阅读说明：本技术 空间目标的天文定位及自动跟踪方法、系统及电子设备 (Astronomical positioning and automatic tracking method and system for space target and electronic equipment ) 是由 赵春梅 何正斌 张浩越 卫志斌 于 2021-07-09 设计创作，主要内容包括：本发明提供一种空间目标的天文定位及自动跟踪方法、系统及电子设备。该方法包括：获取空间目标的天文图像并对天文图像进行预处理；以及将预处理后的天文图像输入至经训练的基于卫星激光测距SLR的空间目标天文定位及自动跟踪模型中,得到空间目标天文定位及自动跟踪模型输出的空间目标的实时位置信息,空间目标天文定位跟踪模型用于通过提取图像质心和预定的底片模型来确定空间目标的位置信息,并基于位置信息实时生成空间目标的位置修正信息以修正空间目标的位置信息,基于修正后的空间目标的实时位置信息来实现对空间目标自动跟踪,其中,通过对天文图像进行背景阈值计算、目标检测和/或星图匹配来生成空间目标的位置修正信息。(The invention provides a space target astronomical positioning and automatic tracking method, a space target astronomical positioning and automatic tracking system and electronic equipment. The method comprises the following steps: acquiring an astronomical image of a space target and preprocessing the astronomical image; and inputting the preprocessed astronomical image into a trained space target astronomical positioning and automatic tracking model based on the satellite laser ranging SLR to obtain real-time position information of the space target output by the space target astronomical positioning and automatic tracking model, wherein the space target astronomical positioning and tracking model is used for determining the position information of the space target by extracting the image centroid and a preset negative film model, generating position correction information of the space target in real time based on the position information to correct the position information of the space target, and realizing automatic tracking of the space target based on the corrected real-time position information of the space target, wherein the position correction information of the space target is generated by performing background threshold calculation, target detection and/or star map matching on the astronomical image.)

1. An astronomical positioning and automatic tracking method for a space target is characterized by comprising the following steps:

acquiring an astronomical image of a space target and preprocessing the astronomical image;

inputting the preprocessed astronomical image into a trained space target astronomical positioning and automatic tracking model based on Satellite Laser Ranging (SLR) to obtain real-time position information of the space target output by the space target astronomical positioning and automatic tracking model, wherein the space target astronomical positioning and tracking model is used for determining the position information of the space target by extracting an image centroid and a preset negative film model, generating position correction information of the space target in real time based on the position information to correct the position information of the space target, and realizing automatic tracking of the space target based on the corrected real-time position information of the space target,

wherein the real-time generation of the position correction information of the spatial target based on the position information comprises: generating position correction information of a spatial target by performing background threshold calculation, target detection and/or star map matching on the astronomical image.

2. The method of claim 1, wherein the space object astronomical positioning and tracking model comprises a position information determination layer and a position information correction layer,

the space coordinate determination layer is used for carrying out PSF fitting based on a Gaussian function to extract a centroid coordinate, and determining space position information of the space target by adopting a preset negative film model; and

the spatial coordinate correction layer is configured to generate position correction information of a spatial target by performing background threshold calculation, target detection, and star map matching, and correct the position information of the spatial target based on the correction information.

3. The method for astronomical positioning of a spatial target and automatic tracking according to claim 1, wherein said preprocessing comprises:

based on the background correction method and the flat field correction method, the astronomical image of the space target is subjected to frequency domain analysis to determine noise characteristics, and the noise characteristics are removed to enhance the astronomical image.

4. The method of claim 2, wherein the PSF fitting based on gaussian function to extract coordinates of center of mass, and using a predetermined negative model, determining spatial position information of the spatial target comprises:

and aiming at image targets with different shapes, taking the length-width ratio as a classification basis, taking the image point track as a constraint condition, and respectively utilizing a Gaussian function to carry out PSF fitting to extract a centroid coordinate.

5. The method of claim 4, wherein the PSF fitting based on Gaussian function extracts centroid coordinates and uses a predetermined negative model, and determining the spatial location information of the spatial target further comprises:

and determining the film model as a six-film model according to the number of the calibration stars detected in the view field based on the requirement of the number of the calibration stars.

6. The method of claim 1, wherein performing a background threshold calculation on the astronomical image comprises:

and aiming at the distinction degree between the foreground and the image background in the astronomical image, analyzing the characteristics of the space target and the image background in the frequency domain or in the space distribution aspect based on the global threshold calculation, removing the noise characteristics in the image background and reserving the space target.

7. The method of claim 1, wherein the target detection of the spatial target comprises:

and aiming at different image targets, converting parameters and thresholds by using an inter-frame difference method by using an aspect ratio and a multi-frame image association method according to the motion characteristics and the shape characteristics of the space target so as to detect the targets.

8. The method of claim 1, wherein the star map matching of the spatial target comprises:

and (3) considering angular distance information among a plurality of space targets in the CCD shot image, and performing star map matching by adopting a trigonometry method according to the requirement of the angular distance information matching algorithm on the number of the targets.

9. An astronomical positioning and automatic tracking system of a space target is characterized in that,

the space target astronomical image preprocessing module is used for acquiring an astronomical image of a space target and preprocessing the astronomical image;

a space target astronomical positioning and automatic tracking module for inputting the preprocessed astronomical image into a trained space target astronomical positioning and automatic tracking model based on Satellite Laser Ranging (SLR) to obtain real-time position information of the space target output by the space target astronomical positioning and automatic tracking model, wherein the space target astronomical positioning and tracking model is used for determining the position information of the space target by extracting an image centroid and a preset negative film model, generating position correction information of the space target in real time based on the position information to correct the position information of the space target, and realizing automatic tracking of the space target based on the corrected real-time position information of the space target,

wherein the real-time generation of the position correction information of the spatial target based on the position information comprises: generating position correction information of a spatial target by performing background threshold calculation, target detection and/or star map matching on the astronomical image.

10. An electronic device comprising a memory, a processor and a computer program stored on the memory and executable on the processor, characterized in that the processor, when executing the program, carries out the steps of the method for astronomical localization and automatic tracking of a spatial target according to any of claims 1-8.

Technical Field

The invention relates to the field of astronomical positioning, in particular to an astronomical positioning and automatic tracking method and system for a space target and electronic equipment.

Background

Space targets include in-orbit spacecraft and space debris, the vast majority of which are space debris. In recent years, human space activities become more frequent, space environment becomes worse, space debris seriously threatens the safety of a spacecraft, and how to accurately identify and track a space target in real time is deeply researched. Laser ranging is used for monitoring space debris and guaranteeing space safety as a means for monitoring the highest precision of the space debris. Compared with an on-orbit spacecraft, the orbit prediction of space debris is poor, and the rapid and accurate identification and tracking cannot be realized. Therefore, the identification and positioning of the space target image become an urgent research subject, and the research result has important application value and practical significance for realizing continuous and stable automatic tracking observation of space debris laser ranging, rapid and precise track determination and prediction of large-scale space debris and space collision early warning.

The Satellite Laser Ranging (SLR) technique utilizes the round-trip flight time of a measurement laser pulse between an observation station and a satellite to calculate the distance from the satellite to the observation station, which is a technical means with the highest precision in the current space target distance measurement. The conventional satellite laser ranging refers to satellite laser ranging of a synthetic target (a space target provided with a corner reflector, such as an Ajisai satellite, a Lageos-1 satellite and the like), and the ranging accuracy of the Lageos satellite can reach a millimeter level at present. The satellite laser ranging technology is a ground space observation technology with highest precision, which realizes the accurate measurement of the orbit, the coordinate of a measuring station and the earth rotation parameters of a space target by the high-precision distance measurement of the space target. In addition, astronomical positioning is a technology for detecting the relative position of a space target and a known star by using a celestial body measuring instrument by taking the star coordinate with a known position in a standard navigation star library as a reference so as to solve the actual position of the space target. Because the method is not influenced by factors such as leveling, north-south pointing errors and the like, the positioning precision can reach 3arcsec for a high-orbit target.

However, with the development and application of spatial technology and the continuous upgrade of observation instrument devices, in the SLR observation process, the manner of acquiring data is more convenient, and the amount of data starts to increase. Based on this, how to acquire the data more effectively, quickly and accurately becomes a difficult problem nowadays. In addition, in the actual tracking and observation process of laser ranging of non-cooperative targets such as space debris, a lot of difficulties exist, and a plurality of factors influence the detection probability of obtaining effective echo photons. The space debris laser ranging mainly adopts two lines of roots as initial orbit prediction, and the prediction deviation is large, so that the detection success rate is greatly reduced. Moreover, there are many technical difficulties in the process from acquiring astronomical images to realizing high-precision positioning of space targets. For the commonly used large-view-field angle measurement equipment, the view field distortion is serious, and according to the common method, a high-order negative film parameter model is required during the reduction. However, for the integrated observation, the star image is lengthened, and the positioning accuracy of the star image center is poor; and the effective exposure time of the stars is short (the stay time of the stars on one pixel is usually shorter than 0.1s), the number of the stars in the field of view is limited, and the non-uniform distribution of the calibration stars around the target is easily caused, which is not beneficial to the calculation of the parameters of the high-order negative film model. At present, most observation means of global 50 SLR stations are low in automation degree, targets are searched manually through a CCD monitoring system basically, the tracking observation effect is good, but the tracking efficiency is low and unstable, and manual observation experience is excessively relied on.

Disclosure of Invention

The invention provides an astronomical positioning and automatic tracking method, a system and electronic equipment for a space target, which overcome the problems that the target tracking in the prior art depends on human-computer interaction and has lower automation degree, realize high-precision astronomical positioning of the space target by adopting a mathematical model, improve the automation degree of SLR observation, greatly improve the success rate of distance measurement, ensure continuous and stable tracking observation of the space target and lay a foundation for space target automatic observation and daytime distance measurement.

Specifically, the embodiment of the invention provides the following technical scheme:

in a first aspect, an embodiment of the present invention provides an astronomical positioning and automatic tracking method for a spatial target, including:

acquiring an astronomical image of a space target and preprocessing the astronomical image;

inputting the preprocessed astronomical image into a trained space target astronomical positioning and automatic tracking model based on Satellite Laser Ranging (SLR) to obtain real-time position information of the space target output by the space target astronomical positioning and automatic tracking model, wherein the space target astronomical positioning and tracking model is used for determining the position information of the space target by extracting an image centroid and a preset negative film model, generating position correction information of the space target in real time based on the position information to correct the position information of the space target, and realizing automatic tracking of the space target based on the corrected real-time position information of the space target,

wherein the real-time generation of the position correction information of the spatial target based on the position information comprises: generating position correction information of a spatial target by performing background threshold calculation, target detection and/or star map matching on the astronomical image.

Further, the astronomical positioning and automatic tracking method of the space target further comprises the following steps:

the space target astronomical positioning and tracking model comprises a position information determining layer and a position information correcting layer,

the space coordinate determination layer is used for carrying out PSF fitting based on a Gaussian function to extract a centroid coordinate, and determining space position information of the space target by adopting a preset negative film model; and

the spatial coordinate correction layer is configured to generate position correction information of a spatial target by performing background threshold calculation, target detection, and star map matching, and correct the position information of the spatial target based on the correction information.

Further, the astronomical positioning and automatic tracking method of the space target further comprises the following steps:

the pretreatment comprises the following steps:

based on the background correction method and the flat field correction method, the astronomical image of the space target is subjected to frequency domain analysis to determine noise characteristics, and the noise characteristics are removed to enhance the astronomical image.

Further, the astronomical positioning and automatic tracking method of the space target further comprises the following steps:

the PSF fitting based on the Gaussian function is used for extracting the coordinates of the center of mass, and the preset negative film model is adopted, and the determination of the spatial position information of the spatial target comprises the following steps:

and aiming at image targets with different shapes, taking the length-width ratio as a classification basis, taking the image point track as a constraint condition, and respectively utilizing a Gaussian function to carry out PSF fitting to extract a centroid coordinate.

Further, the astronomical positioning and automatic tracking method of the space target further comprises the following steps:

the performing PSF fitting based on a gaussian function to extract centroid coordinates and determining spatial location information of the spatial target using a predetermined negative model further comprises:

and determining the film model as a six-film model according to the number of the calibration stars detected in the view field based on the requirement of the number of the calibration stars.

Further, the astronomical positioning and automatic tracking method of the space target further comprises the following steps:

performing a background threshold calculation on the astronomical image comprises:

and aiming at the distinction degree between the foreground and the image background in the astronomical image, analyzing the characteristics of the space target and the image background in the frequency domain or in the space distribution aspect based on the global threshold calculation, removing the noise characteristics in the image background and reserving the space target.

Further, the astronomical positioning and automatic tracking method of the space target further comprises the following steps:

and aiming at different image targets, converting parameters and thresholds by using an inter-frame difference method by using an aspect ratio and a multi-frame image association method according to the motion characteristics and the shape characteristics of the space target so as to detect the targets.

Further, the astronomical positioning and automatic tracking method of the space target further comprises the following steps:

the star map matching of the space target comprises:

and (3) considering angular distance information among a plurality of space targets in the CCD shot image, and performing star map matching by adopting a trigonometry method according to the requirement of the angular distance information matching algorithm on the number of the targets.

In a second aspect, an embodiment of the present invention further provides an astronomical positioning and automatic tracking system for a spatial target, including:

the space target astronomical image preprocessing module is used for acquiring an astronomical image of a space target and preprocessing the astronomical image;

a space target astronomical positioning and automatic tracking module for inputting the preprocessed astronomical image into a trained space target astronomical positioning and automatic tracking model based on Satellite Laser Ranging (SLR) to obtain real-time position information of the space target output by the space target astronomical positioning and automatic tracking model, wherein the space target astronomical positioning and tracking model is used for determining the position information of the space target by extracting an image centroid and a preset negative film model, generating position correction information of the space target in real time based on the position information to correct the position information of the space target, and realizing automatic tracking of the space target based on the corrected real-time position information of the space target,

wherein the real-time generation of the position correction information of the spatial target based on the position information comprises: generating position correction information of a spatial target by performing background threshold calculation, target detection and/or star map matching on the astronomical image.

In a third aspect, an embodiment of the present invention further provides an electronic device, including a memory, a processor, and a computer program stored on the memory and executable on the processor, wherein the processor executes the program to implement the steps of the method for astronomical positioning and automatic tracking of a spatial object as described above.

According to the technical scheme, the astronomical positioning and automatic tracking method, the astronomical positioning and automatic tracking system and the electronic equipment for the space target provided by the embodiment of the invention realize real-time correction of the orientation of the SLR telescope facing space fragments by using a BP neural network, and deep analysis of system delay and stability of SLR observation data of Beijing Mount House by using a time sequence analysis model.

Drawings

In order to more clearly illustrate the technical solutions of the present invention or the prior art, the drawings needed for the description of the embodiments or the prior art will be briefly described below, and it is obvious that the drawings in the following description are some embodiments of the present invention, and those skilled in the art can also obtain other drawings according to the drawings without creative efforts.

Fig. 1 is a flowchart of an astronomical positioning and automatic tracking method for a spatial target according to an embodiment of the present invention;

fig. 2 is a schematic structural diagram of an astronomical positioning and automatic tracking system for a spatial target according to an embodiment of the present invention; and

fig. 3 is a schematic diagram of an electronic device according to an embodiment of the invention.

Detailed Description

In order to make the objects, technical solutions and advantages of the present invention clearer, the technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings, and it is obvious that the described embodiments are some, but not all embodiments of the present invention. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

The various terms or phrases used herein have the ordinary meaning as is known to those skilled in the art, and even then, it is intended that the present invention not be limited to the specific terms or phrases set forth herein. To the extent that the terms and phrases referred to herein have a meaning inconsistent with the known meaning, the meaning ascribed to the present invention controls; and have the meaning commonly understood by a person of ordinary skill in the art if not defined herein.

The high-precision real-time astronomical positioning technology provides the equatorial coordinate of a space target, ensures the stable and continuous tracking of the space target, and the development of the technology promotes the automation degree of the SLR observation station to a great extent, so that the SLR observation station is valued at home and abroad and is applied more and more widely. In order to acquire high-precision observation data and realize automatic acquisition of the observation data, an algorithm and software suitable for an observation process and data processing are required in addition to selection of a proper observation device. In the past half century or more, the SLR observation and data acquisition system has realized a continuous leap from visual observation to photographic observation to the comprehensive application of CCD and other technologies, and the number and precision of the observed data have been significantly improved, with the consequent higher requirements on the system observation, data processing algorithms and software levels. In the conventional SLR observation in the prior art, due to the fact that the conventional SLR observation has the position information of the space target, the space target tracking observation can be changed from visual handheld operation to computer operation, and the tracking accuracy is obviously improved. However, not all spatial target position information accuracy meets the tracking requirement. In addition, due to the limitations of weather conditions, CCD hardware, telescope tracking pointing, spatial target orbit prediction accuracy, spatial target motion, etc., the spatial target position needs to be corrected in real time during SLR tracking observation.

In view of the above, in a first aspect, an embodiment of the present invention provides an astronomical positioning and automatic tracking method for a spatial target.

The astronomical positioning and automatic tracking method of the space target of the present invention is described below with reference to fig. 1.

Fig. 1 is a flowchart of an astronomical positioning and automatic tracking method for a spatial target according to an embodiment of the present invention.

In this embodiment, it should be noted that the astronomical positioning and automatic tracking method for a spatial target may include the following steps:

s1: acquiring an astronomical image of a space target and preprocessing the astronomical image; and

s2: inputting the preprocessed astronomical image into a trained space target astronomical positioning and automatic tracking model based on Satellite Laser Ranging (SLR) to obtain real-time position information of a space target output by the space target astronomical positioning and automatic tracking model, wherein the space target astronomical positioning and tracking model is used for determining the position information of the space target by extracting an image centroid and a preset negative film model, generating position correction information of the space target in real time based on the position information to correct the position information of the space target, and realizing automatic tracking of the space target based on the corrected real-time position information of the space target,

the real-time generation of the position correction information of the space target based on the position information comprises the following steps: position correction information of the space target is generated by performing background threshold calculation, target detection and/or star map matching on the astronomical images.

In this embodiment, it should be noted that the astronomical positioning and automatic tracking method for a spatial target may further include: the space target astronomical positioning tracking model comprises a position information determining layer and a position information correcting layer, wherein the space coordinate determining layer is used for carrying out PSF fitting based on a Gaussian function to extract a centroid coordinate, and a preset negative film model is adopted to determine the space position information of the space target; and the space coordinate correction layer is used for generating position correction information of the space target by performing background threshold calculation, target detection and star map matching, and correcting the position information of the space target based on the correction information.

In this embodiment, it should be noted that the astronomical positioning and automatic tracking method for a spatial target may further include: the pretreatment comprises the following steps: based on the background correction method and the flat field correction method, the astronomical image of the space target is subjected to frequency domain analysis to determine noise characteristics, and the noise characteristics are removed to enhance the astronomical image.

Specifically, the background correction method and the flat field correction method are utilized to perform frequency domain analysis on the astronomical image of the space target, determine the noise characteristics, and remove the noise to enhance the star so as to ensure the image preprocessing effect.

Aiming at the background correction method: due to the presence of CCD readout noise, the brightness value of the image actually obtained fluctuates somewhat compared to the ideal state. Therefore, in order to avoid negative values in some particularly dark places, it is necessary to add a value (which is called a Bias value ("Bias value") obtained by adding a voltage to the CCD/CMOS in advance) to the image in advance, so that the resulting image is positive even if the readout noise is negative. By means of Bias calibration, i.e. subtracting the Bias value from the original image, the image and the original celestial brightness can be linearly related. This would otherwise negatively affect subsequent dark current calibration, flat field calibration, and professional astronomical photometry. The image is typically acquired with the shutter closed, zero second exposure. However, some cameras do not support zero-second exposure, the shortest exposure time (less than 0.01 second) is selected, and shooting is carried out under the condition without any light. It should be noted that since CCD/CMOS is not uniform by itself, each pixel element has a different sensitivity to the same bias voltage. That is, even if there is no readout noise, the offset frame is not a white board, and it has a certain fluctuation itself, and an image formed by the fluctuation information is referred to as a "Bias image". Meanwhile, the 'Bias image' has small fluctuation and is easily interfered by read noise, and a plurality of offset frames (at least 50 frames) need to be shot for superposition to obtain a relatively accurate 'Bias image'. Finally, the image is calibrated using the overlay result, i.e. the sum bias (MasterBias).

Aiming at a flat field correction method: the flat field belongs to one of false signals, and is generated because the sensitivity of each pixel of the CCD/CMOS to light is different. Specifically, the method comprises the following steps:

ADU_i＝K_iL (1)

wherein, ADU_iIs the gray value corresponding to the pixel i, K_iThe sensitivity of the pixel to light, and L is the light condition.

For K of each picture element_iUniformly shooting a uniform light source to obtain a flat field frame, and offsettingAnd (bias) and dark current are calibrated and then superposed to obtain a sum flat field, and the influence caused by the pixel sensitivity difference is eliminated by dividing the bright field subjected to bias and dark current calibration by the sum flat field. In the astronomical observation of the present application, a uniform light source plane is selected and photographed as a flat field, for example, a background of daylight at dusk or dawn or white cloth uniformly irradiated by an incandescent lamp.

Of course, none of the flat fields described above adds the influence of an optical system, only the flat field effect at high frequencies. For example, optical defects of the telescope, inaccurate installation of the filter, uneven focal plane, dust on the CCD/CMOS and the like all bring about flat field effect of medium and low frequency, which is embodied as dark angle, gradual change of the background as a whole, "onion ring" and the like. Specifically, the black circles in the normal image are derived from dust in the optical system, the low frequency gradation is the difference in light sensitivity due to the defect of the optical system, and the high frequency fluctuation is derived from the difference in light sensitivity between the pixels. However, these can all be subtracted by flat field calibration.

In this embodiment, it should be noted that the astronomical positioning and automatic tracking method for a spatial target may further include: performing PSF fitting based on a Gaussian function to extract a centroid coordinate, and determining spatial position information of a spatial target by adopting a preset negative film model comprises the following steps: and aiming at image targets with different shapes, taking the length-width ratio as a classification basis, taking the image point track as a constraint condition, and respectively utilizing a Gaussian function to carry out PSF fitting to extract a centroid coordinate.

Specifically, for space targets with different image shapes, the image point tracks are taken as constraint conditions according to the aspect ratio as a classification basis, and the Gaussian functions are respectively used for carrying out PSF fitting to extract the centroid coordinates so as to establish a high-precision centroid extraction model.

More specifically, astronomical localization is a technique for determining the orientation of an object by background stars in an image. In the positioning process, the star azimuth, the coordinates of the star and the target in the image are needed, and the aim of determining the target azimuth is finally achieved. The centroid extraction method is the key for acquiring coordinates of stars and targets in an image.

Further, the size, shape and brightness of the target are related to the orbit height of the target, the moving speed relative to the telescope and the image exposure time. Specifically, the low-orbit target has a large shape in the image, is quite bright and is greatly different from the background; background fixed stars can have trailing phenomenon and are in a strip shape; the high-orbit target has a small shape in the image, is darker in brightness and is not easy to distinguish from the background; background stars will also appear smeared and have a long strip shape, but compared with background stars tracking low-orbit targets, the smearing phenomenon is slight, and the length of the smearing phenomenon is also short. Due to the above characteristics, the present invention uses the aspect ratio as a classification basis for discriminating the image object.

Specifically, the area of the marked region, i.e., the number of pixels in the region, is first calculated. If the area is small, these areas may be noisy or very dark stars. The number of pixels in each marked region is then counted and if it is less than 5 the region is not considered as a star region. In addition, it is also necessary to determine whether the aspect ratio of the mark region is greater than 2, and if so, the mark region is considered as a background star.

For the gaussian function: in the measurement of the central position of the star image, the shape and the structural information of the star image are covered by background noise, the structural characteristics are smoothed, and the luminosity distribution is closer to Gaussian distribution, so the invention extracts coordinates by a Gaussian fitting method. Specifically, the gaussian fitting method formula (2) is as follows:

wherein x is₀And y₀Is the real position center coordinate of the target, B is the sky light background, R_xAnd R_yThe mean square deviations of the pixel element i and the target center in the x-axis and y-axis directions are related to the object distance, the focal length, the defocus amount and the aperture size, respectively.

The invention considers that in the CCD imaging process, x and y are two independent random variables, wherein p is 0, and p is the occurrence probability of a random event, namely, there is no possibility that the random event causes the connection between the two independent random variables, so that the formula (2) can be simplified as the following formula (3):

whereinThis equation contains 6 parameters (B, H, x) to be solved₀,y₀,R_x,R_y) Where Σ I is the total gray value of the star point projected on the CCD plane, which is related to the light target brightness, exposure time. H is a fixed coefficient, i.e. the peak of the gaussian surface, which can be approximated to the gray value at the center of the target. The six-parameter gaussian fitting method is to solve 6 parameters completely by using a newton nonlinear equation system solution. Taylor expansion of this formula can be found as follows:

wherein, I '(x, y) is a calculated value of the CCD on the pixel (x, y), I (x, y) is an actual gray value on the pixel (x, y), Δ I (x, y) is I' (x, y) -I (x, y); q. q.s_i＝(B,H,x₀,y₀,R_x,R_y),i＝1，2,3，...,6，q_iAt least 6 picture elements are required to solve the equation for the parameters of picture element i, and wherein each q is_iThe differential forms in (1) all follow equation (6). Specifically, the method comprises the following steps:

further, substituting equation (6) into equation (4) performs least squares iterative solution, i.e., let f ═ I' (x, y) -I (x, y)]²The iterative solution is carried out to obtain a solution q of 6 parameters satisfying f-min_inew(B,H,x₀,y₀,R_x,R_y) Wherein, f is min which is the minimum of twoA multiplication criterion. Initial value q_last(B,H,x₀,y₀,R_x,R_y) The method can be obtained by counting the star images:

q_inew＝q_last+Δq_i (7)

wherein, the initial value of the first iteration is obtained by statistics: q. q.s_last＝q_inital(ii) a The initial value of the subsequent iteration is obtained by the last calculation: q. q.s_last＝q_newAnd q is_inew(B,H,x₀,y₀，R_x,R_y) To satisfy f_newNew value for solution in min.

Specifically, | Δ x₀< 0.001 and | Δ y₀If the condition is met, the iteration is ended. The conditions for setting parameter deduction iteration can also be set to be | delta B | < 0.01, | delta H | < 0.01, | delta R_x|≤0.01，|ΔR_yAnd | is less than or equal to 0.01, and only the position center of the star point is set as an iteration exit condition.

The method adopts wiener filtering to restore trailing fixed stars and then uses a Gaussian fitting method to extract the mass center. Wiener filtering is based on considering image and noise as random process, so that the mean square error of the restored image and the original image is minimum. The wiener filtering can automatically inhibit the amplification of noise, and the stronger the noise is, the more obvious the inhibition effect on the noise is. Wiener filtering is not only used for one-dimensional signals, but also used for processing two-dimensional signals, achieves good restoration effect, and has excellent anti-noise performance and smaller calculation amount.

Wherein expression (8) in the frequency domain is as follows:

where H (μ, v) is a degradation function, G (μ, v) is a degraded image,is to restore the image, S_n(mu, v) and S_f(μ, v) are respectively the noise power spectrum and the fadingThe power spectrum of the image is quantized. Wherein, if there is no noise, S_n(μ, ν) ═ 0. However, since the power spectrum of the degraded image is not determined, the signal-to-noise ratio of the image is set to a particular constant K.

In particular, the amount of the solvent to be used,that is to say that the first and second electrodes,

wherein, the K value is generally selected from 0.0001 to 0.1. When the image to be restored does not contain noise, the larger the K value is, the poorer the definition of the restored image is, and the image is dark; the smaller the K value, the better the image restoration definition.

Specifically, the point spread function PSF formula (10) of the two-dimensional uniform linear motion is as follows:

wherein alpha is the angle between the direction of motion and the x-axis, L_xyThe image blur scale is used for measuring the size of the star point tailing in the star map, and h (x, y) is a degradation function in a time domain. By fourier transformation, H (x, y) can be converted to H (μ, ν), which is the representation of the degradation function in the frequency domain, the more accurate the recovery result is, the better.

In this embodiment, it should be noted that the astronomical positioning and automatic tracking method for a spatial target may further include: performing PSF fitting based on a Gaussian function to extract a centroid coordinate, and determining spatial position information of a spatial target by adopting a predetermined negative film model further comprises: and determining the film model as a six-film model according to the number of the calibration stars detected in the view field based on the requirement of the number of the calibration stars.

Specifically, the film model is determined to be a six-film model according to the number of calibration stars detected in the view field by considering the requirements of different models on the number of calibration stars, so that the accuracy and the real-time performance of astronomical positioning are guaranteed.

More specifically, building a negative model is a key step in building a mapping between coordinates (x, y) and astronomical coordinates (ξ, ζ) on an image. Because of error factors such as telescope aberration and CCD installation deviation, the relation between ideal coordinates and actual measurement coordinates cannot be accurately and strictly deduced, and polynomial representation, namely a negative model, is usually used. Negative film models used in the observation of the GEO space debris generally comprise a six-constant model, a twelve-constant model, a four-constant model, a twenty-constant model, a ten-constant model considering radial distortion and tangential distortion and the like.

The invention adopts a six-constant model, the conversion of the six-constant model comprises coordinate origin difference, coordinate axis direction difference and coordinate axis scale difference, and non-linear difference items are not considered. Solving using a six-constant model requires 3 or more calibration stars.

Wherein, for the six-constant model, the mapping equation (11) is as follows:

wherein a, b, c and d are real numbers.

The four-constant model needs more than two calibration stars and is a simplified six-constant model under the assumption that scales of the CCD images in the x direction and the y direction are the same. For the four-constant model, mapping equation (12) is as follows:

compared with a linear six-constant model, the twelve-constant model considers the difference terms of nonlinear terms such as non-perpendicularity of the negative plate to the optical axis, inconsistency of the tangent point coordinates with the actual direction of the optical axis, telescope aberration and the like. At least 6 calibration stars are required using a twelve-constant model. For the twelve-constant model, the mapping equation form (13) is as follows:

wherein, a₁、b₁、c₁、d₁、e₁、f₁、a₂、b₂、c₂、d₂、e₂、f₂Are all real numbers.

Although the number of the film models is increased, the number of the calibration stars is also increased, but the accuracy of the final measurement does not depend on the order of the model, but depends on whether the model is suitable or not.

In this embodiment, it should be noted that the astronomical positioning and automatic tracking method for a spatial target may further include: performing background threshold calculations on the astronomical images comprises: and aiming at the distinction degree between the foreground and the image background in the astronomical image, analyzing the characteristics of the space target and the image background in the frequency domain or in the aspect of space distribution based on the global threshold calculation, removing the noise characteristics in the image background and reserving the space target.

Specifically, aiming at the problem of small degree of distinction between the foreground and the image background in the image, the characteristics of the target and the background in the frequency domain or in the spatial distribution are analyzed, background noise is removed, the target is kept, an evaluation standard is established and secondary detection is carried out according to the evaluation standard, a false target is eliminated, the stability of the algorithm is ensured, and the image segmentation effect is ensured.

More specifically, the CCD image threshold is used to segment the CCD image, distinguishing the background from the target in the image. The global threshold segmentation faces the whole CCD image and is judged by setting a uniform constant as a background. Its advantages are simple calculation and high calculation speed. When the ADU count in the image is greater than or equal to the pixel of the threshold value, the image is determined as a star or a space target; and when the ADU technology is smaller than the pixel of the threshold value, the pixel is considered as the sky light background. Since the noise in the image conforms to a gaussian distribution, the threshold T can be set to (14) as follows:

T＝u+3σ (14)

where u is the image gray scale mean and σ is the image gray scale variance.

The connected domain of the target star image in the real measurement image has a certain pixel number, and the probability of the occurrence of noise is reduced along with the increase of the pixel number occupied by the star image. Therefore, the number of the pixels of the star connected domain is introduced as another judgment, so that the background noise can be effectively removed, and the target detection efficiency is improved.

In this embodiment, it should be noted that the astronomical positioning and automatic tracking method for a spatial target may further include: the target detection of the space target comprises the following steps: aiming at different image targets, according to the motion characteristics and shape characteristics of the space target, an aspect ratio and a multi-frame image correlation method are utilized, and parameters and a threshold value are converted by adopting an inter-frame difference method to detect the targets.

Specifically, aiming at different image targets, according to the motion characteristics and shape characteristics of the image targets, the length-width ratio and the multi-frame image association method are utilized, different strategies are adopted, algorithm parameters and threshold values are converted, and the real-time performance and accuracy of target detection are guaranteed.

Specifically, when the space target identification is performed on the star map, because the short linear distribution of the background stars and the dotted distribution of the space target are performed on the star map, the traditional methods using the image area characteristics, the texture characteristics, the shape characteristics, the color characteristics and the like do not have good adaptability any more when the space target identification is performed. Aiming at the characteristics of space target identification, the invention adopts the motion characteristics of the image to analyze, namely, the interframe image difference algorithm. The three-frame difference global threshold value target identification algorithm is used for marking a space target by a method of carrying out difference frame on continuous three frames of images and finally identifying the space target by a method of global threshold value image segmentation.

More specifically, the three-frame difference global threshold target identification algorithm specifically comprises the following steps: detecting a target image; preprocessing a target image; calculating a global threshold value of each frame of image; calculating a binaryzation mapping table of each frame of image; subtracting the first frame image from the second frame image, and then performing phase comparison with the first frame image; subtracting the second frame image from the third frame image, and performing phase comparison with the second frame image; subtracting the second frame image from the third frame image, and then performing phase comparison with the third frame image; rejecting neighboring pixels and pixels smaller than a given threshold; all the stars on the image after full field scan; judging whether the space target is a space target or not according to a given strategy; and finishing the space target detection.

Furthermore, aiming at a relatively static tracking target, the neighborhood connectivity method has considerable recognition rate and fault tolerance rate, the clustering characteristics of the target point are directly used for analysis, and the target is recognized by utilizing the correlation between the points. Specifically, the algorithm marks points having a distance smaller than a preset threshold as the same cluster; meanwhile, the rule has transitivity, and points which are slightly far away can be connected together through points among the points by tree-type search to form a connected cluster. The most important parameter affecting the method is a threshold value for judging whether two points are adjacent. For example, too large may result in too many associations of unrelated points, while too small may result in splitting of clusters. The evaluation of the parameter values depends on the average uncertainty of the tracking.

In this embodiment, it should be noted that the astronomical positioning and automatic tracking method for a spatial target may further include: the star map matching of the space target comprises the following steps: and (3) considering angular distance information among a plurality of space targets in the CCD shot image, and performing star map matching by adopting a trigonometry method according to the requirement of an angular distance information matching algorithm on the number of the targets.

Specifically, angular distance information among a plurality of targets in a CCD (charge coupled device) shot image is considered, and a matching algorithm is determined according to the requirement of the angular distance information matching algorithm on the number of the targets, so that the real-time performance and the accuracy of identification are guaranteed.

More specifically, a single star cannot provide identification, and two stars are identified by angular separation. Wherein, regarding two stars, let the right ascension and declination of navigation stars i and j be (alpha)_i，δ_i) And (alpha)_j，δ_j) The definition of angular distance in the celestial coordinate system is (15):

whereinAndthe direction vectors of the navigation stars i and j, respectively.

Similarly, the coordinates of the observation star 1 and the observation star 2 in the image plane coordinate system are respectively (X)₁,Y₁) And (X)₂,Y₂) Then the angular distance d in the image coordinate system₁₂Expressed as (16):

whereinAndare the direction vectors of the observation stars 1 and 2 in the image coordinate system.

If the navigation star angular distance and the observation star angular distance can be matched, the following conditions are met (17):

|d(i,j)-d₁₂|≤ε (17)

where ε is the angle uncertainty. And (4) completing the matching of the star diagonal distance by the calculation of the formula.

However, the navigation star pair satisfying the above formula is generally not unique, and the angular distance matching also exists that the two stars in the star pair cannot be separated from each other by only depending on the angular distance value. Based on the above, the invention provides a triangle algorithm, which adds one star on the basis of angular distance matching, and takes the angular distance between three stars as the matching characteristic. Specifically, the matching triangle takes a "side-side" pattern. The triangle algorithm is a process of finding the best matching navigation triangle in the re-navigation star library. The observation triangle and the navigation triangle should satisfy (18):

specifically, the star map matching may include, but is not limited to, the following steps: starting star map matching; judging whether the fixed star in the background to be identified is larger than 2; if the star map matching is more than 2, the star map matching fails, and if the star map matching is less than or equal to 2, the triangle matching is carried out; if the matching is successful, storing the data into a matching table, and checking whether all star point matching is completed or not; if the matching of all the star points is not completed, carrying out triangular matching again, and if the matching of all the star points is completed, checking whether a matching table is empty; if the matching table is not empty, the star map matching fails, and if the matching table is empty, whether the corresponding navigation star can form a triangle is verified; if the navigation star can not form the triangle, the star map matching fails, and if the navigation star can form the triangle, the star map matching succeeds.

More specifically, the system takes the current SLR data acquisition and processing system of Beijing Mount House as a research platform, utilizes CCD (charge coupled device) shooting images collected by the SLR station of Beijing Mount House to construct a high-precision real-time astronomical positioning model, develops a high-precision real-time astronomical positioning and automatic tracking system, is embedded into the current SLR data acquisition and processing platform of the Mount House, and realizes the construction and application of an embedded data acquisition and extraction system.

Aiming at the effect of the astronomical positioning and automatic tracking method of the space target provided by the embodiment of the invention, the following verification is carried out: aiming at the constructed SLR high-precision real-time astronomical positioning model, different space target effect verification schemes are formulated, the results of the experimental result coaxial positioning technology and the manual tracking result are compared, on the basis, the SLR high-precision real-time astronomical positioning and automatic tracking theory, algorithm and software are further analyzed, improved and perfected, and the precision and overall performance indexes of the software are evaluated. In addition, the SLR high-precision real-time astronomical positioning model passing the verification is embedded into the current Beijing Mount House SLR data acquisition and processing platform, meanwhile, the requirement of self-defining correction of space target position information when observers switch observation among low-orbit satellites, high-orbit satellites and space debris is considered, the software platform can input parameters given by users on the basis of realizing a signal identification function, and the system is utilized for actual observation to realize test application and stability evaluation of the software platform.

In conclusion, the invention considers the precision and the real-time performance of astronomical positioning, compares the precision and the time index of various algorithms in the processing flow, and adopts the methods of image processing, target identification, centroid extraction, star map matching, negative film model establishment and the like to realize high-precision real-time astronomical positioning; meanwhile, the real-time requirement of tracking observation is considered, and the position information provided by astronomical positioning is used for correcting tracking observation data, so that a space target high-precision real-time astronomical positioning model is established, and automatic tracking of the space target is realized.

The accuracy and the real-time performance in the astronomical positioning are analyzed, an effective high-accuracy real-time astronomical positioning model is constructed, the performance of a high repetition frequency SLR system is ensured, the detection success rate and the data quality of a space target are effectively improved, and SLR observation data have wide application prospects in the aspects of accurately determining a space target orbit, establishing and maintaining a global earth reference frame, researching the position change of the earth centroid and the earth rotation, determining the earth gravity field long wave component and the time variation thereof and the like.

Based on the same inventive concept, on the other hand, an embodiment of the invention provides an astronomical positioning and automatic tracking system for a space target.

The astronomical positioning and automatic tracking system of a space target provided by the present invention is described below with reference to fig. 2, and the astronomical positioning and automatic tracking system of a space target described below and the astronomical positioning and automatic tracking method of a space target described above can be referred to correspondingly.

Fig. 2 is a schematic structural diagram of an astronomical positioning and automatic tracking system for a spatial target according to an embodiment of the present invention.

In this embodiment, it should be noted that the astronomical positioning and automatic tracking system 1 for a space target includes: the spatial target astronomical image preprocessing module 10 is used for acquiring an astronomical image of a spatial target and preprocessing the astronomical image; a space target astronomical positioning and automatic tracking module 20, configured to input the preprocessed astronomical image into a trained space target astronomical positioning and automatic tracking model based on the satellite laser ranging SLR, to obtain real-time position information of a space target output by the space target astronomical positioning and automatic tracking model, where the space target astronomical positioning and tracking model is configured to determine the position information of the space target by extracting an image centroid and a predetermined negative model, and generate position correction information of the space target in real time based on the position information to correct the position information of the space target, and realize automatic tracking of the space target based on the corrected real-time position information of the space target, where the real-time generation of the position correction information of the space target based on the position information includes: position correction information of the space target is generated by performing background threshold calculation, target detection and/or star map matching on the astronomical images.

The astronomical positioning and automatic tracking system for a space target provided by the embodiment of the invention can be used for executing the astronomical positioning and automatic tracking method for the space target described in the embodiment, and the working principle and the beneficial effect are similar, so detailed description is not provided here, and specific contents can be referred to the introduction of the embodiment.

In this embodiment, it should be noted that each module in the apparatus according to the embodiment of the present invention may be integrated into a whole or may be separately disposed. The modules can be combined into one module, and can also be further split into a plurality of sub-modules.

In another aspect, a further embodiment of the present invention provides an electronic device based on the same inventive concept.

Fig. 3 is a schematic diagram of an electronic device according to an embodiment of the invention.

In this embodiment, it should be noted that the electronic device may include: a processor (processor)310, a communication Interface (communication Interface)320, a memory (memory)330 and a communication bus 340, wherein the processor 310, the communication Interface 320 and the memory 330 communicate with each other via the communication bus 340. The processor 310 may invoke logic instructions in the memory 330 to perform a method of astronomical localization and automatic tracking of a spatial target, the method comprising: acquiring an astronomical image of a space target and preprocessing the astronomical image; inputting the preprocessed astronomical image into a trained space target astronomical positioning and automatic tracking model based on the satellite laser ranging SLR to obtain real-time position information of the space target output by the space target astronomical positioning and automatic tracking model, wherein the space target astronomical positioning and tracking model is used for determining the position information of the space target by extracting an image centroid and a preset negative film model, generating position correction information of the space target in real time based on the position information to correct the position information of the space target, and realizing automatic tracking of the space target based on the corrected real-time position information of the space target, and the real-time generation of the position correction information of the space target based on the position information comprises the following steps: position correction information of the space target is generated by performing background threshold calculation, target detection and/or star map matching on the astronomical images.

The above-described embodiments of the apparatus are merely illustrative, and the units described as separate parts may or may not be physically separate, and parts displayed as units may or may not be physical units, may be located in one place, or may be distributed on a plurality of network units. Some or all of the modules may be selected according to actual needs to achieve the purpose of the solution of the present embodiment. One of ordinary skill in the art can understand and implement it without inventive effort.

Through the above description of the embodiments, those skilled in the art will clearly understand that each embodiment can be implemented by software plus a necessary general hardware platform, and certainly can also be implemented by hardware. With this understanding in mind, the above-described technical solutions may be embodied in the form of a software product, which can be stored in a computer-readable storage medium such as ROM/RAM, magnetic disk, optical disk, etc., and includes instructions for causing a computer device (which may be a personal computer, a server, or a network device, etc.) to execute the methods described in the embodiments or some parts of the embodiments.

Moreover, in the present invention, relational terms such as first and second, and the like may be used solely to distinguish one entity or action from another entity or action without necessarily requiring or implying any actual such relationship or order between such entities or actions. Also, the terms "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus. Without further limitation, an element defined by the phrase "comprising an … …" does not exclude the presence of other identical elements in a process, method, article, or apparatus that comprises the element.

Furthermore, in the present disclosure, reference to the description of the terms "embodiment," "this embodiment," "yet another embodiment," or the like, means that a particular feature, structure, material, or characteristic described in connection with the embodiment or example is included in at least one embodiment or example of the present disclosure. In this specification, the schematic representations of the terms used above are not necessarily intended to refer to the same embodiment or example. Furthermore, the particular features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples. Furthermore, various embodiments or examples and features of different embodiments or examples described in this specification can be combined and combined by one skilled in the art without contradiction.

Finally, it should be noted that: the above examples are only intended to illustrate the technical solution of the present invention, but not to limit it; although the present invention has been described in detail with reference to the foregoing embodiments, it will be understood by those of ordinary skill in the art that: the technical solutions described in the foregoing embodiments may still be modified, or some technical features may be equivalently replaced; and such modifications or substitutions do not depart from the spirit and scope of the corresponding technical solutions of the embodiments of the present invention.