A method and system for detecting low-Earth orbit satellite orbit changes based on starlight background

Abstract

This invention discloses a method and system for detecting low-Earth orbit satellite orbit changes based on stellar background. The method includes: defining a coordinate system, including a geocentric coordinate system, a celestial inertial coordinate system, and a star sensor coordinate system; acquiring star point images through a star sensor, obtaining a stellar database and a satellite ephemeris database; calculating the correspondence between each star point in the star point image and the stellar and satellite ephemeris databases using a triangulation matching algorithm within the coordinate system, and identifying stellar and satellite star points; using the identified stellar star points as a reference, calculating the satellite's spatial position based on the satellite star point's trajectory in the star point image and historical ephemeris data in the satellite ephemeris database, and comparing this position with the predicted spatial position based on historical ephemeris data to determine whether a satellite orbit change has occurred. This invention offers low detection cost, convenient execution of the detection task, and strong autonomy and anti-interference capabilities.

Description

Technical Field

[0001] This invention relates to the field of low-Earth orbit satellite orbit change detection, and in particular to a method and system for low-Earth orbit satellite orbit change detection based on starlight background. Background Technology

[0002] Existing low-Earth orbit (LEO) satellites operate in near-Earth space and are frequently required to perform temporary orbit maneuvers due to space debris avoidance, new satellite launches, and Earth reconnaissance missions. When the ephemeris data of these LEO satellites acquired by ground users is not updated in a timely manner due to environmental factors, it affects ground users' ability to complete measurement, communication, or surveillance tasks. Current satellite orbit change detection primarily relies on detecting ephemeris data broadcast by the changing satellite and ground-based surveillance radar. However, this approach is susceptible to errors due to satellite ephemeris deception or reliance on radar infrastructure, failing to meet the needs of convenient detection applications.

[0003] Therefore, in order to meet the need for convenient detection of low-Earth orbit satellite orbit changes, and to address the problems of erroneous detection or poor detection convenience caused by traditional orbit change detection being rejected by satellite signals or relying on large infrastructure such as radar, it is urgent to design a low-Earth orbit satellite orbit change detection method based on starlight background, consisting of a small starlight measurement device and a low-Earth orbit satellite ephemeris processing module. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to provide a method and system for detecting low-orbit satellite orbit changes based on starlight background, which addresses the deficiencies in the existing technology.

[0005] The technical solution adopted by this invention to solve its technical problem is:

[0006] This invention provides a method for detecting orbit changes of low-Earth orbit satellites based on starlight background. The method includes the following steps:

[0007] Step 1: Define the coordinate system, including the geocentric coordinate system, the celestial inertial coordinate system, and the star sensor coordinate system;

[0008] Step 2: Obtain star point images by measuring with a star sensor, acquire stellar databases and satellite ephemeris databases, and calculate the correspondence between each star point in the star point image and the stellar database and satellite ephemeris database in the coordinate system using a triangulation matching algorithm to identify stellar points and satellite points;

[0009] Step 3: Using the identified star points as a reference, calculate the satellite's spatial motion position based on the satellite star point's trajectory in the star point image and the historical ephemeris in the satellite ephemeris database. Compare this with the spatial motion position predicted based on the historical ephemeris to determine whether a satellite orbit change has occurred.

[0010] Furthermore, the method for defining the coordinate system in step 1 of the present invention specifically includes:

[0011] Geocentric coordinate system: denoted by ECEF, with the Earth's center as the reference origin, the x-axis points to the intersection of the Greenwich 0 longitude line and the 0 latitude line on the equatorial plane, the z-axis points to the Earth's rotation axis, and the y-axis is perpendicular to the plane formed by the x-axis and z-axis, forming a right-handed rectangular coordinate system;

[0012] Celestial inertial coordinate system: denoted by i, with the Earth's center as the reference origin, the z-axis is parallel to the Earth's rotation axis and points to the North Pole, also known as the celestial axis, the x-axis points to the vernal equinox, and the y-axis is perpendicular to the plane formed by the x-axis and z-axis, forming a right-handed rectangular coordinate system;

[0013] Star sensor coordinate system: denoted by m, with the center of the star sensor target surface as the reference origin, the z-axis passing through the origin and pointing along the optical axis, the x-axis passing through the origin and pointing to the right along the optical axis, and the y-axis forming a right-handed coordinate system with the x-axis and z-axis.

[0014] Furthermore, the method in step 2 of the present invention specifically includes:

[0015] Step 21: Star point identification: The star database stores the right ascension and declination coordinates of stars that can be used at any time. The triangulation matching algorithm is used to determine the star point image measured by the current star light sensor and the star points in the star database that correspond to the right ascension and declination.

[0016] Step 22: Satellite Star Point Identification: Use a triangulation matching algorithm to determine the satellite star points in the current star light sensor image that correspond to the right ascension and declination in the satellite ephemeris database.

[0017] Furthermore, the method of step 21 of the present invention specifically includes:

[0018] Step 211: In the star point image, select any three star points with coordinates (x1, y1), (x2, y2), and (x3, y3) relative to the image center. The angular distances of these star points in the star sensor coordinate system are... The calculation formula is:

[0019]

[0020] Where m1, m2, and m3 are the direction vectors of the three star points in the star sensor coordinate system;

[0021] Step 212: Select three stars from the star database. The right ascension and declination coordinates of the three stars are (α1, δ1), (α2, δ2), and (α3, δ3). The angular distance d between the first and second stars is... 12 angular distance d between the first and third star points13 angular distance d between the second and third star points 23 The calculation formula is:

[0022]

[0023] Wherein, s1, s2, and s3 are the direction vectors of three star points, expressed using the right ascension and declination of the stars as follows:

[0024]

[0025] Step 213: Based on the angular distance values ​​of the three stars in the starlight image, examine the differences between these values ​​and the three angular distance values ​​calculated based on the star database. Given a test threshold ε, if the following test criteria are met:

[0026]

[0027] The three star points in the starlight image are the actual measured values ​​of three star points in the star database.

[0028] Furthermore, the specific method of step 22 of the present invention includes:

[0029] Step 221: In the star point image, select any three star points with coordinates (x1, y1), (x2, y2), and (x3, y3) relative to the image center. The angular distances of these star points in the star sensor coordinate system are... The calculation formula is:

[0030]

[0031] Where m1, m2, and m3 are the direction vectors of the three star points in the star sensor coordinate system, respectively;

[0032] Step 222: Select three satellite points in the satellite ephemeris database. Based on the ephemeris database, calculate the orbital position vectors P1, P2, and P3 of the three satellite points in the geocentric-geocentric coordinate system. Let P be the user's position vector in the geocentric-geocentric coordinate system. Then, the formulas for calculating the three observation vectors v1, v2, and v3 when the user observes the three satellites are:

[0033] v1 = P - P1

[0034] v2 = P - P2

[0035] v3 = P - P3

[0036] The three angular distances corresponding to the observed vector are calculated as follows:

[0037]

[0038] Step 223: Based on the angular distance values ​​of the three stars in the starlight image, examine the differences between these values ​​and the three angular distance values ​​calculated based on the satellite ephemeris database. Given a threshold ε, if the following examination criteria are met:

[0039]

[0040] The three star points in the starlight image are the actual measured values ​​of three satellite star points in the satellite ephemeris database.

[0041] Furthermore, the method in step 3 of the present invention specifically includes:

[0042] Suppose that at time k, one satellite point and several star points have been successfully identified from the starlight image. The satellite point image coordinates are (x1, y1), and the satellite's position vector in the Earth-centered Earth-fixed coordinate system is P. k One of the star points in the image has coordinates (x... s ,y s The coordinate transformation matrix determined by the star points is: i is the celestial inertial coordinate system, b is the image coordinate system, and the matrix conversion between the i-system and the geocentric Earth-fixed coordinate system is performed using... express;

[0043] At time k+1, the predicted satellite position vector P is obtained from the satellite orbit prediction. k+1 The satellite star point image coordinates are (x2, y2). Since the star point coordinates remain basically unchanged in the image in the short term, the star coordinates are used as the markers that the image does not need to be rematched. This ensures that after a successful match, the satellite star point will move in the image for a period of time, avoiding the inability to identify satellites with orbital changes that may occur during rematching. The position increment vector ΔP of the satellite star point within the system at time k and time k+1 is calculated. b ;

[0044] The position increment vector is transformed to the geocentric coordinate system, the satellite orbit position is calculated based on the star point image, and a position change threshold is set during orbit change. The satellite orbit position, the predicted satellite position vector, and the position change threshold are used to determine whether a satellite orbit change has occurred.

[0045] Furthermore, the specific calculation method for determining satellite orbit changes in this invention is as follows:

[0046] Calculate the position increment vector ΔP of the satellite point within the system at time k and time k+1. b for:

[0047]

[0048] Among them, R s Let f be the satellite orbital altitude and f be the focal length of the starlight sensor. Transforming the position increment vector to a geocentric coordinate system yields:

[0049]

[0050] The satellite orbital position calculated from the star image is as follows:

[0051]

[0052] The position change threshold ΔP during trajectory change is set based on experience. c If the following conditions are met:

[0053]

[0054] Then it is determined that the satellite has undergone a change-orbit maneuver.

[0055] Furthermore, the method of the present invention also includes a method for merging satellite ephemeris databases and star databases:

[0056] The satellite ephemeris database and the star point database are merged into a new starlight database. The merged starlight database includes two types of data: satellite ephemeris and star positions. It is continuously updated as the satellite ephemeris changes. The merged starlight database includes satellite or star number, time, and angular distance information.

[0057] This invention provides a low-Earth orbit satellite orbit change detection system based on starlight background, comprising:

[0058] Memory, used to store executable computer programs;

[0059] The processor, when executing an executable computer program stored in a memory, implements the low-orbit satellite orbit change detection method based on starlight background as described in any one of claims 1 to 8.

[0060] Furthermore, the system of the present invention includes:

[0061] The star sensor module is used to acquire star images by measuring star points.

[0062] The satellite and star point recognition module is used to acquire star databases and satellite ephemeris databases. In the coordinate system, it uses a triangulation matching algorithm to calculate the correspondence between each star point in the star point image and the star database and satellite ephemeris database, and identifies star points and satellite star points.

[0063] The orbit change detection module is used to calculate the satellite's spatial motion position based on the identified star points as a reference, the satellite star points' motion trajectory in the star point image and the historical ephemeris in the satellite ephemeris database, and compare it with the spatial motion position predicted based on the historical ephemeris to determine whether a satellite orbit change has occurred.

[0064] The beneficial effects of this invention are:

[0065] 1. The method of the present invention utilizes low-orbit satellite ephemeris data and low-orbit satellite images and starlight image information output by starlight measurement equipment. It simultaneously identifies star points and low-orbit satellite star points in the images through a triangulation matching algorithm. Using star points as reference angles, it calculates the position changes of low-orbit satellite star points and compares them with the predicted low-orbit satellite position to determine whether the satellite is performing an orbit change. It can accurately complete the task of detecting low-orbit satellite orbit changes using ground optical observations.

[0066] 2. This invention utilizes a small starlight measurement sensor and a low-Earth orbit satellite ephemeris receiving module to complete the low-Earth orbit satellite orbit change detection task, which is low in detection cost and convenient to execute.

[0067] 3. In the method of the present invention, since stars are not disturbed by human activities, the orbit change detection under strong electromagnetic interference can be realized by using starlight as a stable reference light source and active optical observation. The detection method has strong autonomy and anti-interference ability. Attached Figure Description

[0068] The present invention will be further described below with reference to the accompanying drawings and embodiments. In the accompanying drawings:

[0069] Figure 1 This is a schematic diagram of the celestial inertial coordinate system according to an embodiment of the present invention. Detailed Implementation

[0070] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0071] Example 1

[0072] This invention provides a method for detecting orbit changes in low-Earth orbit (LEO) satellites based on starlight background, including coordinate system definition, satellite and star point identification, and orbit change detection calculation. By defining the coordinate system, the mathematical and physical meanings of the variables involved in the calculation of LEO satellite orbit change detection are clarified; by identifying satellite and star points, the mapping relationship between information measured by starlight sensors and information in the starlight database is given, providing reference starlight information for orbit change detection; and by calculating the orbit change detection, the orbit change detection method is presented.

[0073] (1) Definition of coordinate system

[0074] The present invention relates to a method for detecting low-Earth orbit satellite orbit changes based on starlight background. The coordinate systems involved in the calculation include the geocentric-ground-fixed coordinate system (ECEF), the celestial inertial coordinate system, and the star sensor coordinate system. The definitions of each coordinate system are as follows:

[0075] The geocentric coordinate system, denoted by ECEF, takes the Earth's center as the reference origin. The x-axis points to the intersection of the Greenwich 0° longitude and 0° latitude line on the equatorial plane, the z-axis points to the Earth's rotation axis, and the y-axis is perpendicular to the plane formed by the x-axis and z-axis, forming a right-handed rectangular coordinate system.

[0076] Celestial inertial coordinate system: denoted by i, with the Earth's center as the reference origin, the z-axis is parallel to the Earth's rotation axis and points towards the North Pole, also known as the celestial axis, the x-axis points towards the vernal equinox, and the y-axis is perpendicular to the plane formed by the x-axis and z-axis, forming a right-handed rectangular coordinate system.

[0077] Star sensor coordinate system: denoted by m, with the center of the star sensor target surface as the reference origin, the z-axis passing through the origin and pointing along the optical axis, the x-axis passing through the origin and pointing to the right along the optical axis, and the y-axis forming a right-handed coordinate system with the x-axis and z-axis.

[0078] Figure 1 Here, S represents the starlight coordinates of a star in the celestial coordinate system, where S is a defined star point whose coordinates are expressed in right ascension α. s δ declination s express.

[0079] (2) Satellite and star point identification

[0080] The star images acquired by the star sensor include stellar points and satellite points. Further calculations are needed to determine the correspondence between each star point in the image and the stellar database and satellite ephemeris database. This is to confirm that each star point in the image is a real measured star point and not a false one. This star point identification process is as follows:

[0081] 1) Star point identification

[0082] The stellar database stores the right ascension and declination coordinates of stars that can be used at any given time. To determine which stars in the stellar database correspond to the star point image measured by the current starlight sensor, a triangulation matching algorithm is used to perform angular distance matching to complete the star point identification. The specific process is as follows:

[0083] ① Select three star points in the star sensor measurement image.

[0084] In the star image, the coordinates of any three star points relative to the image center are (x1, y1), (x2, y2), and (x3, y3), respectively. The angular distances of these star points in the coordinate system of the star sensor are... It can be calculated using the following formula:

[0085]

[0086] Where m1, m2, and m3 are the direction vectors of star points 1, 2, and 3 in the star sensor coordinate system, respectively.

[0087] ② Select three stars from the star database

[0088] Assume that in the stellar database, the right ascension and declination coordinates of three stars, points 1, 2, and 3, are (α1, δ1), (α2, δ2), and (α3, δ3), respectively. The angular distance d between points 1 and 2... 12 Angular distance d between points 1 and 3 13 Angular distance d between points 2 and 3 23 It can be calculated using the following formula:

[0089]

[0090] Where s1, s2, and s3 are the direction vectors of stars 1, 2, and 3, respectively, and can be expressed using the right ascension and declination of the stars as follows:

[0091]

[0092] ③ Angular distance matching

[0093] Based on the angular distance values ​​of three stars in the starlight image, examine the differences between these values ​​and the three angular distance values ​​calculated from a star database. Given a test threshold ε, if the following test criteria are met:

[0094]

[0095] The three star points in the starlight image are the actual measured values ​​of the three star points in the star database.

[0096] 2) Satellite point identification

[0097] ① Select three star points in the star sensor measurement image.

[0098] In the star image, the coordinates of any three star points relative to the image center are (x1, y1), (x2, y2), and (x3, y3), respectively. The angular distances of these star points in the coordinate system of the star sensor are... It can be calculated using the following formula:

[0099]

[0100] Where m1, m2, and m3 are the direction vectors of star points 1, 2, and 3 in the star sensor coordinate system, respectively.

[0101] ② Select three stars from the satellite ephemeris database

[0102] Based on the satellite ephemeris database, the orbital position vectors P1, P2, and P3 of the three satellites in the ECEF coordinate system can be calculated. The user's position vector in the ECEF coordinate system is P. Therefore, the three observation vectors v1, v2, and v3 when the user observes the three satellites can be calculated using the following formula:

[0103] v1 = P - P1

[0104] v2 = P - P2

[0105] v3 = P - P3

[0106] The three angular distances corresponding to the observed vector are calculated as follows:

[0107]

[0108] ③ Angular distance matching

[0109] Based on the angular distance values ​​of three stars in the starlight image, examine the differences between these values ​​and those calculated from the satellite ephemeris database. Given a threshold ε, if the following test criteria are met:

[0110]

[0111] The three stars in the starlight image are the actual measured values ​​of the three stars in the satellite ephemeris database.

[0112] (3) Track change detection calculation

[0113] When satellite ephemeris does not reflect orbit change maneuvers in a timely manner, satellite identification cannot be performed directly through angular distance matching. Instead, star identification is required as a basis. Based on the satellite's trajectory in starlight images and historical ephemeris, the satellite's spatial motion position is inverted and compared with the spatial motion position predicted based on historical ephemeris to identify whether the satellite has changed its orbit.

[0114] Suppose that at time k, one satellite point and several star points have been successfully identified from the starlight image. The satellite point's image coordinates are (x1, y1), and its position vector in the ECEF system is P. k One of the star points in the image has coordinates (x... s ,y s The coordinate transformation matrix determined by the star points is: i is the celestial inertial frame, b is the image coordinate system, and the transformation matrix between the i-frame and the ECEF-frame is used. express.

[0115] At time k+1, the predicted satellite position vector P is obtained from the satellite orbit prediction. k+1 The satellite star point image coordinates are (x2, y2). Since the star point coordinates remain essentially unchanged in the image in the short term, using the star coordinates as a marker that eliminates the need for rematching ensures that once a satellite star point is successfully matched, it will move within the image for a period of time, avoiding the problem of unrecognizable satellites undergoing orbit changes during rematching. Calculate the position increment vector ΔP of the satellite star point within the system at times k and k+1. b for:

[0116]

[0117] In the formula, R s Let f be the satellite orbital altitude and f be the focal length of the starlight sensor. Converting the above position increment vector to the ECEF system, we get:

[0118]

[0119] The satellite orbital position calculated from the star image is as follows:

[0120]

[0121] The position change threshold ΔP during trajectory change is set based on experience. c If the following conditions are met:

[0122]

[0123] Then it is determined that the satellite has undergone a change-orbit maneuver.

[0124] Example 2

[0125] This invention provides a method for detecting low-orbit satellite orbit changes based on starlight background, which consists of implementation conditions and implementation process.

[0126] (1) Implementation conditions

[0127] It features a starlight sensor module for measuring stellar light and low-Earth orbit (LEO) satellites. The starlight sensor has a field of view of at least 30° to observe more LEO satellites. It also possesses a stellar light database of a certain number of stars for calculating their theoretical positions in the celestial inertial frame. Finally, it includes a LEO satellite ephemeris information receiving module for receiving and predicting LEO satellite ephemeris data.

[0128] (2) Implementation process

[0129] The implementation process includes three steps: real-time starlight image capture, satellite and star point identification, and satellite orbit change detection.

[0130] Step 1: Real-time capture of starlight images

[0131] The starlight sensor module has an observation field of view of no less than 30°, enabling it to observe more satellite and stellar light simultaneously. The starlight sensor captures and extracts satellite and stellar light from images in real time, and the extracted starlight is sent as an array to the satellite and stellar point recognition module for calculation.

[0132] Step 2: Satellite and star point identification

[0133] 1) Merge satellite ephemeris database and star database

[0134] Starlight sensors capturing star points simultaneously cannot distinguish between stellar and satellite stars. Therefore, any three selected star points in a starlight image may contain a subset of stellar and satellite stars. Matching both stellar and satellite ephemeris databases separately during angular distance matching would incur a massive computational burden, resulting in low efficiency and a low matching success rate. Therefore, the primary task of star point identification is to establish a unified reference star point database. This requires merging the satellite ephemeris and stellar star point databases into a new starlight database. The merged database includes both satellite ephemeris and stellar positions, and is continuously updated as the satellite ephemeris changes. The merged database only contains satellite or star identification numbers, time, and angular distance information. The angular distance calculations for stellar information in the original stellar database and satellite information in the original satellite ephemeris database are as follows:

[0135] ① Calculation of angular distance from stellar information in the original stellar database

[0136] Assume the right ascension and declination coordinates of three stars, points 1, 2, and 3, are (α1, δ1), (α2, δ2), and (α3, δ3), respectively. The angular distance d between points 1 and 2... 12 Angular distance d between points 1 and 3 13 Angular distance d between points 2 and 3 23 It can be calculated using the following formula:

[0137]

[0138] Where s1, s2, and s3 are the direction vectors of stars 1, 2, and 3, respectively, and can be expressed using the right ascension and declination of the stars as follows:

[0139]

[0140] ② Calculation of satellite rotation distance from the original satellite ephemeris database

[0141] Based on the satellite ephemeris database, the orbital position vectors P1, P2, and P3 of the three satellites in the ECEF coordinate system can be calculated. The user's position vector in the ECEF coordinate system is P. Therefore, the three observation vectors v1, v2, and v3 when the user observes the three satellites can be calculated using the following formula:

[0142] v1 = P - P1

[0143] v2 = P - P2

[0144] v3 = P - P3

[0145] The three angular distances corresponding to the observed vector are calculated as follows:

[0146]

[0147] 2) Select three star points in the star sensor measurement image.

[0148] In the star image, the coordinates of any three star points relative to the image center are (x1, y1), (x2, y2), and (x3, y3), respectively. The angular distances of these star points in the coordinate system of the star sensor are... It can be calculated using the following formula:

[0149]

[0150] Where m1, m2, and m3 are the direction vectors of star points 1, 2, and 3 in the star sensor coordinate system, respectively.

[0151] 3) Select three stars from the merged star database.

[0152] Select three angular distance values ​​d from the merged starlight database. 12 d 13 d 23 .

[0153] 4) Angular distance matching

[0154] Based on the angular distance values ​​of three stars in the starlight image, examine the differences between these values ​​and the three angular distance values ​​calculated from a star database. Given a test threshold ε, if the following test criteria are met:

[0155]

[0156] The three star points in the starlight image are the actual measured values ​​of the three star points in the star database.

[0157] Step 3: Satellite orbit change detection

[0158] Suppose that at time k, one satellite point and several star points have been successfully identified from the starlight image. The satellite point's image coordinates are (x1, y1), and its position vector in the ECEF system is P. k One of the star points in the image has coordinates (x... s ,y s The coordinate transformation matrix determined by the star points is: i is the celestial inertial frame, b is the image coordinate system, and the transformation matrix between the i-frame and the ECEF-frame is used. express.

[0159] At time k+1, the predicted satellite position vector P is obtained from the satellite orbit prediction. k+1The satellite star point image coordinates are (x2, y2). Since the star point coordinates remain essentially unchanged in the image in the short term, using the star coordinates as a marker that eliminates the need for rematching ensures that once a satellite star point is successfully matched, it will move within the image for a period of time, avoiding the problem of unrecognizable satellites undergoing orbit changes during rematching. Calculate the position increment vector ΔP of the satellite star point within the system at times k and k+1. b for:

[0160]

[0161] In the formula, R s Let f be the satellite orbital altitude and f be the focal length of the starlight sensor. Converting the above position increment vector to the ECEF system, we get:

[0162]

[0163] The satellite orbital position calculated from the star image is as follows:

[0164]

[0165] The position change threshold ΔP during trajectory change is set based on experience. c If the following conditions are met:

[0166]

[0167] Then it is determined that the satellite has undergone a change-orbit maneuver.

[0168] It should be understood that the sequence number of each step in the above embodiments does not imply the order of execution. The execution order of each process should be determined by its function and internal logic, and should not constitute any limitation on the implementation process of the embodiments of this application.

[0169] It should be understood that those skilled in the art can make improvements or modifications based on the above description, and all such improvements and modifications should fall within the protection scope of the appended claims.

Claims

1. A method for detecting orbit changes of low-Earth orbit satellites based on starlight background, characterized in that, The method includes the following steps: Step 1: Define the coordinate system, including the geocentric coordinate system, the celestial inertial coordinate system, and the star sensor coordinate system; Step 2: Obtain star point images by measuring with a star sensor, acquire stellar databases and satellite ephemeris databases, and calculate the correspondence between each star point in the star point image and the stellar database and satellite ephemeris database in the coordinate system using a triangulation matching algorithm to identify stellar points and satellite points; Step 3: Using the identified star points as a reference, calculate the satellite's spatial motion position based on the satellite star point's trajectory in the star point image and the historical ephemeris in the satellite ephemeris database. Compare this with the spatial motion position predicted based on the historical ephemeris to determine whether a satellite orbit change has occurred. The method in step 3 specifically includes: Suppose that at time k, one satellite point and several star points have been successfully identified from the starlight image, and the coordinates of the satellite point in the image are: The satellite's position vector in the Earth-centered Earth-fixed coordinate system is One of the star points in the image has coordinates of The coordinate transformation matrix determined by the star points is: Let i be the celestial inertial coordinate system, b be the image coordinate system, and the matrix conversion between the i-system and the geocentric Earth-fixed coordinate system is... express; At time k+1, the predicted satellite position vector is obtained from the satellite orbit prediction. The coordinates of the satellite star point image are Since the coordinates of stars remain essentially unchanged in the image over a short period, these star coordinates are used as indicators that eliminate the need for rematching. This ensures that once a satellite point is successfully matched, it will move within the image for a period of time, preventing the unrecognizable satellites that have changed orbits during rematching. The incremental vectors of the satellite point's position within the system at times k and k+1 are calculated. ; The position increment vector is transformed to the geocentric coordinate system, the satellite orbit position is calculated based on the star point image, and the position change threshold is set during the orbit change. The satellite orbit position, the predicted satellite position vector, and the position change threshold are used to determine whether the satellite orbit change has occurred. The specific calculation method for determining satellite orbit changes is as follows: Calculate the position increment vector of the satellite point within the system at time k and time k+1. for: in, The satellite's orbital altitude, Given the focal length of the starlight sensor, transforming the position increment vector to the geocentric coordinate system yields: The satellite orbital position calculated from the star image is as follows: The position change threshold during track change is set based on experience. If the following conditions are met: Then it is determined that the satellite has undergone a change-orbit maneuver.

2. The method for detecting low-orbit satellite orbit changes based on starlight background according to claim 1, characterized in that, The method for defining the coordinate system in step 1 specifically includes: Geocentric coordinate system: denoted by ECEF, with the Earth's center as the reference origin, the x-axis points to the intersection of the Greenwich 0 longitude line and the 0 latitude line on the equatorial plane, the z-axis points to the Earth's rotation axis, and the y-axis is perpendicular to the plane formed by the x-axis and z-axis, forming a right-handed rectangular coordinate system; Celestial inertial coordinate system: denoted by i, with the Earth's center as the reference origin, the z-axis is parallel to the Earth's rotation axis and points to the North Pole, also known as the celestial axis, the x-axis points to the vernal equinox, and the y-axis is perpendicular to the plane formed by the x-axis and z-axis, forming a right-handed rectangular coordinate system; Star sensor coordinate system: denoted by m, with the center of the star sensor target surface as the reference origin, the z-axis passing through the origin and pointing along the optical axis, the x-axis passing through the origin and pointing to the right along the optical axis, and the y-axis forming a right-handed coordinate system with the x-axis and z-axis.

3. The method for detecting low-orbit satellite orbit changes based on starlight background according to claim 1, characterized in that, The method in step 2 specifically includes: Step 21: Star point identification: The star database stores the right ascension and declination coordinates of stars that can be used at any time. The triangulation matching algorithm is used to determine the star point image measured by the current star light sensor and the star points in the star database that correspond to the right ascension and declination. Step 22: Satellite Star Point Identification: Use a triangulation matching algorithm to determine the satellite star points in the current star light sensor image that correspond to the right ascension and declination in the satellite ephemeris database.

4. The method for detecting low-orbit satellite orbit changes based on starlight background according to claim 3, characterized in that, The method in step 21 specifically includes: Step 211: In the star image, select any three star points, whose coordinates relative to the image center are as follows: , , Angular distance of the star point in the star sensor coordinate system The calculation formula is: in, These are the direction vectors of the three star points in the star sensor coordinate system; Step 212: Select three stars from the star database. The right ascension and declination coordinates of the three stars are as follows: , , Angular distance between the first star point and the second star point Angular distance between the first and third star points Angular distance between the second and third star points The calculation formula is: in, , , Let the direction vectors of the three star points be represented using the star's right ascension and declination as follows: Step 213: Based on the angular distance values ​​of three stars in the starlight image, examine the differences between these values ​​and the three angular distance values ​​calculated based on the star database, and set a threshold for the examination. If the following test criteria are met: The three star points in the starlight image are the actual measured values ​​of three star points in the star database.

5. The method for detecting low-orbit satellite orbit changes based on starlight background according to claim 3, characterized in that, The specific method of step 22 includes: Step 221: In the star image, select any three star points, whose coordinates relative to the image center are respectively... , , Angular distance of the star point in the star sensor coordinate system The calculation formula is: in, These are the direction vectors of the three star points in the star sensor coordinate system; Step 222: Select three satellite points from the satellite ephemeris database. Based on the satellite ephemeris database, calculate the orbital position vectors of the three satellite points in the geocentric-geo-fixed coordinate system. The user's position vector in the geocentric coordinate system is Then the three observation vectors when the user observes three satellites The calculation formula is: The three angular distances corresponding to the observed vector are calculated as follows: Step 223: Based on the angular distance values ​​of the three stars in the starlight image, examine the differences between these values ​​and the three angular distance values ​​calculated based on the satellite ephemeris database, and set a threshold for the examination. If the following test criteria are met: The three star points in the starlight image are the actual measured values ​​of three satellite star points in the satellite ephemeris database.

6. The method for detecting low-orbit satellite orbit changes based on starlight background according to claim 1, characterized in that, This method also includes a method for merging satellite ephemeris databases and star databases: The satellite ephemeris database and the star point database are merged into a new starlight database. The merged starlight database includes two types of data: satellite ephemeris and star positions. It is continuously updated as the satellite ephemeris changes. The merged starlight database includes satellite or star number, time, and angular distance information.

7. A low-Earth orbit satellite orbit change detection system based on starlight background, characterized in that, include: Memory, used to store executable computer programs; The processor, when executing an executable computer program stored in the memory, implements the low-orbit satellite orbit change detection method based on starlight background as described in any one of claims 1 to 6.

8. The low-orbit satellite orbit change detection system based on starlight background according to claim 7, characterized in that, The system includes: The star sensor module is used to acquire star images by measuring star points. The satellite and star point recognition module is used to acquire star databases and satellite ephemeris databases. In the coordinate system, it uses a triangulation matching algorithm to calculate the correspondence between each star point in the star point image and the star database and satellite ephemeris database, and identifies star points and satellite star points. The orbit change detection module is used to calculate the satellite's spatial motion position based on the identified star points as a reference, the satellite star points' motion trajectory in the star point image and the historical ephemeris in the satellite ephemeris database, and compare it with the spatial motion position predicted based on the historical ephemeris to determine whether a satellite orbit change has occurred.

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