A method and system for estimating and correcting mis-pointing angle of synthetic aperture altimeter

Abstract

The present application provides a method and system for estimating and correcting the mispointing angle of a synthetic aperture altimeter, the method comprising: estimating the total mispointing angle from the PLRM mode echo using an altimeter echo model; summing the synthetic aperture altimeter echo signal in the range-Doppler domain in the range direction to obtain a RIP curve in the range-Doppler domain, estimating the along-track mispointing angle from the RIP curve, and correcting the along-track mispointing angle; calculating the cross-track mispointing angle based on the along-track mispointing angle and the total mispointing angle. The advantages of the present application are: it is applicable to different synthetic aperture altimeter echo models; it does not rely on the attitude data of the satellite, and estimates the mispointing angle of the synthetic aperture altimeter directly from the echo signal of the synthetic aperture altimeter. The estimated value of the mispointing angle can be further used for the mispointing angle correction of the echo signal to correct the parameter estimation deviation caused by the mispointing angle, especially the deviation of the ranging value.

Description

Technical Field

[0001] The present application belongs to the field of microwave remote sensing technology, and specifically relates to a method and system for estimating and correcting the mis-pointing angle of a synthetic aperture altimeter. Background Art

[0002] Radar altimeter is a microwave remote sensor that can measure the average height of the sea surface in the direction of the sub-satellite point. Its data can be used to invert ocean parameters such as sea surface height, effective wave height, sea surface wind speed, etc., and can be used in many fields such as oceanography, geodesy, geophysics, etc. Synthetic aperture altimeter is based on the traditional altimeter, by introducing the synthetic aperture technology along the track, to further improve the ranging accuracy of the altimeter, thereby improving the inversion accuracy of the sea surface height.

[0003] The mis-pointing angle of the altimeter refers to the angle between the antenna beam axis and the sub-satellite point direction. When there is a mis-pointing angle, the waveform of the echo signal received by the altimeter changes with the change of the mis-pointing angle, resulting in deviations in the estimated values ​​of parameters such as ranging and effective wave height obtained from the echo waveform. The mis-pointing angle of the synthetic aperture altimeter can be further decomposed into the along-track mis-pointing angle and the cross-track mis-pointing angle. Although the current echo model contains mis-pointing angle parameters, the mis-pointing angle parameters of the model cannot completely correct the error caused by the along-track mis-pointing angle. On the other hand, if the along-track and cross-track mis-pointing angles of the synthetic aperture are used as estimated parameters and jointly estimated with the distance, effective wave height and backscatter coefficient, the accuracy of parameter estimation will decrease as the number of parameters increases. Therefore, there is currently no effective method for mis-pointing angle correction of synthetic aperture altimeters. Summary of the invention

[0004] The purpose of the present application is to overcome the defect of low estimation accuracy of mis-pointing angle in the prior art.

[0005] In order to achieve the above object, the present application proposes a method for estimating and correcting the mis-pointing angle of a synthetic aperture altimeter, comprising:

[0006] The altimeter echo model is used to estimate the total mispointing angle from the PLRM mode echo. The synthetic aperture altimeter echo signal in the range-Doppler domain is summed along the range direction to obtain the RIP curve in the range-Doppler domain. The along-track mispointing angle is estimated from the RIP curve and the along-track mispointing angle is corrected.

[0007] The cross-track misdirection angle is calculated based on the along-track misdirection angle and the total misdirection angle.

[0008] As an improvement of the above method, the Gaussian approximate antenna pattern function used in estimating the along-track misdirection angle is:

[0009]

[0010] Among them, G al represents the Gaussian approximation antenna pattern function along the track; θ x represents the half-power beamwidth of the antenna along the track; θ al θ represents the angle between the direction of the target along the track and the direction of the sub-satellite point; p Indicates the along-track misdirection angle.

[0011] As an improvement of the above method, the Gaussian approximate antenna pattern function used in estimating the along-track misdirection angle is:

[0012] G al =exp(-α x (L x 1x p ) 2 )

[0013] Where: G al represents the Gaussian approximation antenna pattern function along the track; α x ≈γ x / h 2 , h represents the orbital height of the satellite, θ x Indicates the half-power beamwidth of the antenna along the track; L x represents the spatial resolution of the altimeter along the track; l represents the index of the Doppler frequency unit corresponding to different along-track beams; x p ≈h·θ p , represents the mis-pointing angle along the track, and the distance that the antenna axis deviates from the sub-satellite point along the track; θ p Indicates the along-track misdirection angle.

[0014] As an improvement of the above method, the method for estimating the along-track misdirection angle includes:

[0015] The least squares principle is used to fit the deviation value of the function through the along-track Gaussian approximate antenna pattern function to obtain the estimated value of the along-track misdirection angle.

[0016] As an improvement of the above method, the method for correcting the along-track misdirection angle includes:

[0017] The correction formula for the along-track mis-pointing angle is:

[0018]

[0019] Among them, K(θ al ) represents the correction amount of the mis-pointing angle along the track. The amplitude value of the echo signal at different azimuth angles along the azimuth in the range-Doppler domain is corrected according to K(θal); θ x represents the half-power beamwidth of the antenna along the track; θal θ represents the angle between the direction of the target along the track and the direction of the sub-satellite point; p Indicates the along-track misdirection angle.

[0020] As an improvement of the above method, the synthetic aperture altimeter echo model is a Brown model or an improved model of the Brown model.

[0021] As an improvement of the above method, the formula for calculating the cross-track misdirection angle is:

[0022]

[0023] Where ξ is the total mispointing angle; θ p represents the along-track misdirection angle; θ r Indicates the cross-track misdirection angle.

[0024] The present application also provides a system for estimating and correcting mis-pointing angles of a synthetic aperture altimeter, which is implemented based on the above method, and the system comprises:

[0025] A module for estimating and correcting the along-track mis-pointing angle is used to sum the synthetic aperture altimeter echo signal in the range-Doppler domain along the range direction to obtain a RIP curve in the range-Doppler domain, estimate the along-track mis-pointing angle from the RIP curve, and correct the along-track mis-pointing angle;

[0026] A total mis-pointing angle estimation module, used to estimate the total mis-pointing angle from the PLRM mode echo using an altimeter echo model; and

[0027] The cross-track mis-pointing angle calculation module is used to calculate the cross-track mis-pointing angle according to the along-track mis-pointing angle and the total mis-pointing angle.

[0028] Compared with the prior art, the advantages of this application are:

[0029] 1. The present application uses Gaussian antenna pattern approximation when performing along-track mis-pointing angle correction. This correction is independent of the selection of the altimeter echo model, so that the along-track mis-pointing angle correction is applicable to different synthetic aperture altimeter echo models;

[0030] 2. When the prior art uses multi-parameter joint estimation, as the estimated parameters increase, the estimation accuracy of each parameter will decrease, which will directly affect the ranging accuracy of the altimeter. At the same time, in the experiment, the inventor also found that in the parameter estimation, adding the cross-track misdirection angle θ r When used as an estimated parameter, its solution method is usually difficult to converge to a stable value, making the parameter estimation result meaningless. The method of this application does not use a multi-parameter joint estimation method to estimate and correct the mis-pointing angle, thus avoiding the defects of this method;

[0031] 3. The present invention can estimate the mis-pointing angle of the synthetic aperture altimeter directly from the echo signal of the synthetic aperture altimeter without relying on the attitude data of the satellite. The estimated value of the mis-pointing angle can be further used for the mis-pointing angle correction of the echo signal to correct the parameter estimation deviation caused by the mis-pointing angle, especially the deviation of the ranging value. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 Shown is a schematic diagram of mis-pointing angle;

[0033] Figure 2 Shown is a flow chart of synthetic aperture altimeter data processing including mis-pointing angle estimation and correction;

[0034] FIG3( a ) is a schematic diagram showing a change in the along-track mis-pointing angle;

[0035] FIG3( b ) shows a second schematic diagram of the change of the along-track mis-pointing angle;

[0036] Figure 4 Shown is a multi-view stack at a mispointing angle of 0°;

[0037] Figure 5 Shown is a multi-view stack when the along-track mispointing angle is 0.2°;

[0038] Figure 6 Shown is the least square solution fitting curve for along-track mispointing angle estimation;

[0039] Figure 7 Shown is the comparison of RIP distribution before and after correction of along-track mispointing angle. DETAILED DESCRIPTION

[0040] The technical solution of the present application is described in detail below with reference to the accompanying drawings.

[0041] The present invention mainly includes two parts: estimation and correction of the mis-pointing angle of a synthetic aperture altimeter, which can estimate the components of the mis-pointing angle in the along-track direction and the cross-track direction from the echo signal of the synthetic aperture altimeter, and is used for the along-track waveform correction and subsequent parameter estimation of the synthetic aperture altimeter signal to correct the parameter estimation deviation caused by the mis-pointing angle.

[0042] The present invention utilizes an antenna pattern compensation method in the along-track direction to correct the parameter estimation deviation caused by the mis-pointing angle in the along-track direction; and utilizes a re-tracking method in the cross-track direction to substitute the mis-pointing angle estimation parameters to correct the mis-pointing angle of the synthetic aperture altimeter.

[0043] The mis-pointing angle of the synthetic aperture altimeter refers to the angle between the antenna beam axis and the sub-satellite point direction. The mis-pointing angle ξ of the synthetic aperture altimeter can be decomposed into the along-track mis-pointing angle θ p and the cross-track misdirection angle θ rThe geometric relationship between the three is as follows: Figure 1 As shown, the three conditions are satisfied:

[0044]

[0045] The antenna pattern of the synthetic aperture altimeter under the approximate condition of the Gaussian circular antenna is approximately:

[0046]

[0047] Among them, G 0 represents the antenna beam center pointing gain, θ al represents the angle between the direction of the target along the track and the direction of the sub-satellite point, θ ac It indicates the angle between the cross-track target direction and the sub-satellite point direction. θ x and θ y Indicates the antenna half-power beamwidth in the along-track and cross-track directions.

[0048] The antenna pattern can be further decomposed into the along-track antenna gain G al (θ al ):

[0049] G al (θ al )=exp(-γ x sin 2 (θ al -θ p ))(3)

[0050] and the cross-track antenna gain G ac (θ ac ):

[0051] G ac (θ ac )=exp(-γ y sin 2 (θ ac -θ r ))(4)

[0052] The along-track antenna gain can be used to estimate and correct the along-track mis-pointing angle of the synthetic aperture altimeter. Assuming that the orbital altitude of the satellite is h, the spatial resolution of the altimeter along the track is L x , the index l of the Doppler frequency unit corresponding to different along-track beams, under the condition of small angle approximation, is:

[0053]

[0054] Suppose the mis-pointing angle along the track is x, and the distance that the antenna axis deviates from the sub-satellite point along the track is x. p ≈h·θ p, transform equation (5) and x p Substituting into equation (3), we can obtain the change of the antenna radiation pattern along the track with the Doppler frequency unit index G al (l):

[0055] (6)

[0056] Among them, α x ≈γ x / h 2 .

[0057] The Gaussian approximate antenna pattern function along the track used in equation (6) or equation (3) can be combined with the synthetic aperture altimeter to sum along the range direction to obtain the integrated power (Range Integrated Power, RIP) in the range direction to solve the mis-pointing angle along the track. The deviation value θ of the Gaussian function of the antenna pattern is fitted using the least squares principle or other estimation methods and equation (6) or equation (3). p , we can get the along-track mis-pointing angle θ p The correction amount of the along-track mis-pointing angle is the ratio of the zero mis-pointing angle pattern to the actual mis-pointing angle:

[0058]

[0059] For the echo signals at different azimuth angles in the range-Doppler domain, the amplitude values ​​are calculated according to K(θ al ) for correction.

[0060] By performing non-correlated processing on the echo signal received by the synthetic aperture altimeter, an echo waveform signal similar to that of a traditional altimeter can be obtained, which is called a pseudo-low resolution mode (Pseudo-Low Resolution Mode, PLRM) signal.

[0061] By using the Brown model and its improved model including the mis-pointing angle and other traditional altimeter echo models to estimate the PLRM echo signal by the least squares method or the maximum likelihood method, four parameters, namely the echo delay, effective wave height, backscatter coefficient and mis-pointing angle ξ, can be obtained from the PLRM echo. Combining equations (1) and (6), the cross-track mis-pointing angle θ of the synthetic aperture altimeter can be obtained: r The estimated value of .

[0062] After obtaining the cross-track mis-pointing angle θ of the synthetic aperture altimeter r Afterwards, the synthetic aperture altimeter echo model including the cross-track mispointing angle parameters is used to re-track the multi-look average signal that has completed the along-track mispointing angle correction, so as to obtain the satellite-to-sea surface distance, effective wave height and backscatter coefficient parameters after the mispointing angle correction.

[0063] For the range-Doppler domain signal of the synthetic aperture altimeter with decoupled along-track and cross-track directions, the leading edges of the echo signal from different directions are aligned to the same range gate. For a fixed range gate, different Doppler beams represent the echo of the range gate in different directions. The gain of the echo of different beams is mainly affected by the along-track antenna radiation pattern G in equation (3). al For a determined Doppler beam, the directional pattern of each unit in the range direction is mainly affected by the directional pattern of the cross-track antenna (4) G ac impact.

[0064] Example 1

[0065] like Figure 2 As shown, combined with the altimeter data processing flow, the method steps for implementing the mis-pointing angle correction of the present invention are as follows:

[0066] Step 1A: Estimate the total mispointing angle ξ of the altimeter;

[0067] Step 1A-1: Read the PLRM mode echo data of the altimeter product;

[0068] Step 1A-2: Estimate the total mispointing angle ξ of the altimeter from the PLRM mode echo using the altimeter echo model; the altimeter echo model includes the Brown model, an improved model of the Brown model, etc.

[0069] Step 1B: Correct the along-track mis-pointing angle gain;

[0070] Step 1B-1: summing the synthetic aperture altimeter echo signal in the range-Doppler domain along the range direction to obtain a RIP curve in the range-Doppler domain;

[0071] Step 1B-2: Estimate the along-track misdirection angle θ from the RIP curve using equation (6) p ;

[0072] Step 1B-3: Correct the antenna gain along the track using equation (7) to obtain a synthetic aperture altimeter echo signal with a misdirection angle of 0° along the track;

[0073] Step 2: Calculate the cross-track misdirection angle θ using equation (1) r The estimated value is used as the cross-track misdirection angle parameter for subsequent signal processing.

[0074] The relationship between the above steps is as follows Figure 2 When there is a mis-pointing angle in the along-track direction as shown in Figure 3(a) or Figure 3(b), due to the change of the antenna gain in the along-track direction, the range-Doppler domain signal in the along-track direction will be Figure 4 The along-track symmetric distribution shown becomes Figure 5 The asymmetric distribution shown. Figure 5The range-Doppler domain signal shown is summed along the range direction to obtain the RIP in the range-Doppler domain. The peak center of the RIP curve in the range-Doppler domain mainly changes with the change of the mis-pointing angle in the along-track direction, and the influence of the mis-pointing angle in the cross-track direction on its center position can be ignored. Therefore, the mis-pointing angle in the along-track direction can be estimated according to step 1B-2, and the mis-pointing angle θ is estimated. p The antenna pattern of formula (3) is calculated, and the fitting result of the antenna pattern and the RIP curve is as follows: Figure 6 shown.

[0075] According to step 1B-3, perform the correction for the mis-pointing angle along the track. The RIP in the range-Doppler domain after correction is compared with the RIP in the range-Doppler domain before and after the mis-pointing angle correction. Figure 7 As shown, the asymmetry of the along-track direction is corrected. Substituting steps 1A-2 and 1B-2 into step 2, the cross-track misdirection angle θ is obtained. r The estimated value of serves as the input for the subsequent parameter estimation process.

[0076] The simulated synthetic aperture altimeter is used to simulate the echo signals of the open-loop mode and the closed-loop mode when the mis-pointing angles in the along-track direction and the cross-track direction are 0.2° respectively, and the echo signals are processed to compare the difference in ranging values ​​obtained by the PLRM mode and the synthetic aperture mode. For the same simulated sea area, there should be no deviation in the ranging results of the two modes in theory. It can be seen from the results of Table 1 and Table 2 that when the mis-pointing angle is ignored during re-tracking, there is a deviation in the distance estimation result, as shown in the first column of Table 1 and Table 2. The mis-pointing angle set in the simulation is used as the input for re-tracking, and the ranging deviation caused by the along-track direction is not significantly corrected, as shown in the second column of Table 1 and Table 2. After the mis-pointing angle is corrected according to the process method shown in the present invention, the ranging deviations of the echo signal in the along-track direction and the cross-track direction are corrected, as shown in the third column of Table 1 and Table 2.

[0077] Table 1 Closed-loop mode simulation results

[0078]

[0079] Table 2 Open-loop mode simulation results

[0080]

[0081] Example 2

[0082] The present application also provides a system for estimating and correcting mis-pointing angles of a synthetic aperture altimeter, which is implemented based on the above method, and the system comprises:

[0083] A module for estimating and correcting the along-track mis-pointing angle is used to sum the synthetic aperture altimeter echo signal in the range-Doppler domain along the range direction to obtain a RIP curve in the range-Doppler domain, estimate the along-track mis-pointing angle from the RIP curve, and correct the along-track mis-pointing angle;

[0084] A total mis-pointing angle estimation module, used to estimate the total mis-pointing angle from the PLRM mode echo using an altimeter echo model; and

[0085] The cross-track mis-pointing angle calculation module is used to calculate the cross-track mis-pointing angle according to the along-track mis-pointing angle and the total mis-pointing angle.

[0086] The present invention realizes a synthetic aperture altimeter signal processing method for estimating and correcting the mis-pointing angle using the synthetic aperture altimeter echo signal. The method realizes the decoupling of the mis-pointing angle estimation and the platform parameters, and can directly extract the mis-pointing angle information of the altimeter from the echo signal of the synthetic aperture altimeter without relying on the attitude data of the satellite and use it for the mis-pointing angle correction of the echo signal to correct the parameter estimation deviation caused by the mis-pointing angle. The mis-pointing angle parameter can also be replaced by the mis-pointing angle data calculated by the attitude information of the satellite platform, but the deviation of the sensor measurement angle needs to be corrected.

[0087] The present application may also provide a computer device, comprising: at least one processor, a memory, at least one network interface and a user interface. The various components in the device are coupled together through a bus system. It is understood that the bus system is used to achieve connection and communication between these components. In addition to the data bus, the bus system also includes a power bus, a control bus and a status signal bus.

[0088] The user interface may include a display, a keyboard or a pointing device, such as a mouse, a trackball, a touch pad or a touch screen.

[0089] It can be understood that the memory in the disclosed embodiments of the present application can be a volatile memory or a non-volatile memory, or can include both volatile and non-volatile memories. Among them, the non-volatile memory can be a read-only memory (ROM), a programmable read-only memory (PROM), an erasable programmable read-only memory (EPROM), an electrically erasable programmable read-only memory (EEPROM), or a flash memory. The volatile memory can be a random access memory (RAM), which is used as an external cache. By way of example but not limitation, many forms of RAM are available, such as static random access memory (SRAM), dynamic random access memory (DRAM), synchronous dynamic random access memory (SDRAM), double data rate synchronous dynamic random access memory (DDRSDRAM), enhanced synchronous dynamic random access memory (ESDRAM), synchronous link dynamic random access memory (SLDRAM), and direct memory bus random access memory (DRRAM). The memory described herein is intended to include, but is not limited to, these and any other suitable types of memory.

[0090] In some embodiments, the memory stores the following elements, executable modules or data structures, or a subset thereof, or an extended set thereof: an operating system and applications.

[0091] The operating system includes various system programs, such as a framework layer, a core library layer, a driver layer, etc., which are used to implement various basic services and process hardware-based tasks. The application includes various application programs, such as a media player (MediaPlayer), a browser (Browser), etc., which are used to implement various application services. The program for implementing the method of the embodiment of the present disclosure can be included in the application.

[0092] In the above embodiment, the processor may also call a program or instruction stored in the memory, specifically, a program or instruction stored in an application program, and is used to:

[0093] Execute the steps of the above method.

[0094] The above method can be applied to a processor or implemented by a processor. The processor may be an integrated circuit chip with signal processing capabilities. In the implementation process, each step of the above method can be completed by an integrated logic circuit of hardware in the processor or an instruction in the form of software. The above processor may be a general processor, a digital signal processor (Digital Signal Processor, DSP), an application specific integrated circuit (Application Specific Integrated Circuit, ASIC), a field programmable gate array (Field Programmable Gate Array, FPGA) or other programmable logic devices, discrete gates or transistor logic devices, discrete hardware components. The above-disclosed methods, steps and logic block diagrams can be implemented or executed. The general processor may be a microprocessor or the processor may also be any conventional processor, etc. The steps of the above-disclosed method can be directly embodied as a hardware decoding processor to execute, or the hardware and software modules in the decoding processor can be combined to execute. The software module can be located in a mature storage medium in the field such as a random access memory, a flash memory, a read-only memory, a programmable read-only memory or an electrically erasable programmable memory, a register, etc. The storage medium is located in the memory, and the processor reads the information in the memory and completes the steps of the above method in combination with its hardware.

[0095] It is understood that the embodiments described in the present application can be implemented by hardware, software, firmware, middleware, microcode or a combination thereof. For hardware implementation, the processing unit can be implemented in one or more application specific integrated circuits (Application Specific Integrated Circuits, ASIC), digital signal processors (Digital Signal Processing, DSP), digital signal processing devices (DSP Device, DSPD), programmable logic devices (Programmable Logic Device, PLD), field programmable gate arrays (Field-Programmable Gate Array, FPGA), general-purpose processors, controllers, microcontrollers, microprocessors, other electronic units for performing the functions described in the present application or a combination thereof.

[0096] For software implementation, the technology of the present application can be implemented by executing the functional modules (such as procedures, functions, etc.) of the present application. The software code can be stored in a memory and executed by a processor. The memory can be implemented in the processor or outside the processor.

[0097] The present application may also provide a non-volatile storage medium for storing a computer program. When the computer program is executed by a processor, each step in the above method embodiment can be implemented.

[0098] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the present application and are not intended to limit it. Although the present application is described in detail with reference to the embodiments, a person skilled in the art should understand that any modification or equivalent replacement of the technical solution of the present application does not depart from the spirit and scope of the technical solution of the present application and should be included in the scope of the claims of the present application.

Claims

1. A method for estimating and correcting mis-pointing angle of a synthetic aperture altimeter, comprising: The total mispointing angle is estimated from the pseudo low-resolution mode echo using the altimeter echo model; The synthetic aperture altimeter echo signal in the range-Doppler domain is summed along the range direction to obtain a range-Doppler domain range-power integral curve, the along-track mis-pointing angle is estimated from the range-power integral curve, and the along-track mis-pointing angle is corrected; Calculate the cross-track misdirection angle according to the along-track misdirection angle and the total misdirection angle; The method for correcting the along-track mis-pointing angle comprises: The correction formula for the along-track mis-pointing angle is: in, It indicates the correction amount of the mis-pointing angle along the track. For the echo signals at different azimuth angles along the azimuth in the range-Doppler domain, the amplitude value is calculated according to Make corrections; Indicates the half-power beamwidth of the antenna along the track; Indicates the angle between the along-track direction to the target and the sub-satellite direction; Indicates the along-track misdirection angle.

2. The method for estimating and correcting mis-pointing angle of a synthetic aperture altimeter according to claim 1, characterized in that: The Gaussian approximation antenna pattern function used in estimating the along-track mis-pointing angle is: in, represents the along-track Gaussian approximate antenna pattern function; Indicates the half-power beamwidth of the antenna along the track; Indicates the angle between the along-track direction to the target and the sub-satellite direction; Indicates the along-track misdirection angle.

3. The method for estimating and correcting mis-pointing angle of a synthetic aperture altimeter according to claim 1, characterized in that: The method for estimating the along-track misdirection angle comprises: The Gaussian approximation antenna pattern function is: in: represents the along-track Gaussian approximate antenna pattern function; , Indicates the orbital altitude of the satellite. , Indicates the half-power beamwidth of the antenna along the track; It represents the spatial resolution of the altimeter along the track; Indicates the index of the Doppler frequency unit corresponding to different along-track beams; , represents the along-track mis-pointing angle, which is the distance that the antenna axis deviates from the sub-satellite point along the along-track direction; Indicates the along-track misdirection angle; Using the least squares principle and Gaussian approximation antenna pattern function to fit the deviation value of the antenna pattern Gaussian function , we can get the along-track mis-pointing angle The estimated value of .

4. The method for estimating and correcting mis-pointing angle of a synthetic aperture altimeter according to claim 1, characterized in that: The synthetic aperture altimeter echo model is a Brown model or an improved model of the Brown model.

5. The method for estimating and correcting mis-pointing angle of a synthetic aperture altimeter according to claim 1, characterized in that: The formula for calculating the cross-track misdirection angle is: in, represents the total mispointing angle; Indicates the along-track misdirection angle; Indicates the cross-track misdirection angle.

6. A system for estimating and correcting mis-pointing angle of a synthetic aperture altimeter, implemented based on the method of any one of claims 1 to 5, characterized in that: The system comprises: The module for estimating and correcting the mis-pointing angle along the track is used to sum the synthetic aperture altimeter echo signal in the range-Doppler domain along the range direction to obtain the range power integral curve in the range-Doppler domain, estimate the mis-pointing angle along the track from the range power integral curve, and correct the mis-pointing angle along the track. a total mis-pointing angle estimation module, for estimating the total mis-pointing angle from the pseudo low-resolution mode echo using a synthetic aperture altimeter echo model; and The cross-track mis-pointing angle calculation module is used to calculate the cross-track mis-pointing angle according to the along-track mis-pointing angle and the total mis-pointing angle.

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