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

Abstract

The application discloses a target initial orbit determination method and device based on spatial filtering velocity measurement, which comprises the following steps: acquiring a star position image; determining an observation target according to the star position image, and establishing a mapping relationship between a measurement coordinate and an angle position of the observation target; modulating the star position image to obtain a distribution signal of target brightness of the observation target changing with time; acquiring a velocity of the observation target according to the distribution signal of the target brightness changing with time; obtaining an angular velocity and an acceleration of the observation target according to the velocity of the observation target through the mapping relationship between the measurement coordinate and the angle position of the observation target; and obtaining a position vector and an initial orbit velocity of the observation target relative to the earth center through an initial orbit determination algorithm. Compared with a traditional initial orbit determination method, the application directly measures the angular velocity of the target, reduces the coupling between the angle position error and the angular motion quantity, improves the initial orbit determination precision of the target under the observation error condition, and realizes the rapid orbit determination of the target.

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 to 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] Current research on situational awareness of space targets focuses on the orbit determination process, which is divided into preliminary orbit determination and precise orbit determination. Preliminary orbit determination primarily involves determining the target's orbit for non-cooperative targets. This method primarily uses short-arc measurements (equivalent to one-eighth the target's orbital length) to determine the target's orbit through observation. Precise orbit determination, on the other hand, relies on a complete mechanical system, combining initial values ​​obtained from preliminary orbit determination with extensive observational data to achieve precise orbit determination.

[0004] The Laplace method and Gaussian method are traditional preliminary orbit determination algorithms. They were originally proposed for asteroid prediction. They complete the preliminary 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 show improved performance on short-arc data, and their solution accuracy can be improved by an order of magnitude compared to the Laplace and Gauss methods. However, when using angular observation data from short arc segments for initial orbit determination, the orbital geometry strength of the angular measurement data is weak, resulting in ill-conditioning of the observation equation. This is manifested in the algorithm's strong sensitivity to angular 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 complex. Summary of the Invention

[0007] The purpose of the present invention is to provide a method and apparatus for initial target 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 embodiments disclosed in the present invention, a first aspect of the present invention provides a method for initial target orbit determination based on spatial filtering velocity measurement, comprising: acquiring a star point position image;

[0009] determining an observation target based on the star point position image, and establishing a mapping relationship between the measurement coordinates of the observation target in a measurement coordinate system and the angular position of the observation target in a 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 a speed of the observed target in the measurement coordinate system based on 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 changing 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 based on the velocity of the observed target in the measurement coordinate system by mapping 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 observation target in the celestial coordinate system according to the angular velocity of the observation 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 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 acquiring of 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.

[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 star points on the star point position image that have bad points based on 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 pixels 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 k-th frame is the observation target.

[0024] Preferably, 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 includes:

[0025] Using an astronomical positioning method, 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 is established through a film model;

[0026] The mapping relationship between the measurement coordinates of the observation target in the measurement 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, modulating the star point position image to obtain a distribution signal of target brightness of the observed target in a metric coordinate system that varies with time; and obtaining the speed of the observed target in the metric coordinate system according to the distribution signal of target brightness that varies with 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. The expression is:

[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 an 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 using 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 includes:

[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, a 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 a 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] Obtaining a mapping relationship between the angular velocity of the observed target in the celestial coordinate system and the velocity in the measurement coordinate system according to a 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 a mapping relationship between the velocity of the observed target in the ideal plane coordinate system and the velocity in the measurement coordinate system;

[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 follows:

[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 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 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, and filtering it with a bandpass filter to eliminate 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 calculating the angular acceleration of the observation target in the celestial coordinate system according to the angular velocity of the observation target in the celestial coordinate system includes:

[0051] The angular velocity of the observation target in the celestial coordinate system is calculated based on the three-step difference method to obtain the angular acceleration of the observation 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 based on 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 is established with the observation vector, the changing velocity vector of the observation vector and the changing acceleration vector of the observation vector, the position and velocity of the observation target are obtained, and the initial orbit of the observation target is determined.

[0055] According to the specific embodiments disclosed in the present invention, a 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, configured to determine an observation target based on the star point position image, and establish a mapping relationship between the measurement coordinates of the observation target in a measurement coordinate system and the angular position of the observation target in a celestial coordinate system;

[0058] a brightness measurement module, 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; and obtaining a speed of the observed target in the measurement coordinate system based on the distribution signal of the target brightness over time;

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

[0060] Calculating the angular acceleration of the observation target in the celestial coordinate system according to the angular velocity of the observation 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 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, thereby reducing the coupling between the angular position error and the angular motion, improving the accuracy of angular velocity measurement under certain error conditions, and improving the robustness of the initial orbit determination. BRIEF DESCRIPTION OF THE DRAWINGS

[0064] The accompanying drawings are incorporated into and constitute a part of the specification, illustrating embodiments consistent with the present disclosure and, together with the specification, explaining the principles of the present disclosure. Obviously, the drawings described below are only some embodiments of the present disclosure, and those skilled in the art can derive other drawings based on these drawings without inventive effort. In the drawings:

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

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

[0067] Figure 3 This is a block diagram of the process of performing preliminary orbit determination of a target preliminary orbit determination device based on spatial filtering velocity measurement according to 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 velocity measurement according to the present invention. DETAILED DESCRIPTION

[0069] To make the objectives, technical solutions, and advantages disclosed in the present invention more clearly apparent, the present invention will be further described in detail below with reference to the accompanying drawings. It is apparent that the embodiments described are only some of the embodiments disclosed in the present invention, rather than all of them. All other embodiments obtained by persons of ordinary skill in the art based on the embodiments disclosed in the present invention without inventive effort shall fall within the scope of protection disclosed in the present invention.

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

[0071] It should be understood that the term "and / or" as used herein is merely a description of the relationship between associated objects, indicating that three possible relationships exist. For example, "A and / or B" can represent: A exists alone, A and B exist simultaneously, or B exists alone. Furthermore, the character " / " in this document generally indicates that the associated objects are in an "or" relationship.

[0072] It should also be noted that the terms "include," "comprises," or any other variations thereof are intended to encompass non-exclusive inclusion, such that a product or device comprising a series of elements includes not only those elements but also other elements not explicitly listed, or elements inherent to such product or device. In the absence of further limitations, an element defined by the phrase "comprises a..." does not exclude the presence of other identical elements in the product or device comprising the element.

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

[0074] Example 1

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

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

[0077] In a preferred embodiment of the present invention, an optical astronomical telescope is used to gaze at the sky, thereby observing a space target and acquiring a star position image. In this embodiment, staring observation enables the target to move relative to the CCD camera's target surface, enabling subsequent filtering and modulation of the target using a grating.

[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 based on 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 a stationary target.

[0082] In this embodiment, the connected domain analysis method is used to obtain the positions (x, y) of all star points on the kth frame of the star point position image, and the inter-frame difference method is used to obtain the positions (x', y') of all star points on the k+1th frame. Due to the limitations of CCD cameras, image defects may appear during the observation process, resulting in different numbers of star points on the kth and k+1th frames. Therefore, it is necessary to remove these image defects.

[0083] Specifically, by applying the connected component analysis method to the k-th frame image, the number of star points on the k-th frame image is determined to be m; by applying the connected component analysis method to the k+1-th frame image, the number of star points on the k-th frame image is determined to be 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 k-th 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, we traverse and subtract all the star points on the k+1th frame from the star point, and then calculate the modulus length p of each difference. 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 obtain 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 it is maximum, then (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 a method of determining the angular position of the observation target based on 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 that obtains 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: modulate 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 obtain the speed of the observed target in the measurement coordinate system based on the distribution signal of the target brightness over time.

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

[0105] Step S106-1: Use a Ronchi grating to modulate the measurement target, 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 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 observation target projected onto the Ronchi grating.

[0114] In a preferred embodiment of the present invention, after modulating the measurement target using a Ronchi grating and processing the star point position image using an out-of-phase differential filtering method to obtain a distribution signal of the target brightness of the observed target over time in a measurement coordinate system, the method further includes:

[0115] The distribution signal of the target brightness changing with time 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 convert 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, which is 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 the modulation periods of the Ronchi grating in the x-direction and the y-direction of the measurement coordinate system, respectively;

[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: Obtain the angular velocity of the observed target in the celestial coordinate system based on the mapping relationship between the metric coordinates of the observed target in the metric coordinate system and the angular position in the celestial coordinate system, according to the velocity of the observed target in the metric coordinate system. This includes the following steps:

[0126] Step S108-1: Derivative 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 angular position (α, δ) of the measurement target in the celestial coordinate system is obtained by taking the partial derivative at time t 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: Calculate 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, the angular acceleration of the observed target in the celestial coordinate system at time t is obtained by a three-step difference method according to the angular velocity calculation of the observed target in the celestial coordinate system. Right now

[0136] Step S112: Based on the angular position, angular velocity, and acceleration of the observed target in the celestial coordinate system, the position vector and initial orbit velocity of the observed target relative to the center of the Earth are obtained by using an 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 coordinate origin, 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] Among them, the expression of u is:

[0140]

[0141] The position vector r and velocity of the observed 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 slant range ρ and slant range change rate Expressed as:

[0146]

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

[0148] es = 0.0000729212 rad / 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 slant range ρ and slant range change rate are solved by expression (9): Combined with formula (8), the target position r and velocity are determined 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 interpretation 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] Observation module 10, used to obtain star point position images;

[0156] An imaging module 20 is configured to determine an observation target based on 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 of the observation target 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 based on the distribution signal of the target brightness over time;

[0158] a signal processing module 40 configured to obtain an angular velocity of the observed target in the celestial coordinate system based on a mapping relationship between the metric coordinates of the observed target in the metric coordinate system and the angular position in the celestial coordinate system and the velocity of the observed target in the metric coordinate system;

[0159] Calculating the angular acceleration of the observation target in the celestial coordinate system according to the angular velocity of the observation 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 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 passing through the zoom projection lens 300 is modulated using a filter 301. This filter utilizes a 10 lp / mm Ronchi grating, whose period is large, far exceeding the diffraction wavelength, thus negligible diffraction effects. The image is then projected through a projection lens 302 onto a photosensor 303, where it is processed using out-of-phase differential filtering to detect changes in target brightness. The photosensor utilizes SPAD array technology, which boasts a temporal resolution of 100 ps. To ensure the continuity of the brightness signal, the detector acquisition frequency should be greater than 50 Hz.

[0163] Furthermore, in imaging module 20, after the target image passes through beam splitter 23, it is imaged onto CCD imaging sensor 21 via projection objective lens assembly 22, which consists of two projection lenses. Imaging module 20 images the target through continuous exposure, and uses astronomical positioning methods to determine the target's angular position. Imaging module 20 requires an acquisition frequency greater than 10 Hz, with no specific requirements for spatial or temporal resolution.

[0164] The signal processing module 40 in this embodiment processes the brightness signal at the front end and determines the initial trajectory at the back end.

[0165] The flow charts and block diagrams in the accompanying drawings illustrate the possible implementation architecture, functions and operations of the systems, methods and computer program products disclosed in various embodiments of the present invention. In this regard, each box in the flow chart or block diagram can represent a module, program segment, or a part of code, and the module, program segment, or a part of code contains one or more executable instructions for realizing the specified logical function. It should also be noted that in some alternative implementations, the functions marked in the box can also occur in a different order than that marked in the accompanying drawings. For example, two 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 box in the block diagram and / or flow chart, and the combination of the 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 described in the present invention may be implemented in software or hardware, wherein the name of a unit does not necessarily limit the unit itself.

Claims

1. A method for initial target orbit determination based on spatial filtering velocity measurement, characterized in that: include: Get star point position image; determining an observation target based on the star point position image, and establishing a mapping relationship between the measurement coordinates of the observation target in a measurement coordinate system and the angular position of the observation target in a celestial coordinate system; The star point position image is modulated, the observation target is modulated using 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 varying with time in the measurement coordinate system; based on the distribution signal of the target brightness varying with time, the distribution signal of the target brightness varying with time is converted into a distribution signal in the frequency domain by using a short-time Fourier transform, and the velocity of the observation target in the measurement coordinate system is obtained by calculation using expression (1); 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 changing 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 measurement 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 observation target in the celestial coordinate system according to the angular velocity of the observation 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 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 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.

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 star points on the star point position image that have bad points based on 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 pixels 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 k-th frame is the observation target.

4. The method according to claim 1, wherein 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 includes: Using an astronomical positioning method, 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 is established through a film model; The mapping relationship between the measurement coordinates of the observation target in the measurement 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 unknown parameters in the six-constant model; (α, δ) is the angular position of the observed target in the celestial coordinate system.

5. The method according to claim 1, wherein 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; Obtaining the speed of the observed target in the measurement coordinate system according to the distribution signal of the target brightness changing over time, comprising: The observed 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 observed target changing with time in a 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 observation target in the measurement coordinate system is obtained according to the expression of the speed of the observation target in the measurement coordinate system.

6. The method according to claim 1, characterized in that 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 based on 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 includes: 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, a 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 a 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; Obtaining a mapping relationship between the angular velocity of the observed target in the celestial coordinate system and the velocity in the measurement coordinate system according to a 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 a mapping relationship between the velocity of the observed target in the ideal plane coordinate system and the velocity in the measurement coordinate system; 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 follows: 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; (a, b, c, d, e, f) are the unknown parameters in the six-constant model.

7. The method according to claim 5, characterized in that The method further includes: modulating the observation target by using a Ronchi grating, processing the star point position image by using an out-of-phase differential 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 including: amplifying the distribution signal of the target brightness of the observed target changing with time, and filtering it with a bandpass filter to eliminate 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 calculating, based on the angular velocity of the observation target in the celestial coordinate system, to obtain the angular acceleration of the observation target in the celestial coordinate system includes: The angular velocity of the observation target in the celestial coordinate system is calculated based on the three-step difference method to obtain the angular acceleration of the observation target in the celestial coordinate system at time t.

9. The method according to claim 1, characterized in that The method of obtaining a position vector and a preliminary orbit velocity of the observed target relative to the center of the earth by using a preliminary orbit determination algorithm based on 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 is established with the observation vector, the changing velocity vector of the observation vector and the changing acceleration vector of the observation vector, the position and velocity of the observation target are obtained, and the initial orbit of the observation target is determined.

10. A target initial orbit determination device based on spatial filtering velocity measurement, characterized in that: Use according to the method of any one of claims 1 to 9, comprising: Observation module, used to obtain star point position images; an imaging module, configured to determine an observation target based on the star point position image, and establish a mapping relationship between the measurement coordinates of the observation target in a measurement coordinate system and the angular position of the observation target in a celestial coordinate system; a brightness measurement module that modulates the star point position image to obtain a distribution signal of the target brightness of the observed target over time in the measurement coordinate system established by the imaging module; and obtains the speed of the observed target in the measurement coordinate system based on the distribution signal of the target brightness over time; a signal processing module, configured to obtain an angular velocity of the observed target in the celestial coordinate system based on 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 and the velocity of the observed target in the measured coordinate system; Calculating the angular acceleration of the observation target in the celestial coordinate system according to the angular velocity of the observation 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 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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