Low earth orbit satellite orbital transfer detection method and system based on fixed star starlight background

Abstract

The invention discloses a fixed star starlight background-based low-orbit satellite orbital transfer detection method and system, and the method comprises the steps: defining coordinate systems which comprise an earth-centered earth-fixed coordinate system, a celestial sphere inertial coordinate system and a star sensor coordinate system; a star point image, a fixed star database and a satellite ephemeris database are obtained through measurement of a starlight sensor, in a coordinate system, the corresponding relation between each star point in the star point image and the fixed star database and the corresponding relation between each star point and the satellite ephemeris database are calculated through a triangular matching algorithm, and fixed star points and satellite star points are recognized; and by taking the identified fixed star point as a reference basis, according to the movement track of the satellite star point in the star point image and the historical ephemeris in the satellite ephemeris database, carrying out inversion calculation on a satellite space movement position, comparing the satellite space movement position with a space movement position predicted based on the historical ephemeris, and judging whether satellite orbital transfer occurs or not. According to the invention, the detection cost is low, the detection task is convenient to execute, and the detection method has strong autonomy and anti-interference performance.

Description

Technical Field

[0001] The present invention relates to the field of low-orbit satellite orbit change detection, and in particular to a low-orbit satellite orbit change detection method and system based on stellar starlight background. Background Art

[0002] Existing low-orbit satellites operating in near-Earth space are often required to perform temporary orbit maneuvers due to missions such as space debris collision avoidance, new satellite launches, and Earth reconnaissance and observation. When the ephemeris of these low-orbit satellites obtained by ground users is not updated in a timely manner due to environmental influences, this can hinder ground users from completing measurement, communication, or surveillance tasks. Existing satellite orbit change detection is primarily achieved through the detection of ephemeris data broadcast by the orbit-changing satellite and ground-based surveillance radar. However, this can lead to erroneous detection in environments with deceptive satellite ephemeris or the need to rely on radar infrastructure, making it unable to meet the needs of convenient detection applications.

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

[0004] The technical problem to be solved by the present invention is to provide a low-orbit satellite orbit change detection method and system based on stellar starlight background in response to the defects in the existing technology.

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

[0006] The present invention provides a method for detecting low-orbit satellite orbit changes based on starlight background, the method comprising the following steps:

[0007] Step 1: Define the coordinate system, including the Earth-centered Earth-fixed coordinate system, the celestial inertial coordinate system, and the star sensor coordinate system;

[0008] Step 2: Obtain star point images through starlight sensor measurement, obtain star database and satellite ephemeris database, and calculate the correspondence between each star point in the star point image and the star database and satellite ephemeris database in the coordinate system through triangulation matching algorithm to identify star points and satellite points;

[0009] Step 3: Based on the identified star points, the satellite's spatial motion position is inverted and calculated according to the motion trajectory of the satellite star point in the star point image and the historical ephemeris in the satellite ephemeris database. The calculated position is then compared with the spatial motion position predicted based on the historical ephemeris to determine whether the satellite has changed its orbit.

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

[0011] Earth-centered, Earth-fixed coordinate system: denoted by ECEF, with the center of the Earth as the reference origin, the x-axis pointing to the intersection of the Greenwich zero longitude and zero latitude lines on the equatorial plane, the z-axis pointing to the Earth's rotation axis, and the y-axis 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 center of the Earth as the reference origin, the z-axis parallel to the Earth's rotation axis pointing to the North Pole, also known as the celestial axis, the x-axis pointing to the vernal equinox, and the y-axis 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 starlight 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 of 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. A triangulation matching algorithm is used to determine the star point image measured by the current starlight sensor and the star point corresponding to the right ascension and declination in the star database.

[0016] Step 22: Satellite star point identification: Use the triangulation matching algorithm to determine the satellite star point image measured by the current starlight sensor and the right ascension and declination corresponding to the satellite star point 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, whose coordinates relative to the image center are (x1, y1), (x2, y2), and (x3, y3). The angular distances of the star points in the star sensor coordinate system are The calculation formula is:

[0019]

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

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

[0022]

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

[0024]

[0025] Step 213: Based on the angular distance values ​​of the three star points in the starlight image, the difference between the angular distance values ​​calculated based on the star database is checked. A test threshold ε is given. If the following test criteria are met:

[0026]

[0027] The three star points in the starlight image are the actual measured values ​​of the 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, whose coordinates relative to the image center are (x1, y1), (x2, y2), and (x3, y3). The angular distances of the star points in the star sensor coordinate system are The calculation formula is:

[0030]

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

[0032] Step 222: Select three satellite star points from the satellite ephemeris database. The orbital position vectors P1, P2, and P3 of the three satellite star points in the Earth-centered Earth-fixed coordinate system can be calculated based on the satellite ephemeris database. The user's position vector in the Earth-centered Earth-fixed coordinate system is P. The three observation vectors v1, v2, and v3 when the user observes the three satellites are calculated as follows:

[0033] v1=P-P1

[0034] v2=P-P2

[0035] v3=P-P3

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

[0037]

[0038] Step 223: Based on the three star point angular distance values ​​in the starlight image, check the difference between the three angular distance values ​​calculated based on the satellite ephemeris database. A test threshold ε is given. If the following test criteria are met:

[0039]

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

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

[0042] Assume that at time k, a satellite star point and multiple star points that have been successfully identified are found from the starlight image. The coordinates of the satellite star point image are (x1, y1), and the position vector of the satellite in the Earth-centered Earth-fixed coordinate system is P k , where the image coordinates of a star point are (x s ,y s ), the coordinate transformation matrix determined by the star point is i is the celestial inertial coordinate system, b is the image coordinate system, and the matrix between i and the Earth-centered Earth-fixed coordinate system is express;

[0043] At the k+1th moment, the satellite position vector P is obtained based on the satellite orbit prediction. k+1 , the satellite star point image coordinates are (x2, y2). Since the star point coordinates in the image are basically unchanged in the short term, the star coordinates are used as a sign that the image does not need to be re-matched. This ensures that after a successful matching of the satellite star point, it will move in the image for a period of time to avoid the inability to identify the orbit-changing satellite when re-matching. Calculate the position increment vector ΔP of the satellite star point in the carrier system at time k and time k+1. b ;

[0044] The position increment vector is converted to the Earth-centered Earth-fixed coordinate system, the satellite orbit position is calculated based on the star point image, and the position change threshold during orbit change is set. Whether the satellite orbit change occurs is determined based on the satellite orbit position, the satellite predicted position vector and the position change threshold.

[0045] Furthermore, the specific calculation method for determining satellite orbit change of the present invention is:

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

[0047]

[0048] Among them, R s is the satellite orbit height, f is the focal length of the starlight sensor, and the position increment vector is converted to the Earth-centered Earth-fixed coordinate system:

[0049]

[0050] The satellite orbital position calculated based on the star point image is:

[0051]

[0052] Set the position change threshold ΔP when changing track based on experience c , if:

[0053]

[0054] It is determined that the satellite has undergone orbit change maneuver.

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

[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 position data. It is continuously updated as the satellite ephemeris changes. The merged starlight database includes satellite or star star number, time and angular distance information.

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

[0058] a memory for storing executable computer programs;

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

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

[0061] Starlight sensor module, used to obtain star point images through starlight sensor measurement,

[0062] The satellite and star point identification module is used to obtain the star database and satellite ephemeris database, calculate the correspondence between each star point in the star point image and the star database and satellite ephemeris database in the coordinate system through the triangulation matching algorithm, and identify the star points and satellite points;

[0063] The orbit change detection module is used to inversely calculate the satellite's spatial motion position based on the identified star points and the motion trajectory of the satellite star points 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 the satellite has changed its orbit.

[0064] The beneficial effects produced by the present 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 image through a triangulation matching algorithm. Using the star points as reference angles, it calculates the position change of the low-orbit satellite star points. This is compared with the predicted low-orbit satellite position to determine whether the satellite is currently performing an orbit change. This method can accurately complete the task of detecting low-orbit satellite orbit changes using ground-based optical observations.

[0066] 2. The present invention utilizes a small starlight measurement sensor and a low-orbit satellite ephemeris receiving module to complete the low-orbit satellite orbit change detection task, with low detection cost and convenient detection task execution.

[0067] 3. In the method of the present invention, since stars are not disturbed by human activities, the use of starlight as a stable reference light source and optical active observation can realize track change detection under strong electromagnetic interference. The detection method has strong autonomy and anti-interference ability. BRIEF DESCRIPTION OF THE DRAWINGS

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

[0069] Figure 1 Schematic diagram of the celestial inertial coordinate system according to an embodiment of the present invention. DETAILED DESCRIPTION

[0070] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present 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 only used to explain the present invention and are not intended to limit the present invention.

[0071] Example 1

[0072] An embodiment of the present invention provides a method for detecting low-orbit satellite orbit changes based on a stellar background, including coordinate system definition, satellite and stellar point identification, and orbit change detection calculations. The coordinate system definition clarifies the mathematical and physical meanings of the calculation variables involved in low-orbit satellite orbit change detection. Satellite and stellar point identification provides a mapping relationship between information measured by starlight sensors and information in a starlight database, providing reference starlight information for orbit change detection. The orbit change detection calculations provide a method for detecting orbit changes.

[0073] (1) Coordinate system definition

[0074] The present invention relates to a method for detecting low-orbit satellite orbit changes based on the background of stellar starlight. The coordinate systems involved in the calculation include the Earth-centered Earth-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] Earth-centered, Earth-fixed coordinate system: denoted by ECEF, with the center of the Earth as the reference origin, the x-axis points to the intersection of the Greenwich 0 longitude and 0 latitude lines 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: represented by i, with the center of the earth as the reference origin, the z-axis parallel to the earth's rotation axis pointing to the North Pole, also known as the celestial axis, the x-axis pointing to the vernal equinox, and the y-axis perpendicular to the plane formed by the x-axis and the z-axis, forming a right-handed rectangular coordinate system.

[0077] Star sensor coordinate system: denoted by m, with the center of the starlight 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 is the starlight coordinate expressed in the celestial coordinate system, S is a defined star point, and its coordinates are expressed in right ascension α s , declination δ s express.

[0079] (2) Satellite and star point identification

[0080] The star point image obtained by the starlight sensor measurement includes both stellar star points and satellite star points. It is necessary to further calculate the correspondence between each star point in the image and the star database and satellite ephemeris database to confirm that each star point in the image is a real measured star point rather than a false star point. The star point recognition process is as follows:

[0081] 1) Stellar point identification

[0082] The star database stores the right ascension and declination coordinates of stars that can be used at any time. The star point image measured by the current starlight sensor corresponds to the right ascension and declination of stars in the star database. The angular distance matching needs to be performed using a triangulation matching algorithm to complete star point identification. The specific process is as follows:

[0083] ① Select three star points in the image measured by the starlight sensor

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

[0085]

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

[0087] ②Select three star points in the star database

[0088] Assume that in the star database, the right ascension and declination coordinates of the three star points 1, 2, and 3 are (α1, δ1), (α2, δ2), and (α3, δ3), and the angular distance d between star points 1 and 2 is 12 , the angular distance d between star points 1 and 3 13 , the angular distance d between star points 2 and 3 23 , which can be calculated by the following formula:

[0089]

[0090] Among them, s1, s2, and s3 are the direction vectors of stars 1, 2, and 3, respectively, which can be expressed by the star right ascension and declination as follows:

[0091]

[0092] ③Angular distance matching

[0093] According to the angular distance values ​​of the three star points in the starlight image, the difference between the three angular distance values ​​calculated based on the star database is tested. Given a test threshold ε, if the following test criteria are met:

[0094]

[0095] Then 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 star point identification

[0097] ① Select three star points in the image measured by the starlight sensor

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

[0099]

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

[0101] ②Select three star points in the satellite ephemeris database

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

[0103] v1=P-P1

[0104] v2=P-P2

[0105] v3=P-P3

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

[0107]

[0108] ③Angular distance matching

[0109] According to the angular distance values ​​of the three star points in the starlight image, the difference between the three angular distance values ​​calculated based on the satellite ephemeris database is checked. Given a test threshold ε, if the following test criteria are met:

[0110]

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

[0112] (3) Track change detection calculation

[0113] When the satellite ephemeris does not reflect the orbit change maneuver in a timely manner, it is impossible to directly identify the satellite through angular distance matching. It is necessary to base it on star identification. According to the satellite's motion trajectory in the starlight image and the historical ephemeris, the satellite's spatial motion position is inverted. By comparing it with the spatial motion position predicted based on the historical ephemeris, it is possible to identify whether the satellite has changed its orbit.

[0114] Assume that at time k, a satellite star point and multiple star points that have been successfully identified are found from the starlight image. The coordinates of the satellite star point image are (x1, y1), and the position vector of the satellite in the ECEF system is P k , where the image coordinates of a star point are (x s ,y s ), the coordinate transformation matrix determined by the star point is i is the celestial inertial system, b is the image coordinate system, and the transformation matrix between i and ECEF is express.

[0115] At the k+1th moment, the satellite position vector P is obtained based on the satellite orbit prediction. k+1 , the satellite star point image coordinates are (x2, y2). Since the star point coordinates in the image are basically unchanged in the short term, the star coordinates are used as a sign that the image does not need to be re-matched. This ensures that after a successful match, the satellite star point will move in the image for a period of time, avoiding the problem of unrecognizable satellites with changed orbits during re-matching. Calculate the position increment vector ΔP of the satellite star point in the carrier system at time k and time k+1 b for:

[0116]

[0117] Where R s is the satellite orbit height, and f is the focal length of the starlight sensor. Converting the above position increment vector to the ECEF system yields:

[0118]

[0119] The satellite orbital position calculated based on the star point image is:

[0120]

[0121] Set the position change threshold ΔP when changing track based on experience c , if:

[0122]

[0123] It is determined that the satellite has undergone orbit change maneuver.

[0124] Example 2

[0125] An embodiment of the present invention provides a low-orbit satellite orbit change detection method based on stellar starlight background, which consists of implementation conditions and an implementation process.

[0126] (1) Implementation conditions

[0127] The system is equipped with a starlight sensor module for measuring starlight and low-orbit satellites. The starlight sensor has a field of view of at least 30° to enable observation of a larger number of low-orbit satellites. It also includes a starlight database for a certain number of stars to calculate their theoretical positions in the celestial inertial system. It also includes a low-orbit satellite ephemeris information receiver module for receiving and forecasting low-orbit satellite ephemeris.

[0128] (2) Implementation process

[0129] The implementation process includes three steps: real-time shooting of starlight images, 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 a field of view of at least 30°, enabling it to observe more satellite and starlight simultaneously. The starlight sensor captures and extracts satellite and starlight from images in real time, sending the extracted starlight in array form to the satellite and star point recognition module for calculation.

[0132] Step 2: Satellite and Star Identification

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

[0134] The star point information captured by the starlight sensor at the same time cannot distinguish between stellar star points and satellite star points. Therefore, for any three star points selected in the starlight image, some are stellar star points and some are satellite star points. If the star database and the satellite ephemeris database are matched separately during the angular distance matching process, it will bring a huge amount of calculation, and the calculation efficiency and matching success rate will be low. Therefore, the first task of star point recognition is to establish a unified reference star point database. The satellite ephemeris database and the stellar star point database need to be merged into a new starlight database. The merged database includes two types of data: satellite ephemeris and star position, and is continuously updated as the satellite ephemeris changes. The merged database only contains satellite or star star number, time and angular distance information. The calculation of angular distance of star information in the original star database and the calculation of angular distance of satellite information in the original satellite ephemeris database are as follows:

[0135] ①Calculation of angular distance of star information in the protostellar database

[0136] Assume that the right ascension and declination coordinates of the three star points 1, 2, and 3 are (α1, δ1), (α2, δ2), and (α3, δ3), and the angular distance d between the star points 1 and 2 is 12 , the angular distance d between star points 1 and 3 13 , the angular distance d between star points 2 and 3 23 , which can be calculated by the following formula:

[0137]

[0138] Among them, s1, s2, and s3 are the direction vectors of stars 1, 2, and 3, respectively, which can be expressed by the star right ascension and declination as follows:

[0139]

[0140] ②Calculation of satellite information angular distance in the original satellite ephemeris database

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

[0142] v1=P-P1

[0143] v2=P-P2

[0144] v3=P-P3

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

[0146]

[0147] 2) Select three star points in the image measured by the starlight sensor

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

[0149]

[0150] Among them, 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 star points from the merged starlight database

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

[0153] 4) Angular distance matching

[0154] According to the angular distance values ​​of the three star points in the starlight image, the difference between the three angular distance values ​​calculated based on the star database is tested. Given a test threshold ε, if the following test criteria are met:

[0155]

[0156] Then 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] Assume that at time k, a satellite star point and multiple star points that have been successfully identified are found from the starlight image. The coordinates of the satellite star point image are (x1, y1), and the position vector of the satellite in the ECEF system is P k , where the image coordinates of a star point are (x s ,y s ), the coordinate transformation matrix determined by the star point is i is the celestial inertial system, b is the image coordinate system, and the transformation matrix between i and ECEF is express.

[0159] At the k+1th moment, the satellite position vector P is obtained based on the satellite orbit prediction. k+1, the satellite star point image coordinates are (x2, y2). Since the star point coordinates in the image are basically unchanged in the short term, the star coordinates are used as a sign that the image does not need to be re-matched. This ensures that after a successful match, the satellite star point will move in the image for a period of time, avoiding the problem of unrecognizable satellites with changed orbits during re-matching. Calculate the position increment vector ΔP of the satellite star point in the carrier system at time k and time k+1 b for:

[0160]

[0161] Where R s is the satellite orbit height, and f is the focal length of the starlight sensor. Converting the above position increment vector to the ECEF system yields:

[0162]

[0163] The satellite orbital position calculated based on the star point image is:

[0164]

[0165] Set the position change threshold ΔP when changing track based on experience c , if:

[0166]

[0167] It is determined that the satellite has undergone orbit change maneuver.

[0168] It should be understood that the size of the serial numbers of the steps in the above embodiments does not mean 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 changes based on the above description, and all such improvements and changes should fall within the scope of protection of the appended claims of the present invention.

Claims

1. A method for detecting orbit change of low-orbit satellite based on starlight background, characterized in that: The method comprises the following steps: Step 1: Define the coordinate system, including the Earth-centered Earth-fixed coordinate system, the celestial inertial coordinate system, and the star sensor coordinate system; Step 2: Obtain star point images through starlight sensor measurement, obtain star database and satellite ephemeris database, calculate the corresponding relationship between each star point in the star point image and the star database and satellite ephemeris database in the coordinate system through triangulation matching algorithm, and identify star points and satellite points; Step 3: Using the identified star points as a reference, inversely calculate the satellite's space motion position based on the motion trajectory of the satellite star point in the star point image and the historical ephemeris in the satellite ephemeris database, and compare it with the space motion position predicted based on the historical ephemeris to determine whether the satellite has changed its orbit.

2. The method for detecting orbit change of low-orbit satellite based on starlight background according to claim 1, characterized in that: The method for defining the coordinate system in step 1 specifically includes: Earth-centered Earth-fixed coordinate system: denoted by ECEF, with the center of the earth 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 the z-axis, forming a right-handed rectangular coordinate system; Celestial inertial coordinate system: denoted by i, with the center of the earth as the reference origin, the z-axis parallel to the earth's rotation axis pointing to the North Pole, also known as the celestial axis, the x-axis pointing to the vernal equinox, and the y-axis perpendicular to the plane formed by the x-axis and the z-axis, forming a right-handed rectangular coordinate system; Star sensor coordinate system: denoted by m, with the center of the starlight 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, x-axis and z-axis forming a right-handed coordinate system.

3. The method for detecting orbit change of low-orbit satellite based on starlight background according to claim 1, characterized in that: The method of 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 star point image measured by the current starlight sensor is judged by the triangular matching algorithm with the star point corresponding to the right ascension and declination in the star database; Step 22: Satellite star point identification: Use the triangulation matching algorithm to determine the satellite star point corresponding to the right ascension and declination in the satellite ephemeris database and the star point image measured by the current starlight sensor.

4. The method for detecting orbit change of low-orbit satellite based on starlight background according to claim 3 is characterized in that: The method of step 21 specifically includes: Step 211: In the star point image, select any three star points, whose coordinates relative to the image center are (x1, y1), (x2, y2), and (x3, y3), respectively. The angular distances of the star points in the star sensor coordinate system are The calculation formula is: Among them, m1, m2, and m3 are the direction vectors of the three star points in the star sensor coordinate system; Step 212: Select three star points in the star database. The right ascension and declination coordinates of the three star points are (α1, δ1), (α2, δ2), and (α3, δ3). The angular distance d between the first star point and the second star point is 12 , the angular distance d between the first and third star points 13 , the angular distance d between the second and third star points 23 , the calculation formula is: Among them, s1, s2, and s3 are the direction vectors of three star points, respectively, and are expressed using star right ascension and declination as follows: Step 213: According to the angular distance values ​​of the three star points in the starlight image, the difference between the angular distance values ​​calculated based on the star database is checked, and a test threshold ε is given. If the following test criteria are met: Then the three star points in the starlight image are the actual measured values ​​of the three star points in the star database.

5. The method for detecting orbit change of low-orbit satellite based on starlight background according to claim 3, characterized in that: The specific method of step 22 includes: Step 221: In the star point image, select any three star points, whose coordinates relative to the image center are (x1, y1), (x2, y2), and (x3, y3), respectively. The angular distances of the star points in the star sensor coordinate system are The calculation formula is: Among them, m1, m2, and m3 are the direction vectors of the three star points in the star sensor coordinate system; Step 222: Select three satellite star points in the satellite ephemeris database. The orbital position vectors P1, P2, and P3 of the three satellite star points in the geocentric earth-fixed coordinate system can be calculated according to the satellite ephemeris database. The position vector of the user in the geocentric earth-fixed coordinate system is P. Then, the calculation formulas for the three observation vectors v1, v2, and v3 when the user observes the three satellites are: v1=P-P1 v2=P-P2 v3=P-P3 The three angular distances corresponding to the observation vector are calculated as: Step 223: According to the three star point angular distance values ​​in the starlight image, the difference between the three angular distance values ​​calculated based on the satellite ephemeris database is checked, and a test threshold ε is given. If the following test criteria are met: Then the three star points in the starlight image are the actual measured values ​​of the three satellite star points in the satellite ephemeris database.

6. The method for detecting orbit change of low-orbit satellite based on starlight background according to claim 1, characterized in that: The method of step 3 specifically includes: Assume that at the kth moment, a satellite star point and multiple star star points that have been successfully identified are found from the starlight image. The coordinates of the satellite star point image are (x1, y1), and the position vector of the satellite in the Earth-centered Earth-fixed coordinate system is P k , where the image coordinates of a star point are (x s ,y s ), the coordinate transformation matrix determined by the star point is i is the celestial inertial coordinate system, b is the image coordinate system, and the matrix of i system and earth-centered earth-fixed coordinate system is used express; At the k+1th moment, the satellite predicted position vector P is obtained according to the satellite orbit prediction. k+1 , the satellite star point image coordinates are (x2, y2). Since the star point coordinates in the image are basically unchanged in the short term, the star coordinates are used as a sign that the image does not need to be re-matched. This ensures that after a successful match, the satellite star point will move in the image for a period of time to avoid the re-matching of the orbit-changing satellite that cannot be identified; calculate the position increment vector ΔP of the satellite star point in the carrier system at time k and time k+1 b ; The position increment vector is converted to the Earth-centered Earth-fixed coordinate system, the satellite orbit position is calculated based on the star point image, and the position change threshold when changing orbit is set. It is determined whether the satellite orbit change occurs based on the satellite orbit position, the satellite predicted position vector and the position change threshold.

7. The method for detecting orbit change of low-orbit satellite based on starlight background according to claim 6, characterized in that: The specific calculation method for determining satellite orbit change is: Calculate the position increment vector ΔP of the satellite point in the carrier system at time k and time k+1 b for: Among them, R s is the satellite orbit height, f is the focal length of the starlight sensor, and the position increment vector is converted to the Earth-centered Earth-fixed coordinate system: The satellite orbital position calculated from the star point image is: Set the position change threshold ΔP when changing track based on experience c , if it satisfies: It is determined that the satellite has undergone orbit change maneuver.

8. The method for detecting orbit change of low-orbit satellite based on starlight background according to claim 1, characterized in that: The method also includes a method for merging the satellite ephemeris database and the star database: 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 position data, and is continuously updated as the satellite ephemeris changes. The merged starlight database includes satellite or star sign, time and angular distance information.

9. A low-orbit satellite orbit change detection system based on starlight background, characterized in that: include: a memory for storing executable computer programs; A processor, used to implement the low-orbit satellite orbit change detection method based on stellar starlight background as described in any one of claims 1 to 8 when executing an executable computer program stored in a memory.

10. The low-orbit satellite orbit change detection system based on starlight background according to claim 9, characterized in that: The system includes: The starlight sensor module is used to obtain star point images through starlight sensor measurement. The satellite and star point recognition module is used to obtain the star database and the satellite ephemeris database, and calculate the corresponding relationship between each star point in the star point image and the star database and the satellite ephemeris database in the coordinate system through the triangular matching algorithm to identify the star points and satellite points; The orbit change detection module is used to inversely calculate the satellite's space motion position based on the identified star points as a reference, according to the motion trajectory of the satellite star points in the star point image and the historical ephemeris in the satellite ephemeris database, and compare it with the space motion position predicted based on the historical ephemeris to determine whether the satellite has changed its orbit.

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