Rain measuring radar system for micro-nano satellite networking

Abstract

The invention discloses a rain-measuring radar system for micro-nano satellite networking. The rain-measuring radar system comprises a Ka-frequency-band deployable parabolic antenna, a Ka-frequency-band comprehensive channel combination and a signal processor. During signal emission, the signal processor generates a digital signal and converts the digital signal into an intermediate frequency signal; the Ka frequency band comprehensive channel combination is used for carrying out up-conversion on the intermediate frequency signal to a Ka frequency band and filtering and amplifying the intermediate frequency signal to obtain a to-be-transmitted signal; the Ka-band deployable parabolic antenna synthesizes a signal to be transmitted and radiates the signal to the space. During signal receiving, the Ka-frequency-band expandable parabolic antenna receives Ka-frequency-band echo signals scattered in a designated area, and the Ka-frequency-band echo signals are synthesized, amplified and then sent to the Ka-frequency-band comprehensive channel combination; the Ka frequency band comprehensive channels are combined to obtain intermediate frequency echo signals; the signal processor collects and processes the intermediate-frequency echo signal and sends the intermediate-frequency echo signal to a satellite platform. According to the invention, space-based cloud and rainfall three-dimensional high-precision chromatography detection is realized.

Description

Technical Field

[0001] The invention belongs to the technical field of satellite-borne meteorological active microwave remote sensing, and in particular relates to a rain measuring radar system for micro-nano satellite networking. Background Art

[0002] At present, there is no active meteorological remote sensing instrument on a micro-nano satellite platform in China that is autonomous, controllable, can quickly revisit a designated area, and can capture the dynamic atmospheric process of rapid scanning evolution. The current observation data mainly comes from rain gauges on the ground, ground-based radars, and satellite-borne active and passive remote sensing. Rain gauges directly measure the rainfall near the ground, and the results obtained are relatively true, but they can only represent the point distribution of rainfall. The statistical method from point to surface to calculate the rainfall in a region has a large error. Ground-based radars use active remote sensing, which can cover a large area and give relatively accurate rainfall, but it is very expensive to establish a radar network, and there is a problem of unified calibration between radars. In addition, the observation range of rain gauges and ground-based radar networks is affected by geography and cannot cover vast seas, deserts, and mountainous areas; satellite-borne active meteorological observation radars have not yet formed a network observation, and the revisit timeliness cannot meet the requirements of high-time detection.

[0003] Launched in May 2018, RainCube successfully acquired the first storm images over Mexico during its time in orbit and observed the heavy rainfall from Hurricane Florence.

[0004] The space weather radar small satellite constellation is managed by Tomorrow, an American company. Tomorrow-R1 is the first demonstration satellite of the space weather radar small satellite constellation. On April 14, 2023, the satellite was launched from the launch base in California, USA on a SpaceX Falcon 9. After successful networking, it can provide high-resolution precipitation data with an average global revisit period of 1 hour. There is no active remote sensing instrument for rain measurement in China that meets the 3-hour revisit period. Summary of the invention

[0005] The technology of the present invention solves the problem of overcoming the shortcomings of the revisit period of the existing active meteorological remote sensing technology and providing a miniaturized rain measuring radar system that can be used for micro-nano satellite networking.

[0006] The technical solution of the present invention is:

[0007] A rain detection radar system for micro-nano satellite networking, comprising a Ka-band deployable parabolic antenna, a Ka-band integrated channel combination and a signal processor;

[0008] When the signal is transmitted:

[0009] The signal processor is used to generate digital signals and convert them into intermediate frequency signals. The Ka-band integrated channel combination is used to modulate the intermediate frequency signals, up-convert them to the Ka-band, filter them, and amplify them to obtain the signals to be transmitted. The Ka-band deployable parabolic antenna is used to synthesize the signals to be transmitted and radiate them into space to complete the signal transmission.

[0010] When receiving a signal:

[0011] The Ka-band deployable parabolic antenna is used to receive the Ka-band echo signal scattered in the designated area, synthesize and amplify the Ka-band echo signal and send it to the Ka-band integrated channel combination; the Ka-band integrated channel combination is used to filter, amplify and down-convert the Ka-band echo signal to obtain an intermediate frequency echo signal; the signal processor is used to collect and process the intermediate frequency echo signal and send the processed remote sensing data to the satellite platform.

[0012] Preferably, the Ka-band deployable parabolic antenna is also used to receive control instructions from a satellite platform, and after being launched into orbit, implement switching from a stowed state to an deployed state of the antenna according to the control instructions of the satellite platform; and report the deployed state of the antenna to the satellite platform;

[0013] The Ka-band integrated channel combination is also used to send the reference local oscillator clock signal to the signal processor; switch between the transmission, reception and standby modes according to the control instructions of the signal processor; and report telemetry parameters to the signal processor; the telemetry parameters include working status, power detection, and multiple temperature points inside the radar;

[0014] The signal processor is also used to receive control instructions sent by an external satellite platform and perform instruction parsing; issue control instructions to the Ka-band integrated channel combination, monitor status and handle abnormal status; collect the working status of the Ka-band integrated channel combination and the temperature of multiple points inside the radar and report them to the satellite platform; control the power-off switching of the Ka-band integrated channel combination; and output the intermediate frequency linear frequency modulation signal to the Ka-band integrated channel combination according to the design requirements, and collect, pulse compress, average the power and perform data processing based on the artificial intelligence SOC chip on the intermediate frequency echo signal after the downlink frequency conversion of the Ka-band integrated channel combination.

[0015] Preferably, the Ka-band integrated channel combination includes: a transmitting channel, a receiving channel, a frequency synthesis unit, and a circulator;

[0016] Transmitting channel: modulates the transmitting excitation signal, up-converts it to the Ka band, filters it, amplifies it, and then outputs a 20W power signal. It also has the function of transmitting output power detection.

[0017] Receiving channel: The Ka-band echo signal sent from the antenna is down-converted to the intermediate frequency through a frequency conversion scheme for signal processing. The gain of the receiving channel is adjustable;

[0018] Frequency synthesis unit: provides local oscillator signals for the transmitting channel, receiving channel and signal processor;

[0019] Circulator: Completes the Ka-band deployable parabolic antenna to transmit and receive signals, minimizing interconnect cables.

[0020] Preferably, the signal processor comprises a power board, a signal processing board, and a signal processing daughter card;

[0021] Power board: complete the short-circuit protection, surge suppression, filtering and power conversion functions of the primary bus input power;

[0022] Signal processing board: used for radar intermediate frequency signal generation, signal acquisition, processing, radar control, and telemetry acquisition;

[0023] Signal processing daughter card: adopts the minimum system design and cooperates with the signal processing board to complete the artificial intelligence processing of remote sensing data. The signal processing daughter card is connected to the signal processing board through an inter-board connector, which can be quickly disassembled and assembled without affecting the independent use of the signal processing board.

[0024] Preferably, the radar system adopts a pulse signal linear frequency modulation system to transmit electromagnetic wave signals and collect target echo signals according to a determined working sequence.

[0025] Preferably, the radar system pulse repetition frequency PRF satisfies:

[0026]

[0027] Where m is an integer, R min , R max They represent the maximum slant distance and the minimum slant distance corresponding to the footprint, which vary with the satellite orbit altitude and the radius of the earth; C represents the speed of light;

[0028]

[0029] Among them, SNR e represents the effective signal-to-noise ratio, p t represents the peak power of the transmitter, G represents the antenna gain, c represents the speed of light, λ represents the wavelength, τ represents the pulse width, β φ represents the 3dB beam width in the antenna azimuth, R represents the effective range, k represents the Boltzmann constant, B represents the bandwidth, T represents the equivalent noise temperature of the receiver, and L represents the s represents the system loss, σ 0 represents the backscatter coefficient of the target, N aIt indicates the number of pulses accumulated in azimuth direction; SNR indicates signal-to-noise ratio.

[0030] Preferably, the working modes of the rain measuring radar system include: precipitation observation mode, external calibration mode, internal calibration mode, standby mode and safety mode.

[0031] Preferably, in the precipitation observation mode, the rain radar transmits Ka-band signals to the target area, and collects, processes, outputs meteorological remote sensing data of the target echo signal and transmits it to the ground for data inversion;

[0032] In the internal calibration mode, the signal processor transmits the intermediate frequency signal to the Ka-band integrated channel combination, and after the uplink amplification link, the coupled signal is sent to the signal processor through the detector for signal acquisition;

[0033] In the external calibration mode, the radar's on-orbit operation status is calibrated by continuously collecting echo signals from the specified sea surface area. At the same time, the GPS time, satellite platform attitude, and position-related information corresponding to the calibration pulse are recorded and transmitted to the ground for time and space synchronization with ARC to achieve measurement and calibration of the backscatter coefficient.

[0034] In standby mode, the signal processor and Ka-band integrated channel combination work to update system parameters on-orbit;

[0035] In the safety mode, at the initial stage of entering orbit or when a single or complete failure occurs in the rain measuring radar system, the rain measuring radar system will stop working immediately and enter the emergency working mode.

[0036] Preferably, the entire radar adopts a modular and lightweight design, and the size in the stored state is ≤4U.

[0037] Preferably, a Walker constellation is constructed by 24 satellites to achieve a quick scan and revisit of a designated area within 0.5 to 3 hours.

[0038] The present invention has the following advantages:

[0039] The present invention discloses a miniaturized and lightweight rain-measuring radar system for micro-nano satellite networking, which can fill the technical gap in the domestic small satellite platform networking active meteorological observation remote sensing equipment. Through multi-satellite joint observation and satellite-to-ground rapid data transmission, high-frequency and high-sensitivity small-area intensive observation of sudden disaster weather can be carried out, and the satellite emergency response capability can be enhanced to meet the needs of weather forecasting for high-revisit observation of the changeable dynamic and thermal fields of small and medium-scale disaster weather systems such as typhoons, heavy rains, and severe convection. The high-revisit observation capability of the rapidly evolving dynamic atmospheric process can be economically and effectively improved, and the space-based three-dimensional high-precision tomographic detection of clouds and precipitation can be realized.

[0040] The present invention discloses a rain measuring radar system for micro-nano satellite networking, which adopts an umbrella-shaped deployable parabolic antenna design, and ensures the requirements of miniaturization and lightweight design while meeting the requirements of indicators such as bandwidth and gain. Through the miniaturized radar design, the radar weight is controlled to be ≤10kg, which meets the application requirements of low cost, lightweight, rapid integration test and rapid launch of small satellite platforms.

[0041] The present invention ensures 0.5-3 hours of coverage and revisit detection in the rainfall time and space area, thereby expanding the observation width. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] Figure 1 It is a schematic diagram of storage and deployment of a micro-nano satellite networked rain detection radar system of the present invention;

[0043] Figure 2 This is a schematic diagram of an on-orbit networking of a micro-nano satellite networked rain detection radar system of the present invention;

[0044] Figure 3 It is a block diagram of a rain measuring radar system of a micro-nano satellite network of the present invention;

[0045] Figure 4 The present invention discloses a signal processing flow chart of a rain measuring radar system of a micro-nano satellite network. DETAILED DESCRIPTION

[0046] In order to make the objectives, technical solutions and advantages of the present invention more clear, the embodiments disclosed in the present invention will be further described in detail below with reference to the accompanying drawings.

[0047] like Figure 1 The following is a schematic diagram of the storage and deployment of the rain radar system. Figure 2 The block diagram of the rain detection radar of the micro-nano satellite network is shown in Figure 1. The rain detection radar system of the micro-nano satellite network mainly includes a Ka-band deployable parabolic antenna, a Ka-band integrated channel combination and a signal processor, such as Figure 3 shown.

[0048] When transmitting signals, there are: a signal processor, which is used to generate digital signals and convert them into intermediate frequency signals; a Ka-band integrated channel combination, which is used to modulate the intermediate frequency signal, up-convert it to the Ka-band, filter it, and amplify it to obtain the signal to be transmitted; and a Ka-band deployable parabolic antenna, which is used to synthesize the signal to be transmitted and radiate it into space to complete the signal transmission.

[0049] When receiving signals, there are: a Ka-band deployable parabolic antenna, which is used to receive the Ka-band echo signal scattered in the designated area, synthesize and amplify the Ka-band echo signal and send it to the Ka-band integrated channel combination; the Ka-band integrated channel combination, which is used to filter, amplify and down-convert the Ka-band echo signal to obtain an intermediate frequency echo signal; and a signal processor, which is used to collect and process the intermediate frequency echo signal.

[0050] In the above-mentioned micro-nano satellite network rain radar system,

[0051] The Ka-band deployable parabolic antenna is also used to receive control instructions from the satellite platform. After being launched into orbit, the antenna is switched from the stowed state to the deployed state through the hot knife and the rotating joint; and the deployed state of the antenna is reported to the satellite platform.

[0052] The Ka-band integrated channel combination is also used to send the reference local oscillator clock signal to the signal processor; receive the control instructions of the signal processor to switch between the transmission, reception and standby modes; and report the working status and telemetry parameters to the signal processor;

[0053] The signal processor is also used to receive control instructions sent by an external satellite platform and perform instruction parsing; issue control instructions to the Ka-band integrated channel combination, monitor its status and handle abnormal status; collect the working status of the Ka-band integrated channel combination and multi-point temperature telemetry inside the radar and report them to the satellite platform; control the power-off switching of the Ka-band integrated channel combination; and output the intermediate frequency linear frequency modulation signal to the Ka-band integrated channel combination according to the design requirements, and collect, pulse compress, and power average the echo data of the Ka-band integrated channel combination after downlink frequency conversion, and expand the data processing function based on the artificial intelligence SOC chip.

[0054] Figure 4 This is the signal processing flow chart of the rain radar system.

[0055] In the above-mentioned micro-nano satellite network rain radar system,

[0056] The Ka-band deployable parabolic antenna comprises: a deployable main reflector, a Ka-band feed source, a sub-reflector, a waveguide feed line, a rotating joint, a locking and unlocking device, etc.

[0057] The Ka-band integrated channel combination includes: transmitting channel, receiving channel, frequency synthesis unit, circulator, etc., which mainly realizes the up-conversion function of radar transmitting signal and the down-conversion function of radar echo signal.

[0058] Transmitting channel: It is mainly composed of amplifier, LC filter, digitally controlled attenuator, mixer, power amplifier tube, combiner group, etc. It up-converts the transmitting excitation signal to the Ka band and amplifies it, then outputs a 20W power signal and has the transmitting output power detection function.

[0059] Receiving channel: It is mainly composed of a limiter, a low-noise amplifier, a down-conversion circuit, and a filtering circuit. The Ka-band signal sent by the antenna is down-converted to an intermediate frequency through a double-conversion scheme for signal processing. The gain of the receiving channel is adjustable from 0 to 15dB.

[0060] Frequency synthesizer unit: mainly composed of a crystal oscillator, a local oscillator source, a second local oscillator source, a sampling clock signal, etc., mainly provides local oscillator signals for the transmitting channel, the receiving channel and the signal processor.

[0061] Circulator: Completes the transmission of Ka-band antenna signals, minimizes interconnection cables, and reduces the weight of each unit.

[0062] The signal processor includes: a power board, a signal processing board, and a signal processing subcard, which mainly realizes the functions of signal generation, acquisition and processing.

[0063] Power board: It is mainly composed of input circuit protection circuit, surge soft start circuit, EMI filter circuit, DC / DC module output conversion unit, etc. It mainly completes the short-circuit protection, surge suppression, filtering and power conversion functions of the primary bus input power supply.

[0064] Signal processing board: The signal processing board is used for radar intermediate frequency signal generation, signal acquisition, processing, radar control, telemetry acquisition and other functions. It mainly includes FPGA, AD, DA, clock, power supply, telemetry acquisition and interface circuits.

[0065] Signal processing daughter card: The signal processing daughter card adopts the minimum system design, mainly composed of artificial intelligence SOC, FLASH, DDR and peripheral interface circuits, etc. Its main function is to cooperate with FPGA to complete the artificial intelligence processing of remote sensing data and other functions. The processor daughter card is a separate CPU working minimum system, which is connected to the FPGA unit through the inter-board connector and can be easily disassembled and assembled without affecting the independent use of the FPGA unit. The processor daughter card can assist FPGA in radar signal processing and form front-level meteorological observation data for ground analysis.

[0066] In the above-mentioned micro-nano satellite networking rain detection radar system, the rain detection radar adopts a modular size design that meets universal standards. The radar weight is controlled to ≤10kg, and the size of the radar system in the stored state is 4U (120mm*240mm*240mm), which can be adapted to multiple satellite platforms.

[0067] In the above-mentioned micro-nano satellite networked rain measuring radar system, the working modes of the radar system include: precipitation observation mode, external calibration mode, internal calibration mode, standby mode and safety mode.

[0068] In the above-mentioned micro-nano satellite network rain detection radar system, in the precipitation observation mode, the rain detection radar transmits Ka-band signals to the target area, collects, processes, outputs meteorological remote sensing data of the target echo, and transmits it to the ground for data inversion;

[0069] The rain radar system of the micro-nano satellite network adopts a pulse signal linear frequency modulation system. The radar system transmits electromagnetic wave signals and collects target echo signals according to a certain working sequence. In the signal processor, the collected echo signals are extracted and filtered, matched with pulse pressure, and pulse accumulated before being sent to the satellite platform.

[0070] In the above-mentioned micro-nano satellite network rain radar system,

[0071] The pulse repetition frequency is selected as follows:

[0072]

[0073] Where m is an integer, R min , R max They represent the maximum and minimum slant ranges corresponding to the footprint, respectively, and vary with the satellite orbit altitude and the radius of the Earth;

[0074]

[0075] Among them, SNR e represents the effective signal-to-noise ratio, P t represents the peak power of the transmitter, G represents the antenna gain, c represents the speed of light, λ represents the wavelength, τ represents the pulse width, β φ represents the 3dB beam width in the antenna azimuth, R represents the effective range, k represents the Boltzmann constant, B represents the bandwidth, T represents the equivalent noise temperature of the receiver, and L represents the s represents the system loss, σ 0 represents the backscatter coefficient of the target, N a Indicates the number of pulses accumulated in azimuth.

[0076] In the above-mentioned micro-nano satellite network rain radar system,

[0077] In the internal calibration mode, the signal processor transmits the intermediate frequency signal to the Ka-band integrated channel combination, and after the uplink amplification link, the coupled signal is sent to the signal processor through the detector for signal acquisition;

[0078] In the external calibration mode, the radar's on-orbit operation status is calibrated by continuously collecting echo signals from the specified sea surface area. At the same time, the GPS time corresponding to the calibration pulse, the attitude and position of the satellite platform are recorded and transmitted to the ground for time and space synchronization with ARC to achieve measurement and calibration of the backscatter coefficient.

[0079] In standby mode, the signal processor and Ka-band integrated channel combination local oscillator module work, which can be used for in-orbit update of system parameters.

[0080] In the safety mode, when a single unit or the entire unit of the rain measuring radar system fails in the initial stage of orbit entry or in the micro-nano satellite network, the rain measuring radar will stop working immediately and enter the emergency working mode.

[0081] The Walker constellation is constructed by 24 satellites, which can achieve a quick scan and revisit of the designated area every 0.5 to 3 hours.

[0082] like Figure 2 Shown is a schematic diagram of the in-orbit network. Through a constellation of 12 or 24 active rainfall radar satellites, high-efficiency revisit detection of rainfall in the Jianghuai region and the Qinghai-Tibet Plateau can be achieved.

[0083] Example:

[0084] The present invention is further described below by describing in detail a preferred specific embodiment.

[0085] In this embodiment, the satellite flies at an altitude of 400km, and the rain measuring radar is installed on the ground of the satellite. The radar beam illuminates the ground from the sub-satellite point, and the radar beam forms a quasi-circular ground track with a diameter of about 8km on the earth's surface, thereby realizing the observation of the target area within the resolution unit.

[0086] The signal processor generates a 120MHz intermediate frequency coherent pulse frequency modulated signal, which is radiated to the detection target through the antenna after frequency conversion, filtering and power amplification.

[0087] The electromagnetic waves radiated by the antenna encounter the same meteorological targets such as clouds and rain, generating backscattering and becoming the echo signal of the meteorological target. The echo signal received by the antenna is sent to the Ka-band integrated channel combination. After low-noise amplification, down-conversion, filtering, and amplification, the echo signal forms a 120MHz intermediate frequency signal and is sent to the signal processor.

[0088] The signal processor receives the intermediate frequency signal, performs digital quantization sampling through the ADC and sends it to the FPGA, and performs signal processing such as orthogonal down-conversion, filtering, pulse compression, and power summing inside the FPGA.

[0089] The signal processor will frame the on-orbit processing results in the remote sensing communication protocol format according to the communication requirements of the satellite platform and send them to the satellite platform, and then send them to the ground processing system through the data transmission system.

[0090] The ground processing system receives the downlinked data and first revises the data according to the calibration results. After data processing and inversion, it outputs data products such as water vapor content, droplet spectrum distribution, average droplet diameter, and number concentration per unit volume.

[0091] Through the antenna aperture design, the horizontal resolution of radar rainfall detection can be better than 8km.

[0092] The radar uses pulse width design to achieve a vertical resolution of better than 250m for rain detection.

[0093] The present invention can use rain particles as tracers and utilize the echo intensity of rain particles to carry out three-dimensional detection and measurement of a rainfall environment.

[0094] The invention discloses a rainfall radar system for micro-nano satellite networking. The system adopts an integrated, modular and lightweight design concept, can realize rapid system integration, testing and launching, and can be adapted to multiple satellite platforms. The radar weight is ≤10kg, and the size envelope of the storage state is ≤4U (120mm*240mm*240mm). The radar system adopts fixed beam pointing, and receives scattered echoes at different distances to invert the horizontal and vertical structure information of rainfall. Through multi-satellite networking joint observation and active and passive microwave information joint inversion, combined detection is performed, which can expand the observation width, improve the inversion accuracy, and realize high-efficiency meteorological observation data information, so as to have the ability to capture rapidly evolving dynamic atmospheric processes. The product can meet the needs of disastrous weather monitoring and early warning, climate change research, and numerical weather forecasting applications.

[0095] Although the present invention has been disclosed as above in the form of a preferred embodiment, it is not intended to limit the present invention. Any person skilled in the art may make possible changes and modifications to the technical solution of the present invention by using the methods and technical contents disclosed above without departing from the spirit and scope of the present invention. Therefore, any simple modifications, equivalent changes and modifications made to the above embodiments based on the technical essence of the present invention without departing from the content of the technical solution of the present invention shall fall within the protection scope of the technical solution of the present invention.

[0096] The contents not described in detail in the specification of the present invention belong to the common knowledge of the professionals in this field.

Claims

1. A rain detection radar system for micro-nano satellite networking, characterized in that: It includes Ka-band deployable parabolic antenna, Ka-band integrated channel combination and signal processor; When the signal is transmitted: The signal processor is used to generate digital signals and convert them into intermediate frequency signals. The Ka-band integrated channel combination is used to modulate the intermediate frequency signals, up-convert them to the Ka-band, filter them, and amplify them to obtain the signals to be transmitted. The Ka-band deployable parabolic antenna is used to synthesize the signals to be transmitted and radiate them into space to complete the signal transmission. When receiving a signal: The Ka-band deployable parabolic antenna is used to receive the Ka-band echo signal scattered in the designated area, synthesize and amplify the Ka-band echo signal and send it to the Ka-band integrated channel combination; the Ka-band integrated channel combination is used to filter, amplify and down-convert the Ka-band echo signal to obtain an intermediate frequency echo signal; the signal processor is used to collect and process the intermediate frequency echo signal and send the processed remote sensing data to the satellite platform.

2. The rain measuring radar system for micro-nano satellite networking according to claim 1, characterized in that: The Ka-band deployable parabolic antenna is also used to receive control instructions from the satellite platform. After being launched into orbit, it switches the antenna from the stowed state to the deployed state according to the control instructions of the satellite platform; and reports the deployed state of the antenna to the satellite platform. The Ka-band integrated channel combination is also used to send the reference local oscillator clock signal to the signal processor; switch between the transmission, reception and standby modes according to the control instructions of the signal processor; and report telemetry parameters to the signal processor; the telemetry parameters include working status, power detection, and multiple temperature points inside the radar; The signal processor is also used to receive control instructions sent by the external satellite platform and perform instruction parsing; issue control instructions, monitor status, and handle abnormal status for the Ka-band integrated channel combination; Collect the working status of the Ka-band integrated channel combination and the temperature of multiple points inside the radar and report them to the satellite platform; control the power-off switching of the Ka-band integrated channel combination; In addition, according to the design requirements, the intermediate frequency linear frequency modulation signal is output to the Ka-band integrated channel combination, and the intermediate frequency echo signal after downlink frequency conversion of the Ka-band integrated channel combination is collected, pulse pressure, power averaged and data processed based on the artificial intelligence SOC chip.

3. The rain measuring radar system for micro-nano satellite networking according to claim 2 is characterized in that: Ka-band integrated channel combination, including: transmitting channel, receiving channel, frequency synthesis unit, circulator; Transmitting channel: modulates the transmitting excitation signal, up-converts it to the Ka band, filters it, amplifies it, and then outputs a 20W power signal. It also has the function of transmitting output power detection. Receiving channel: The Ka-band echo signal sent from the antenna is down-converted to the intermediate frequency through a frequency conversion scheme for signal processing. The gain of the receiving channel is adjustable; Frequency synthesis unit: provides local oscillator signals for the transmitting channel, receiving channel and signal processor; Circulator: Completes the transmission of Ka-band deployable parabolic antenna signals, minimizing interconnect cables.

4. The rain measuring radar system for micro-nano satellite networking according to claim 2, characterized in that: Signal processor, including power board, signal processing board, signal processing daughter card; Power board: complete the short-circuit protection, surge suppression, filtering and power conversion functions of the primary bus input power; Signal processing board: used for radar intermediate frequency signal generation, signal acquisition, processing, radar control, and telemetry acquisition; Signal processing daughter card: adopts the minimum system design and cooperates with the signal processing board to complete the artificial intelligence processing of remote sensing data. The signal processing daughter card is connected to the signal processing board through an inter-board connector, which can be quickly disassembled and assembled without affecting the independent use of the signal processing board.

5. The rain measuring radar system for micro-nano satellite networking according to claim 1, characterized in that: The radar system adopts a pulse signal linear frequency modulation system to transmit electromagnetic wave signals and collect target echo signals according to a certain working sequence.

6. The rain measuring radar system for micro-nano satellite networking according to claim 1, characterized in that: The radar system pulse repetition frequency PRF meets the following requirements: Where m is an integer, R min , R max They represent the maximum slant distance and the minimum slant distance corresponding to the footprint, which vary with the satellite orbit altitude and the radius of the earth; C represents the speed of light; Among them, SNR e represents the effective signal-to-noise ratio, P t represents the peak power of the transmitter, G represents the antenna gain, c represents the speed of light, λ represents the wavelength, τ represents the pulse width, β φ represents the 3dB beam width in the antenna azimuth, R represents the effective range, k represents the Boltzmann constant, B represents the bandwidth, T represents the equivalent noise temperature of the receiver, and L represents the s represents the system loss, σ 0 represents the backscatter coefficient of the target, N a It indicates the number of pulses accumulated in azimuth direction; SNR indicates signal-to-noise ratio.

7. The rain measuring radar system for micro-nano satellite networking according to claim 1, characterized in that: The working modes of the rain measuring radar system include: precipitation observation mode, external calibration mode, internal calibration mode, standby mode and safety mode.

8. The rain measuring radar system for micro-nano satellite networking according to claim 7, characterized in that: In precipitation observation mode, the rain radar transmits Ka-band signals to the target area, collects and processes the target echo signals, outputs meteorological remote sensing data and transmits them to the ground for data inversion; In the internal calibration mode, the signal processor transmits the intermediate frequency signal to the Ka-band integrated channel combination, and after the uplink amplification link, the coupled signal is sent to the signal processor through the detector for signal acquisition; In the external calibration mode, the radar's on-orbit operation status is calibrated by continuously collecting echo signals from the specified sea surface area. At the same time, the GPS time, satellite platform attitude, and position-related information corresponding to the calibration pulse are recorded and transmitted to the ground for time and space synchronization with ARC to achieve measurement and calibration of the backscatter coefficient. In standby mode, the signal processor and Ka-band integrated channel combination work to update system parameters on-orbit; In the safety mode, at the initial stage of entering orbit or when a single or complete failure occurs in the rain measuring radar system, the rain measuring radar system will stop working immediately and enter the emergency working mode.

9. The rain measuring radar system for micro-nano satellite networking according to claim 1, characterized in that: The entire radar adopts a modular and lightweight design, and its size in the stored state is ≤4U.

10. The rain measuring radar system for micro-nano satellite networking according to claim 1, characterized in that: The Walker constellation is constructed by 24 satellites, which can achieve a quick scan and revisit of the designated area every 0.5 to 3 hours.

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