An adaptive spatial filtering method for reducing false alarm rate of laser ranging

Abstract

This invention discloses an adaptive spatial filtering method to reduce the false alarm rate in laser ranging. An adaptive spatial filtering module is introduced into the laser ranging system. A real-time sky background noise acquisition module detects changes in sky background light intensity and feeds this information back to the control system for immediate response. Based on the acquired control signals, a receiving field-of-view control module enables automatic control of a series of mechanisms and circuits. A variable aperture with adjustment function limits the background noise entering the laser ranging system; when the background light radiation intensity is high, the aperture diameter decreases, and vice versa. This design is simple in structure, easy to operate, stable, and highly automated. It not only balances the system's target acquisition capability and noise suppression capability but also has good adaptability, allowing for real-time, intelligent, and efficient adjustment of system structural parameters according to observation conditions, thereby improving system stability and automation.

Description

Technical Field

[0001] This invention relates to the field of laser ranging technology, and in particular to an adaptive spatial filtering method for reducing the false alarm rate of laser ranging. Background Technology

[0002] Laser ranging (LR) technology is a comprehensive technology that uses lasers as the detection medium to measure distances. It boasts advantages such as a wide measurement range, high accuracy, non-contact measurement capabilities, and insensitivity to electromagnetic interference, making it widely used in aerospace, geophysics, robot vision, remote sensing mapping, precision measurement, and intelligent control. Common laser ranging systems mainly consist of a laser emitting and receiving optical-mechanical system, a control system, a photodetector, and a laser pulse time-of-flight recording and processing unit. Depending on the observed target, laser ranging systems are classified into satellite laser ranging (SLR), debris laser ranging (DLR), and lunar laser ranging (LLR), among others.

[0003] As a weak signal detection technique, laser ranging data contains a large number of outliers. Especially during daytime ranging or at night when the sky background is bright, the amount of noise data caused by the background light is far greater than the effective ranging data, reaching up to 10¹⁰ photoelectrons. When the projection of the observed target's trajectory onto the celestial sphere approaches or crosses the position of the sun, the strong background noise will overwhelm the satellite echo signal and may even damage the core components of the receiving system. As the maximum detection distance of laser ranging systems further increases, the echo signal weakens, the false alarm probability increases, and the impact of background noise on the detection results of laser ranging systems becomes increasingly significant. Therefore, many laser ranging stations adopt a method of observing at night and shutting down during the day, resulting in discontinuous observation data and severely limiting the application and development of this technology.

[0004] Currently, laser ranging systems commonly use Geiger-mode single-photon avalanche diodes (G-SPADs) as echo receivers. Their photoelectric conversion process is a uniform Poisson process. When the detector is operating, photons from both noise and signal sources can trigger the detector to produce a 0 / 1 digital output. Once triggered, it results in a saturated avalanche output, making it impossible to distinguish between signal and noise. Therefore, laser ranging systems are highly susceptible to noise, resulting in a high false alarm probability. Existing technical solutions include:

[0005] Existing technical solution 1: For laser ranging systems, sky background noise mainly refers to noise photons generated by the scattering of sunlight by aerosols and atmospheric molecules. The sun's spectral irradiance is a function of wavelength, with the majority falling within the visible light range. To reduce the influence of background light, a matching narrowband filter is typically placed in the laser ranging system to eliminate most of the background noise at other wavelengths, thereby reducing the false alarm rate of the laser ranging system.

[0006] The diagram below shows the optical path of the laser receiving telescope. The main optical path uses a Cassegrain-type RC (Ritchey-Chretien) reflecting telescope system. A meniscus beam splitter is used, enabling the system to both receive laser echoes and perform visual tracking. The first surface of the meniscus beam splitter is coated with a narrow-band total reflection film. The main optical path receives laser photons returning from the satellite, reflects them from the primary mirror to the secondary mirror, and then reflects them again from the first surface of the meniscus, converging them onto the focal plane of the receiving system. After passing through a variable field stop and a collimating lens, the light becomes parallel. To reduce the false alarm probability, an ultra-narrow-band interference filter is typically inserted in the parallel optical path to eliminate most of the background noise. The echo signal is then focused by the SPAD's focusing lens onto the SPAD's sensitive surface for detection.

[0007] The existing technical solution has the following drawbacks: the center wavelength of the filter used in the laser ranging system changes with temperature, and ultra-narrow filters suffer from temperature drift and other problems. Furthermore, because background noise changes in real time, filters with fixed bandwidth cannot meet the application requirements of laser ranging systems.

[0008] Existing technical solution two: Distance gating technology is a time-filtering technique. Its basic principle is to accurately calculate the expected time of laser echo reflection based on forecast parameters, and then activate the echo receiving system slightly earlier than the expected echo time to minimize background noise interference. A typical schematic diagram of SPAD in gating mode is shown below. Figure 1 As shown in the figure, Tg represents the duration of the range gate (range gate width). Under the control of the range gate signal, the SPAD detector only responds to the incident light signal within the range gate (detection cycle) time, and the timing circuit records the corresponding photon signal timestamp. The range gate control subsystem calculates the generation time of the range gate based on the main wave latch time and the space target prediction, and generates the detector's gate control signal by comparing it with the system time. The control software calculates the generation time of the range gate control signal corresponding to the main wave time in the laser ranging system based on the observation prediction, and sends this time into the FIFO array. The values ​​in this array are sequentially sent to the gate control signal comparator according to the current time. When the system time is equal to the value in the gate control signal comparator, the gate control signal is generated. Figure 2This is a block diagram of the distance gating system for a high-repetition-rate laser ranging system. Most of the distance gating circuitry is implemented using a single FPGA, as indicated by the dashed box in the system structure diagram. The peripheral circuitry only provides parallel and serial ports, as well as some signal level conversion circuits. The control card first introduces the high-precision second pulse and 10MHz frequency signal generated by the GPS clock into the FPGA. The FPGA's internal PLL (phase-locked loop) is used to phase-lock and multiply the stable 10MHz external frequency to 200MHz. Two 32-bit counters are constructed using the FPGA's internal gating circuitry resources: one counts the input second signal, and the other counts the 100MHz signal to 1*10⁸ before being reset. These two values ​​are stored in a buffer, forming an internal time system with a resolution of 10ns. The FPGA only records the cumulative count within a second, strictly synchronizing with the GPS second at every whole second and resetting the counter within that second. All signals operate under the same coordination of this time system. When the computer issues a light emission command, a trigger pulse is sent to the laser. Simultaneously, the real-time distance gating time sent by the computer is received and stored in a FIFO memory. Then the FPGA controls the gate control signal according to the corresponding distance gate time, and controls the detector to start detection.

[0009] The shortcomings of the existing technical solution two are as follows: 1. Distance gating accuracy issue. In high-repetition-rate SLRs, the noise level is much higher than in low-repetition-rate SLRs. High-precision distance gating is beneficial for suppressing noise and improving the ranging success rate. However, traditional designs often use discrete components, resulting in limited distance gating accuracy, making it difficult to adapt to increasingly higher frequency SLR systems. 2. System real-time issue. In traditional distance gating designs, distance gating calculations are performed in a computer and then transmitted to the distance gating circuit through a corresponding interface. As the ranging frequency increases, the single ranging time of the control software is shortened. The large amount of data processing and transmission will consume the already limited CPU resources, resulting in a waste of system resources and time.

[0010] Existing technical solution three: For laser ranging systems, a larger receiving field of view is beneficial for target acquisition and saves observation time. However, increasing the receiving field of view also increases the background light noise received. During daytime ranging, the number of background noise photons is about 107 times that at night. In order to effectively suppress stray light from the background of the target being measured, spatial filtering technology is often used to improve the ranging capability of the system. A variable field of view aperture is added to the optical structure of the laser ranging receiving system to make full use of the limiting characteristic of the variable field of view aperture on the imaging range. Figure 3This is a structural diagram of a laser ranging and receiving system. As shown in the diagram, the laser ranging and receiving optical system consists of six parts: an objective lens, a beam splitter, an ICCD, a variable field of view stop, an eyepiece, a filter, a converging lens, and a detector. After the echo signal is received by the telescope, it passes through the beam splitter. Part of the signal reaches the ICCD for auxiliary tracking, while the other part passes through the variable field of view stop, collimating lens, and narrowband filter to reach the single-photon detector, ultimately obtaining the laser pulse signal. Reducing the field angle will significantly suppress background light interference during the day. The key factor in designing the variable field of view stop is parametric design; that is, the variable field of view stop must match the receiving field of view to suppress stray light outside the receiving field of view. The relationship between the diameter d of the variable field of view stop and the receiving field of view ω is shown in the following formula.

[0011] d=f tanω

[0012] In the formula, d is the diameter of the variable field stop in mm; f is the focal length of the objective lens; and ω is the receiving field of view. As can be seen from the formula, once the focal length f of the receiving objective lens and the receiving field of view ω are determined, the size of the variable field stop diameter d is also determined. However, in actual engineering design, other factors such as the application background, characteristics, and processing capabilities of each project must be considered.

[0013] The shortcomings of the existing technical solution three: The field-of-view variable aperture is divided into fixed and variable apertures. For the fixed aperture, due to its small aperture size, installation and adjustment are extremely difficult. When the aperture center deviates from the field-of-view center, the echo signal will be blocked by the field-of-view variable aperture. Although the smallest aperture center can be aligned with the field-of-view center as closely as possible through precise telescope optical path adjustments, this deviation cannot be completely avoided regardless of the adjustment. Furthermore, this deviation will change with variations in temperature. In addition, the reduction in the aperture size of the field-of-view variable aperture places higher demands on the entire optical system. To adapt to the complexity of the observation environment, the variable aperture was developed. The variable aperture can be adjusted by changing the aperture size to maintain a certain level of background noise from the sky entering the ranging system. However, existing variable apertures are usually adjusted manually, a method that relies heavily on human experience and is highly susceptible to subjective judgment. Moreover, with the development of laser ranging system hardware and the significant increase in data volume and transmission rate, manual adjustment can no longer meet the application requirements of future SLR systems.

[0014] In summary, how to design an adaptive spatial filtering method that can reduce the false alarm probability of laser systems is a problem that urgently needs to be solved by those skilled in the art. Summary of the Invention

[0015] The main objective of this invention is to propose an adaptive spatial filtering method to reduce the false alarm rate of laser ranging, aiming to design an adaptive spatial filtering method that can reduce the false alarm probability of laser systems.

[0016] The technical solution of this invention to solve the above-mentioned technical problems is to provide an adaptive spatial filtering method for reducing the false alarm rate of laser ranging, comprising the following steps:

[0017] Control the laser emission to generate a range gate, which in turn controls the activation of the detector;

[0018] Obtain the main wave emission time of the laser;

[0019] The detected background light intensity is compared with the standard illuminance value. When the background illuminance is consistent, the variable aperture is stationary. When the background illuminance changes, the aperture of the variable aperture in the field of view is adjusted in real time.

[0020] The laser echo signal is converged by the receiving system, passes through a variable field-of-view aperture and a narrowband filter, and reaches the C-SPAD target surface, where it is then converted by photoelectric conversion. The arrival time of the echo is recorded, and the ranging value is obtained through algorithm and data synthesis. The difference between the ranging value and the predicted value is then calculated to obtain the ranging residual.

[0021] Echo signals are obtained by gating the position or distance of the telescope.

[0022] Furthermore, an adaptive spatial filtering method that can reduce the false alarm probability of laser systems also includes:

[0023] Before observation, the satellite CPF ephemeris issued by the satellite forecasting center is received through the ground equipment control unit;

[0024] The forecasting software converts the mission target data into target distance, elevation angle, and azimuth angle data in the telescope station coordinate system;

[0025] The ground equipment control unit sends out command signals to drive the azimuth and altitude of the telescope, while simultaneously opening the variable aperture of the field of view to put the ranging system into standby mode.

[0026] The work procedure is initiated when the predicted task time arrives.

[0027] Furthermore, the step of comparing the detected background light intensity with the standard illuminance value, where the variable aperture remains stationary when the background illuminance is consistent, and controlling the variable aperture aperture in real time to adjust in real time when the background illuminance changes includes:

[0028] Obtain the background radiance L(θ) of the sky h ,θ,ζ);

[0029] The energy of the background noise from the sky incident on the detector target surface is:

[0030] P b =L(θ) h ,θ,ζ)(Δλ)(Ωfv Z 2 (A) r / Z 2 )=L(θ h ,θ,ζ)×(Δλ)×Ω fv ×A r ×K r ;

[0031] Among them, A r For the receiving lens area, Ω fv For SLR receiver field of view, Δλ is the narrowband filter bandwidth, and K is the SLR receiver field of view. r The solid angle Ω represents the optical efficiency of the ranging system; given the receiving field of view ψ and the receiving aperture D, the corresponding solid angle Ω is... fv and receiving area A r The expressions are as follows:

[0032]

[0033]

[0034] Based on the sky background radiance L(θ) h The relationship between (θ, ζ) and the receiving field of view angle ψ is used to adjust the variable aperture of the field of view.

[0035] Furthermore, the acquisition of the sky background radiance L(θ) h The steps (θ, ζ) include:

[0036] A chopper is placed in front of the laser. When the laser emits laser light, the chopper "cuts off" or "connects" the laser light, generating alternating "noise" or "echo + noise".

[0037] Obtain the background radiance L(θ) of the "noise" sky. h ,θ,ζ).

[0038] Furthermore, the acquisition of the sky background radiance L(θ) h The steps (θ, ζ) include:

[0039] Obtain the solar altitude angle, observation point location, solar azimuth angle, observation point azimuth angle, and solar angle, and calculate the zenith brightness L of a completely clear sky using the brightness calculation formula. z (θ h The formula for calculating brightness (θ, ζ) is:

[0040]

[0041] in,

[0042]

[0043] ζ=arccos(sinθ h sinθ+cosθ h cosθcos|α s -α|),

[0044]

[0045] Where, θ h α is the solar altitude angle, θ is the observation point (telescope altitude angle), and α is the solar altitude angle. s α is the azimuth of the sun (measured from south), and α is the azimuth of the observation point (43.7905N from south).

[0046] ζ is the solar angle (the angle between the sun and the line of sight of the receiving field of view).

[0047] Furthermore, the acquisition of the sky background radiance L(θ) h The steps (θ, ζ) include:

[0048] The system uses a photosensitive device installed in the optical path to monitor the background radiance L(θ) of the sky entering the system in real time. h ,θ,ζ).

[0049] Furthermore, the statement based on the sky background radiance L(θ) h The relationship between (θ, ζ) and the receiving field of view angle ψ, and the steps for adjusting the variable aperture of the field of view include:

[0050] When the background light radiation intensity is high, the aperture of the diaphragm is reduced.

[0051] When the background light radiation intensity is low, adjust the aperture of the diaphragm to open wider.

[0052] Furthermore, the step of comparing the detected background light intensity with the standard illuminance value, where the variable aperture remains stationary when the background illuminance is consistent, and controlling the variable aperture aperture in real time to adjust in real time when the background illuminance changes includes:

[0053] Hall effect sensors are used to detect the limit position of the variable aperture.

[0054] Furthermore, an adaptive spatial filtering method that can reduce the false alarm probability of laser systems also includes:

[0055] The observation time, satellite distance, azimuth and altitude are stored in a file that includes the laser emission time, echo arrival time and encoder status values ​​near the time of the laser emission;

[0056] To measure ground targets and obtain local temperature, humidity, and air pressure parameters;

[0057] The saved observation data is processed, and the mean square error is used to characterize the intrinsic accuracy of the observation arc. The data is then uploaded to the data processing center.

[0058] The technical solution of this invention introduces an adaptive spatial filtering module into the laser ranging system. A real-time sky background noise acquisition module detects changes in the intensity of the sky background light, feeding this information back to the control system for immediate response. Based on the acquired control signals, a receiving field-of-view control module enables automatic control of a series of mechanisms and circuits. An adjustable variable aperture limits the background noise entering the laser ranging system; when the background light radiation intensity is high, the aperture diameter decreases, and vice versa. By reducing the background noise in the system response, the probability of false alarms is lowered. This design is simple in structure, easy to operate, stable, and highly automated. It not only balances the system's target acquisition and noise suppression capabilities but also possesses excellent adaptability, allowing for real-time, intelligent, and efficient adjustment of system structural parameters according to observation conditions, thereby improving system stability and automation. It shows promising application prospects in fields such as ultra-high repetition rate laser ranging and automated daytime laser ranging. Attached Figure Description

[0059] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the structures shown in these drawings without creative effort.

[0060] Figure 1 This is a flowchart of the adaptive spatial filtering method for reducing the false alarm rate of laser ranging as described in this invention.

[0061] Figure 2 This is a schematic diagram illustrating the relationship between sky background noise measurement in this invention;

[0062] Figure 3 This is a graph showing the relationship between the zenith brightness of the SLR system at Changchun Station and the solar altitude angle.

[0063] Figure 4 This is a graph showing the relationship between the sky background radiance and the receiving field of view ψ in this invention.

[0064] Figure 5 This invention relates the detection probability, false alarm rate, and noise photon number of the laser ranging system.

[0065] Figure 6 This is a flowchart of the preprocessing steps of the adaptive spatial filtering method for reducing the false alarm rate of laser ranging as described in this invention.

[0066] Figure 7 This is a flowchart of the post-processing steps of the adaptive spatial filtering method for reducing the false alarm rate of laser ranging as described in this invention.

[0067] Figure 8 This is a diagram of the laser ranging system with adaptive spatial filtering function of the present invention;

[0068] Figure 9 This is a diagram of a laser ranging system with adaptive spatial filtering function according to Example 1 of the present invention;

[0069] Figure 10 This is a diagram of a laser ranging system with adaptive spatial filtering function according to Example 2 of the present invention. Detailed Implementation

[0070] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of them. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0071] It should be noted that all directional indications (such as up, down, left, right, front, back, etc.) in the embodiments of the present invention are only used to explain the relative positional relationship and movement of each component in a certain specific posture (as shown in the figure). If the specific posture changes, the directional indication will also change accordingly.

[0072] Furthermore, in this invention, descriptions involving "first," "second," etc., are for descriptive purposes only and should not be construed as indicating or implying their relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one of that feature. In the description of this invention, "several" or "a plurality of" means at least two, such as two, three, etc., unless otherwise explicitly specified.

[0073] In this invention, unless otherwise explicitly specified and limited, the terms "connection," "fixed," etc., should be interpreted broadly. For example, "fixed" can mean a fixed connection, a detachable connection, or an integral part; it can mean a mechanical connection or an electrical connection; it can mean a direct connection or an indirect connection through an intermediate medium; it can mean the internal communication of two components or the interaction between two components, unless otherwise explicitly limited. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0074] Furthermore, the technical solutions of the various embodiments of the present invention can be combined with each other, but only if they are feasible for those skilled in the art. If the combination of technical solutions is contradictory or cannot be implemented, it should be considered that such combination of technical solutions does not exist and is not within the scope of protection claimed by the present invention.

[0075] This invention proposes an adaptive spatial filtering method to reduce the false alarm rate of laser ranging, aiming to design an adaptive spatial filtering method that can reduce the false alarm probability of laser systems.

[0076] The adaptive spatial filtering method for reducing the false alarm rate of laser ranging proposed in this invention will be described below in specific embodiments:

[0077] An adaptive spatial filtering method for reducing the false alarm rate of laser ranging is presented. Using a Changchun station as a test point, the method demonstrates that sky background noise has a significant impact on the background noise of the laser ranging system during the daytime.

[0078] For daytime laser ranging systems, SLR background noise mainly refers to solar background noise formed by Rayleigh scattering and Mie scattering of sunlight by the atmosphere. Sky background radiance is an important parameter characterizing the intensity of solar background noise, and it is related to the sun's position, the direction of the line of sight, and the meteorological conditions at the time of observation. For any observation point P, the sky background radiance L(θ) h The formulas for calculating (θ, ζ) are:

[0079]

[0080] in,

[0081]

[0082] ζ=arccos(sinθ h sinθ+cosθ h cosθcos|α s -α|),

[0083]

[0084] Where, θ h α is the solar altitude angle, θ is the observation point (telescope altitude angle), and α is the solar altitude angle. s α is the azimuth angle of the sun (measured from south), α is the azimuth angle of the observation point (43.7905N from south), ζ is the solar angle (the angle between the sun and the line of sight of the receiving field of view), and L is the solar angle. z (θ h ,θ,ζ) represent the zenith brightness of a completely clear sky. Figure 2 The diagram shows the positional relationship between the sun and the observation point (telescope) P.

[0085] The zenith brightness under different solar altitude angles was simulated and calculated using the SBDAR model, and the characteristic relationship between solar zenith brightness and solar altitude angle was obtained. The results are as follows:

[0086] L z (θ h ,θ,ζ)=0.0027372*θ h 3 -0.19412*θ h 2 +4.8028*θ h -9.2932

[0087] Figure 3 The graph shows the relationship between zenith brightness at Changchun Station and solar altitude angle. As can be seen from the graph, the zenith radiance gradually increases with the increase of solar altitude angle. For daytime laser ranging systems, the projection of the observed target's trajectory onto the celestial sphere sometimes approaches or crosses the sun's position. When the telescope tracks the observed target, the background noise entering the laser ranging system changes in real time with the telescope's altitude angle. Table 1 shows the number of sky background noise photons received by the Changchun Station SLR system (observation elevation angle 45°, observation azimuth angle 120°) at different times on July 15, 2023. For daytime laser ranging systems, as shown in Table 1, the sun's position has a significant impact on sky background noise. When the solar altitude angle is less than 40°, the intensity of sky background light noise tends to stabilize. As the solar altitude angle gradually increases, the radiation of sky background light gradually approaches that of direct sunlight. When the observation time is 9:00 AM, the angle between the telescope and the sun is the smallest, and the number of sky background noise photons reaches its peak, increasing by approximately 107 times compared to nighttime. When an SLR system enters a region of strong background light, it becomes difficult to identify and process the effective SLR echo. Therefore, it is crucial to control the line of sight of the SLR receiving system and the angle of sunlight illumination within a reasonable range to avoid damage to the detection devices.

[0088] Table 1. Number of sky background noise photons received by the SLR system at Changchun Station during different time periods

[0089]

[0090] Table 1 shows that for daytime SLR systems, the sun's position has a significant impact on sky background noise. When the sun's altitude angle is less than 40°, the intensity of sky background noise tends to stabilize. As the sun's altitude angle gradually increases, the radiation of the sky background light gradually approaches that of direct sunlight. When the observation time is 9:00 AM, the angle between the telescope and the sun is the smallest, and the number of sky background noise photons reaches its peak, increasing by approximately 107 times compared to nighttime. The SLR system enters the strong background light region, which is detrimental to the identification and processing of effective SLR echoes.

[0091] For the SLR system, the sky background light is a surface source. Assuming the sky background within the field of view is a Lambertian volume and the telescope tube is facing the measurement direction, according to the Lambertian volume model, the sky background noise energy incident on the SLR detector target surface is:

[0092] P b =L(θ) h ,θ,ζ)(Δλ)(Ω fv Z 2 (A) r / Z 2 )=L(θ h ,θ,ζ)×(Δλ)×Ω fv ×A r ×K r

[0093] Where A r For the receiving lens area, Ω fv For SLR receiver field of view, Δλ is the narrowband filter bandwidth, and K is the SLR receiver field of view. r This represents the optical efficiency of the ranging system. Given the receiving field of view ψ and the receiving aperture D, the corresponding solid angle Ω is... fv and receiving area A r The expressions are as follows:

[0094]

[0095]

[0096] For the Changchun Station SLR system, the relationship between sky background radiance and receiving field of view is as follows: Figure 4 .from Figure 4 As can be seen, the background noise from the sky gradually increases with the increase of the field stop aperture. Therefore, it can be concluded that the background noise received by the SLR can be effectively controlled by adjusting the size of the field stop aperture.

[0097] Background noise has a significant impact on the performance of laser ranging systems. Detection probability, false alarm probability, and false negative rate are important parameters characterizing the detection performance of laser ranging systems. The false alarm probability is determined by both the detection probability and the false negative rate of the laser ranging system. The false alarm probability refers to the probability of echo data generated by noise when there is no laser echo signal; its specific expression is as follows:

[0098] P target =exp(-fN)[1-exp(-SN / b)]

[0099] P none =exp(-SN)

[0100] P false =1-P target -P none

[0101] Where f is the ratio of the time interval between the start of the range gate and the arrival of the signal photon to the range gate width (f = 0 when the signal photon arrives at the start of the gate, and f = 1 when the signal photon arrives at the end of the gate), b is the number of gate samples, S is the effective echo photon count of the laser ranging system, and N is the number of noise photoelectrons generated by the sky background and the detector during the range gate time. Compared to the noise caused by the sky background light, the dark count generated by the detector itself is very weak, differing by several orders of magnitude, and can be ignored in the analysis. During laser ranging, due to prediction errors and the detector's own response time, a certain gate signal advance is required from the arrival of the gate signal at the detector current to the complete activation of the Geiger detection mode; therefore, f ≠ 0. Figure 5 The relationship between the detection probability, false alarm rate and noise photon number of a laser ranging system is presented.

[0102] from Figure 5 The results show an increasing relationship between the false alarm rate and the number of noise photons under different signal-to-noise ratios. This means that the false alarm rate is only affected by the number of noise photons, and not by the signal-to-noise ratio. When the number of noise photons decreases from 2 to 0.1, the false alarm rate drops rapidly from approximately 0.85 to 0.095. Furthermore, there is an approximately one-to-one match between the number of noise photons and the false alarm probability. Therefore, we conclude that simply reducing noise can lower the false alarm probability of the system.

[0103] The laser source used in this application may be 532nm, 1064nm, 1550nm, etc., and the applicable wavelength is not unique. The laser repetition rate may be 1kHz, 2kHz, 100kHz, etc., and the laser repetition rate is not unique. The observation target may be artificial satellites, space debris, the moon, spacecraft, etc., and the observation target is not unique. The optical telescope system used may be a separate transmit / receive system or a coaxial transmit / receive system, and the choice of telescope system is not unique. The optical telescope used may be 60cm, 120cm, 250cm, and the telescope aperture is not unique. The single-photon detector used may be APD, PMT, SNSPD, etc., and the choice of detector is not unique. The photosensitive device used may be CdS, CdSe, Cd2SSe, etc., and the choice of photosensitive device is not limited. The aperture used may be circular, a circular variable aperture structure, or a square variable aperture structure, and the choice of aperture is not unique.

[0104] Specifically, an adaptive spatial filtering method for reducing the false alarm rate of laser ranging is described in the system structure design diagram below. Figure 8 As shown, it includes a laser emission optical system, an echo receiving system, an adaptive spatial filtering module, a detector, a timer, a delay and gating system, a laser, and a host computer.

[0105] like Figure 1 As shown, it includes the following steps:

[0106] S10: Controls laser emission to generate a range gate, controlling the activation of the detector;

[0107] S20: Obtain the main wave emission time of the laser;

[0108] S30: Compare the detected background light intensity with the standard illuminance value. When the background illuminance is consistent, the variable aperture is stationary. When the background illuminance changes, the field of view variable aperture is adjusted in real time.

[0109] S40: The laser echo signal is converged by the receiving system, passes through the field-of-view variable aperture and narrowband filter, and reaches the C-SPAD target surface, and then undergoes photoelectric conversion; the arrival time of the echo is recorded, and the ranging value is obtained by algorithm and data synthesis, and the difference with the prediction value is obtained to obtain the ranging residual;

[0110] S50: Obtain echo signals by gating the position or distance of the telescope.

[0111] Understandably, this application adjusts the field-of-view aperture based on the relationship between sky background noise and field-of-view aperture, no longer relying on manual judgment experience, resulting in a high degree of automation and good system stability. By dynamically adjusting the size of the field-of-view aperture, a large field-of-view aperture is used to track and capture targets, reducing the difficulty of observation. After the tracking is stable, the field-of-view aperture is adaptively reduced according to the sky background noise, which reduces the difficulty of observation of the laser ranging system during the day and effectively reduces the probability of false alarms of the system.

[0112] In one feasible implementation, the background illumination intensity can be detected by setting a photosensitive device in the receiving system to obtain the sky background radiance L(θ). h ,θ,ζ), and finally based on the sky background radiance L(θ) h (θ, ζ) Adjust the aperture of the variable aperture.

[0113] In one feasible implementation, a chopper is used to block light, allowing for alternating measurements of "noise" and "satellite echo + noise" signals. The chopper is used to "connect" or "interrupt" the laser, generating alternating photon counts of "echo + noise" and "noise" signals. By dynamically adjusting the aperture size through real-time monitoring of pure background noise, the noise signal is controlled within a certain range, effectively reducing the false alarm probability and improving detection performance.

[0114] Furthermore, prior to step S10, an adaptive spatial filtering method for reducing the false alarm probability of a laser system further includes:

[0115] S01: Before observation, receive the satellite CPF ephemeris issued by the satellite forecasting center through the ground equipment control unit;

[0116] S02: The forecasting software converts the mission target data into target distance, elevation angle, and azimuth angle data in the telescope station coordinate system;

[0117] S03: The ground equipment control unit sends a command signal to drive the azimuth and altitude of the telescope, and at the same time opens the field of view variable aperture to put the ranging system into standby mode.

[0118] S04: Start the working procedure when the predicted task time arrives.

[0119] Furthermore, the step of comparing the detected background light intensity with the standard illuminance value, where the variable aperture remains stationary when the background illuminance is consistent, and controlling the variable aperture aperture in real time to adjust in real time when the background illuminance changes includes:

[0120] Obtain the background radiance L(θ) of the sky h ,θ,ζ);

[0121] The energy of the background noise from the sky incident on the detector target surface is:

[0122] P b =L(θ) h ,θ,ζ)(Δλ)(Ω fv Z 2 (A) r / Z 2 )=L(θ h ,θ,ζ)×(Δλ)×Ω fv ×A r ×K r ;

[0123] Among them, A r For the receiving lens area, Ω fv For SLR receiver field of view, Δλ is the narrowband filter bandwidth, and K is the SLR receiver field of view. r The solid angle Ω represents the optical efficiency of the ranging system; given the receiving field of view ψ and the receiving aperture D, the corresponding solid angle Ω is... fv and receiving area A r The expressions are as follows:

[0124]

[0125]

[0126] Based on the sky background radiance L(θ) h The relationship between (θ, ζ) and the receiving field of view angle ψ is used to adjust the variable aperture of the field of view.

[0127] Furthermore, the acquisition of the sky background radiance L(θ) h The steps (θ, ζ) include:

[0128] A chopper is placed in front of the laser. When the laser emits laser light, the chopper "cuts off" or "connects" the laser light, generating alternating "noise" or "echo + noise".

[0129] Obtain the background radiance L(θ) of the "noise" sky. h ,θ,ζ).

[0130] Furthermore, the acquisition of the sky background radiance L(θ) h The steps (θ, ζ) include:

[0131] Obtain the solar altitude angle, observation point location, solar azimuth angle, observation point azimuth angle, and solar angle, and calculate the zenith brightness L of a completely clear sky using the brightness calculation formula. Z (θ h The formula for calculating brightness (θ, ζ) is:

[0132]

[0133] in,

[0134]

[0135] ζ=arccos(sinθ h sinθ+cosθ h cosθcos|α s -α|),

[0136]

[0137] Where, θ h α is the solar altitude angle, θ is the observation point (telescope altitude angle), and α is the solar altitude angle. s α is the azimuth of the sun (measured from south), and α is the azimuth of the observation point (43.7905N from south).

[0138] ζ is the solar angle (the angle between the sun and the line of sight of the receiving field of view).

[0139] Furthermore, the acquisition of the sky background radiance L(θ) h The steps (θ, ζ) include:

[0140] The system uses a photosensitive device installed in the optical path to monitor the background radiance L(θ) of the sky entering the system in real time. h ,θ,ζ).

[0141] Furthermore, the statement based on the sky background radiance L(θ) h The relationship between (θ, ζ) and the receiving field of view angle ψ, and the steps for adjusting the variable aperture of the field of view include:

[0142] When the background light radiation intensity is high, the aperture of the diaphragm is reduced.

[0143] When the background light radiation intensity is low, adjust the aperture of the diaphragm to open wider.

[0144] Furthermore, the step of comparing the detected background light intensity with the standard illuminance value, where the variable aperture remains stationary when the background illuminance is consistent, and controlling the variable aperture aperture in real time to adjust in real time when the background illuminance changes includes:

[0145] Hall effect sensors are used to detect the limit position of the variable aperture.

[0146] Understandably, the Hall element is used to limit the movement of the aperture, protecting the field of view aperture from damage due to excessive rotation.

[0147] Furthermore, after step S50, an adaptive spatial filtering method that can reduce the false alarm probability of the laser system further includes:

[0148] S60: Save the observation time, satellite distance, azimuth and altitude into a file that includes the laser emission time, echo arrival time and encoder near-time status values;

[0149] S70: To measure ground targets and obtain local temperature, humidity, and air pressure parameters;

[0150] S80: Process the saved observation data, use the mean square error to characterize the intrinsic accuracy of the observation arc, and upload the data to the data processing center.

[0151] Specifically, this patent introduces an adaptive spatial filtering module into the laser ranging system. A real-time sky background noise acquisition module detects changes in sky background light intensity, feeding this information back to the control system for immediate response. Based on the acquired control signals, a receiving field-of-view control module enables automatic control of a series of mechanisms and circuits. An adjustable variable aperture limits background noise entering the laser ranging system; when the background light radiation intensity is high, the aperture diameter decreases, and vice versa. By reducing the background noise in the system response, the probability of false alarms is lowered. This design is simple in structure, easy to operate, stable, and highly automated. It not only balances the system's target acquisition and noise suppression capabilities but also possesses excellent adaptability, allowing for real-time, intelligent, and efficient adjustment of system structural parameters based on observation conditions. This improves system stability and automation, making it a promising candidate for applications in ultra-high repetition rate laser ranging and automated daytime laser ranging.

[0152] Example 1

[0153] An adaptive spatial filtering method for reducing the false alarm rate of laser ranging is shown in the system structure design diagram below. Figure 9 As shown, it includes the following steps:

[0154] Step 1: Before observation, receive the satellite CPF ephemeris issued by the satellite forecasting center through the ground equipment control unit;

[0155] Understandably, before observation, the satellite CPF ephemeris released by the satellite forecasting center is received through the ground equipment control unit.

[0156] Step 2: The forecasting software converts the mission target data into target distance, elevation angle, and azimuth angle data in the telescope station coordinate system;

[0157] Step 3: The ground equipment control unit sends a command signal to drive the azimuth and altitude of the telescope, and at the same time opens the field of view variable aperture to put the ranging system into standby mode.

[0158] Step 4: When the predicted task time arrives, start the work procedure;

[0159] Step 5: Control the laser to emit light, generate a range gate, and control the activation of the single-photon detector (C-SPAD);

[0160] Step 6: Obtain the precise moment of laser emission (referred to as the main wave emission moment) through the event timer interface.

[0161] Step 7: Set up a photosensitive device (photoresistor) in the system's optical path to monitor the ambient radiance L(θ) of the sky entering the system in real time. h The system's detection circuit employs a balanced bridge circuit. One arm of the balanced bridge is a Cd2SSe photoresistor, placed near the edge of the receiving optical path. It directly receives the background sky light converged from the main optical path and passed through the variable aperture, measuring the portion of light energy separated from the main optical path in real time. The output voltage of the photoresistor is then taken and used as a control signal, fed back to the ground equipment control unit. Communication with a computer is achieved via an RS232 interface. The computer can send control commands via the serial port to adjust the field-of-view aperture in real time. The detected background light intensity is compared with a pre-defined standard illuminance value. When the background illuminance is consistent, the bridge is in a balanced state with no error signal output, and the variable aperture remains stationary. When the background illuminance changes, an error signal is output, amplified, and used to drive the servo motor controlling the aperture shutter. The drive unit is controlled by a microcontroller, which drives the variable aperture. The mechanical components employ a DC reducer and gear transmission structure to drive the variable field-of-view aperture lever, rotating it in the direction of reducing error signals. This decreases the aperture diameter, ensuring the background illumination matches the given standard illumination and effectively controlling background noise. Simultaneously, a Hall effect sensor is used to limit the aperture movement, protecting the field-of-view aperture from damage due to excessive rotation.

[0162] Specifically, taking Changchun Station as the launch base, such as Figure 2 The diagram shows the positional relationship between the sun and the observation point (telescope) P. The sky background light is a surface source for the SLR system. Assuming the sky background within the field of view is a Lambertian volume and the telescope tube is aligned with the measurement direction, according to the Lambertian volume model, the energy of the sky background noise incident on the SLR detector target surface is:

[0163] P b =L(θ) h ,θ,ζ)(Δλ)(Ω fv Z 2 (A) r / Z 2 )=L(θ h ,θ,ζ)×(Δλ)×Ω fv ×A r ×K r

[0164] Where Ar For the receiving lens area, Ω fv For SLR receiver field of view, Δλ is the narrowband filter bandwidth, and K is the SLR receiver field of view. r This represents the optical efficiency of the ranging system. Given the receiving field of view ψ and the receiving aperture D, the corresponding solid angle Ω is... fv and receiving area A r The expressions are as follows:

[0165]

[0166]

[0167] For the Changchun Station SLR system, the relationship between the sky background radiance and the receiving field of view ψ is as follows: Figure 4 As shown. By Figure 4 The linear relationship between sky background radiance and the receiving field of view can be derived as: y = p1*x^2 + p2*x + p3, with fitting coefficients: p1 = 1.9213e+05, p2 = -4.5574e-10, p3 = 1.7773e-08. This means that as the aperture of the field stop increases, the sky background radiance noise gradually increases. Therefore, adjusting the size of the field stop aperture can effectively control the background noise received by the SLR. Specifically, when the background light radiance is high, the aperture is decreased; when the background light radiance is low, the aperture is increased.

[0168] Step 8: The laser echo signal is converged by the receiving system, passes through the field of view aperture and narrowband filter, and arrives on the C-SPAD target surface. After photoelectric conversion, the arrival time of the echo is recorded by the event timer. The ranging value (time interval) is obtained through a certain algorithm and data synthesis, and the difference is calculated with the predicted value to obtain the ranging residual (OC).

[0169] Step 9: Real-time display (OC), the program automatically or the operator determines whether the ranging is successful. The echo signal is finally obtained by the operator through the search of the telescope's position or distance gate.

[0170] Step 10: Save the observation time, satellite distance, azimuth and altitude into a file (laser main wave time, corresponding time interval, position information, but the position information is the state value of the telescope encoder at a nearby moment).

[0171] Step 11: After the observation is completed, the ground target is measured for calibration of system errors.

[0172] Step 12: Read meteorological measurements to obtain local temperature, humidity, and air pressure parameters for distance correction.

[0173] Step 13: Process the saved observation data, remove outliers, and use the mean square error to characterize the accuracy of the observation arc. Finally, upload the observation data to the data processing center.

[0174] Example 2

[0175] An adaptive spatial filtering method for reducing the false alarm rate of laser ranging is shown in the system structure design diagram below. Figure 10 As shown, it includes the following steps:

[0176] Step 1: Before observation, receive the satellite CPF ephemeris issued by the satellite forecasting center through the ground equipment control unit;

[0177] Understandably, before observation, the satellite CPF ephemeris released by the satellite forecasting center is received through the ground equipment control unit.

[0178] Step 2: The forecasting software converts the mission target data into target distance, elevation angle, and azimuth angle data in the telescope station coordinate system;

[0179] Step 3: The ground equipment control unit sends a command signal to drive the azimuth and altitude of the telescope, and at the same time opens the field of view variable aperture to put the ranging system into standby mode.

[0180] Step 4: When the predicted task time arrives, start the work procedure;

[0181] Step 5: Control the laser to emit light, generate a range gate, and control the activation of the single-photon detector (C-SPAD);

[0182] Step 6: Obtain the precise moment of laser emission (referred to as the main wave emission moment) through the event timer interface.

[0183] Step 7: By setting up a chopper, the light is blocked to achieve alternating measurement of "noise" and "satellite echo + noise" signals; the chopper is used to "connect" or "cut off" the laser, generating photon counts of alternating "echo + noise" and "noise" signals. The aperture size is dynamically adjusted by real-time monitoring of pure background noise.

[0184] Specifically, when the laser emits a laser for the first time, the chopper is activated to "cut off" the laser, thereby obtaining the pure background noise of the "noise" and directly adjusting the size of the aperture in real time based on the pure background noise.

[0185] When the laser emits a second laser beam, the chopper is turned off, and the system acquires echo information consisting of "echo + noise"; the chopper is then turned on or off alternately in sequence.

[0186] Step 8: The laser echo signal is converged by the receiving system, passes through the field of view aperture and narrowband filter, and arrives on the C-SPAD target surface. After photoelectric conversion, the arrival time of the echo is recorded by the event timer. The ranging value (time interval) is obtained through a certain algorithm and data synthesis, and the difference is calculated with the predicted value to obtain the ranging residual (OC).

[0187] Step 9: Real-time display (OC), the program automatically or the operator determines whether the ranging is successful. The echo signal is finally obtained by the operator through the search of the telescope's position or distance gate.

[0188] Step 10: Save the observation time, satellite distance, azimuth and altitude into a file (laser main wave time, corresponding time interval, position information, but the position information is the state value of the telescope encoder at a nearby moment).

[0189] Step 11: After the observation is completed, the ground target is measured for calibration of system errors.

[0190] Step 12: Read meteorological measurements to obtain local temperature, humidity, and air pressure parameters for distance correction.

[0191] Step 13: Process the saved observation data, remove outliers, and use the mean square error to characterize the accuracy of the observation arc. Finally, upload the observation data to the data processing center.

[0192] Example 3

[0193] An adaptive spatial filtering method for reducing the false alarm rate of laser ranging is shown in the system structure design diagram below. Figure 8 As shown, taking the Changchun Station SLR system as an example, the steps include:

[0194] Step 1: Before observation, receive the satellite CPF ephemeris issued by the satellite forecasting center through the ground equipment control unit;

[0195] Understandably, before observation, the satellite CPF ephemeris released by the satellite forecasting center is received through the ground equipment control unit.

[0196] Step 2: The forecasting software converts the mission target data into target distance, elevation angle, and azimuth angle data in the telescope station coordinate system;

[0197] Step 3: The ground equipment control unit sends a command signal to drive the azimuth and altitude of the telescope, and at the same time opens the field of view variable aperture to put the ranging system into standby mode.

[0198] Step 4: When the predicted task time arrives, start the work procedure;

[0199] Step 5: Control the laser to emit light, generate a range gate, and control the activation of the single-photon detector (C-SPAD);

[0200] Step 6: Obtain the precise moment of laser emission (referred to as the main wave emission moment) through the event timer interface.

[0201] Step 7: The ground equipment control unit records the azimuth and altitude of the receiving telescope, as well as the aperture size of the field of view, in real time, according to the formula:

[0202]

[0203] in,

[0204]

[0205] ζ=arccos(sinθ h sinθ+cosθ h cosθcos|α s -α|),

[0206]

[0207] Where, θ h α is the solar altitude angle, θ is the observation point (telescope altitude angle), and α is the solar altitude angle. s α is the azimuth of the sun (measured from south), and α is the azimuth of the observation point (43.7905N from south).

[0208] ζ is the solar angle (the angle between the sun and the line of sight of the receiving field of view), which can be obtained through the ground control system.

[0209] The ground control system calculates the background noise entering the ranging system in real time according to the formula, and obtains the zenith brightness L of a clear sky. z (θ h ,θ,ζ); and then adjust the size of the aperture in real time.

[0210] Step 8: The laser echo signal is converged by the receiving system, passes through the field of view aperture and narrowband filter, and arrives on the C-SPAD target surface. After photoelectric conversion, the arrival time of the echo is recorded by the event timer. The ranging value (time interval) is obtained through a certain algorithm and data synthesis, and the difference is calculated with the predicted value to obtain the ranging residual (OC).

[0211] Step 9: Real-time display (OC), the program automatically or the operator determines whether the ranging is successful. The echo signal is finally obtained by the operator through the search of the telescope's position or distance gate.

[0212] Step 10: Save the observation time, satellite distance, azimuth and altitude into a file (laser main wave time, corresponding time interval, position information, but the position information is the state value of the telescope encoder at a nearby moment).

[0213] Step 11: After the observation is completed, the ground target is measured for calibration of system errors.

[0214] Step 12: Read meteorological measurements to obtain local temperature, humidity, and air pressure parameters for distance correction.

[0215] Step 13: Process the saved observation data, remove outliers, and use the mean square error to characterize the accuracy of the observation arc. Finally, upload the observation data to the data processing center.

[0216] The above description is merely a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. An adaptive spatial filtering method for reducing the false alarm rate of laser ranging, characterized in that, Includes the following steps: Control the laser emission to generate a range gate, which in turn controls the activation of the detector; Obtain the main wave emission time of the laser; The detected background light intensity is compared with the standard illuminance value. When the background illuminance is consistent, the variable aperture is stationary. When the background illuminance changes, the aperture of the variable aperture in the field of view is adjusted in real time. The laser echo signal is focused by the receiving system, passes through a variable field-of-view aperture and a narrowband filter, reaches the C-SPAD target surface, and is then converted by photoelectric conversion. Record the arrival time of the echo, obtain the ranging value through algorithm and data synthesis, and subtract it from the predicted value to obtain the ranging residual; Echo signals are obtained by gating the position or distance of the telescope. The detected background light intensity is compared with the standard illuminance value. When the background illuminance is consistent, the variable aperture is in a stationary state. When the background illumination changes, the steps for real-time adjustment of the variable aperture of the field of view include: Obtain the background radiance of the sky ; The energy of the background noise from the sky incident on the detector target surface is: ； in, For the receiving lens area, For SLR receiving field of view, For narrowband filter bandwidth, Indicates the optical efficiency of the ranging system; given the receiving field of view angle is... If the receiving aperture is D, then the corresponding solid angle is... and receiving area The expressions are as follows: ， ， Based on the sky background radiance With receiving field of view The relationship between the field of view and the variable aperture is adjusted accordingly. The acquisition of sky background radiance The steps include: Obtain the solar altitude angle, observation point location, solar azimuth angle, observation point azimuth angle, and solar angle, and calculate the zenith brightness of a clear sky using the brightness calculation formula. The formula for calculating brightness is: ， in, , ), , ； in, The solar altitude angle, For the observation point, the telescope elevation angle, This is the azimuth of the sun, measured from south. The azimuth of the observation point is 43.7905N, measured from south. The solar angle is the angle between the sun and the line of sight of the receiving field of view.

2. The adaptive spatial filtering method for reducing the false alarm rate of laser ranging according to claim 1, characterized in that, Also includes: Before observation, the satellite CPF ephemeris issued by the satellite forecasting center is received through the ground equipment control unit; The forecasting software converts the mission target data into target distance, elevation angle, and azimuth angle data in the telescope station coordinate system; The ground equipment control unit sends out command signals to drive the azimuth and altitude of the telescope, while simultaneously opening the variable aperture of the field of view to put the ranging system into standby mode. The work procedure is initiated when the predicted task time arrives.

3. The adaptive spatial filtering method for reducing the false alarm rate of laser ranging according to claim 1, characterized in that, The acquisition of sky background radiance The steps include: A chopper is placed in front of the laser. When the laser emits laser light, the chopper "cuts off" or "connects" the laser light, generating alternating "noise" or "echo + noise". Obtain the background radiance of the "noise" sky .

4. The adaptive spatial filtering method for reducing the false alarm rate of laser ranging according to claim 1, characterized in that, The acquisition of sky background radiance The steps include: The system uses photosensitive devices installed in its optical path to monitor the ambient radiance of the sky entering the system in real time. .

5. The adaptive spatial filtering method for reducing the false alarm rate of laser ranging according to claim 1, 3, or 4, characterized in that, According to the sky background radiance With receiving field of view The steps for adjusting the variable aperture of the field of view, based on the relationship between the two, include: When the background light radiation intensity is high, the aperture of the diaphragm is reduced. When the background light radiation intensity is low, adjust the aperture of the diaphragm to open larger.

6. The adaptive spatial filtering method for reducing the false alarm rate of laser ranging according to claim 1, characterized in that, The detected background light intensity is compared with the standard illuminance value. When the background illuminance is consistent, the variable aperture is in a stationary state. When the background illumination changes, the steps for real-time adjustment of the variable aperture of the field of view include: Hall effect sensors are used to detect the limit position of the variable aperture.

7. The adaptive spatial filtering method for reducing the false alarm rate of laser ranging according to claim 1, characterized in that, Also includes: The observation time, satellite distance, azimuth and altitude are stored in a file that includes the laser emission time, echo arrival time and encoder status values ​​near the time of the laser emission; To measure ground targets and obtain local temperature, humidity, and air pressure parameters; The saved observation data is processed, and the mean square error is used to characterize the intrinsic accuracy of the observation arc. The data is then uploaded to the data processing center.

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