A method and device for determining echo power of satellite radar altimeter with small incidence angle

Abstract

The present invention provides a method and device for determining echo power of a satellite radar altimeter at a small incident angle, belonging to the field of microwave remote sensor measurement technology, and the method includes: determining a target flat sea surface impulse response function at a small incident angle based on a flat sea surface impulse response function at a quasi-vertical incident angle; obtaining a rough sea surface height probability density function and a point target response function of a satellite radar altimeter, and constructing a small incident angle echo power model based on the target flat sea surface impulse response function, the height probability density function and the point target response function; determining the echo power based on the small incident angle echo power model; the angle range of the quasi-vertical incident angle is greater than or equal to 0° and less than 1°, and the angle range of the small incident angle is greater than or equal to 1° and less than 20°. The present invention improves the accuracy and efficiency of the echo power determined in a small incident angle scenario.

Description

Technical Field

[0001] The invention relates to the technical field of microwave remote sensor measurement, and in particular to a method and a device for determining the echo power of a small-incident-angle satellite radar altimeter. Background Art

[0002] Satellite radar altimeter is an important marine microwave remote sensor. It can measure sea surface height, effective wave height and backscatter coefficient by transmitting electromagnetic waves to the sea surface and receiving echoes from the sea surface. The further inversion results of its measurement data can be applied to marine geophysics, ocean dynamics, marine climate and environment, sea ice monitoring, etc. In the radar altimeter measurement process, the altimeter transmits microwave pulse signals to the surface of the observed target and tracks the echo signals. The distance between the radar altimeter and the observed target is calculated based on the time when the echo arrives. The waveform characteristics of the echo signal are used to invert the characteristics of the target surface, such as the backscatter coefficient of the rough sea surface, effective wave height and other parameters.

[0003] In order to extract the ocean information contained in the echo, the theoretical model of the altimeter echo power is particularly important. In 1977, Brown theoretically deduced the echo formation based on the physical optics theory and proposed that the echo power of the sea surface is the three-term convolution of the flat sea surface pulse response function, the height probability density function and the point target response function. However, the existing technology studies the scenario when the incident angle is less than 1°. That is to say: the echo power model derived based on the three-term convolution in the existing technology is only applicable to the scenario when the incident angle is less than 1°. As satellite remote sensing needs to accelerate the increase in global space coverage, the incident angle gradually develops from quasi-vertical to small angles. The echo power model of the existing technology is not suitable for small angles of incidence. When the incident angle is greater than or equal to 1°, the determined echo power is inaccurate. If it is determined directly by numerical convolution, the inversion is complex and time-consuming, resulting in low efficiency in determining the echo power.

[0004] Therefore, there is an urgent need to provide a method and device for determining the echo power of a satellite radar altimeter with a small incidence angle, so as to achieve accurate determination of the echo power under small incidence angle conditions while improving the determination efficiency. Summary of the invention

[0005] In view of this, it is necessary to provide a method and device for determining the echo power of a satellite radar altimeter with a small incidence angle, so as to solve the technical problems in the prior art that the echo power model is not suitable for small incidence angles, resulting in inaccurate echo power determined under small incidence angles, and the echo power is determined based on data convolution, resulting in low efficiency in determining the echo power.

[0006] On the one hand, in order to solve the above technical problems, the present invention provides a method for determining the echo power of a satellite radar altimeter with a small incidence angle, comprising:

[0007] Based on the flat sea surface impulse response function at quasi-vertical incidence angle, the target flat sea surface impulse response function at small incidence angle is determined;

[0008] Acquire a rough sea surface height probability density function and a point target response function of a satellite radar altimeter, and construct a small incident angle echo power model based on the target flat sea surface impulse response function, the height probability density function and the point target response function;

[0009] Determining the echo power based on the small incident angle echo power model;

[0010] Among them, the angle range of the quasi-vertical incident angle is greater than or equal to 0° and less than 1°, and the angle range of the small incident angle is greater than or equal to 1° and less than 20°.

[0011] In a possible implementation, the target flat sea surface impulse response function is:

[0012]

[0013] A ( σ 0 ( ψ ))=

[0014]

[0015]

[0016]

[0017]

[0018]

[0019] In the formula, is the target flat sea surface impulse response; G 0 is the radar antenna boresight gain; λ The wavelength of the electromagnetic wave signal emitted by the radar; σ 0 ( ψ ) is the backscatter coefficient of the sea surface when the subsatellite point is incident; c is the speed of light; is the atmospheric loss for two-way propagation; θ w is the 3dB beamwidth of the antenna main lobe; h is the satellite altitude; ξ is the angle value of the incident angle; t For time; H3 , H 4 , H 5 is the Hermite polynomial.

[0020] In a possible implementation, the rough sea surface height probability density function is:

[0021]

[0022]

[0023] In the formula, is the probability density value of rough sea surface height; SWH is the effective wave height of the sea surface.

[0024] In a possible implementation, the point target response function is:

[0025]

[0026] or,

[0027]

[0028] In the formula, is the point target response value; is a constant related to the radar transmission power; is the experience value; B is the signal bandwidth.

[0029] In a possible implementation, the small incident angle echo power model is:

[0030]

[0031]

[0032]

[0033] In the formula, W(t) is the echo power; is the skewness of the probability density function of the rough sea surface height; is the skewness of the point target response function; is the kurtosis of the probability density function of the rough sea surface height; is the kurtosis of the point target response function.

[0034] In a possible implementation, the method further includes:

[0035] Determine whether the angle of incidence is greater than 8°;

[0036] When the angle value of the incident angle is greater than 8°, simplifying the echo power determined by the small incident angle echo power model to obtain a simplified small incident angle echo power model;

[0037] The echo power is determined based on the simplified small-incident-angle echo power model.

[0038] In a possible implementation, the simplified small incident angle echo power model is:

[0039]

[0040]

[0041]

[0042]

[0043] A ( σ 0 ( ψ ))=

[0044]

[0045] In the formula, W(t) is the echo power; G 0 is the radar antenna boresight gain; λ The wavelength of the electromagnetic wave signal emitted by the radar; σ 0 ( ψ ) is the backscatter coefficient of the sea surface when the subsatellite point is incident; c is the speed of light; is the atmospheric loss for two-way propagation; θ w is the 3dB beamwidth of the antenna main lobe; h is the satellite altitude; ξ is the angle value of the incident angle; t For time; H 3 , H 4 , H 5 is the Hermite polynomial; is the experience value; SWH is the effective wave height of the sea surface.

[0046] In a possible implementation, the method further includes:

[0047] Obtaining a Brown model flat sea surface impulse response function under oblique incidence, and determining a Brown model flat sea surface impulse response value, a height probability density function value, and a point target response function value based on the Brown model flat sea surface impulse response function, the height probability density function, and the point target response function;

[0048] Performing three convolutions on the Brown model flat sea surface impulse response value, the height probability density function value, and the point target response function value to obtain a reference echo power;

[0049] A power difference between the reference echo power and the echo power is determined, and when the power difference is less than a preset difference, it is determined that the small incident angle echo power model is reliable.

[0050] In a possible implementation, the reference echo power includes multiple reference echo powers corresponding to multiple incident angles with different values; the echo power includes multiple echo powers corresponding to multiple incident angles with different values; then determining the power difference between the reference echo power and the echo power is specifically:

[0051] A plurality of power difference values ​​between a plurality of reference echo powers and the plurality of echo powers are determined.

[0052] On the other hand, the present invention also provides a device for determining echo power of a satellite radar altimeter with a small incidence angle, comprising:

[0053] A sea surface impulse response function determination unit is used to determine a target flat sea surface impulse response function at a small incident angle based on the flat sea surface impulse response function at a quasi-vertical incident angle;

[0054] An echo power model building unit is used to obtain a rough sea surface height probability density function and a point target response function of a satellite radar altimeter, and to build a small incident angle echo power model based on the target flat sea surface impulse response function, the height probability density function and the point target response function;

[0055] An echo power determination unit, configured to determine the echo power based on the small incident angle echo power model;

[0056] Among them, the angle range of the quasi-vertical incident angle is greater than or equal to 0° and less than 1°, and the angle range of the small incident angle is greater than or equal to 1° and less than 20°.

[0057] The beneficial effects of the present invention are as follows: the method for determining the echo power of a satellite radar altimeter with a small incidence angle provided by the present invention determines the pulse response function of a target flat sea surface with a small incidence angle, obtains a flat sea surface pulse response function that is more matched with the small incidence angle, and constructs a small incidence angle echo power model based on the target platform sea surface pulse response function, the height probability density function and the point target response function, and can directly realize accurate determination of the echo power at a small incidence angle based on the constructed small incidence angle echo power model.

[0058] Furthermore, the present invention can accurately determine the echo power at small incident angles directly based on the small incident angle echo power model. Compared with the scheme of obtaining the echo power by deriving the convolution calculation of three function values, it reduces the complexity of parameter inversion, shortens the parameter inversion time, and thus improves the efficiency of determining the echo power at small incident angles. BRIEF DESCRIPTION OF THE DRAWINGS

[0059] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following briefly introduces the drawings required for use in the description of the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative work.

[0060] Figure 1 A schematic flow chart of an embodiment of a method for determining echo power of a satellite radar altimeter with a small incidence angle provided by the present invention;

[0061] Figure 2 A schematic diagram of a flow chart of an embodiment of the present invention for simplifying a small incident angle echo power model;

[0062] Figure 3 A schematic diagram of a flow chart of an embodiment of verifying the reliability of a small-incident-angle echo power model provided by the present invention;

[0063] Figure 4 The comparison result between the echo power determined based on the small incident angle echo power model and the reference echo power when the incident angle is 2 degrees provided by the present invention;

[0064] Figure 5 The comparison result between the echo power determined based on the small incident angle echo power model and the reference echo power when the incident angle is 3 degrees provided by the present invention;

[0065] Figure 6 The comparison result between the echo power determined based on the small incident angle echo power model and the reference echo power when the incident angle is 5 degrees provided by the present invention;

[0066] Figure 7The comparison result between the echo power determined based on the small incident angle echo power model and the reference echo power when the incident angle is 10 degrees provided by the present invention;

[0067] Figure 8 The comparison result between the echo power determined based on the small incident angle echo power model and the reference echo power when the incident angle is 15 degrees provided by the present invention;

[0068] Fig. 9 The comparison result between the echo power determined based on the small incident angle echo power model and the reference echo power when the incident angle is 20 degrees provided by the present invention;

[0069] Fig.10 The comparison result between the echo power determined based on the simplified small incident angle echo power model and the reference echo power when the incident angle is 2 degrees provided by the present invention;

[0070] Fig.11 The comparison result between the echo power determined based on the simplified small incident angle echo power model and the reference echo power when the incident angle is 3 degrees provided by the present invention;

[0071] Fig.12 The comparison result between the echo power determined based on the simplified small incident angle echo power model and the reference echo power when the incident angle is 5 degrees provided by the present invention;

[0072] Fig.13 The comparison result between the echo power determined based on the simplified small incident angle echo power model and the reference echo power when the incident angle is 6 degrees provided by the present invention;

[0073] Fig.14 The comparison result between the echo power determined based on the simplified small incident angle echo power model and the reference echo power when the incident angle is 10 degrees provided by the present invention;

[0074] Fig.15 The comparison result between the echo power determined based on the simplified small incident angle echo power model and the reference echo power when the incident angle is 15 degrees provided by the present invention;

[0075] Fig.16 The comparison result between the echo power determined based on the simplified small incident angle echo power model and the reference echo power when the incident angle is 20 degrees provided by the present invention;

[0076] Fig.17 A schematic structural diagram of an embodiment of a device for determining echo power of a satellite radar altimeter with a small incidence angle provided by the present invention. DETAILED DESCRIPTION

[0077] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative work are within the scope of protection of the present invention.

[0078] It should be understood that the schematic drawings are not drawn to scale. The flowchart used in the present invention shows the operations implemented according to some embodiments of the present invention. It should be understood that the operations of the flowchart can be implemented out of order, and the steps without logical context can be reversed in order or implemented simultaneously. In addition, those skilled in the art, under the guidance of the content of the present invention, can add one or more other operations to the flowchart, and can also remove one or more operations from the flowchart. Some of the block diagrams shown in the accompanying drawings are functional entities, which do not necessarily correspond to physically or logically independent entities. These functional entities can be implemented in software form, or in one or more hardware modules or integrated circuits, or in different networks and / or processor systems and / or microcontroller systems.

[0079] Reference to an "embodiment" herein means that a particular feature, structure, or characteristic described in conjunction with the embodiment may be included in at least one embodiment of the present invention. The appearance of the phrase in various places in the specification does not necessarily refer to the same embodiment, nor is it an independent or alternative embodiment that is mutually exclusive with other embodiments. It is explicitly and implicitly understood by those skilled in the art that the embodiments described herein may be combined with other embodiments.

[0080] The present invention provides a method and device for determining the echo power of a satellite radar altimeter with a small incidence angle, which are respectively described below.

[0081] Figure 1 A schematic flow chart of an embodiment of a method for determining echo power of a satellite radar altimeter with a small incidence angle provided by the present invention is shown in FIG. Figure 1 As shown, the method for determining the echo power of a small-incident-angle satellite radar altimeter includes:

[0082] S101, determining a target flat sea surface impulse response function at a small incidence angle based on a flat sea surface impulse response function at a quasi-vertical incidence angle;

[0083] S102, obtaining a rough sea surface height probability density function and a point target response function of a satellite radar altimeter, and constructing a small incident angle echo power model based on the target flat sea surface impulse response function, the height probability density function and the point target response function;

[0084] S103, determining the echo power based on a small incident angle echo power model;

[0085] Among them, the angle range of the quasi-vertical incident angle is greater than or equal to 0° and less than 1°, and the angle range of the small incident angle is greater than or equal to 1° and less than 20°.

[0086] It should be noted that the relationship between the flat sea surface impulse response function under the quasi-vertical incident angle in step S101 and the target flat sea surface impulse response function under the small incident angle is as follows: the flat sea surface impulse response function is generalized to the small incident angle condition, and the flat sea surface impulse response function is adjusted based on the asymmetry of the flat sea surface impulse response when the incident angle is small. And the peak value of the target flat sea surface impulse response function is the maximum value of the flat sea surface impulse response function.

[0087] The incident angle may also be called the antenna mispointing angle.

[0088] It should be understood that when the incident angle is less than 1°, the echo power at the quasi-vertical incident angle may be determined based on an echo power model such as the Hayne model, the first-order exponential approximation model, the second-order exponential approximation model, or the like.

[0089] Compared with the prior art, the method for determining the echo power of a satellite radar altimeter with a small incidence angle provided in an embodiment of the present invention determines the target flat sea surface pulse response function with a small incidence angle to obtain a flat sea surface pulse response function that better matches the small incidence angle, and constructs a small incidence angle echo power model based on the target platform sea surface pulse response function, the height probability density function and the point target response function. The method can directly realize accurate determination of the echo power with a small incidence angle based on the constructed small incidence angle echo power model.

[0090] Furthermore, the embodiments of the present invention can accurately determine the echo power at small incident angles directly based on the small incident angle echo power model. Compared with the scheme of obtaining the echo power by deriving the convolution calculation of three function values, it reduces the complexity of parameter inversion, shortens the parameter inversion time, and thus improves the efficiency of determining the echo power at small incident angles.

[0091] In a specific embodiment of the present invention, the target flat sea surface impulse response function is:

[0092]

[0093] A ( σ 0 ( ψ ))=

[0094]

[0095]

[0096]

[0097]

[0098]

[0099] In the formula, is the target flat sea surface impulse response; G 0 is the radar antenna boresight gain; λ The wavelength of the electromagnetic wave signal emitted by the radar; σ 0 ( ψ ) is the backscatter coefficient of the sea surface when the subsatellite point is incident; c is the speed of light; is the atmospheric loss for two-way propagation; θ w is the 3dB beamwidth of the antenna main lobe; h is the satellite altitude; ξ is the angle value of the incident angle; t For time; H 3 , H 4 , H 5 is the Hermite polynomial.

[0100] In a specific embodiment of the present invention, the probability density function of the rough sea surface height is:

[0101]

[0102]

[0103] In the formula, is the probability density value of rough sea surface height; SWH is the effective wave height of the sea surface.

[0104] In a specific embodiment of the present invention, the point target response function is:

[0105]

[0106] or,

[0107]

[0108] In the formula, is the point target response value; is a constant related to the radar transmission power; is the experience value; Bis the signal bandwidth.

[0109] In a specific embodiment of the present invention, the small incident angle echo power model is:

[0110]

[0111]

[0112]

[0113] In the formula, W(t) is the echo power; is the skewness of the probability density function of the rough sea surface height; is the skewness of the point target response function; is the kurtosis of the probability density function of the rough sea surface height; is the kurtosis of the point target response function.

[0114] The embodiment of the present invention takes into account the asymmetry of the target flat sea surface impulse response at small incident angles, and introduces the skewness and kurtosis of the rough sea surface height probability density function and the point target response function into the small incident angle echo power model, so that it is more adapted to the asymmetry of the impulse response at small incident angles. Specifically, the peak position is the maximum value moment of the target flat sea surface impulse response waveform, and the standard deviation is proportional to the waveform width.

[0115] Further, it is verified by experiments that when the incident angle is greater than 8°, the asymmetry of the target flat sea surface impulse response function disappears, which conforms to the Gaussian distribution characteristics. Therefore, in order to further improve the efficiency of determining the echo power, in some embodiments of the present invention, Figure 2 As shown, the method for determining the echo power of a small-incident-angle satellite radar altimeter also includes:

[0116] S201, determining whether the angle value of the incident angle is greater than 8°;

[0117] S202, when the angle value of the incident angle is greater than 8°, simplifying the echo power determined by the small incident angle echo power model to obtain a simplified small incident angle echo power model;

[0118] S203: Determine the echo power based on a simplified small incident angle echo power model.

[0119] The embodiment of the present invention simplifies the echo power determined by the small incident angle echo power model when the angle value of the incident angle is greater than 8°, thereby obtaining a simplified small incident angle echo power model. This can simplify the small incident angle echo power model while ensuring its accuracy, thereby further improving the efficiency of determining the echo power while ensuring its accuracy.

[0120] In a specific embodiment of the present invention, the simplified small incident angle echo power model is:

[0121]

[0122]

[0123]

[0124]

[0125] A ( σ 0 ( ψ ))=

[0126]

[0127] The meaning of each parameter in the above formula can be found in the parameter meaning of the small incident angle echo power model, which will not be repeated here.

[0128] In order to verify the reliability and validity of the determined echo power, in some embodiments of the present invention, Figure 3 As shown, the method for determining the echo power of a small-incident-angle satellite radar altimeter also includes:

[0129] S301, obtaining a Brown model flat sea surface impulse response function under oblique incidence, and determining a Brown model flat sea surface impulse response value, a height probability density function value, and a point target response function value based on the Brown model flat sea surface impulse response function, the height probability density function, and the point target response function;

[0130] S302, performing three-item convolution on the Brown model flat sea surface impulse response value, the height probability density function value, and the point target response function value to obtain a reference echo power;

[0131] S303: Determine a power difference between a reference echo power and an echo power. When the power difference is less than a preset difference, determine that the small incident angle echo power model is reliable.

[0132] Among them, the impulse response function of the Brown model flat sea surface is:

[0133]

[0134]

[0135]

[0136]

[0137] It should be understood that the echo power in step S303 may also be the echo power determined based on the simplified small-incident-angle echo power model, so as to verify the validity and accuracy of the simplified small-incident-angle echo power model.

[0138] The embodiment of the present invention can ensure the feasibility and effectiveness of the small-incident-angle echo power model and the simplified small-incident-angle echo power model by verifying the constructed small-incident-angle echo power model and the simplified small-incident-angle echo power model.

[0139] Since the angle range of the small incident angle is greater than or equal to 1° and less than 20°, in order to improve the comprehensiveness of the verification, the reference echo power includes multiple reference echo powers corresponding to multiple incident angles with different values; the echo power includes multiple echo powers corresponding to multiple incident angles with different values; then the power difference between the reference echo power and the echo power determined in step S303 is specifically:

[0140] A plurality of power difference values ​​between a plurality of reference echo powers and a plurality of echo powers are determined.

[0141] When each power difference is smaller than a preset difference, it is determined that the constructed small-incident-angle echo power model and the simplified small-incident-angle echo power model are reliable.

[0142] In the specific embodiment of the present invention, the parameters are set as follows: the satellite altitude is 960 km, the 3dB beam width is 1.6 degrees, and the incident angles are set to 2 degrees, 3 degrees, 5 degrees, 10 degrees, 15 degrees, and 20 degrees. The results of the small incident angle echo power model verification based on the above parameters are as follows Figure 4-Figure 9 , Figure 4-Figure 9 The comparison results are 2 degrees, 3 degrees, 5 degrees, 10 degrees, 15 degrees, and 20 degrees. Figure 4-Figure 9 It can be seen that the deviation between the reference echo power and the echo power is very small. The evaluation results using the root mean square error RMSE as the evaluation index are shown in Table 1:

[0143] Table 1 The RMS error between the echo power of the small incident angle echo model and the reference echo power

[0144]

[0145] It can be seen from Table 1 that the power difference between the reference echo power and the echo power is very small, and as the incident angle increases, the deviation becomes smaller and smaller, which verifies the accuracy of the small incident angle echo power model constructed in the embodiment of the present invention in determining the power under small incident angle scenarios.

[0146] The calculation formula of RMSE is:

[0147]

[0148] Where N is the number of sampling gates; is the echo power corresponding to the i-th sampling gate time; is the reference echo power corresponding to the i-th sampling gate time.

[0149] In some embodiments of the present invention, the parameters are set as follows: satellite altitude is 960 km, 3dB beam width is 1.6 degrees, and the incident angles are set to 2 degrees, 3 degrees, 5 degrees, 8 degrees, 10 degrees, 15 degrees, and 20 degrees. The results of verifying the simplified small incident angle echo power model based on the above parameters are as follows: Figure 10-Figure 16 As shown, Figure 10-12 As shown in the figure, there is still a large deviation between the echo power determined by the simplified small incident angle echo power model and the reference echo power. The root mean square error RMSE between the echo power and the reference echo power is 2.8767e-20, 1.1199e-20, and 3.6065e-21, respectively. The deviation decreases with the increase of the incident angle. Figure 13-Figure 16 As shown in the figure, the root mean square error RMSE when the incident angle is 8 degrees, 10 degrees, 15 degrees, and 20 degrees is 9.9928e-22, 7.1074e-22, 2.6458e-22, and 1.2939e-22 respectively. It can be seen that the simplified small incident angle echo power model has higher accuracy when the incident angle is greater than 8 degrees.

[0150] In summary, the method for determining the echo power of a satellite radar altimeter with a small incidence angle proposed in an embodiment of the present invention provides a small incidence angle echo power model of a satellite radar altimeter under small incidence angles (1 to 20 degrees). The model is simple in form and easy to re-track the waveform. The amount of computation is smaller than that of three-term numerical convolution, which is convenient for rapid processing of satellite echo data and parameter inversion in practical applications.

[0151] In order to better implement the method for determining the echo power of a satellite radar altimeter with a small incidence angle in the embodiment of the present invention, based on the method for determining the echo power of a satellite radar altimeter with a small incidence angle, the embodiment of the present invention also provides a device for determining the echo power of a satellite radar altimeter with a small incidence angle, such as Fig.17 As shown, the small-incident-angle satellite radar altimeter echo power determination device 1700 includes:

[0152] The sea surface impulse response function determining unit 1701 is used to determine the target flat sea surface impulse response function at a small incidence angle based on the flat sea surface impulse response function at a quasi-vertical incidence angle;

[0153] The echo power model building unit 1702 is used to obtain the rough sea surface height probability density function and the point target response function of the satellite radar altimeter, and build a small incident angle echo power model based on the target flat sea surface impulse response function, the height probability density function and the point target response function;

[0154] An echo power determination unit 1703, configured to determine the echo power based on a small incident angle echo power model;

[0155] Among them, the angle range of the quasi-vertical incident angle is greater than or equal to 0° and less than 1°, and the angle range of the small incident angle is greater than or equal to 1° and less than 20°.

[0156] The small-incident-angle satellite radar altimeter echo power determination device 1700 provided in the above embodiment can implement the technical solution described in the above embodiment of the small-incident-angle satellite radar altimeter echo power determination method. The specific implementation principles of the above modules or units can refer to the corresponding contents in the above embodiment of the small-incident-angle satellite radar altimeter echo power determination method, which will not be repeated here.

[0157] Accordingly, an embodiment of the present invention also provides a computer-readable storage medium, which is used to store computer-readable programs or instructions. When the program or instructions are executed by a processor, it can implement the steps or functions of the method for determining the echo power of a satellite radar altimeter with a small incidence angle provided in the above-mentioned method embodiments.

[0158] Those skilled in the art will appreciate that all or part of the processes of the above-mentioned embodiments can be implemented by instructing related hardware (such as a processor, a controller, etc.) through a computer program, and the computer program can be stored in a computer-readable storage medium, wherein the computer-readable storage medium is a disk, an optical disk, a read-only storage memory, or a random access memory, etc.

[0159] The above is a detailed introduction to a method and device for determining the echo power of a satellite radar altimeter with a small incidence angle provided by the present invention. Specific examples are used in this article to illustrate the principles and implementation methods of the present invention. The description of the above embodiments is only used to help understand the method of the present invention and its core idea; at the same time, for technical personnel in this field, according to the idea of ​​the present invention, there will be changes in the specific implementation method and application scope. In summary, the content of this specification should not be understood as a limitation on the present invention.

Claims

1. A method for determining the echo power of a satellite radar altimeter with a small incidence angle, characterized in that: include: Based on the flat sea surface impulse response function at quasi-vertical incidence angle, the target flat sea surface impulse response function at small incidence angle is determined; Acquire a rough sea surface height probability density function and a point target response function of a satellite radar altimeter, and construct a small incident angle echo power model based on the target flat sea surface impulse response function, the height probability density function and the point target response function; Determining the echo power based on the small incident angle echo power model; Among them, the angle range of the quasi-vertical incident angle is greater than or equal to 0° and less than 1°, and the angle range of the small incident angle is greater than or equal to 1° and less than 20°; The target flat sea surface impulse response function is: A ( σ 0 ( ψ ))= In the formula, is the target flat sea surface impulse response; G 0 is the radar antenna boresight gain; λ The wavelength of the electromagnetic wave signal emitted by the radar; σ 0 ( ψ ) is the backscatter coefficient of the sea surface when the subsatellite point is incident; c is the speed of light; is the atmospheric loss for two-way propagation; θ w is the 3dB beamwidth of the antenna main lobe; h is the satellite altitude; ξ is the angle value of the incident angle; t For time; H 3. H 4. H 6 is the Hermite polynomial; The rough sea surface height probability density function is: In the formula, is the probability density value of rough sea surface height; SWH is the effective wave height of the sea surface; The point target response function is: or, In the formula, is the point target response value; is a constant related to the radar transmission power; is the experience value; B is the signal bandwidth; The small incident angle echo power model is: In the formula, W(t) is the echo power; is the skewness of the probability density function of the rough sea surface height; is the skewness of the point target response function; is the kurtosis of the probability density function of the rough sea surface height; is the kurtosis of the point target response function.

2. The method for determining the echo power of a small-incident-angle satellite radar altimeter according to claim 1, characterized in that: The method further comprises: Determine whether the angle of incidence is greater than 8°; When the angle value of the incident angle is greater than 8°, simplifying the echo power determined by the small incident angle echo power model to obtain a simplified small incident angle echo power model; The echo power is determined based on the simplified small-incident-angle echo power model.

3. The method for determining the echo power of a small-incident-angle satellite radar altimeter according to claim 2, characterized in that: The simplified small incident angle echo power model is: A ( σ 0 ( ψ ))= In the formula, W(t) is the echo power; G 0 is the radar antenna boresight gain; λ The wavelength of the electromagnetic wave signal emitted by the radar; σ 0 ( ψ ) is the backscatter coefficient of the sea surface when the subsatellite point is incident; c is the speed of light; is the atmospheric loss for two-way propagation; θ w is the 3dB beamwidth of the antenna main lobe; h is the satellite altitude; ξ is the angle value of the incident angle; t For time; H 3. H 4. H 6 is the Hermite polynomial; is the experience value; SWH is the effective wave height of the sea surface.

4. The method for determining the echo power of a small-incident-angle satellite radar altimeter according to claim 1, characterized in that: The method further comprises: Obtaining a Brown model flat sea surface impulse response function under oblique incidence, and determining a Brown model flat sea surface impulse response value, a height probability density function value, and a point target response function value based on the Brown model flat sea surface impulse response function, the height probability density function, and the point target response function; Performing three convolutions on the Brown model flat sea surface impulse response value, the height probability density function value, and the point target response function value to obtain a reference echo power; A power difference between the reference echo power and the echo power is determined, and when the power difference is less than a preset difference, it is determined that the small incident angle echo power model is reliable.

5. The method for determining the echo power of a small-incident-angle satellite radar altimeter according to claim 4, characterized in that: The reference echo power includes multiple reference echo powers corresponding to multiple incident angles with different values; the echo power includes multiple echo powers corresponding to multiple incident angles with different values; then the power difference between the reference echo power and the echo power is determined as follows: A plurality of power difference values ​​between a plurality of reference echo powers and the plurality of echo powers are determined.

6. A device for determining echo power of a satellite radar altimeter with a small incidence angle, characterized in that: include: A sea surface impulse response function determination unit is used to determine a target flat sea surface impulse response function at a small incident angle based on the flat sea surface impulse response function at a quasi-vertical incident angle; An echo power model building unit is used to obtain a rough sea surface height probability density function and a point target response function of a satellite radar altimeter, and to build a small incident angle echo power model based on the target flat sea surface impulse response function, the height probability density function and the point target response function; An echo power determination unit, configured to determine the echo power based on the small incident angle echo power model; Among them, the angle range of the quasi-vertical incident angle is greater than or equal to 0° and less than 1°, and the angle range of the small incident angle is greater than or equal to 1° and less than 20°; The target flat sea surface impulse response function is: A ( σ 0 ( ψ ))= In the formula, is the target flat sea surface impulse response; G 0 is the radar antenna boresight gain; λ The wavelength of the electromagnetic wave signal emitted by the radar; σ 0 ( ψ ) is the backscatter coefficient of the sea surface when the subsatellite point is incident; c is the speed of light; is the atmospheric loss for two-way propagation; θ w is the 3dB beamwidth of the antenna main lobe; h is the satellite altitude; ξ is the angle value of the incident angle; t For time; H 3. H 4. H 6 is the Hermite polynomial; The rough sea surface height probability density function is: In the formula, is the probability density value of rough sea surface height; SWH is the effective wave height of the sea surface; The point target response function is: or, In the formula, is the point target response value; is a constant related to the radar transmission power; is the experience value; B is the signal bandwidth; The small incident angle echo power model is: In the formula, W(t) is the echo power; is the skewness of the probability density function of the rough sea surface height; is the skewness of the point target response function; is the kurtosis of the probability density function of the rough sea surface height; is the kurtosis of the point target response function.

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