Radar satellite imaging segmental arc on-orbit calculation method and system for moving target

Abstract

The invention provides a moving target-oriented radar satellite imaging segmental arc on-orbit calculation method and system. The method comprises the following steps of: determining an initial parameter, a task period length and a radar antenna imaging mode of a moving target; obtaining orbit determination data of the satellite in the task period; calculating a three-axis attitude angle of the satellite at each time point in the task cycle; calculating a position vector of the moving target at each time point; calculating an included angle between the satellite-ground vector at each time point and the X axis of the satellite body system; a one-dimensional search algorithm is used for calculating the top passing moment in the task cycle; calculating a radar antenna lower visual angle corresponding to the satellite-ground vector at the overhead moment; and carrying out constraint check, and calculating a radar starting-up arc section. According to the method, high-precision orbit data on a satellite bus are directly used for calculation, complex orbit recursion is avoided, the imaging opportunity of a moving target can be calculated autonomously, meanwhile, the method has the advantages of being small in calculation amount and short in calculation time, and satellite deployment can be achieved.

Description

Technical Field

[0001] The present invention relates to the field of satellite observation technology, and in particular to an on-orbit calculation method and system for radar satellite imaging arc segments for moving targets. Background Art

[0002] With the development of the marine economy and the advancement of radar satellite technology, radar satellites are required to have strong imaging autonomous mission planning capabilities for moving targets at sea to meet the increasingly urgent needs of space-based support for ships at sea.

[0003] When planning a radar satellite's imaging mission for a ground target, the first step is to determine the imaging arc. When calculating the radar satellite's imaging arc while in orbit, the satellite must precisely calculate the target's overhang time, taking into account constraints such as the radar antenna's downward viewing angle and the duration of the satellite's attitude maneuvers. Traditional radar satellite imaging missions require ground-based mission planning, which then generates a mission package and sends it to the satellite for execution. This approach suffers from poor timeliness and low mission execution efficiency.

[0004] To address the above issues, it is necessary to study an on-orbit calculation method for the imaging arc of a radar satellite for a moving target, so that the satellite can autonomously calculate the imaging arc of the moving target to improve the imaging efficiency.

[0005] The patent document "A Passive Positioning Method and System Based on Satellite Overpass Time Measurement" (CN115201803A) discloses a method for obtaining a range migration curve by pulse compressing radar signals in the range direction, and then using quadratic fitting to determine the satellite overpass time. This method requires data processing of the actual received radar signals to calculate the satellite overpass time, making it unsuitable for overpass time prediction or mission planning.

[0006] The patent document "A Method and Application for Calculating the Overpass Time of a Circular Orbit Satellite" (CN112849434A) discloses an iterative calculation method for determining the overpass time of a satellite based on parameters such as the longitude range covered by a satellite orbital cycle, the time when the satellite passes over the latitude of a ground target, and the number of orbital cycles required for the satellite to reach the ground target. However, this method only calculates the overpass time during each orbital ascent, lacking high-precision orbital data. This method has limited accuracy and is unsuitable for radar satellite imaging.

[0007] The patent document "A Fast and High-Precision Calculation Method for Satellite Earth Observation Overpass Moments" (CN114676580A) discloses a method for finding the minimum ground distance between a satellite's subsatellite point and a target, and the corresponding time. If a particular minimum is less than the equivalent width of the satellite's Earth observation, the corresponding time is the overpass moment. This method does not consider the field of view constraints of the satellite payload and requires complex orbit recursion, resulting in a high computational load. It is therefore unsuitable for onboard implementation of moving target imaging planning.

[0008] The patent document "A Method and System for Calculating and Tracking Station Overpasses and Predicting Overpasses" (CN115292405A) discloses a method for obtaining satellite ephemeris through orbit extrapolation, then calculating the maximum elevation angle within the forecast period using a search algorithm based on the golden section to determine the overpass time. This method determines overpasses based solely on elevation angle, resulting in certain calculation errors and failing to consider constraints such as the satellite payload's field of view. It is therefore unsuitable for onboard implementation on radar imaging satellites.

[0009] The patent document "A Method for Calculating Satellite Roll Angle and In-Orbit Mission Planning Method" (CN118820640A) discloses a method for calculating the time te corresponding to the maximum satellite elevation angle and the minimum distance ts from the ground target to the satellite, and then determining whether the two are equal. If they are equal, te is the satellite's overpass time, and the roll angle is calculated. This method also fails to consider the satellite payload's field of view constraints and target motion, making it unsuitable for predicting the overpass time of moving targets by radar satellites. Summary of the Invention

[0010] In view of the defects in the prior art, the purpose of the present invention is to provide an on-orbit calculation method and system for radar satellite imaging arc segments for moving targets.

[0011] According to the present invention, an on-orbit calculation method for radar satellite imaging arc segments for moving targets includes:

[0012] Step S1: Determine the initial parameters of the moving target, the mission cycle length, and the radar antenna imaging mode;

[0013] Step S2: Obtaining the satellite's orbit determination data during the mission period;

[0014] Step S3: Calculate the satellite's three-axis attitude angles at each time point during the mission cycle;

[0015] Step S4: Calculate the position vector of the moving target at each time point;

[0016] Step S5: Calculate the angle between the satellite-to-ground vector and the X-axis of the satellite system at each time point;

[0017] Step S6: Calculate the over-the-top time within the mission cycle using a one-dimensional search algorithm;

[0018] Step S7: Calculate the radar antenna downward viewing angle corresponding to the satellite-to-ground vector at the moment of passing overhead;

[0019] Step S8: Perform constraint check and calculate the radar power-on arc.

[0020] Furthermore, in step S4, t i The target position vector R at this moment LiThe calculation formula is:

[0021] R Li =R L0 +(t i -t L0 )V L0

[0022] Where i = 1, 2, ..., t L0 Find the moment for the goal, R L0 is the target initial position vector, V L0 is the target initial velocity vector.

[0023] Furthermore, the step S5 includes:

[0024] Step S5.1: Calculate the satellite position vector at each time point in the WGS84 coordinate system;

[0025] Step S5.2: Calculate the satellite-to-ground vector at each time point in the WGS84 coordinate system. The satellite-to-ground vector is the vector pointing from the satellite to the moving target. In the WGS84 coordinate system, t i The star-to-ground vector P at this moment iECF The calculation formula is:

[0026] P iECF =R Li -R SECFi

[0027] Among them, R SECFi t i Satellite position vector in the WGS84 coordinate system at the moment, R Li t i The target position vector in the WGS84 coordinate system at the moment;

[0028] Step S5.3: Calculate the satellite-to-ground vector P at each time point in the satellite coordinate system ibody , t i The satellite-to-ground vector P in the satellite coordinate system at this moment ibody By P iECF After a series of coordinate transformations, the calculation formula is:

[0029] P ibody =M orb2body (M orb2ECI ) T M ECF2ECI P iECF

[0030] Where M orb2ECI is the transformation matrix from the satellite orbit coordinate system to the J2000.0 geocentric equatorial inertial coordinate system, M ECF2ECIis the transformation matrix from the WGS84 coordinate system to the J2000.0 geocentric equatorial inertial coordinate system, M orb2body The conversion matrix from the satellite orbit coordinate system to the satellite body coordinate system calculated according to the attitude conversion sequence "123" is calculated as follows:

[0031] V sECIi =Q i ·v pi

[0032] Y a =(V sECIi ×R sECIi )

[0033] X a =R sECIi ×Y a

[0034]

[0035] Where Q i t i The transformation matrix from the near-focus coordinate system to the J2000.0 geocentric equatorial inertial coordinate system at time v pi t i Satellite velocity vector in the near-focus coordinate system at time Y a is the reverse direction of the satellite's orbital angular momentum, R sECIi and V sECIi t i The satellite position vector and velocity vector in the geocentric equatorial inertial coordinate system at time J2000.0, X a R sECIi and Y a The cross product of i ,θ i and t i The satellite roll angle, pitch angle and yaw angle at the moment, β is the radar satellite side swing angle, R x (A) represents the rotation angle A around the X axis, R y (B) represents the rotation angle B around the Y axis, R Z (C) represents the rotation angle C around the Z axis;

[0036] Step S5.4: Calculate the angle between the satellite-to-ground vector and the X-axis of the satellite system at each time point, t i Time P ibody Angle γ with the X-axis of this system i The calculation formula is:

[0037] X b =[1,0,0] T

[0038]

[0039] Among them, X b is the X-axis vector of this system, and acos is the inverse trigonometric cosine function.

[0040] Furthermore, step S6 includes:

[0041] Step S6.1: For the first N-1 time points, after traversal search, it is found that there is γ at the kth time point k -90°<0 and γ k+1 When -90°>0, k=1, 2, 3, ...N-1, then the time interval [t k ,t k+1 ], step S6.2 is triggered; otherwise, there is no over-the-top moment in this mission cycle, the satellite has no imaging opportunity for the target, and the calculation ends;

[0042] Step S6.2: In the time interval [t k ,t k+1 ], use the one-dimensional search algorithm to calculate the time t corresponding to the angle between the satellite-ground vector and the X-axis of the satellite system equals 90° * For the over-the-top moment.

[0043] 5. The on-orbit calculation method for radar satellite imaging arc segments for moving targets according to claim 1, wherein step S7 comprises:

[0044] Step S7.1: Use the interpolation algorithm to calculate the satellite position vector in the WGS84 coordinate system at the time of passing

[0045] Step S7.2: Calculate the target position vector in the WGS84 coordinate system at the time of passing The calculation formula is:

[0046]

[0047] Among them, t * is the time of passing the top, t L0 Find the moment for the goal, R L0 is the target initial position vector, V L0 is the target initial velocity vector;

[0048] Step S7.3: Calculate t * Radar antenna downward viewing angle ξ corresponding to the satellite-to-ground vector at this moment * ,ξ * The calculation formula is

[0049]

[0050] In the formula is the satellite-to-ground vector in the WGS84 coordinate system at the moment of overpass, acos is the inverse trigonometric cosine function, P kbody (2) is t k The Y-axis component of the satellite-to-ground vector in the satellite's coordinate system at the moment;

[0051] When * When ≥0, it means the target is on the left side of the satellite, ξ * When <0, it means the target is on the right side of the satellite. When the satellite attitude is right-view attitude, if the target is on the right side, the satellite attitude is on the same side as the target, and the satellite can image without maneuvering; if the target is on the left side, the satellite attitude is on a different side from the target, and the satellite needs to perform attitude maneuvers before imaging.

[0052] Furthermore, the step S8 includes:

[0053] Step S8.1: Determine the time t when the top passes * , Star-Earth Vector and downward viewing angleξ * Whether the relevant constraints are met at the same time. If so, there is an imaging opportunity, triggering step S8.2; otherwise, there is no imaging opportunity, and the calculation ends;

[0054] Step S8.2: Calculate the imaging arc of the radar antenna based on the time of passing the top and the imaging duration. The imaging arc is calculated using [t on ,t off ] indicates that the calculation formula is

[0055]

[0056] Among them, t m The imaging time of this imaging mode.

[0057] Furthermore, the overhead time constraint is:

[0058]

[0059] Where, t att is the time length required for the satellite to maneuver the left and right side views. isMan indicates whether attitude maneuvering is required. If the current satellite attitude is on a different side from the target, isMan takes 1, otherwise isMan takes 0. The satellite attitude includes the left side view attitude and the right side view attitude.

[0060] Furthermore, the satellite-to-ground distance constraint is:

[0061]

[0062] Where asin is the inverse trigonometric sine function, R eis the equatorial radius of the Earth (6378137m), a k t k The major axis of the moment, ξ max is the maximum downward viewing angle of the radar antenna in this imaging mode.

[0063] Furthermore, the lower viewing angle constraint is:

[0064] |ξ * |∈[ξ min ,ξ max ]

[0065] Where, ξ min is the minimum downward viewing angle of the radar antenna in this imaging mode.

[0066] According to the present invention, an on-orbit calculation system for radar satellite imaging arc segments for moving targets is provided, comprising:

[0067] Module M1: Determine the initial parameters of the moving target, the mission cycle length and the radar antenna imaging mode;

[0068] Module M2: Acquires satellite orbit determination data during the mission cycle;

[0069] Module M3: Calculates the satellite's three-axis attitude angles at each time point during the mission cycle;

[0070] Module M4: Calculate the position vector of the moving target at each time point;

[0071] Module M5: Calculate the angle between the satellite-ground vector and the X-axis of the satellite system at each time point;

[0072] Module M6: Calculate the time of passing the top within the mission cycle using a one-dimensional search algorithm;

[0073] Module M7: Calculate the radar antenna downward viewing angle corresponding to the satellite-to-ground vector at the moment of overpass;

[0074] Module M8: Perform constraint checks and calculate radar power-on arcs.

[0075] Compared with the prior art, the present invention has the following beneficial effects:

[0076] The present invention provides an on-orbit calculation method for radar satellite imaging arcs for moving targets, suitable for solving the problem of autonomous on-orbit calculation of radar satellite imaging arcs for moving targets. This method first acquires equally spaced orbital data within a mission cycle via the satellite bus. It then estimates the target's trajectory and calculates the angle between the satellite-to-ground vector pointing to the target and the X-axis of the satellite itself within the mission cycle. Using a one-dimensional search algorithm, the moment when the angle reaches 90° is the overpass time. Finally, the imageable arc is determined by comprehensively considering constraints such as the satellite-to-ground distance, the radar satellite payload's field of view, the payload mode operating time, and the duration of the attitude maneuver. This method can estimate the trajectory of moving targets and meet the needs of imaging moving targets. Furthermore, it utilizes high-precision orbital data from the satellite bus for calculations, avoiding complex orbital recursion. A one-dimensional search algorithm is used to obtain the overpass time within a relatively short mission cycle. Non-imaging opportunities are eliminated based on the satellite-to-ground distance, payload field of view, and time constraints, reducing unnecessary calculations. The method has the advantages of low algorithm complexity, high computational accuracy, low computational effort, and short computation time, making it more convenient for onboard software implementation.

[0077] The present invention directly uses high-precision orbit data on the satellite bus for calculation, avoiding complex orbit recursion, and taking into account constraints such as the radar satellite payload field of view, payload working mode and attitude maneuvering duration. It can independently calculate the imaging timing of moving targets and has the advantages of small calculation amount and short calculation time. It can be deployed on the satellite and solves many defects of the existing technology from the aspect of engineering implementation. BRIEF DESCRIPTION OF THE DRAWINGS

[0078] Other features, objects and advantages of the present invention will become more apparent upon reading the detailed description of non-limiting embodiments with reference to the following drawings:

[0079] Figure 1 It is the workflow diagram of the present invention. DETAILED DESCRIPTION

[0080] The present invention will be described in detail below with reference to specific embodiments. The following examples will help those skilled in the art to further understand the present invention, but are not intended to limit the present invention in any form. It should be noted that, for those skilled in the art, several changes and improvements can be made without departing from the scope of the present invention. These all fall within the scope of protection of the present invention.

[0081] like Figure 1 As shown, the present invention provides an on-orbit calculation method for radar satellite imaging arc segments for moving targets, comprising:

[0082] Step S1: Determine the initial parameters of the moving target, the mission cycle length, and the radar antenna imaging mode. These initial parameters include the target discovery time, the initial three-axis position, and the initial velocity in the WGS84 coordinate system. The mission cycle for this calculation is [t0, t0 + Δt]. Here, t0 is the onboard time at the start of the calculation, and Δt is the mission cycle length. To minimize onboard orbit extrapolation errors and improve calculation accuracy, Δt is required to be no longer than 60 minutes.

[0083] Step S2: Acquire orbit determination data for the satellite during the mission cycle. Continuously read satellite orbit determination data from the satellite bus at regular intervals, after an extrapolation time of Δt. This avoids complex orbit extrapolation. To improve calculation accuracy, a reading interval of 1 second is required. Once orbit data for N time points over a period of Δt has been accumulated, subsequent imaging arc calculations can be performed.

[0084] The satellite bus is the main path for transmitting data between different satellite subsystem devices. The orbit determination data is the satellite orbit elements in the J2000.0 geocentric equatorial inertial coordinate system, namely the semi-major axis, eccentricity, orbit inclination, right ascension of the ascending node, argument of perigee and true anomaly.

[0085] Step S3: Calculate the satellite's three-axis attitude angle at each time point during the mission cycle. The satellite's three-axis attitude angle includes roll angle, pitch angle, and yaw angle. In order to compensate for the effect of the Earth's rotation on the radar payload imaging, the radar satellite's attitude needs to be two-dimensionally guided and controlled. Under the two-dimensional guidance law, t i The calculation formula of the satellite three-axis attitude angle at time (i=1, 2, ..., N) is:

[0086]

[0087] Where, θ i and ψ i t i Roll angle, pitch angle and yaw angle at the moment; a i 、e i 、i i 、w i and f i t i The semi-major axis, eccentricity, inclination, argument of perigee and true anomaly of the satellite orbit at this moment; ω e is the angular velocity of the Earth's rotation; μ is the gravitational constant.

[0088] Step S4: Calculate the position vector of the moving target at each time point. i Target position vector R at time (i=1, 2, ..., N) Li The calculation formula is

[0089] R Li =R L0 +(t i -t L0 )V L0

[0090] Where, t L0 Find the moment for the goal, R L0 is the target initial position vector, V L0 is the target initial velocity vector.

[0091] Step S5: Calculate the angle between the satellite-ground vector and the X-axis of the satellite system at each time point. The specific steps include steps S5.1 to S5.3.

[0092] Step S5.1: Calculate the satellite position vector at each time point in the WGS84 coordinate system. i Satellite position vector R in the WGS84 coordinate system at time (i=1, 2, ..., N) SECFi The calculation formula is

[0093]

[0094] Q i =(R Z (Ω i )) T (R X (i i )) T (R Z (w i )) T

[0095] R sECIi =Q i ·r pi

[0096] R SECFi =(M ECF2ECI ) T R sECIi

[0097] Where, Ω i t i R is the right ascension of the satellite's ascending node at the moment; sECIi t i Satellite position vector in the geocentric equatorial inertial coordinate system at time J2000.0; M ECF2ECI t i The transformation matrix from the WGS84 coordinate system to the J2000.0 geocentric equatorial inertial coordinate system at the moment. The calculation method can be found in the relevant literature.

[0098] Step S5.2: Calculate the satellite-to-ground vector at each time point in the WGS84 coordinate system. The satellite-to-ground vector is the vector that the satellite points to the moving target. In the WGS84 coordinate system, t i The star-to-ground vector P at time (i=1, 2, ..., N) iECF The calculation formula is

[0099] P iECF =R Li -R SECFi

[0100] R SECFi t i Satellite position vector in the WGS84 coordinate system at the moment, R Li t i The target position vector in the WGS84 coordinate system at the moment.

[0101] Step S5.3: Calculate the satellite-to-ground vector P at each time point in the satellite coordinate system ibody . t i P at time (i=1, 2, ..., N) ibody By P iECF After a series of coordinate transformations, the calculation formula is:

[0102] P ibody =M orb2body (M orb2ECI ) T M ECF2ECI P iECF

[0103] Where M orb2ECI is the transformation matrix from the satellite orbit coordinate system to the J2000.0 geocentric equatorial inertial coordinate system; M ECF2ECI is the transformation matrix from the WGS84 coordinate system to the J2000.0 geocentric equatorial inertial coordinate system, M orb2body is the transformation matrix from the satellite orbit coordinate system to the satellite body coordinate system calculated according to the attitude transformation sequence "123". The calculation formula is

[0104] V sECIi =Q i ·v pi

[0105] Y a =(V sECIi ×R sECIi )

[0106] X a =R sECIi ×Y a

[0107]

[0108]

[0109] Where Q i t i The transformation matrix from the near-focus coordinate system to the J2000.0 geocentric equatorial inertial coordinate system at time v pi t i Satellite velocity vector in the near-focus coordinate system at time Y a is the reverse direction of the satellite's orbital angular momentum, R sECIi and V sECIi t i The satellite position vector and velocity vector in the geocentric equatorial inertial coordinate system at time J2000.0, X a R sECIi and Y a The cross product of i ,θ i and t i The satellite roll angle, pitch angle and yaw angle at the moment, β is the radar satellite side swing angle; R x (A) represents the rotation angle A around the X axis, R y (B) represents the rotation angle B around the Y axis, R Z (C) represents the rotation angle C around the Z axis.

[0110] Step S5.4: Calculate the angle between the satellite-ground vector and the X-axis of the satellite system at each time point. i Time P ibody Angle γ with the X-axis of this system i The calculation formula is

[0111] X b =[1,0,0] T

[0112]

[0113] X b is the X-axis vector of this system, and acos is the inverse trigonometric cosine function.

[0114] Step S6: Calculate the overpass time within the mission cycle using a one-dimensional search algorithm. When the angle between the satellite-ground vector and the X-axis of the satellite system at a certain moment is equal to 90°, the moment is the overpass time t * The specific steps include steps S6.1 to S6.2:

[0115] Step S6.1: For the first N-1 time points, after traversal search, it is found that the k-th time point (k = 1, 2, 3, ... N-1) has γ k -90°<0 and γ k+1When -90°>0, the time interval [t k ,t k+1 ] If there is an over-the-top moment within the mission cycle, step S6.2 is triggered; otherwise, there is no over-the-top moment within this mission cycle, the satellite has no imaging opportunity for the target, and the calculation ends.

[0116] Step S6.2: In the time interval [t k ,t k+1 ], use the one-dimensional search algorithm to calculate the time t corresponding to the angle between the satellite-ground vector and the X-axis of the satellite system equals 90° * , t * The one-dimensional search algorithm uses a binary method, which has been widely described in relevant public literature.

[0117] Step S7: Calculate the radar antenna downward viewing angle corresponding to the satellite-to-ground vector at the time of passing overhead. The specific steps include steps S7.1 to S7.3:

[0118] Step S7.1: Use the interpolation algorithm to calculate the satellite position vector in the WGS84 coordinate system at the time of passing The interpolation algorithm uses cubic spline interpolation, which has been widely described in relevant public literature.

[0119] Step S7.2: Calculate the target position vector in the WGS84 coordinate system at the time of passing The calculation formula is

[0120]

[0121] Step S7.3: Calculate t * Radar antenna downward viewing angle ξ corresponding to the satellite-to-ground vector at this moment * ξ * The calculation formula is

[0122]

[0123] Where, is the star-to-ground vector at the moment of passing the top, P kbody (2) is t k The Y-axis component of the satellite-to-ground vector in the satellite coordinate system at that moment; * When ≥0, it means the target is on the left side of the satellite, ξ * When <0, it means the target is on the right side of the satellite. When the satellite attitude is right-facing, if the target is on the right side, the satellite attitude and the target are on the same side, and the satellite can image without maneuvering; if the target is on the left side, the satellite attitude and the target are on different sides, and the satellite needs to perform attitude maneuvers before imaging.

[0124] Step S8: Perform constraint checks and calculate the radar power-on arc. Based on the overhead time constraints, the satellite-to-ground distance constraints, and the downward viewing angle constraints, determine whether imaging is possible and calculate the radar power-on arc. This includes steps S8.1 through S8.2.

[0125] Step S8.1: Determine the time t when the top passes * , distance between the star and the earth and downward viewing angleξ * Are the relevant constraints satisfied at the same time? If so, there is an imaging opportunity, triggering step S8.2; otherwise, there is no imaging opportunity, and the calculation ends.

[0126] The overhead moment constraint is:

[0127]

[0128] Where, t att The length of time required for the satellite to maneuver left and right; t m is the imaging duration for this imaging mode; isMan indicates whether attitude maneuvers are required. If the current satellite attitude is on a different side from the target, isMan is 1; otherwise, isMan is 0. The satellite attitude includes the left-view attitude and the right-view attitude.

[0129] The satellite-to-ground distance constraint is

[0130]

[0131] Where asin is the inverse trigonometric sine function, R e is the equatorial radius of the Earth (6378137m), a k t k The major axis of the moment, ξ max is the maximum downward viewing angle of the radar antenna in this imaging mode.

[0132] The lower viewing angle constraint is

[0133] |ξ * |∈[ξ min ,ξ max ]

[0134] Where, ξ min The minimum downward viewing angle of the radar antenna in this imaging mode.

[0135] Step S8.2: Calculate the imaging arc of the radar antenna based on the time of passing the top and the imaging duration. The imaging arc is calculated using [t on ,t off ] indicates that the calculation formula is

[0136]

[0137] Aiming at the problem of radar satellite imaging of moving targets, the present invention proposes an on-orbit calculation method for radar satellite imaging arc segments for moving targets. The method uses high-precision orbit data on the satellite bus for calculation. Based on the estimation of the trajectory of the moving target, the method comprehensively considers constraints such as the radar satellite payload field of view, payload operating mode, and attitude maneuver duration, and performs on-orbit calculation of the imaging timing of the moving target.

[0138] The present invention also provides an on-orbit calculation system for radar satellite imaging arc segments for moving targets. The on-orbit calculation system for radar satellite imaging arc segments for moving targets can be implemented by executing the process steps of the on-orbit calculation method for radar satellite imaging arc segments for moving targets. That is, those skilled in the art can understand the on-orbit calculation method for radar satellite imaging arc segments for moving targets as a preferred embodiment of the on-orbit calculation system for radar satellite imaging arc segments for moving targets. The system includes:

[0139] Module M1: Determine the initial parameters of the moving target, mission cycle length and radar antenna imaging mode.

[0140] Module M2: Obtain the satellite's orbit determination data during the mission cycle.

[0141] Module M3: Calculates the satellite's three-axis attitude angles at each time point during the mission cycle.

[0142] Module M4: Calculate the position vector of the moving target at each time point.

[0143] Module M5: Calculate the angle between the satellite-ground vector and the X-axis of the satellite system at each time point.

[0144] Module M6: Calculate the time of passing the top within the mission cycle using a one-dimensional search algorithm.

[0145] Module M7: Calculate the downward viewing angle of the radar antenna corresponding to the satellite-to-ground vector at the moment of overpass.

[0146] Module M8: Perform constraint checks and calculate radar power-on arcs.

[0147] Those skilled in the art will appreciate that, in addition to implementing the system and its various devices, modules, and units provided by the present invention in purely computer-readable program code, it is entirely possible to implement the same functions of the system and its various devices, modules, and units provided by the present invention in the form of logic gates, switches, application-specific integrated circuits, programmable logic controllers, and embedded microcontrollers by logically programming the method steps. Therefore, the system and its various devices, modules, and units provided by the present invention can be considered a hardware component, and the devices, modules, and units included therein for implementing various functions can also be considered as structures within the hardware component; the devices, modules, and units for implementing various functions can also be considered as both software modules implementing the method and structures within the hardware component.

[0148] The above describes specific embodiments of the present invention. It should be understood that the present invention is not limited to the specific embodiments described above, and those skilled in the art may make various changes or modifications within the scope of the claims, which do not affect the essence of the present invention. The embodiments of this application and the features in the embodiments may be combined with each other in any manner unless there is a conflict.

Claims

1. An on-orbit calculation method for radar satellite imaging arc segments for moving targets, characterized in that: include: Step S1: Determine the initial parameters of the moving target, the mission cycle length, and the radar antenna imaging mode; Step S2: Obtaining the satellite's orbit determination data during the mission period; Step S3: Calculate the satellite's three-axis attitude angles at each time point during the mission cycle; Step S4: Calculate the position vector of the moving target at each time point; Step S5: Calculate the angle between the satellite-to-ground vector and the X-axis of the satellite system at each time point; Step S6: Calculate the over-the-top time within the mission cycle using a one-dimensional search algorithm; Step S7: Calculate the radar antenna downward viewing angle corresponding to the satellite-to-ground vector at the moment of passing overhead; Step S8: Perform constraint check and calculate the radar power-on arc.

2. The on-orbit calculation method for radar satellite imaging arc segments for moving targets according to claim 1, characterized in that: In step S4, t i The target position vector R at this moment Li The calculation formula is: R Li =R L0 +(t i -t L0 )V L0 Where i = 1, 2, ..., t L0 Find the moment for the goal, R L0 is the target initial position vector, V L0 is the target initial velocity vector.

3. The on-orbit calculation method for radar satellite imaging arc segments for moving targets according to claim 1, characterized in that: The step S5 comprises: Step S5.1: Calculate the satellite position vector at each time point in the WGS84 coordinate system; Step S5.2: Calculate the satellite-to-ground vector at each time point in the WGS84 coordinate system. The satellite-to-ground vector is the vector pointing from the satellite to the moving target. In the WGS84 coordinate system, t i The star-to-ground vector P at this moment iECF The calculation formula is: P iECF =R Li -R SECFi Among them, R SECFi t i Satellite position vector in the WGS84 coordinate system at the moment, R Li t i The target position vector in the WGS84 coordinate system at the moment; Step S5.3: Calculate the satellite-to-ground vector P at each time point in the satellite coordinate system ibody , t i The satellite-to-ground vector P in the satellite coordinate system at this moment ibody By P iECF After a series of coordinate transformations, the calculation formula is: P ibody =M orb2body (M orb2ECI ) T M ECF2ECI P iECF Where M orb2ECI is the transformation matrix from the satellite orbit coordinate system to the J2000.0 geocentric equatorial inertial coordinate system, M ECF2ECI is the transformation matrix from the WGS84 coordinate system to the J2000.0 geocentric equatorial inertial coordinate system, M orb2body is the transformation matrix from the satellite orbit coordinate system to the satellite body coordinate system calculated according to the attitude transformation sequence "123". The calculation formula is: V sECIi =Q i ·v pi Y a =(V sECIi ×R sECIi ) X a =R sECIi ×Y a Where Q i t i The transformation matrix from the near-focus coordinate system to the J2000.0 geocentric equatorial inertial coordinate system at time v pi t i Satellite velocity vector in the near-focus coordinate system at time, Y a is the reverse direction of the satellite's orbital angular momentum, R sECIi and V sECIi t i The satellite position vector and velocity vector in the geocentric equatorial inertial coordinate system at time J2000.0, X a R sECIi and Y a The cross product of i ,θ i and t i The satellite roll angle, pitch angle and yaw angle at the moment, β is the radar satellite side swing angle, R x (A) represents the rotation angle A around the X axis, R y (B) represents the rotation angle B around the Y axis, R Z (C) represents the rotation angle C around the Z axis; Step S5.4: Calculate the angle between the satellite-to-ground vector and the X-axis of the satellite system at each time point, t i Time P ibody Angle γ with the X-axis of this system i The calculation formula is: X b ＝[1,0,0] T Among them, X b is the X-axis vector of this system, and acos is the inverse trigonometric cosine function.

4. The on-orbit calculation method for radar satellite imaging arc segments for moving targets according to claim 1, characterized in that: The step S6 comprises: Step S6.1: For the first N-1 time points, after traversal search, it is found that there is γ at the kth time point k -90°<0 and γ k+1 When -90°>0, k=1, 2, 3, ...N-1, then the time interval [t k ,t k+1 ], step S6.2 is triggered; otherwise, there is no over-the-top moment in this mission cycle, the satellite has no imaging opportunity for the target, and the calculation ends; Step S6.2: In the time interval [t k ,t k+1 ], use the one-dimensional search algorithm to calculate the time t corresponding to the angle between the satellite-ground vector and the X-axis of the satellite system equals 90° * For the over the top moment.

5. The on-orbit calculation method for radar satellite imaging arc segments for moving targets according to claim 1, characterized in that: The step S7 comprises: Step S7.1: Use the interpolation algorithm to calculate the satellite position vector in the WGS84 coordinate system at the time of passing Step S7.2: Calculate the target position vector in the WGS84 coordinate system at the time of passing The calculation formula is: Among them, t * is the time of passing the top, t L0 Find the moment for the goal, R L0 is the target initial position vector, V L0 is the target initial velocity vector; Step S7.3: Calculate t * Radar antenna downward viewing angle ξ corresponding to the satellite-to-ground vector at this moment * ,ξ * The calculation formula is In the formula is the satellite-to-ground vector in the WGS84 coordinate system at the moment of overpass, acos is the inverse trigonometric cosine function, P kbody (2) is t k The Y-axis component of the satellite-to-ground vector in the satellite's coordinate system at the moment; When * When ≥0, it means the target is on the left side of the satellite, ξ * When <0, it means the target is on the right side of the satellite. When the satellite attitude is right-view attitude, if the target is on the right side, the satellite attitude is on the same side as the target, and the satellite can image without maneuvering; if the target is on the left side, the satellite attitude is on a different side from the target, and the satellite needs to perform attitude maneuvers before imaging.

6. The on-orbit calculation method for radar satellite imaging arc segments for moving targets according to claim 1, characterized in that: The step S8 comprises: Step S8.1: Determine the time t when the top passes * , Star-Earth Vector and downward viewing angleξ * Whether the relevant constraints are met at the same time. If so, there is an imaging opportunity, triggering step S8.2; otherwise, there is no imaging opportunity, and the calculation ends; Step S8.2: Calculate the imaging arc of the radar antenna based on the time of passing the top and the imaging duration. The imaging arc is calculated using [t on ,t off ] indicates that the calculation formula is Among them, t m The imaging time of this imaging mode.

7. The on-orbit calculation method for radar satellite imaging arc segments for moving targets according to claim 6, characterized in that: The overhead moment constraint is: Where, t att is the time required for the satellite to maneuver the left and right side views. isMan indicates whether attitude maneuvering is required. If the current satellite attitude is on a different side from the target, isMan takes 1, otherwise isMan takes 0. The satellite attitude includes the left side view attitude and the right side view attitude.

8. The on-orbit calculation method for radar satellite imaging arc segments for moving targets according to claim 7, characterized in that: The satellite-to-ground distance constraint is: Where asin is the inverse trigonometric sine function, R e is the equatorial radius of the Earth (6378137m), a k t k The major axis of the moment, ξ max is the maximum downward viewing angle of the radar antenna in this imaging mode.

9. The on-orbit calculation method for radar satellite imaging arc segments for moving targets according to claim 8, characterized in that: The following viewing constraints are: |x * |∈[ξ min ,x max ] Where, ξ min is the minimum downward viewing angle of the radar antenna in this imaging mode.

10. An on-orbit calculation system for radar satellite imaging arc segments for moving targets, characterized in that: include: Module M1: Determine the initial parameters of the moving target, the mission cycle length and the radar antenna imaging mode; Module M2: Acquires satellite orbit determination data during the mission cycle; Module M3: Calculates the satellite's three-axis attitude angles at each time point during the mission cycle; Module M4: Calculate the position vector of the moving target at each time point; Module M5: Calculate the angle between the satellite-ground vector and the X-axis of the satellite system at each time point; Module M6: Calculate the time of passing the top within the mission cycle using a one-dimensional search algorithm; Module M7: Calculate the radar antenna downward viewing angle corresponding to the satellite-to-ground vector at the moment of overpass; Module M8: Perform constraint checks and calculate radar power-on arcs.

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