Target initial orbit determination method and device based on spatial filtering velocity measurement

Abstract

The invention discloses a target initial orbit determination method and device based on spatial filtering velocity measurement. The method comprises the following steps: acquiring a star point position image; determining an observation target according to the star point position image, and establishing a mapping relation between a measurement coordinate and an angle position of the observation target; modulating the star point position image to obtain a distribution signal that the target brightness of the observation target changes along with time; acquiring the speed of the observation target according to the distribution signal of the target brightness changing along with time; the method comprises the following steps: obtaining the angular velocity and acceleration of an observation target according to the velocity of the observation target through the mapping relation between the measurement coordinate and the angular position of the observation target, and obtaining the position vector and the initial orbit determination velocity of the observation target relative to the earth center through an initial orbit determination algorithm. Compared with a traditional initial orbit determination method, by directly measuring the angular velocity of the target, coupling of the angular position error and the angular motion amount is reduced, the initial orbit determination precision of the target under the observation error condition is improved, and rapid orbit determination of the target is achieved.

Description

Technical Field

[0001] The present invention relates to the technical field of target initial orbit determination, and in particular to a method and device for target initial orbit determination based on spatial filtering velocity measurement. Background Art

[0002] In recent years, with the continuous development of aerospace technology in various countries, in addition to the normal spacecraft in orbit, there are also many space debris and rocket hulls in the space orbit. Although some of these space debris may gradually fall into the earth due to the resistance of the outer atmosphere, this will take a lot of time, and during this period of time it still poses a great threat to normal spacecraft.

[0003] The current research on situational awareness of space targets is mainly focused on the orbit determination process of space targets. The orbit determination process is mainly divided into preliminary orbit determination and precise orbit determination. Preliminary orbit determination is mainly a method to determine the target orbit under the premise of non-cooperative targets. It is mainly based on the condition of short arc, that is, equivalent to one eighth of the target's orbit length, to achieve the orbit positioning of the target through observation. Precise orbit determination is based on a complete mechanical system, and the initial value obtained by preliminary orbit determination is combined with a large amount of observation data to achieve precise orbit determination of the target.

[0004] The Laplace method and Gaussian method are traditional preliminary orbit determination algorithms. They were originally proposed for asteroid prediction. They complete the initial orbit determination by solving the octal equation to estimate the position of the target at the intermediate moment. However, in the case of short arc segments, the calculation is prone to non-convergence or convergence to a trivial solution.

[0005] The Double-R method and the GOODING method have improved performance on short arc data, and the solution accuracy can be improved by an order of magnitude compared to the Laplace and Gauss methods. However, when using the angle observation data of the short arc segment for initial orbit determination, the orbit geometry strength of the angle measurement data is weak, which leads to the pathological nature of the observation equation, which is manifested in the algorithm's strong sensitivity to angle errors, low orbit determination accuracy, and poor robustness.

[0006] Therefore, effective initial orbit determination of the target requires a longer observation arc, and long-term observation may result in target tracking loss, and the algorithm for solving short-arc optical observation data is more complicated. Summary of the invention

[0007] The purpose of the present invention is to provide a method and device for initial orbit determination based on spatial filtering velocity measurement, which can solve at least one of the above-mentioned technical problems. The specific solution is as follows:

[0008] According to the specific implementation mode disclosed in the present invention, the first aspect of the present invention provides a method for initial orbit determination of a target based on spatial filtering velocity measurement, comprising: acquiring a star point position image;

[0009] Determine an observation target according to the star point position image, and establish a mapping relationship between the measurement coordinates of the observation target in the measurement coordinate system and the angular position in the celestial coordinate system;

[0010] Modulating the star point position image to obtain a distribution signal of the target brightness of the observed target in the measurement coordinate system over time; obtaining the speed of the observed target in the measurement coordinate system according to the distribution signal of the target brightness over time;

[0011] The expression of the speed of the observed target in the measurement coordinate system is:

[0012]

[0013] Wherein, (u, v) are the instantaneous spatial frequencies of the distribution signal of the target brightness varying with time in the x direction and the y direction of the measurement coordinate system respectively;

[0014] (p x ,p y ) are respectively the modulation periods of the filter in the x direction and the y direction of the measurement coordinate system;

[0015] (M x ,M y ) are respectively the magnifications of the projection lens in the x-direction and the y-direction of the measurement coordinate system;

[0016] Obtaining the angular velocity of the observed target in the celestial coordinate system according to the velocity of the observed target in the measurement coordinate system through a mapping relationship between the metric coordinates of the observed target in the measurement coordinate system and the angular position in the celestial coordinate system;

[0017] Calculating the angular acceleration of the observed target in the celestial coordinate system according to the angular velocity of the observed target in the celestial coordinate system;

[0018] According to the angular position, angular velocity and acceleration of the observed target in the celestial coordinate system, the position vector and the initial orbit velocity of the observed target relative to the center of the earth are obtained through the initial orbit determination algorithm.

[0019] Preferably, the obtaining of the star point position image comprises: obtaining the star point position image by gazing at the sky region using an optical astronomical telescope and adopting a gazing method.

[0020] Preferably, determining the observation target according to the star point position image includes:

[0021] Obtaining all star point positions and the number of star points on the kth frame of the star point position image and all star point positions and the number of star points on the k+1th frame, and judging and removing the star points on the star point position image where there are bad points according to the star point positions and the number of star points;

[0022] Subtracting the star point position matrix on the star point position image of the kth frame after removing bad points from the star point position matrix on the star point position image of the k+1th frame to obtain a new matrix;

[0023] When the value of the new matrix is ​​the largest, the star point located at the star point position on the kth frame is the observed target.

[0024] Preferably, the establishing of a mapping relationship between the measurement coordinates of the observation target in the measurement coordinate system and the angular position in the celestial coordinate system comprises:

[0025] Using an astronomical positioning method, a mapping relationship between the measured coordinates of the observed target in the measured coordinate system and the angular position in the celestial coordinate system is established through a film model;

[0026] The mapping relationship between the measured coordinates of the observed target in the measured coordinate system and the angular position in the celestial coordinate system is expressed as follows:

[0027]

[0028] Wherein, (ζ, η) is the position coordinate of the observed target in the ideal plane coordinate system;

[0029] (α0, δ0) is the optical axis pointing position of the device for acquiring the star point position image;

[0030] (a, b, c, d, e, f) are the unknown parameters in the six-constant model.

[0031] Preferably, the step of modulating the star point position image to obtain a distribution signal of target brightness of the observed target in a measurement coordinate system over time; and obtaining a speed of the observed target in the measurement coordinate system according to the distribution signal of target brightness over time includes:

[0032] The measurement target is modulated by a Ronchi grating, and the star point position image is processed by an out-of-phase differential filtering method to obtain a distribution signal of the target brightness of the observation target changing with time in the measurement coordinate system, which is expressed as:

[0033]

[0034] Where f(x,y) is the brightness distribution of the modulated image of the observed target;

[0035] h(x,y) is the transmittance distribution of the Ronchi grating;

[0036] (x0, y0) is the position coordinate of the observation target projected onto the Ronchi grating;

[0037] Using short-time Fourier transform, the distribution signal of the target brightness of the observed target that varies with time is converted into a distribution signal in the frequency domain, and the instantaneous spatial frequency of the distribution signal of the target brightness that varies with time in the x direction and the y direction of the measurement coordinate system is extracted;

[0038] The speed of the observed target in the measurement coordinate system is obtained according to the expression of the speed of the observed target in the measurement coordinate system.

[0039] Preferably, obtaining the angular velocity of the observed target in the celestial coordinate system according to the velocity of the observed target in the measurement coordinate system by a mapping relationship between the measurement coordinates of the observed target in the measurement coordinate system and the angular position in the celestial coordinate system comprises:

[0040] According to the mapping relationship between the measured coordinates of the observed target in the measured coordinate system and the angular position in the celestial coordinate system, the mapping relationship between the velocity of the observed target in the ideal plane coordinate system and the angular velocity in the celestial coordinate system and the mapping relationship between the velocity of the observed target in the ideal plane coordinate system and the velocity in the measured coordinate system are obtained respectively;

[0041] According to the mapping relationship between the velocity of the observation target in the ideal plane coordinate system and the angular velocity in the celestial sphere coordinate system and the mapping relationship between the velocity of the observation target in the ideal plane coordinate system and the velocity in the measurement coordinate system, a mapping relationship between the angular velocity of the observation target in the celestial sphere coordinate system and the velocity in the measurement coordinate system is obtained;

[0042] The mapping relationship between the angular velocity of the observed target in the celestial coordinate system and the velocity in the measurement coordinate system is expressed as:

[0043]

[0044] Wherein, (α, δ) is the angular position of the observed target in the celestial coordinate system;

[0045] The velocity of the observed target in the measurement coordinate system;

[0046] (ζ, η) is the position of the observed target in the ideal coordinate system.

[0047] Preferably, the Ronchi grating is used to modulate the measurement target, and the star point position image is processed by a phase difference filtering method to obtain a distribution signal of the target brightness of the observation target changing with time in a measurement coordinate system, and then the method further includes:

[0048] Amplifying the distribution signal of the target brightness of the observed target changing with time, filtering it with a bandpass filter, and eliminating low-frequency and high-frequency noise;

[0049] The bandpass filter is a 3rd order Butterworth bandpass filter with a passband range of 0.1 to 50 Hz.

[0050] Preferably, the step of calculating the angular acceleration of the observed target in the celestial coordinate system according to the angular velocity of the observed target in the celestial coordinate system comprises:

[0051] The angular velocity calculation of the observed target in the celestial coordinate system is based on the three-step difference method to obtain the angular acceleration of the observed target in the celestial coordinate system at time t.

[0052] Preferably, obtaining the position vector and the initial orbit velocity of the observed target relative to the center of the earth by using an initial orbit determination algorithm according to the angular position, angular velocity and acceleration of the observed target in the celestial coordinate system includes:

[0053] Taking the observation station as the origin of the celestial coordinate system, establishing an observation vector expression of the observation target according to the angular position of the observation target in the celestial coordinate system;

[0054] By measuring the angular position, angular velocity and acceleration of the observation target in the celestial coordinate system at time t, a mapping relationship between the observation vector, the changing velocity vector of the observation vector and the changing acceleration vector of the observation vector is established to obtain the position and velocity of the observation target and realize the initial orbit determination of the observation target.

[0055] According to the specific implementation mode disclosed in the present invention, the second aspect of the present invention discloses a target initial orbit determination device based on spatial filtering velocity measurement, which is used to implement the above method, including:

[0056] Observation module, used to obtain star point position images;

[0057] An imaging module, used to determine an observation target according to the star point position image, and establish a mapping relationship between the measurement coordinates of the observation target in the measurement coordinate system and the angular position in the celestial coordinate system;

[0058] A brightness measurement module modulates the star point position image to obtain a distribution signal of the target brightness of the observed target in the measurement coordinate system over time; and obtains the speed of the observed target in the measurement coordinate system according to the distribution signal of the target brightness over time;

[0059] A signal processing module, configured to obtain the angular velocity of the observed target in the celestial coordinate system according to the velocity of the observed target in the measurement coordinate system through a mapping relationship between the metric coordinates of the observed target in the measurement coordinate system and the angular position in the celestial coordinate system;

[0060] Calculating the angular acceleration of the observed target in the celestial coordinate system according to the angular velocity of the observed target in the celestial coordinate system;

[0061] According to the angular position, angular velocity and acceleration of the observed target in the celestial coordinate system, the position vector and the initial orbit velocity of the observed target relative to the center of the earth are obtained through the initial orbit determination algorithm.

[0062] Compared with the prior art, the above solution disclosed in the present invention has at least the following beneficial effects:

[0063] The present invention can directly measure the angular velocity of the observed target by modulating the star point position image, reduces the coupling between the angular position error and the angular motion, improves the accuracy of angular velocity measurement under certain error conditions, and improves the robustness of the initial orbit determination. BRIEF DESCRIPTION OF THE DRAWINGS

[0064] The drawings herein are incorporated into the specification and constitute a part of the specification, showing embodiments consistent with the disclosure of the present invention, and together with the specification, are used to explain the principles disclosed in the present invention. Obviously, the drawings described below are only some embodiments disclosed in the present invention, and for ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work. In the drawings:

[0065] Figure 1 This is a flow chart of a method for initial orbit determination of a target based on spatial filtering velocity measurement of the present invention;

[0066] Figure 2 This is the principle diagram of speed measurement using the spatial filtering method;

[0067] Figure 3 A block diagram of a preliminary orbit determination process of a target preliminary orbit determination device based on spatial filtering velocity measurement of the present invention;

[0068] Figure 4 The figure is a schematic diagram of the optical path of a target initial orbit determination device based on spatial filtering speed measurement according to the present invention. DETAILED DESCRIPTION

[0069] In order to make the purpose, technical scheme and advantages disclosed in the present invention clearer, the present invention will be further described in detail below in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments disclosed in the present invention, rather than all the embodiments. Based on the embodiments disclosed in the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection disclosed in the present invention.

[0070] The terms used in the embodiments disclosed in the present invention are only for the purpose of describing specific embodiments, and are not intended to limit the disclosure of the present invention. The singular forms "a", "said" and "the" used in the embodiments disclosed in the present invention and the appended claims are also intended to include plural forms, unless the context clearly indicates other meanings, and "multiple" generally includes at least two.

[0071] It should be understood that the term "and / or" used in this article is only a description of the association relationship of associated objects, indicating that there can be three relationships. For example, A and / or B can represent: A exists alone, A and B exist at the same time, and B exists alone. In addition, the character " / " in this article generally indicates that the associated objects before and after are in an "or" relationship.

[0072] It should also be noted that the term "includes", "comprising" or any other variation thereof is intended to cover non-exclusive inclusion, so that a commodity or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such commodity or device. In the absence of more restrictions, the elements defined by the sentence "comprising a ..." do not exclude the existence of other identical elements in the commodity or device including the elements.

[0073] The following is combined with Figure 1-Figure 4 Detailed description of the alternative embodiments of the present disclosure.

[0074] Example 1

[0075] The first embodiment of the present invention provides a method for initial orbit determination of a target based on spatial filtering velocity measurement, such as Figure 1 and Figure 3 As shown, the following steps are included:

[0076] Step S102: Obtain a star point position image.

[0077] In a preferred embodiment of the present invention, an optical astronomical telescope is used to stare at the sky through a staring observation method to achieve observation of a space observation target and obtain a star point position image. In this embodiment, by using staring observation to enable the observation target to move relatively on the target surface of the CCD camera, filtering and modulating the observation target through a grating in the subsequent steps can be achieved.

[0078] Specifically, the optical astronomical telescope has a field of view of (8°, 8°), an aperture of 10 cm, and an F number of 3.

[0079] Step S104, determining an observation target according to the star point position image, and establishing a mapping relationship between the measurement coordinates of the observation target in the measurement coordinate system and the angular position in the celestial coordinate system, including:

[0080] Step S104-1: Determine the observation target based on the star point position image to achieve positioning and tracking of the observation target

[0081] Specifically, since the observed target is moving relative to the background star map, it is equivalent to obtaining the position of the moving observed target against the background of the stationary target.

[0082] In this embodiment, the connected domain analysis method is used to obtain all the star point positions (x, y) on the kth frame of the star point position image, and the inter-frame difference method is used to obtain all the star point positions (x', y') on the k+1th frame. Due to the limitation of the CCD camera, bad pixels may appear in the image during the observation process, resulting in different numbers of star points on the kth frame and the k+1th frame, so the bad pixels need to be removed.

[0083] Specifically, by applying the connected domain analysis method to the k-th frame image, it is determined that the number of star points on the k-th frame image is m; by applying the connected domain analysis method to the k+1-th frame image, it is determined that the number of star points on the k-th frame image is n.

[0084] When n>m, there is a bad pixel on the k+1th frame:

[0085] The position of any star point on the k+1th frame is (x i ′,y i ′), i∈(1, n), by traversing and subtracting all the star points of the kth frame from the star point, and then calculating the modulus length p of each difference, the expression is as follows:

[0086] p = norm((x′ i ,y′ i )-(x j ,y j ), i∈(1,n), j∈(1,m)

[0087] When p>tol, the star point is considered to be a bad point, tol is a set threshold, preferably tol=5.

[0088] When m>n, the kth frame has a bad pixel;

[0089] For any star point position on the kth frame, all the star points on the k+1th frame are traversed and subtracted from the star point, and then the modulus length p of each difference is calculated. The expression is as follows:

[0090] p = norm((x i ,y i )-(x′ j , y′ j ), i∈(1, m)), j∈(1, n)

[0091] When p>tol, the star point is considered to be a bad point, tol is a set threshold, preferably tol=5.

[0092] After removing bad pixels, calculate the moving target on the kth frame, subtract the star point position matrix of the adjacent kth frame and the k+1th frame image to get a new matrix l. The l of the new matrix l is i The elements can be expressed as:

[0093] l i =norm((x i ,y i )-(x i ′,y i ′)), i∈(1,min(n,m))

[0094] When l i When the maximum value is reached, (x i ,y i ) is the observed moving target, thereby realizing the recognition and tracking of the moving target.

[0095] Step S104-2: establishing a mapping relationship between the measurement coordinates of the observation target in the measurement coordinate system and the angular position in the celestial coordinate system, so as to obtain the angular position of the observation target in the celestial coordinate system.

[0096] In this embodiment, the astronomical positioning of the observation target is performed by using the method of determining the angular position of the observation target by using the relative position of the space observation target and the stars, and the celestial coordinate system is the J2000 coordinate system.

[0097] Specifically, the mapping relationship between the measured coordinates (x, y) of the observed target on the CCD camera film and the angular position (α, δ) in the celestial coordinate system is established through the film model. The expression is as follows:

[0098]

[0099] Among them, (ζ, η) is the position coordinate of the observed target in the ideal plane coordinate system;

[0100] (α0, δ0) is the optical axis pointing position of the device for acquiring the star point position image, and the ideal plane is tangent to the optical axis of the observation device;

[0101] (a, b, c, d, e, f) are the unknown parameters in the six-constant model.

[0102] Furthermore, in order to obtain the unknown parameters in expression (3), in a preferred embodiment of the present invention, at least three reference stars located in the star point position image are obtained in combination with the Hipparcos star catalog to perform star map matching calculation.

[0103] Step S106, modulating the star point position image to obtain a distribution signal of the target brightness of the observed target in the measurement coordinate system that varies with time; and obtaining a speed of the observed target in the measurement coordinate system according to the distribution signal of the target brightness that varies with time.

[0104] In this step, the angular velocity of the observed target in the celestial coordinate system is measured by a spatial filtering method using a brightness measurement device, thereby avoiding the method of calculating the angular velocity by taking the first-order derivative of the angular position of the observed target, and reducing the influence of the time baseline on the angular velocity measurement error, and comprising the following steps:

[0105] Step S106-1: modulate the measurement target using a Ronchi grating, such as Figure 2 shown.

[0106] When the observed target moves at a speed v, the light emitted or scattered by the moving object itself is imaged onto the spatial filter (Ronchi grating) through the lens L. The photoelectric sensor will receive a sine wave-like signal, and the target brightness value of the observed target after grating filtering at time t can be obtained. The expression is:

[0107] I(t)=∑∑I(x,y,t)

[0108] Wherein, I(x,y,t) is the brightness value of the observed target at the measurement coordinate (x,y);

[0109] By integrating the target brightness value at time t in the time domain, we can obtain the distribution signal I(t) of the target brightness changing with time in the measurement coordinate system, which is expressed as:

[0110]

[0111] Where f(x,y) is the brightness distribution of the modulated image of the observed target;

[0112] h(x,y) is the transmittance distribution of the Ronchi grating;

[0113] (x0, y0) is the position coordinate of the observed target projected onto the Ronchi grating.

[0114] In a preferred embodiment of the present invention, after the Ronchi grating is used to modulate the measurement target, the star point position image is processed by the out-of-phase differential filtering method to obtain a distribution signal of the target brightness of the observed target changing with time in the measurement coordinate system, and then the method further includes:

[0115] The distribution signal of the target brightness changing with time of the observed target is amplified and filtered using a bandpass filter to eliminate low-frequency and high-frequency noise;

[0116] The bandpass filter is a 3rd order Butterworth bandpass filter with a passband range of 0.1 to 50 Hz.

[0117] Step S106-2: Use short-time Fourier transform to transform the distribution signal I(t) of the target brightness of the observed target over time into a distribution signal G(u, v) in the frequency domain, expressed as:

[0118] G(u,μ)=F(u,v)H(u,v)

[0119] Where, F(u, v) is the Fourier transform of f(x, y); H(u, v) is the Fourier transform of h(x, y);

[0120] (u, v) are the instantaneous spatial frequencies of the distribution signal of the target brightness changing with time in the x direction and the y direction of the measurement coordinate system respectively.

[0121] Step S106-3, extract (u, v), and obtain the speed of the observed target in the measurement coordinate system through expression (1):

[0122]

[0123] Among them, (p x , p y ) are respectively the modulation periods of the Ronchi grating in the x-direction and the y-direction of the measurement coordinate system;

[0124] (M x , M y ) are the magnifications of the zoom projection lens in the x-direction and y-direction of the measurement coordinate system, respectively.

[0125] Step S108, by mapping the metric coordinates of the observed target in the measurement coordinate system and the angular position in the celestial coordinate system, and according to the velocity of the observed target in the measurement coordinate system, the angular velocity of the observed target in the celestial coordinate system is obtained. The following steps are included:

[0126] Step S108-1, derive the position (ζ, η) of the measurement target in the ideal plane coordinate system at time t to obtain the velocity of the measurement target in the ideal plane coordinate system The partial derivative of the angular position (α, δ) of the measurement target in the celestial coordinate system at time t is obtained to obtain the angular velocity of the measurement target in the celestial coordinate system. Derivative the measurement coordinates (x, y) of the measurement target in the measurement coordinate system to obtain the velocity of the measurement target in the measurement coordinate system

[0127] Step S108-2: Based on the mapping relationship between the measured coordinates of the observed target in the measured coordinate system and the angular position in the celestial coordinate system, i.e., Expression (2) and Expression (3), the velocity of the measured target in the ideal plane coordinate system can be obtained. and the angular velocity in the J2000 celestial coordinate system The mapping relationship is:

[0128]

[0129] And measure the speed of the target in the ideal plane coordinate system and the velocity in the measurement coordinate system The mapping relationship is:

[0130]

[0131] According to equations (5) and (6), the mapping relationship between the angular velocity of the observed target in the celestial coordinate system and the velocity in the measurement coordinate system can be obtained as follows:

[0132]

[0133] Among them, the unknown parameter matrix Acquired through step S104-2.

[0134] Step S110, calculating the angular acceleration of the observed target in the celestial coordinate system according to the angular velocity of the observed target in the celestial coordinate system.

[0135] In a preferred embodiment of the present invention, according to the angular velocity calculation of the observed target in the celestial coordinate system, the angular acceleration of the observed target in the celestial coordinate system at time t is obtained by a three-step difference method. Right now

[0136] Step S112, according to the angular position, angular velocity and acceleration of the observed target in the celestial coordinate system, the position vector and the initial orbit velocity of the observed target relative to the center of the earth are obtained by using the initial orbit determination algorithm, including:

[0137] Establish the J2000 celestial coordinate system with the observation station as the origin.

[0138] Taking the observation station as the origin of coordinates, the position vector of the observation target relative to the center of the earth is r, and the vector of the observation station relative to the center of the earth is R observer , ρ is the target slant distance from the observation station to the target, u is the observation vector of the observed target,

[0139] The expression of u is:

[0140]

[0141] Observe the position vector r and velocity of the target relative to the center of the earth for:

[0142]

[0143] Among them, R observer is the velocity vector of the observation station relative to the center of the earth;

[0144] Represents the changing velocity vector of the observation vector u.

[0145] So the target slope range ρ and slope range change rate It is expressed as:

[0146]

[0147] in, R x and R y For R observer The x and y components of

[0148] es = 0.0000729212rad / s is the first derivative of Greenwich sidereal time;

[0149] and About the angle (α, δ) and angular velocity of the measurement target in the J2000 celestial coordinate system and angular acceleration There is an expression relationship:

[0150]

[0151] The target slope range ρ and slope range change rate are solved by expression (9): Combined with formula (8), determine the position r and speed of the target Then the initial orbit of the target is determined.

[0152] Example 2

[0153] The present invention also provides an apparatus embodiment that is consistent with the above embodiment, which is used to implement the method steps described in the above embodiment. The explanation based on the same name meaning is the same as the above embodiment, and has the same technical effect as the above embodiment, which will not be repeated here.

[0154] like Figure 4 As shown, the present invention discloses a target initial orbit determination device based on spatial filtering velocity measurement, comprising:

[0155] An observation module 10 is used to obtain a star point position image;

[0156] An imaging module 20, configured to determine an observation target according to the star point position image, and establish a mapping relationship between the measurement coordinates of the observation target in the measurement coordinate system and the angular position in the celestial coordinate system;

[0157] The brightness measurement module 30 modulates the star point position image to obtain a distribution signal of the target brightness of the observed target in the measurement coordinate system over time; and obtains the speed of the observed target in the measurement coordinate system according to the distribution signal of the target brightness over time;

[0158] The signal processing module 40 is used to obtain the angular velocity of the observed target in the celestial coordinate system according to the velocity of the observed target in the measurement coordinate system through the mapping relationship between the metric coordinates of the observed target in the measurement coordinate system and the angular position in the celestial coordinate system;

[0159] Calculating the angular acceleration of the observed target in the celestial coordinate system according to the angular velocity of the observed target in the celestial coordinate system;

[0160] According to the angular position, angular velocity and acceleration of the observed target in the celestial coordinate system, the position vector and the initial orbit velocity of the observed target relative to the center of the earth are obtained through the initial orbit determination algorithm.

[0161] Furthermore, in order to reduce the mutual influence caused by the imaging module and the brightness measurement module not sharing the same entrance pupil, the target image is acquired through the astronomical telescope 11, and the imaging of the observed target is split by the spectroscope 23. One part is used by the brightness measurement module 30 to measure the brightness change of the observed target after passing through the filter, and the other part is used by the imaging module 20 to realize astronomical measurement of the observed target.

[0162] Furthermore, the observed target after the zoom projection lens 300 is modulated by the filter 301. The filter 301 is a Ronchi grating of 10lp / mm. The grating period is large, much larger than the diffraction wavelength, so the diffraction effect can be ignored. Then it is projected onto the photoelectric sensor 303 through the projection lens 302, and the image is processed by the out-of-phase differential filtering method to obtain the change of the target brightness. The photoelectric sensor adopts SPAD array technology. The time resolution of this type of detector can reach 100ps. In order to ensure the continuity of the brightness signal, the detector acquisition frequency should be greater than 50Hz.

[0163] Furthermore, in the imaging module 20, after the observation target is imaged through the beam splitter 23, the target is imaged onto the CCD imaging sensor 21 through the projection lens group 22 composed of two projection lenses. The imaging module 20 realizes the imaging of the observation target through continuous exposure and obtains the angular position of the target using the astronomical positioning method. The imaging module 20 requires that the acquisition frequency should be greater than 10 Hz, and there is no specific requirement for the spatial resolution and temporal resolution of the imaging.

[0164] The signal processing module 40 in this embodiment is responsible for processing the brightness signal at the front end and determining the initial track at the back end.

[0165] The flow chart and block diagram in the accompanying drawings illustrate the possible architecture, function and operation of the system, method and computer program product according to the various embodiments disclosed in the present invention. In this regard, each square box in the flow chart or block diagram can represent a module, a program segment or a part of a code, and the module, the program segment or a part of the code contains one or more executable instructions for realizing the specified logical function. It should also be noted that in some implementations as replacements, the functions marked in the square box can also occur in a sequence different from that marked in the accompanying drawings. For example, two square boxes represented in succession can actually be executed substantially in parallel, and they can sometimes be executed in the opposite order, depending on the functions involved. It should also be noted that each square box in the block diagram and / or flow chart, and the combination of the square boxes in the block diagram and / or flow chart can be implemented with a dedicated hardware-based system that performs the specified function or operation, or can be implemented with a combination of dedicated hardware and computer instructions.

[0166] The units involved in the embodiments disclosed in the present invention may be implemented by software or hardware, wherein the name of a unit does not limit the unit itself in some cases.

Claims

1. A method for initial orbit determination of a target based on spatial filtering velocity measurement, characterized in that: include: Get star point position image; Determine an observation target according to the star point position image, and establish a mapping relationship between the measurement coordinates of the observation target in the measurement coordinate system and the angular position in the celestial coordinate system; Modulating the star point position image to obtain a distribution signal of the target brightness of the observed target in the measurement coordinate system over time; obtaining the speed of the observed target in the measurement coordinate system according to the distribution signal of the target brightness over time; The expression of the speed of the observed target in the measurement coordinate system is: Wherein, (u, v) are the instantaneous spatial frequencies of the distribution signal of the target brightness varying with time in the x direction and the y direction of the measurement coordinate system respectively; (p x ,p y ) are respectively the modulation periods of the filter in the x direction and the y direction of the measurement coordinate system; (M x ,M y ) are respectively the magnifications of the projection lens in the x-direction and the y-direction of the measurement coordinate system; Obtaining the angular velocity of the observed target in the celestial coordinate system according to the velocity of the observed target in the measurement coordinate system through a mapping relationship between the metric coordinates of the observed target in the measurement coordinate system and the angular position in the celestial coordinate system; Calculating the angular acceleration of the observed target in the celestial coordinate system according to the angular velocity of the observed target in the celestial coordinate system; According to the angular position, angular velocity and acceleration of the observed target in the celestial coordinate system, the position vector and the initial orbit velocity of the observed target relative to the center of the earth are obtained through the initial orbit determination algorithm.

2. The method according to claim 1, characterized in that: The step of acquiring the star point position image comprises: acquiring the star point position image by gazing at the sky region using an optical astronomical telescope and adopting a gazing method.

3. The method according to claim 1, characterized in that: Determining the observation target according to the star point position image includes: Obtaining all star point positions and the number of star points on the kth frame of the star point position image and all star point positions and the number of star points on the k+1th frame, and judging and removing the star points on the star point position image where there are bad points according to the star point positions and the number of star points; Subtracting the star point position matrix on the star point position image of the kth frame after removing bad points from the star point position matrix on the star point position image of the k+1th frame to obtain a new matrix; When the value of the new matrix is ​​the largest, the star point located at the star point position on the kth frame is the observed target.

4. The method according to claim 1, characterized in that The step of establishing a mapping relationship between the measured coordinates of the observation target in the measured coordinate system and the angular position in the celestial coordinate system includes: Using an astronomical positioning method, a mapping relationship between the measured coordinates of the observed target in the measured coordinate system and the angular position in the celestial coordinate system is established through a film model; The mapping relationship between the measured coordinates of the observed target in the measured coordinate system and the angular position in the celestial coordinate system is expressed as follows: Wherein, (ζ, η) is the position coordinate of the observed target in the ideal plane coordinate system; (α0, δ0) is the optical axis pointing position of the device for acquiring the star point position image; (a, b, c, d, e, f) are the unknown parameters in the six-constant model.

5. The method according to claim 1, characterized in that: The star point position image is modulated to obtain a distribution signal of the target brightness of the observed target changing with time in a measurement coordinate system; Acquiring the speed of the observed target in the metric coordinate system according to the distribution signal of the target brightness changing with time, including: The measurement target is modulated by a Ronchi grating, and the star point position image is processed by an out-of-phase differential filtering method to obtain a distribution signal of the target brightness of the observation target changing with time in the measurement coordinate system, which is expressed as: Where f(x,y) is the brightness distribution of the modulated image of the observed target; h(x,y) is the transmittance distribution of the Ronchi grating; (x0, y0) is the position coordinate of the observation target projected onto the Ronchi grating; Using short-time Fourier transform, the distribution signal of the target brightness of the observed target that varies with time is converted into a distribution signal in the frequency domain, and the instantaneous spatial frequency of the distribution signal of the target brightness that varies with time in the x direction and the y direction of the measurement coordinate system is extracted; The speed of the observed target in the measurement coordinate system is obtained according to the expression of the speed of the observed target in the measurement coordinate system.

6. The method according to claim 1, characterized in that The step of obtaining the angular velocity of the observed target in the celestial coordinate system according to the velocity of the observed target in the measurement coordinate system by mapping the measurement coordinates of the observed target in the measurement coordinate system and the angular position in the celestial coordinate system comprises: According to the mapping relationship between the measured coordinates of the observed target in the measured coordinate system and the angular position in the celestial coordinate system, the mapping relationship between the velocity of the observed target in the ideal plane coordinate system and the angular velocity in the celestial coordinate system and the mapping relationship between the velocity of the observed target in the ideal plane coordinate system and the velocity in the measured coordinate system are obtained respectively; According to the mapping relationship between the velocity of the observation target in the ideal plane coordinate system and the angular velocity in the celestial sphere coordinate system and the mapping relationship between the velocity of the observation target in the ideal plane coordinate system and the velocity in the measurement coordinate system, a mapping relationship between the angular velocity of the observation target in the celestial sphere coordinate system and the velocity in the measurement coordinate system is obtained; The mapping relationship between the angular velocity of the observed target in the celestial coordinate system and the velocity in the measurement coordinate system is expressed as: Wherein, (α, δ) is the angular position of the observed target in the celestial coordinate system; The velocity of the observed target in the measurement coordinate system; (ζ, η) is the position of the observed target in the ideal coordinate system.

7. The method according to claim 5, characterized in that The method comprises: modulating the measurement target by using a Ronchi grating, processing the star point position image by using a phase difference filtering method, and obtaining a distribution signal of the target brightness of the observation target changing with time in a measurement coordinate system, and then further comprising: Amplifying the distribution signal of the target brightness of the observed target changing with time, filtering it with a bandpass filter, and eliminating low-frequency and high-frequency noise; The bandpass filter is a 3rd order Butterworth bandpass filter with a passband range of 0.1 to 50 Hz.

8. The method according to claim 1, characterized in that: The step of calculating the angular acceleration of the observed target in the celestial coordinate system according to the angular velocity of the observed target in the celestial coordinate system comprises: The angular velocity calculation of the observed target in the celestial coordinate system is based on the three-step difference method to obtain the angular acceleration of the observed target in the celestial coordinate system at time t.

9. The method according to claim 1, characterized in that: The method of obtaining the position vector and the initial orbit velocity of the observed target relative to the center of the earth by using an initial orbit determination algorithm according to the angular position, angular velocity and acceleration of the observed target in the celestial coordinate system includes: Taking the observation station as the origin of the celestial coordinate system, establishing an observation vector expression of the observation target according to the angular position of the observation target in the celestial coordinate system; By measuring the angular position, angular velocity and acceleration of the observation target in the celestial coordinate system at time t, a mapping relationship between the observation vector, the changing velocity vector of the observation vector and the changing acceleration vector of the observation vector is established to obtain the position and velocity of the observation target and realize the initial orbit determination of the observation target.

10. A target initial orbit determination device based on spatial filtering velocity measurement, characterized in that: include: Observation module, used to obtain star point position images; An imaging module, used to determine an observation target according to the star point position image, and establish a mapping relationship between the measurement coordinates of the observation target in the measurement coordinate system and the angular position in the celestial coordinate system; A brightness measurement module modulates the star point position image to obtain a distribution signal of the target brightness of the observed target in the measurement coordinate system over time; and obtains the speed of the observed target in the measurement coordinate system according to the distribution signal of the target brightness over time; A signal processing module, configured to obtain the angular velocity of the observed target in the celestial coordinate system according to the velocity of the observed target in the measurement coordinate system through a mapping relationship between the metric coordinates of the observed target in the measurement coordinate system and the angular position in the celestial coordinate system; Calculating the angular acceleration of the observed target in the celestial coordinate system according to the angular velocity of the observed target in the celestial coordinate system; According to the angular position, angular velocity and acceleration of the observed target in the celestial coordinate system, the position vector and the initial orbit velocity of the observed target relative to the center of the earth are obtained through the initial orbit determination algorithm.

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