Ku / Ka dual-band satellite-borne rainfall measurement radar space radiation calibration method

Abstract

The invention relates to a Ku / Ka dual-band space radiometric calibration method for a satellite-borne rainfall measurement radar, and the method specifically comprises the steps: S1, carrying out the radiometric calibration of the satellite-borne rainfall measurement radar through a space radiometric calibrator, obtaining a corresponding relation between a radar working parameter and a radiation measurement error, and constructing a satellite-borne rainfall measurement radar radiation measurement error database; s2, training and learning the neural network through the satellite-borne rainfall measurement radar radiation measurement error database, and generating a satellite-borne rainfall measurement radar radiation measurement error estimation model; and S3, obtaining radar working parameters of the spaceborne rainfall measurement radar, performing radiation measurement error estimation of the spaceborne rainfall measurement radar through the spaceborne rainfall measurement radar radiation measurement error estimation model, and performing radiation error compensation according to a radiation measurement error estimation result. According to the invention, the calibration precision of the spaceborne rainfall measurement radar is effectively improved, and the rainfall inversion precision is further improved.

Description

Technical Field

[0001] This invention relates to the field of radar technology in the electronics and information industry, and in particular to a space radiation calibration method for a Ku / Ka dual-band spaceborne precipitation measurement radar. Background Technology

[0002] Spaceborne precipitation measurement radar is a crucial remote sensing instrument for global precipitation monitoring and precipitation retrieval. Its working mechanism is based on the scattering characteristics of raindrops in the Ku-band (12-18 GHz) and Ka-band (26.5-40 GHz) electromagnetic waves and the differences between the two bands to retrieve precipitation amounts. Accurate measurement of the scattering characteristics of raindrops in both the Ku and Ka bands is a key prerequisite for ensuring the accuracy and reliability of the precipitation retrieval results.

[0003] To ensure the accuracy of spaceborne precipitation measurement radar in measuring the scattering characteristics of dual-band signals, its radiation measurement performance needs to be calibrated periodically. Ground calibration technology is currently a widely used calibration method. This technology utilizes ground calibration stations to transmit Ku-band and Ka-band electromagnetic wave signals with known power. After receiving these signals, the spaceborne precipitation measurement radar compares the measured signal power with the theoretical signal power to calculate the radiation measurement error. Based on this error, the radar's measurement results are corrected, thereby calibrating the radar's radiation measurement performance.

[0004] However, existing ground-based calibration technologies have significant limitations, mainly in the following aspects: First, the electromagnetic wave signals emitted by ground calibration stations must pass through the atmosphere during transmission to the spaceborne precipitation measurement radar. The water vapor, clouds, aerosols, and other components in the atmosphere absorb, scatter, and refract the electromagnetic waves, causing power attenuation and waveform distortion in the calibration signal. This results in the calibration signal received by the spaceborne precipitation measurement radar failing to accurately reflect the original characteristics of the signal emitted by the ground calibration station, leading to inaccurate calibration of radiation measurement errors. Second, the atmospheric environment is complex and variable; parameters such as humidity, temperature, and air pressure exhibit significant differences at different times and in different regions. The spatiotemporal dynamics make it difficult to accurately quantify and fully compensate for the influence of the atmosphere on electromagnetic waves using existing models. This severely restricts the stability and reliability of ground calibration results, making it impossible to provide a continuous and stable calibration benchmark for spaceborne precipitation measurement radar. Finally, the distribution of ground calibration stations is limited by geographical conditions, and their observations are also constrained by time windows, making it difficult to achieve long-term, continuous, and real-time calibration of spaceborne precipitation measurement radar. This results in the inability to promptly and effectively correct radiation measurement errors when spaceborne precipitation measurement radar detects rainfall outside of calibration periods, thus affecting the measurement accuracy of dual-band scattering characteristics in rainfall areas. Ultimately, this restricts the accuracy of rainfall inversion and makes it difficult to meet the needs of precise rainfall weather forecasting. Summary of the Invention

[0005] To address the technical problems existing in the prior art, the present invention aims to provide a Ku / Ka dual-band spaceborne precipitation measurement radar space radiation calibration method, which effectively improves the calibration accuracy of spaceborne precipitation measurement radar, thereby improving the precipitation inversion accuracy.

[0006] To achieve the above-mentioned objectives, this invention provides a space radiometric calibration method for a Ku / Ka dual-band spaceborne precipitation measurement radar, comprising the following steps:

[0007] Step S1: Use a space radiometric calibrator to perform radiometric calibration on the spaceborne precipitation measurement radar, obtain the correspondence between radar operating parameters and radiometric measurement errors, and construct a database of radiometric measurement errors for the spaceborne precipitation measurement radar.

[0008] Step S2: Train the neural network using the satellite-borne rainfall measurement radar radiation measurement error database to generate a satellite-borne rainfall measurement radar radiation measurement error estimation model; the satellite-borne rainfall measurement radar radiation measurement error estimation model is used to output the radiation measurement error based on the input radar operating parameters;

[0009] Step S3: Obtain the radar operating parameters of the spaceborne rainfall measurement radar, estimate the radiation measurement error of the spaceborne rainfall measurement radar using the radiation measurement error estimation model, and perform radiation error compensation based on the radiation measurement error estimation results.

[0010] According to a technical solution of the present invention, step S1 specifically includes:

[0011] Using a space-based radiometric calibrator mounted on a micro-nano calibration satellite, periodic radiometric calibration was performed on a spaceborne precipitation measurement radar to obtain the Ku / Ka dual-frequency fully polarized echo power and its corresponding radar operating parameters for different RCS values. The radar operating parameters include the radar's internal temperature, operating voltage, and operating current. The Ku / Ka dual-frequency fully polarized echo power covers both Ku and Ka frequency bands, with each band including four polarization channels: VV, VH, HH, and HV.

[0012] Based on different RCS values ​​and their corresponding Ku / Ka dual-frequency fully polarized echo power, the variation characteristics of the "calibrator RCS-echo power" curve are analyzed to obtain the calibration constant of the Ku / Ka dual-frequency fully polarized echo power of the spaceborne precipitation measurement radar under different RCS values.

[0013] Based on the Ku / Ka dual-frequency fully polarized echo power of the spaceborne rainfall measurement radar at different RCS values ​​and the corresponding radar operating parameters and calibration constants of the spaceborne rainfall measurement radar, a radiation measurement error database for the spaceborne rainfall measurement radar is constructed.

[0014] According to one technical solution of the present invention, the accuracy of the radar operating parameters of the spaceborne rainfall measurement radar satisfies:

[0015] The internal temperature accuracy is better than ±1℃, the operating voltage accuracy is better than ±0.1V, and the operating current accuracy is better than ±0.1A.

[0016] According to one technical solution of the present invention, in step S1, when performing periodic radiometric calibration, the RCS value of each group of data in the satellite-borne precipitation measurement radar radiometric measurement error database is not less than three.

[0017] According to one technical solution of the present invention, a spaceborne precipitation measurement radar is calibrated using a space radiation calibrator, specifically including:

[0018] During a single calibration period, a V-polarized calibration signal is transmitted via a spaceborne precipitation measurement radar;

[0019] Multiple different RCS values ​​are generated by a space radiation calibrator, and based on the different RCS values ​​and the V-polarization calibration signal, co-polarization calibration signals and cross-polarization calibration signals of the V-polarization calibration signal are generated.

[0020] H-polarization calibration signals are transmitted via a spaceborne precipitation measurement radar.

[0021] Multiple different RCS values ​​are generated by a space radiation calibrator, and based on the different RCS values ​​and the H-polarization calibration signal, a co-polarization calibration signal and a cross-polarization calibration signal corresponding to the H-polarization calibration signal are generated.

[0022] The satellite-borne precipitation measurement radar receives the co-polarization calibration signal and cross-polarization calibration signal corresponding to the V-polarization calibration signal and the H-polarization calibration signal.

[0023] According to one technical solution of the present invention, the space radiation calibrator includes a Ku / Ka dual-frequency dual-polarized transmitting antenna, a Ku / Ka dual-frequency dual-polarized receiving antenna, and an active calibration signal control module;

[0024] The active calibration signal control module is used to control the multi-channel gain of dual-frequency full polarization, simulating different RCS values ​​in the multi-channel gain;

[0025] The Ku / Ka dual-band dual-polarization transmitting antenna and the Ku / Ka dual-band dual-polarization receiving antenna are isolated by a shield, with an isolation degree ≥80dB;

[0026] The polarization isolation between the Ku / Ka dual-frequency dual-polarization transmitting antenna and the Ku / Ka dual-frequency dual-polarization receiving antenna is ≥30dB, and the highest sidelobe level is ≤-40dBi.

[0027] According to one technical solution of the present invention, during the simulation of different RCS values, the space radiation calibrator simulates the adjustment of the RCS value in 2dB steps within the range of 50dBsm-80dBsm, and sets the step response time to ≤1μs.

[0028] According to one technical solution of the present invention, the space radiation calibrator is mounted on the micro-nano calibration satellite platform via a three-axis attitude adjustment device.

[0029] According to one technical solution of the present invention, the method further includes the following step before step S3:

[0030] Before the spaceborne rainfall measurement radar detects, ground calibration data is acquired, and the trained spaceborne rainfall measurement radar radiation measurement error estimation model is corrected using the ground calibration data.

[0031] According to one technical solution of the present invention, step S3 specifically includes:

[0032] The rainfall area is detected by a spaceborne rainfall measurement radar, and the dual-frequency scattered echo of the rainfall area and the radar operating parameters at the time of detection are obtained.

[0033] The satellite-borne rainfall measurement radar radiation measurement error estimation model is used to generate the satellite-borne rainfall measurement radar radiation measurement error based on the input radar operating parameters.

[0034] Radiation error compensation is performed on the dual-frequency scattered echoes in the rainfall area by generating radiation measurement errors from the satellite-borne rainfall measurement radar.

[0035] Compared with the prior art, the present invention has the following advantages:

[0036] This invention proposes a Ku / Ka dual-band spaceborne precipitation measurement radar radiometric calibration method. It employs a space radiometric calibrator to measure and calibrate the radiation characteristics of the spaceborne precipitation measurement radar, effectively avoiding signal power attenuation caused by atmospheric water vapor and clouds. This allows for more accurate measurement of the radiation characteristics of the spaceborne precipitation measurement radar. Furthermore, the space radiometric calibration method is not limited by geographical conditions, improving the timeliness of radiometric calibration. These advantages effectively enhance the accuracy of precipitation inversion from spaceborne precipitation measurement radar.

[0037] This invention utilizes a radiation measurement error database and a neural network training model to establish a radiation error prediction model. It rationally characterizes the correlation characteristics of "radar internal temperature - operating voltage - operating current - radiation measurement error" data, enabling accurate mapping of the three-dimensional parameters of "temperature - voltage - current" with radiation measurement errors. This effectively improves the estimation accuracy of radiation errors and adapts to the performance drift of radar during long-term operation. Attached Figure Description

[0038] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments will be briefly described below. Obviously, the drawings described below are merely some embodiments of the present invention, and those skilled in the art can obtain other drawings based on these drawings without creative effort.

[0039] Figure 1 The schematic diagram illustrates the principle of the Ku / Ka dual-band spaceborne precipitation measurement radar space radiation calibration method provided by the present invention;

[0040] Figure 2 This schematic diagram illustrates a flowchart of the space radiation calibration method for Ku / Ka dual-band spaceborne precipitation measurement radar provided by the present invention.

[0041] Figure 3 This illustration shows a scenario where a space-based active calibrator, according to an embodiment of the present invention, performs pre-detection calibration on a spaceborne precipitation radar.

[0042] Figure 4 This schematic diagram illustrates the composition of a space active calibrator provided in one embodiment of the present invention.

[0043] Figure 5 This schematic diagram illustrates a Ku / Ka dual-band space calibration timing diagram according to an embodiment of the present invention.

[0044] Figure 6 This illustration illustrates the radiation error correction process of a spaceborne precipitation measurement radar provided in one embodiment of the present invention. Detailed Implementation

[0045] The description of the embodiments in this specification should be taken in conjunction with the accompanying drawings, which should form part of the complete specification. In the drawings, the shape or thickness of the embodiments may be exaggerated and may be indicated in a simplified or convenient manner. Furthermore, parts of the various structures in the drawings will be described separately; it is worth noting that elements not shown in the figures or not described in words are in a form known to those skilled in the art.

[0046] The descriptions of the embodiments herein, including any references to directions and orientations, are for ease of description only and should not be construed as limiting the scope of the invention. The following description of preferred embodiments involves combinations of features, which may exist independently or in combination; the invention is not particularly limited to the preferred embodiments. The scope of the invention is defined by the claims.

[0047] like Figure 1 As shown, the principle of the Ku / Ka dual-band spaceborne precipitation measurement radar space radiation calibration method of the present invention includes two parts. The first part 10 is that the space calibrator calibrates the radiation measurement error of the spaceborne precipitation measurement radar. A Ku / Ka dual-band active calibrator is carried on a micro-nano satellite to calibrate the radiation measurement error of the spaceborne precipitation measurement radar and to construct a correlation database between the internal temperature of the spaceborne precipitation measurement radar, the radar operating voltage and current and the radiation measurement error, that is, the radiation measurement error database. The second part 20 is to compensate for the radiation measurement error of the spaceborne precipitation measurement radar. The spaceborne precipitation measurement radar is used to detect the precipitation area and obtain the dual-band scattered echo of the precipitation area. The power of the dual-band scattered echo of the precipitation area is calculated using the radiation measurement error.

[0048] like Figure 2 As shown, this invention provides a space radiometric calibration method for a Ku / Ka dual-band spaceborne precipitation measurement radar, comprising the following steps:

[0049] Step S1: Use a space radiometric calibrator to perform radiometric calibration on the spaceborne precipitation measurement radar, obtain the correspondence between radar operating parameters and radiometric measurement errors, and construct a database of radiometric measurement errors for the spaceborne precipitation measurement radar.

[0050] Step S2: Train the neural network using the satellite-borne rainfall measurement radar radiation measurement error database to generate a satellite-borne rainfall measurement radar radiation measurement error estimation model; the satellite-borne rainfall measurement radar radiation measurement error estimation model is used to output the radiation measurement error based on the input radar operating parameters;

[0051] Step S3: Obtain the radar operating parameters of the spaceborne rainfall measurement radar, estimate the radiation measurement error of the spaceborne rainfall measurement radar through the radiation measurement error estimation model, and perform radiation error compensation based on the radiation measurement error estimation results.

[0052] The method provided by this invention addresses the problem that existing spaceborne precipitation measurement radars heavily rely on ground calibration stations for measuring raindrop scattering characteristics. Furthermore, ground calibration is limited in accuracy due to the influence of atmospheric water vapor, leading to limited accuracy in precipitation retrieval. This invention uses a space-based radiometric calibrator to calibrate the radiometric measurement error of the spaceborne precipitation measurement radar and constructs a correlation database between the radar's internal temperature, operating voltage and current, and radiometric measurement error. A neural network is trained using this correlation database to obtain a radiometric measurement error estimation model for the spaceborne precipitation measurement radar. The radiometric measurement error output by this model is used to compensate for the echo radiation error of the spaceborne precipitation measurement radar, effectively improving the accuracy of dual-band scattering characteristic measurement. The compensation accuracy is unaffected by atmospheric conditions, further improving precipitation retrieval accuracy and supporting precise precipitation weather forecasting.

[0053] In this embodiment of the invention, preferably, step S1 specifically includes:

[0054] Step S11: Using the space radiometric calibrator mounted on the micro-nano calibration satellite, periodically calibrate the spaceborne precipitation measurement radar to obtain the Ku / Ka dual-frequency fully polarized echo power and the corresponding radar operating parameters of the spaceborne precipitation measurement radar at different RCS values.

[0055] The micro-nano calibration satellite is located in low Earth orbit, and the space radiation calibrator is set on the micro-nano calibration satellite platform through a three-axis attitude adjustment device to ensure that the receiving antenna and transmitting antenna of the space radiation calibrator are aligned with the polarization direction of the rainfall measurement radar, with a deviation of less than 1°.

[0056] Radar operating parameters include internal temperature, operating voltage, and operating current. The Ku / Ka dual-frequency fully polarized echo power covers both the Ku and Ka bands, with each band including four polarization channels: VV, VH, HH, and HV. To ensure the reliability of the model output results, the data measurement error database for spaceborne precipitation measurement radar covers the radar at different orbital positions (e.g., sunlit / shaded sides) and different operating durations, ensuring the database covers all operating conditions.

[0057] The dual-frequency fully polarized echo power simulated by the calibrator at different RCS values ​​is expressed as follows:

[0058]

[0059]

[0060] In the formula, This indicates the RCS value of the space radiation calibrator.

[0061] During periodic radiometric calibration, the radar's operating parameters are collected using sensors built into the spaceborne precipitation measurement radar, and the internal temperature of the radar is recorded. Operating voltage Operating current The three core parameters are as follows: the accuracy of the radar internal temperature (covering key heat-generating parts such as the radio frequency module and signal processing unit) is better than ±1℃; the accuracy of the operating voltage (output by the power supply system) is better than ±0.1V; and the accuracy of the operating current (output by the power supply system) is better than ±0.1A.

[0062] Each data set must have at least three RCS values.

[0063] Step S12: Based on different RCS values ​​and their corresponding Ku / Ka dual-frequency fully polarized echo power, perform a "calibrator RCS-echo power" curve variation characteristic analysis to obtain the calibration constant of the Ku / Ka dual-frequency fully polarized echo power of the spaceborne precipitation measurement radar under different RCS values;

[0064] Step S13: Based on the Ku / Ka dual-frequency fully polarized echo power of the spaceborne rainfall measurement radar at different RCS values ​​and the corresponding radar operating parameters and calibration constants of the spaceborne rainfall measurement radar, construct a radiation measurement error database for the spaceborne rainfall measurement radar.

[0065] A set of parameters in the satellite-borne precipitation measurement radar radiation measurement error database is represented as follows:

[0066]

[0067] in, This is the scaling constant.

[0068] like Figure 5 As shown, the calibration of a spaceborne precipitation measurement radar using a space-based radiation calibrator specifically includes:

[0069] During a single calibration period, a V-polarized calibration signal is transmitted via a spaceborne precipitation measurement radar;

[0070] Multiple different RCS values ​​are generated using a space radiometric calibrator, and based on the different RCS values ​​and the V-polarization calibration signal, co-polarization calibration signals and cross-polarization calibration signals of the V-polarization calibration signal are generated.

[0071] H-polarization calibration signals are transmitted via a spaceborne precipitation measurement radar.

[0072] Multiple different RCS values ​​are generated by a space radiation calibrator, and based on the different RCS values ​​and the H-polarization calibration signal, the same polarization calibration signal and the cross-polarization calibration signal corresponding to the H-polarization calibration signal are generated.

[0073] The satellite-borne precipitation measurement radar receives the co-polarization calibration signal and cross-polarization calibration signal corresponding to the V-polarization calibration signal and the H-polarization calibration signal.

[0074] The echo signals received by the spaceborne precipitation measurement radar are processed to calculate the signal power corresponding to different RCS values. Establish the relationship curve between "calibrator RCS value and echo power" to obtain the calibration constant. .

[0075] like Figure 4 As shown, in this embodiment of the invention, preferably, the space radiation calibrator includes a Ku / Ka dual-band dual-polarized transmitting antenna 100, a Ku / Ka dual-band dual-polarized receiving antenna 200, and an active calibration signal control module 300. The active calibration signal control module 300 is used to control the multi-channel gain of the dual-band full polarization, simulating different RCS values ​​in the multi-channel gain. The Ku / Ka dual-band dual-polarized transmitting antenna 100 and the Ku / Ka dual-band dual-polarized receiving antenna 200 are isolated by a shield, with an isolation ≥80dB, to suppress transmit-receive crosstalk. The polarization isolation between the Ku / Ka dual-band dual-polarized transmitting antenna and the Ku / Ka dual-band dual-polarized receiving antenna is ≥30dB, which can be achieved through orthogonal array layout and independent feed network. The highest sidelobe level of the Ku / Ka dual-band dual-polarized transmitting antenna and the Ku / Ka dual-band dual-polarized receiving antenna is ≤-40dBi, which can be achieved through array optimization design to ensure concentrated calibration signal energy and reduce spurious interference.

[0076] The active calibration signal control module 300 can independently control the gain of dual-frequency fully polarized multi-channels. By controlling the signal gain in multiple channels, it can simulate different RCS values, achieving RCS value adjustment in the range of 50dBsm-80dBsm in 2dB steps. The step response time is ≤1μs, which is suitable for high-speed satellite flight scenarios. It can quickly simulate multiple RCS values ​​in the rendezvous time of 10ms to 1s to complete the space calibration experiment.

[0077] In a preferred embodiment of the present invention, the method further includes the following step before step S3:

[0078] Before the satellite-borne precipitation measurement radar detects, ground calibration data is obtained, and the trained satellite-borne precipitation measurement radar radiation measurement error estimation model is corrected using the ground calibration data.

[0079] In this embodiment of the invention, preferably, step S3 specifically includes:

[0080] Step S31: Detect the rainfall area using a spaceborne rainfall measurement radar to obtain the dual-frequency scattered echo of the rainfall area and the radar operating parameters during detection;

[0081] Step S33: Using the spaceborne rainfall measurement radar radiation measurement error estimation model, generate the spaceborne rainfall measurement radar radiation measurement error based on the input radar operating parameters;

[0082] Step S33: Compensate for radiation error of dual-frequency scattered echo in the rainfall area by using the generated radiation measurement error of the spaceborne rainfall measurement radar.

[0083] By utilizing a spaceborne precipitation measurement radar to emit dual-polarized electromagnetic waves in both the Ku and Ka bands, the radar detects dual-band fully polarized scattered echoes from the precipitation area. During the detection process, the radar also collects its internal temperature data in real time. Operating voltage Operating current Three core parameters are used to obtain the calibration constants corresponding to the detection data through a radiation measurement error estimation model. The scattering characteristics of raindrops to dual-frequency electromagnetic waves and the difference between the two are calculated by calibration constant, thereby completing the inversion of rainfall. The time difference between the calibration period and the detection period of the rainfall area should not be greater than 10 minutes, so that the radiation error obtained by calibration before detection is highly matched with the "radar state" of subsequent detection, thus improving the accuracy of radiation error compensation.

[0084] like Figure 6 As shown, Figure 6The radiation error correction process in one embodiment of the present invention is illustrated. It mainly includes performing sample learning based on neural networks on the radiation measurement error database 1000 of the spaceborne rainfall measurement radar 2000, establishing a radiation measurement error estimation model 3000 for the spaceborne rainfall measurement radar, and combining it with the pre-detection calibration data 4000 of the spaceborne rainfall measurement radar to achieve accurate estimation of the radiation error of the spaceborne rainfall measurement radar. Radiation error compensation is performed on the dual-frequency multi-polarization data 5000 of the spaceborne rainfall measurement radar to obtain the corrected dual-frequency multi-polarization data 6000 of the spaceborne rainfall measurement radar and the scattering characteristics of the rainfall area, thereby completing the rainfall parameter inversion 7000 of the rainfall area.

[0085] The parts of this invention not described in detail are well-known in the field.

[0086] Finally, it should be noted that the above are preferred embodiments of the present invention. It should be pointed out that although preferred embodiments of the present invention have been described, those skilled in the art, once they understand the basic inventive concept of the present invention, can make several improvements and modifications without departing from the principles of the present invention. These improvements and modifications should also be considered within the scope of protection of the present invention. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments as well as all changes and modifications falling within the scope of the embodiments of the present invention.

Claims

1. A method for space radiometric calibration of a Ku / Ka dual-band spaceborne precipitation measurement radar, characterized in that, Includes the following steps: Step S1: Use a space radiometric calibrator to perform radiometric calibration on the spaceborne precipitation measurement radar, obtain the correspondence between radar operating parameters and radiometric measurement errors, and construct a database of radiometric measurement errors for the spaceborne precipitation measurement radar. Step S2: Train the neural network using the satellite-borne rainfall measurement radar radiation measurement error database to generate a satellite-borne rainfall measurement radar radiation measurement error estimation model; The satellite-borne precipitation measurement radar radiation measurement error estimation model is used to output the radiation measurement error based on the input radar operating parameters; Step S3: Obtain the radar operating parameters of the spaceborne rainfall measurement radar, estimate the radiation measurement error of the spaceborne rainfall measurement radar using the radiation measurement error estimation model, and perform radiation error compensation based on the radiation measurement error estimation results.

2. The space radiation calibration method for Ku / Ka dual-band spaceborne precipitation measurement radar according to claim 1, characterized in that, Step S1 specifically includes: Using a space-based radiometric calibrator mounted on a micro-nano calibration satellite, periodic radiometric calibration was performed on a spaceborne precipitation measurement radar to obtain the Ku / Ka dual-frequency fully polarized echo power and its corresponding radar operating parameters for different RCS values. The radar operating parameters include the radar's internal temperature, operating voltage, and operating current. The Ku / Ka dual-frequency fully polarized echo power covers both Ku and Ka frequency bands, with each band including four polarization channels: VV, VH, HH, and HV. Based on different RCS values ​​and their corresponding Ku / Ka dual-frequency fully polarized echo power, the variation characteristics of the "calibrator RCS-echo power" curve are analyzed to obtain the calibration constant of the Ku / Ka dual-frequency fully polarized echo power of the spaceborne precipitation measurement radar under different RCS values. Based on the Ku / Ka dual-frequency fully polarized echo power of the spaceborne rainfall measurement radar at different RCS values ​​and the corresponding radar operating parameters and calibration constants of the spaceborne rainfall measurement radar, a radiation measurement error database for the spaceborne rainfall measurement radar is constructed.

3. The space radiation calibration method for Ku / Ka dual-band spaceborne precipitation measurement radar according to claim 2, characterized in that, The accuracy of the radar operating parameters of the aforementioned spaceborne precipitation measurement radar meets the following requirements: The internal temperature accuracy is better than ±1℃, the operating voltage accuracy is better than ±0.1V, and the operating current accuracy is better than ±0.1A.

4. The space radiation calibration method for Ku / Ka dual-band spaceborne precipitation measurement radar according to claim 2, characterized in that, In step S1, when performing periodic radiometric calibration, each set of data in the satellite-borne precipitation measurement radar radiation measurement error database has no fewer than three RCS values.

5. The space radiation calibration method for Ku / Ka dual-band spaceborne precipitation measurement radar according to claim 2, characterized in that, The calibration of a spaceborne precipitation measurement radar using a space-based radiation calibrator specifically includes: During a single calibration period, a V-polarized calibration signal is transmitted via a spaceborne precipitation measurement radar; Multiple different RCS values ​​are generated by a space radiation calibrator, and based on the different RCS values ​​and the V-polarization calibration signal, co-polarization calibration signals and cross-polarization calibration signals of the V-polarization calibration signal are generated. H-polarization calibration signals are transmitted via a spaceborne precipitation measurement radar. Multiple different RCS values ​​are generated by a space radiation calibrator, and based on the different RCS values ​​and the H-polarization calibration signal, a co-polarization calibration signal and a cross-polarization calibration signal corresponding to the H-polarization calibration signal are generated. The satellite-borne precipitation measurement radar receives the co-polarization calibration signal and cross-polarization calibration signal corresponding to the V-polarization calibration signal and the H-polarization calibration signal.

6. The space radiation calibration method for Ku / Ka dual-band spaceborne precipitation measurement radar according to claim 1, characterized in that, The space radiation calibrator includes a Ku / Ka dual-frequency dual-polarization transmitting antenna, a Ku / Ka dual-frequency dual-polarization receiving antenna, and an active calibration signal control module; The active calibration signal control module is used to control the multi-channel gain of dual-frequency full polarization, simulating different RCS values ​​in the multi-channel gain; The Ku / Ka dual-band dual-polarization transmitting antenna and the Ku / Ka dual-band dual-polarization receiving antenna are isolated by a shield, with an isolation degree ≥80dB; The polarization isolation between the Ku / Ka dual-frequency dual-polarization transmitting antenna and the Ku / Ka dual-frequency dual-polarization receiving antenna is ≥30dB, and the highest sidelobe level is ≤-40dBi.

7. The space radiation calibration method for Ku / Ka dual-band spaceborne precipitation measurement radar according to claim 6, characterized in that, During the simulation of different RCS values, the space radiation calibrator simulates the adjustment of the RCS value in 2 dB steps within the range of 50 dBsm-80 dBsm, with the step response time set to ≤1 μs.

8. The space radiation calibration method for Ku / Ka dual-band spaceborne precipitation measurement radar according to claim 6, characterized in that, The space radiation calibrator is mounted on a micro-nano calibration satellite platform via a three-axis attitude adjustment device.

9. The space radiation calibration method for Ku / Ka dual-band spaceborne precipitation measurement radar according to claim 1, characterized in that, The procedure before step S3 also includes: Before the spaceborne rainfall measurement radar detects, ground calibration data is acquired, and the trained spaceborne rainfall measurement radar radiation measurement error estimation model is corrected using the ground calibration data.

10. The space radiation calibration method for Ku / Ka dual-band spaceborne precipitation measurement radar according to claim 1, characterized in that, Step S3 specifically includes: The rainfall area is detected by a spaceborne rainfall measurement radar, and the dual-frequency scattered echo of the rainfall area and the radar operating parameters at the time of detection are obtained. The satellite-borne rainfall measurement radar radiation measurement error estimation model is used to generate the satellite-borne rainfall measurement radar radiation measurement error based on the input radar operating parameters. Radiation error compensation is performed on the dual-frequency scattered echoes in the rainfall area by generating radiation measurement errors from the satellite-borne rainfall measurement radar.

Images