis according to formula (10). First, define the constants , the speed of light , the number of looks , the range bandwidth , the vegetation height , the one-way extinction coefficient of electromagnetic waves in vegetation , the standard deviation of phase errors caused by other factors . Respectively simulate the relationship between the elevation accuracy and the ratio of the vertical baseline to the critical baseline under the conditions of slopes of 0°, ±10°, ±20° and incident angles of 25°, 35°, 45°. The results are as Figure 2a , Figure 2b , Figure 2c , Figure 2d , Figure 2e shown. Among them, Figure 2a is the case of a slope of -20°, Figure 2b is the case of a slope of -10°, Figure 2c is the case of a slope of 0°, Figure 2d is the case of a slope of 10°, Figure 2e is the case of a slope of 20°. The improvement of elevation accuracy is manifested as the reduction of elevation error. As the ratio of the vertical baseline to the critical baseline increases, the elevation accuracy generally shows a trend of first increasing and then decreasing. For the same slope and different incident angles, the elevation error reaches the minimum value at the same ratio of the vertical baseline to the critical baseline, that is, the elevation accuracy reaches the maximum value at this time. For different slopes and the same incident angles, the elevation error changes with the slope and reaches the minimum value at the ratio of the vertical baseline to the critical baseline of 24% - 30%.

[0083] In the design of SAR systems, the length of the vertical baseline used for interferometric altimetry is usually about 10% of the critical baseline. According to the simulation experiment, it is found that when the vertical baseline is greater than 25% - 30% of the critical baseline, the elevation accuracy will start to decline. Here, in order to distinguish the boundary between long baselines and ultra-long baselines, the vertical baseline of 10% of the critical baseline is defined as the conventional system, and when it exceeds 10%, it is a long baseline, and the ultra-long baseline is twice the length of the long baseline.

[0084] To sum up, in flat terrain areas, the ratio of the vertical baseline to the critical baseline of 10% - 20% is defined as a long baseline, and the ratio of the vertical baseline to the critical baseline of 20% - 30% is defined as an ultra-long baseline. As the terrain complexity increases and the slope increases, considering the increased difficulty of phase unwrapping, the elevation accuracy will decrease faster. In complex terrain areas, the ratio of the vertical baseline to the critical baseline of 10% - 17% is defined as a long baseline, and the ratio of the vertical baseline to the critical baseline of 17% - 25% is defined as an ultra-long baseline.

[0085] Example 2

[0086] First, simulations are carried out on the measurement accuracy of the temporal length variation and deformation rate for each error source, as Figure 3 shown. The temporal series length (i.e., time) years, revisit period days, coherence time baseline days, long-term coherence coefficient , the phase standard deviation of the residual atmospheric delay error (here the atmospheric delay error refers to the error after correction by the mainstream atmospheric delay correction method), the standard deviation of the system phase noise error , the orbit error and DEM error are set to 0. It can be seen that the measurement accuracy increases with the increase of the temporal series length. The contributions of uncertainties are: atmospheric delay > decoherence noise > system noise. Among them, the atmospheric delay, system phase noise, orbit error, and DEM error are all linearly and positively correlated with the deformation measurement accuracy. The atmospheric delay belongs to the external environmental error and can be independent of the design of the InSAR system; the system phase error and orbit error have negligible influence under the current engineering hardware level. Therefore, the present invention focuses on the influence of decoherence noise.

[0087] Secondly, regarding the relationship between decoherence noise and coherence time baseline, revisit period, and long-term coherence, simulations are carried out on its influence on the deformation measurement accuracy, as Figure 4a , Figure 4b , Figure 4c shown. Among them, Figure 4a is the influence of the coherence time baseline on the deformation measurement accuracy, Figure 4b is the influence of the revisit period on the deformation measurement accuracy, Figure 4c is the influence of the long-term coherence on the deformation measurement accuracy. Among them, the temporal series length years, revisit period days, long-term coherence coefficient , coherence time baseline days. It can be seen that the decoherence noise is determined by the coherence time baseline, revisit period, and long-term coherence, and has a non-linear correlation with the deformation measurement accuracy; the influences of the coherence time baseline and revisit period are dominant, and the influence of the long-term coherence is the smallest.

[0088] Based on the above, the present invention simulates the relationship between the deformation rate accuracy and the ratio of the coherence time baseline to the revisit period, as Figure 5a , Figure 5b shown. Among them, Figure 5a is the two-dimensional relationship between the coherence time baseline, revisit period, and deformation rate accuracy, Figure 5bThe relationship between the ratio of the coherent time baseline to the revisit period and the deformation rate accuracy. It can be seen that the two show non-linearity, and the larger the ratio, the more accurate the rate measurement. When the rate measurement accuracy reaches 1 mm / year, the corresponding ratio of the coherent time baseline to the revisit period is 3.85. Therefore, the present invention gives the definition: The interferometric SAR system with the ratio of the coherent time baseline to the revisit period ≥ 3.85 is the ultra-long time baseline interferometric SAR. At this time, the coherent time baseline is the time baseline length with the coherence greater than or equal to 0.36 (=1 / e), and this parameter depends on the radar wavelength, ground object type, etc. The definition of this ultra-long time baseline of this ratio is independent of the radar wavelength and can be used to guide the parameter design of the revisit period of the interferometric SAR system. For example: According to the ground object type to be covered, after selecting the radar wavelength, calculate the coherent time baseline, and then select the revisit period required by the system according to the ultra-long time baseline principle.

[0089] The present invention also provides a spaceborne ultra-long baseline interferometric SAR system design device, including the following modules:

[0090] Derivation module, for bistatic interferometry, analyze the relationship between elevation accuracy, phase error, and coherence, so as to derive the relationship between elevation accuracy and vertical baseline;

[0091] Analysis module, for bistatic interferometry, combined with the critical baseline, analyze the relationship between coherence, vertical baseline, and critical baseline;

[0092] Ratio and elevation accuracy acquisition module, combined with the derivation module and the analysis module, obtain the relationship between the ratio of the vertical baseline to the critical baseline and the elevation accuracy;

[0093] Error analysis module, conduct error analysis on the deformation rate of the interferometric SAR time series, so as to derive the relationship between the deformation rate accuracy and each error source;

[0094] Relationship acquisition module, derive the influence of decoherence noise on the deformation rate accuracy; combined with the error analysis module, obtain the relationship between the ratio of the coherent time baseline to the revisit period and the deformation rate accuracy.

[0095] The present invention also provides an electronic device, including a memory, a processor, and a computer program stored on the memory and executable on the processor. When the processor executes the program, it implements the steps of the above-mentioned spaceborne ultra-long baseline interferometric SAR system design method.

[0096] The present invention also provides a non-transitory computer-readable storage medium, on which a computer program is stored. When the computer program is executed by a processor, it implements the steps of the above-mentioned spaceborne ultra-long baseline interferometric SAR system design method.

[0097] Those skilled in the art should understand that the embodiments of the present invention can be provided as a method, a system, or a computer program product. Therefore, the present invention can take the form of a complete hardware embodiment, a complete software embodiment, or an embodiment combining software and hardware aspects. Moreover, the present invention can take the form of a computer program product implemented on one or more computer-usable storage media including but not limited to disk memory, CD-ROM, optical memory, etc. that include computer-usable program code. The solutions in the embodiments of the present invention can be implemented in various computer languages, for example, object-oriented programming languages such as Java and interpreted scripting languages such as JavaScript.

[0098] The present invention is described with reference to the flowcharts and / or block diagrams of methods, apparatuses (systems), and computer program products according to embodiments of the present invention. It should be understood that each flow and / or block in the flowchart and / or block diagram, and the combination of flows and / or blocks in the flowchart and / or block diagram, can be realized by computer program instructions. These computer program instructions can be provided to the processor of a general-purpose computer, a special-purpose computer, an embedded processor, or other programmable data processing devices to generate a machine, such that the instructions executed by the processor of the computer or other programmable data processing devices generate means for realizing the functions specified in one Figure 1 one flow or multiple flows and / or blocks Figure 1 or multiple blocks.

[0099] These computer program instructions can also be stored in a computer-readable memory that can direct a computer or other programmable data processing device to work in a specific manner, such that the instructions stored in the computer-readable memory generate a manufactured article including instruction means that realizes the functions specified in one Figure 1 one flow or multiple flows and / or blocks Figure 1 or multiple blocks.

[0100] These computer program instructions can also be loaded onto a computer or other programmable data processing device, such that a series of operation steps are executed on the computer or other programmable device to generate a computer-implemented process, so that the instructions executed on the computer or other programmable device provide steps for realizing the functions specified in one Figure 1 one flow or multiple flows and / or blocks Figure 1 or multiple blocks.

[0101] Although the preferred embodiments of the present invention have been described, those skilled in the art can make additional changes and modifications once they learn the basic creative concepts. Therefore, the appended claims are intended to be construed to include the preferred embodiments as well as all changes and modifications falling within the scope of the present invention.

[0102] Obviously, those skilled in the art can make various changes and modifications to the present invention without departing from the spirit and scope of the present invention. Thus, if these modifications and variations of the present invention fall within the scope of the claims of the present invention and their equivalent technologies, the present invention is also intended to include these modifications and variations.

Claims

1. A method for designing a space-based ultra-long baseline interferometric SAR system, characterized in that: The steps include: Step 101: Analyze the relationship between elevation accuracy and phase error and coherence for bi-basic interferometry, so as to derive the relationship between elevation accuracy and vertical baseline; Step 102, for dual-base interference, combined with the critical baseline, analyze the relationship between coherence and the vertical baseline and the critical baseline; Step 103, combining step 101 and step 102, deriving the relationship between the ratio of the vertical baseline to the critical baseline and the elevation accuracy; Step 104: Performing an interferometric SAR time series deformation rate error analysis to derive the relationship between the deformation rate accuracy and various error sources, including: Consider the relationship between deformation rate measurement accuracy and atmospheric delay, decoherence noise, system phase noise, orbit error, and DEM error; Step 105, derive the influence of decoherence noise on deformation rate accuracy; combine the relationship derived in step 104 to obtain the relationship between the ratio of coherence time baseline to revisit period and deformation rate accuracy, including: analyzing the covariance matrix of the time series of decoherence noise; comprehensively considering the coherence time baseline, revisit period, and long-term coherence to obtain the relationship between the ratio of coherence time baseline to revisit period and deformation rate accuracy.

2. The method for designing a space-based ultra-long baseline interferometric SAR system according to claim 1, characterized in that: The step 101 includes: obtaining the relationship between the elevation accuracy and the vertical baseline according to the relationship between the elevation accuracy and the phase error and the relationship between the phase error and the coherence of the dual-base interferometer.

3. The method for designing a space-based ultra-long baseline interferometric SAR system according to claim 2, characterized in that: The step 102 includes: The analysis utilizes an expression for a critical baseline; the coherence includes quantization noise decorrelation, Doppler decorrelation, sidelobe decorrelation, registration error decorrelation, blur decorrelation, thermal noise decorrelation, volume scattering decorrelation, and spatial baseline decorrelation.

4. The method for designing a space-based ultra-long baseline interferometric SAR system according to claim 3, characterized in that: The step 102 further includes: By analyzing the volume scattering decoherence and spatial baseline decoherence, the relationship between coherence, elevation accuracy, vertical baseline and critical baseline is obtained as follows: (9) (10) in, is the coherence, the intermediate parameter , is the value The constant, is the quantization noise decorrelation coefficient, is the Doppler decorrelation coefficient, is the sidelobe decorrelation coefficient, is the registration error decorrelation coefficient, is the fuzzy decorrelation coefficient, is the thermal noise decorrelation coefficient; is the standard deviation of elevation accuracy, is the speed of light, is the incident angle, is the local slope angle, is the distance bandwidth, is the vertical baseline, is the critical baseline, is the standard deviation of the phase error caused by other factors, For multiple views, is the one-way extinction coefficient of electromagnetic waves in vegetation, is the independent variable of integration, is the vegetation height, is an exponential function, is an imaginary unit, Indicates that the independent variable is Function .

5. The method for designing a space-based ultra-long baseline interferometric SAR system according to claim 1, characterized in that: The relationship between the ratio of the coherence time baseline to the revisit period and the deformation rate accuracy is: (11) (12) (13) (14) (15) (16) (17) in, is the standard deviation of the deformation rate measurement accuracy, is the design matrix of the linear deformation model, is the covariance matrix of the deformation time series, is the atmospheric delay covariance matrix, is the incoherent noise covariance matrix, is the system phase noise covariance matrix, is the orbit error covariance matrix, is the DEM error covariance matrix, is the generalized inverse of the matrix, the superscript T is the transpose of the matrix, is a diagonal matrix, is the phase standard deviation of the residual atmospheric delay error, is the standard deviation of the system phase noise error, is the number of time, is the design matrix for phase estimation using the small baseline set method, is the covariance matrix of the interferometric stack of decoherent noise, is the standard deviation of the decoherence noise, is the inverse of the matrix, is the standard deviation of the decoherence noise, , For multiple views, For coherence; is the spatial baseline decorrelation coefficient, is the temporal decorrelation coefficient, is the thermal noise decorrelation coefficient, is the signal-to-noise ratio, is the coherence time baseline, is the length of the time series, For the revisit cycle, is the long-term coherence coefficient.

6. A space-based ultra-long baseline interferometric SAR system design device, characterized in that: Includes the following modules: The derivation module analyzes the relationship between elevation accuracy and phase error and coherence for bi-basic interferometry, thereby deriving the relationship between elevation accuracy and vertical baseline; The analysis module analyzes the relationship between coherence and vertical baseline and critical baseline in combination with the critical baseline for dual-base interference; The ratio and elevation accuracy acquisition module combines the relationship derived by the derivation module and the relationship analyzed by the analysis module to derive the relationship between the ratio of the vertical baseline to the critical baseline and the elevation accuracy; The error analysis module performs deformation rate error analysis on interferometric SAR time series, thereby deriving the relationship between deformation rate accuracy and various error sources, including: Consider the relationship between deformation rate measurement accuracy and atmospheric delay, decoherence noise, system phase noise, orbit error, and DEM error; The relationship acquisition module derives the influence of decoherence noise on the deformation rate accuracy; combined with the relationship derived by the error analysis module, the relationship between the ratio of the coherence time baseline to the revisit period and the deformation rate accuracy is obtained, including: analyzing the covariance matrix of the time series of decoherence noise; comprehensively considering the coherence time baseline, revisit period, and long-term coherence, and obtaining the relationship between the ratio of the coherence time baseline to the revisit period and the deformation rate accuracy.

7. 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 program, the steps of a method for designing a space-based ultra-long baseline interferometric SAR system are implemented as described in any one of claims 1 to 5.

8. A non-transitory computer-readable storage medium having a computer program stored thereon, characterized in that: When the computer program is executed by a processor, the steps of a method for designing a space-based ultra-long baseline interferometric SAR system as claimed in any one of claims 1 to 5 are implemented.

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