A method for controlling remote sensing satellite imaging tasks while recording and releasing them in motion

Abstract

The present invention proposes a remote sensing satellite imaging-while-recording-and-releasing task control method, firstly checks the necessity and feasibility of the imaging-while-recording-and-releasing task, then adopts a segmented planning method to design the attitude trajectory of the imaging-while-recording-and-releasing process in order to ensure that no large angular velocity attitude changes occur during the task, and on this basis controls the payload subsystem, attitude control subsystem and data transmission subsystem to jointly complete the imaging-while-recording-and-releasing task in the motion. The present invention achieves the control of the satellite attitude by allocating task time periods and using a polynomial control method, that is, it ensures that the satellite is aligned with the target imaging area, and that the data transmission antenna is aligned with the ground station, thereby achieving the stability of the data transmission link.

Description

Technical Field

[0001] The invention relates to a satellite attitude control method, in particular to a remote sensing satellite in-motion imaging while recording and releasing task control method. Background Art

[0002] Imaging remote sensing satellites (if not otherwise specified in the present invention, imaging remote sensing satellites are referred to as remote sensing satellites) are an important means of global observation. A satellite imaging or a ground data transmission can be called a mission. In the actual operation process, the ground station first uploads the task to be performed to the remote sensing satellite. When the satellite flies over the target or the ground station, it completes the corresponding imaging or ground data transmission action according to the time information in the mission. In some special cases, the satellite is visible to the ground target and the ground station at the same time. At this time, the satellite needs to implement ground data transmission during the imaging process. This type of task is called a recording and releasing task.

[0003] When traditional remote sensing satellites are imaging, the satellite attitude remains unchanged, and the payload relies on the movement of the satellite relative to the earth to achieve push-broom imaging. Therefore, when performing a recording and release mission, the satellite only needs to maneuver to the imaging attitude in advance, and then perform payload imaging and data transmission to the ground respectively.

[0004] With the continuous development of new remote sensing technologies, the imaging-in-motion mode has been adopted by more and more remote sensing satellites. In this mode, the satellite body and the data transmission antenna jointly change their attitude to complete the recording-and-releasing task. However, the satellite changes according to specific motion laws during the imaging process, which will bring difficulties to the control of the recording-and-releasing task, mainly including the following aspects:

[0005] If the angular velocity of the attitude is too large during the imaging process, it may exceed the rotation capacity of the data transmission antenna, resulting in failure of data transmission to the ground;

[0006] Since the satellite attitude changes continuously during imaging, the traditional control method of maintaining a fixed attitude is no longer suitable for the task of recording and releasing while imaging in motion;

[0007] The duration of imaging in motion generally does not exceed 1 minute, while the data transmission arc is as long as 7 to 10 minutes. If the attitude motion law during the imaging period is extended to the entire data transmission arc, it is easy to cause attitude motion divergence, endangering the safety of the entire satellite.

[0008] Therefore, it is necessary to adopt a special control method for the imaging-in-motion-recording-and-releasing mission, so that the satellite will not undergo large angular velocity attitude changes during the entire imaging-in-motion-recording-and-releasing mission, thereby ensuring the effective execution of imaging-in-motion and data transmission to the ground. Summary of the invention

[0009] In view of this, the present invention proposes a control method for remote sensing satellite imaging-recording-and-releasing tasks for imaging-in-motion. The present invention first checks the necessity and feasibility of the imaging-recording-and-releasing tasks, and then uses a segmented planning method to design the satellite's attitude trajectory during the imaging-recording-and-releasing process, so as to achieve a smooth change in the satellite's attitude, thereby providing a good foundation for the attitude change of the data transmission antenna, and finally completing the imaging-recording-and-releasing tasks.

[0010] Specifically include the following:

[0011] Step 1: According to the start and end time of the imaging in motion and the attitude requirement, the start and end time of the data transmission arc segment, the load startup and shutdown time, the data transmission startup and shutdown time, and the maximum rotation angular velocity of the data transmission antenna, it is determined whether to execute the imaging in motion while recording and releasing task. If not, the method ends. Otherwise, the imaging in motion while recording and releasing task is executed and the process goes to step 2.

[0012] Step 2: Divide the task of recording and releasing while imaging in motion into five different stages, namely, the pre-imaging holding stage, the pre-imaging setting stage, the imaging in motion stage, the post-imaging setting stage, and the post-imaging holding stage, and set different posture trajectories for each stage;

[0013] Step three: Calculate the command start time of the imaging-in-motion while recording and releasing mission based on the start time of the mission, the satellite data transmission startup time, the payload startup time, the maximum satellite attitude maneuver time and other parameters, and plan the satellite's attitude trajectory from the command start time to the mission start time.

[0014] Step 4: Design the action sequence of the three subsystems, namely attitude control, data transmission, and payload, according to the moments and attitude trajectories obtained in steps 2 and 3.

[0015] Step five, the subsystem action sequence obtained in step four is injected into the satellite in the form of instructions. The satellite integrated electronic subsystem controls the data transmission, attitude control, and payload subsystems at the specified time to jointly complete the imaging-in-motion and recording-and-releasing task.

[0016] Beneficial effects:

[0017] 1) It breaks through the limitation that the satellite must maintain a fixed attitude during data transmission. By setting the attitude holding segment and the preset segment before and after the in-motion imaging, the satellite's attitude can change smoothly during the entire data transmission arc, thereby enabling the satellite to achieve data transmission to the ground during the attitude movement process of in-motion imaging, which can enhance the satellite's ability to cope with complex on-orbit tasks and improve application efficiency.

[0018] 2) The present invention proposes a method for calculating the pre-preset attitude and the post-preset attitude based on the attitude at the start and end times of in-motion imaging. The calculation of the pre-preset attitude and the post-preset attitude takes into account the angle, angular velocity, and angular acceleration of the satellite's in-motion imaging, so that the satellite's attitude does not change drastically in the two stages of pre-imaging and post-imaging, which makes it easy to implement the satellite attitude control system.

[0019] 3) The present invention has no restrictions on the relative time relationship between the data transmission arc segment and the imaging period in motion, and can be applied to various situations where the data transmission arc segment and the imaging period in motion overlap with each other;

[0020] 4) The control method described in the present invention realizes the coordination among subsystems such as payload, data transmission and control by performing timing control through an integrated electronic subsystem, without increasing the functions of each subsystem on the satellite, thus achieving flexible implementation and wide application range. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 It is a schematic diagram of the process of the present invention.

[0022] Figure 2 This is a schematic diagram of the phase division and posture trajectory of the imaging-while-recording-while-releasing task. DETAILED DESCRIPTION

[0023] To facilitate the description of the implementation steps of the present invention, the following parameters are first defined. These parameters are obtained from satellite imaging requirements, ground stations or satellite design solutions and are inputs of the present invention:

[0024] ·Record the start and end time of imaging in motion as T img_start , T img_end , obtained from satellite orbit, target position, and imaging requirements;

[0025] ·The imaging posture trajectory requirement in motion is a set of discrete points in the form of Where n+1 is the number of discrete points, θ i ,ω i ,a i Represents T i The attitude angle, angular velocity vector, and angular acceleration vector required for satellite imaging at all times;

[0026] The start and end time of the data transmission arc segment is T trans_start , T trans_end , which are uniformly allocated by the ground station;

[0027] The maximum angular velocity of the data transmission antenna is w trans_max , the load startup time is t pl_on , the load shutdown time is t pl_off , the time taken for digital transmission startup is t trans_on , the time taken for the digital transmission to shut down is ttrans_off The startup time here refers to the time it takes for the satellite device to receive the startup command and be ready to execute the action. The shutdown time refers to the time it takes for the satellite device to receive the shutdown command and be shut down and ready to receive subsequent commands. Both are determined by the satellite design plan.

[0028] The maximum time required for the satellite to switch between any two possible attitudes is t man .

[0029] Based on the above input parameters, the specific implementation steps of the present invention are:

[0030] Step 1: Determine whether to execute the task of recording and releasing the imaging in motion based on the start and end time of imaging in motion and the attitude requirement, the start and end time of the data transmission arc, the time taken to start and shut down the payload, the time taken to start and shut down the data transmission, and the maximum rotation angular velocity of the data transmission antenna. If the interval between the imaging in motion period and the data transmission arc is long, or the attitude angular velocity required for imaging in motion is too large, the imaging in motion and the ground data transmission should not be merged into one imaging in motion task of recording and releasing. Otherwise, the imaging in motion task of recording and releasing should be executed, and the process goes to step 2.

[0031] The specific judgment method is as follows:

[0032] Case 1: If the start and end times of the imaging in motion and the start and end times of the data transmission arc are separated by a sufficiently long period of time, that is, the relationship shown in equation (1) or equation (2) is satisfied, then the imaging and data transmission can be scheduled as two independent tasks, and there is no need to schedule the imaging in motion task while recording and releasing the task.

[0033] T trans_start -T img_end >t pl_off +t trans_on (1)

[0034] T img_end -T trans_start >t trans_off +t pl_on (2)

[0035] Case 2: If the satellite attitude maneuvering angular velocity during in-motion imaging is greater than 0.5 times the maximum rotation angular velocity of the data transmission antenna, there is a risk that the data transmission antenna will be unable to track the ground station.

[0036] If at least one of the above two situations is satisfied, it indicates that the imaging in motion and ground data transmission tasks should not be combined into one imaging in motion recording and releasing task, and this method ends; otherwise, proceed to step 2.

[0037] Step 2: Calculate the start and end times of the imaging-in-motion task based on the start and end times of the imaging-in-motion and data transmission arc segments; divide the time period from the start time to the end time of the task into five different stages, namely, hold before imaging, preset before imaging, imaging-in-motion, preset after imaging, and hold after imaging; and set different attitude trajectories for each stage, wherein the satellite maintains a fixed attitude in the hold before imaging and hold after imaging stages, and adopts a polynomial attitude trajectory in the preset before imaging and preset after imaging stages. The satellite attitude trajectory in the imaging-in-motion stage is consistent with the attitude trajectory requirements for imaging-in-motion.

[0038] The specific implementation process is as follows: First, calculate the task start time T mission_start 、Task end time T mission_end :

[0039] T mission_start =min(T img_start -t pre ,T trans_start )

[0040] T mission_end =max(T img_end +t pre ,T trans_end )

[0041] where t pre It is a preset duration, which is a fixed value of 10s in the present invention.

[0042] Then the period [T mission_start ,T mission_end ] is divided into the following five stages to achieve satellite attitude smoothing and create conditions for data transmission by the data transmission antenna:

[0043] Phase 1: Pre-imaging holding phase, the corresponding time is [T mission_start , T img_start -t pre ]. During this phase, the satellite will maintain a fixed pre-set attitude angle, with both attitude angular velocity and angular acceleration being 0, where the pre-set attitude angle is set to:

[0044]

[0045] In the above formula, θ pre is the preset attitude angle, θ0, ω0, a0 are the imaging start time T img_start The satellite attitude angle, angular velocity vector, and angular acceleration vector can be obtained from the attitude requirements of imaging in motion.

[0046] Phase 2: Pre-imaging pre-setting phase, the corresponding time is (T img_start -t pre , Timg_start ]. At this stage, the satellite will be set to the previously preset attitude angle θ pre Start the maneuver gradually and start imaging at time T img_start The attitude angle θ0, angular velocity ω0, and angular acceleration a0 required for satellite imaging in motion are achieved. The attitude motion trajectory is represented by a polynomial curve, which can achieve smooth changes in attitude angular velocity and angular acceleration. Among them, the polynomial curve represents the trajectory planning using a polynomial-based satellite attitude maneuvering method, which is an existing technology.

[0047] Stage 3: In-motion imaging stage, the corresponding time is (T img_start , T img_end ]. During this phase, the satellite will strictly track the attitude trajectory required for satellite imaging in motion.

[0048] Phase 4: Preset phase after imaging, the corresponding time is (T img_end , T img_end +t pre ]. In this phase, the satellite will start moving from the attitude at the end of imaging and at time T img_end +t pre The post-preset attitude angle is reached, and the satellite angular velocity and angular acceleration both reach 0. The attitude motion trajectory is represented by a polynomial curve, which can achieve a smooth change of the attitude angular velocity and angular acceleration. Among them, the polynomial curve represents a satellite attitude maneuvering method based on polynomials for trajectory planning, which is a prior art. The post-preset attitude angle is set to:

[0049]

[0050] In the above formula, θ aft is the post-preset attitude angle, θ n ,ω n 、a n are respectively the imaging end time T img_end The satellite attitude angle, angular velocity vector, and angular acceleration vector can be obtained from the attitude requirements of imaging in motion.

[0051] Stage 5: Post-imaging holding stage, the corresponding time is (T img_end +t pre , T mission_end ]. During this phase, the satellite will maintain a fixed post-preset attitude angle θ aft The angular velocity and acceleration of the attitude are both 0.

[0052] Step 3: Calculate the command start time of the imaging-in-motion recording and releasing mission (hereinafter referred to as "command start time") based on the start time of the imaging-in-motion recording and releasing mission, the satellite data transmission startup time, the payload startup time, the maximum satellite attitude maneuver time and other parameters, and plan the satellite's attitude trajectory from the command start time to the mission start time. The specific implementation process is as follows:

[0053] First, calculate the instruction start time T com :

[0054] T com =T mission_start -t max

[0055] t max =max{t man ,t trans_on ,t pl_on}

[0056] Among them, T mission_start ,t man ,t trans_on ,t pl_on The definitions are consistent with those in the previous text.

[0057] Then plan the satellite's attitude trajectory from the command start time to the mission start time. com , the satellite attitude is in the initial state, and the satellite attitude angle, angular velocity, and angular acceleration at this moment are θ com ,ω com 、a com ; At the start time of the task T mission_start , the satellite should maneuver to the preset attitude θ pre , and the angular velocity and angular acceleration reach 0. The present invention uses a fifth-order polynomial curve to represent the posture trajectory of this stage, which can achieve a smooth change of the posture angular velocity and angular acceleration, which is a prior art.

[0058] Step 4: Design the action sequence of the three subsystems of attitude control, data transmission, and payload according to the moments and attitude trajectories obtained in steps 2 and 3. The attitude control subsystem is used to complete the attitude pointing control of the satellite body, meet the ground target pointing attitude and maneuvering requirements of the payload camera or radar during the mission, and meet the requirements of attitude charging to the sun during non-mission periods; the data transmission subsystem is a high-speed communication channel for satellite payload data to be transmitted to the ground receiving station; the payload is the specific unit of the satellite to perform on-orbit missions, such as optical cameras, radars and other specific equipment. The detailed action sequence is arranged as follows:

[0059] When the command is initiated, the data transmission subsystem and the payload subsystem are turned on, and the data transmission antenna begins to track the ground station;

[0060] When the command is started, the attitude control subsystem starts to move according to the attitude trajectory of step 2 and step 3. The complete attitude trajectory is as follows Figure 2 As shown, it includes 6 stages. Figure 2 In the process, stage 0 corresponds to the start time T from the instruction in step 3 com To the task start time T mission_start The period of time; Stages 1 to 5 correspond to the stages in step 2 one by one. Figure 2 The two curves in the figure respectively illustrate the changing trends of the satellite attitude angle and angular velocity at different stages.

[0061] At the start of imaging, the payload subsystem begins imaging;

[0062] At the end of imaging, the payload subsystem ends imaging and enters standby mode;

[0063] At the start of data transmission, the data transmission subsystem starts to transmit data to the ground;

[0064] At the end of the data transmission, the data transmission subsystem stops transmitting data to the ground, and the data transmission antenna no longer tracks the ground station;

[0065] At the end of the mission, the data transmission subsystem is shut down, the payload subsystem is shut down, and the attitude control subsystem enters the subsequent operation state.

[0066] Step five, the action sequence of each subsystem obtained in step four is injected into the satellite in the form of instructions, and stored in the satellite service computer of the satellite integrated electronic subsystem; the satellite service computer sends instructions to the data transmission, attitude control, and payload subsystems according to the command issuance time in the instructions, completes various actions such as attitude trajectory control, ground data transmission, and payload imaging, thereby realizing the task of recording and releasing imaging in motion.

Claims

1. A remote sensing satellite in-motion imaging and recording and releasing task control method, characterized in that: The following steps are included: Step 1: According to the start and end time of the imaging in motion and the attitude requirement, the start and end time of the data transmission arc segment, the load startup and shutdown time, the data transmission startup and shutdown time, and the maximum rotation angular velocity of the data transmission antenna, it is determined whether to execute the imaging in motion while recording and releasing task. If not, the method ends. Otherwise, the imaging in motion while recording and releasing task is executed and the process goes to step 2. Step 2: Divide the task of recording and releasing while imaging in motion into five different stages, namely, the pre-imaging holding stage, the pre-imaging setting stage, the imaging in motion stage, the post-imaging setting stage, and the post-imaging holding stage, and set different posture trajectories for each stage; Step 3: Calculate the command start time of the imaging-in-motion recording and releasing mission, and plan the attitude trajectory of the satellite from the command start time to the start time of the imaging-in-motion recording and releasing mission; Step 4: Design the action sequence of the three subsystems of attitude control, data transmission and payload for the stages obtained in steps 2 and 3; The attitude control subsystem is used to complete the attitude pointing control of the satellite body, and the data transmission subsystem is used to transmit the satellite payload data to the ground receiving station. The payload is the specific unit of the satellite to perform on-orbit tasks; Step 5: The action sequence of each subsystem obtained in step 4 is injected into the satellite in the form of instructions to realize the task of recording and releasing the imaging in motion; The pre-imaging hold phase is used to keep the satellite at a fixed pre-set attitude angle; The pre-imaging stage is used to gradually maneuver the satellite from the pre-set attitude angle and achieve the attitude angle, angular velocity and angular acceleration required for satellite imaging in motion at the beginning of imaging; The imaging-in-motion phase is used to make the satellite perform imaging attitude; The post-imaging preset phase is used to make the satellite start moving from the attitude at the end of imaging and reach the post-preset attitude angle; The post-imaging holding phase is used to keep the satellite fixed at the post-preset attitude angle; In the pre-imaging and post-imaging pre-imaging stages, the satellite adopts a polynomial attitude trajectory, and the satellite attitude trajectory in the in-motion imaging stage is consistent with the in-motion imaging attitude trajectory requirements; Remember and put the task start time T mission_start The calculation method is as follows: Get the starting time T of the data transmission arc segment in the recording and playing task trans_start ; Get the start time T of the imaging in motion during the task of recording and playing img_start , and calculate T img_start Forward preset time t pre After the time T img_start -t pre ; From time T trans_start and time T img_start -t pre Select an earlier time as the start time of the task of recording and playing at the same time; Task end time T mission_end The calculation method is as follows: Get the end time T of the data transmission arc segment in the recording and releasing task trans_end ; Get the end time T of the imaging in motion during the task of recording and playing img_end , and calculate T img_end Backward preset time t pre After the time T img_end +t pre ; From time T trans_end and time T img_end +t pre Select a later time as the end time of the task of recording and playing simultaneously; The time corresponding to the holding phase before imaging is [T mission_start , T img_start -t pre ], at this stage, the satellite will maintain a fixed pre-set attitude angle, with both attitude angular velocity and angular acceleration being 0, where the pre-set attitude angle is set to: In the above formula, θ pre is the preset attitude angle, θ0, ω0, a0 are the imaging start time T img_start Satellite attitude angle, angular velocity vector, angular acceleration vector; The time corresponding to the preset stage before imaging is (T img_start -t pre , T img_start ], at this stage, the satellite will be preset to the attitude θ pre Start the maneuver gradually and start imaging at time T img_start To achieve the attitude angle θ0, angular velocity ω0, and angular acceleration a0 required for satellite imaging in motion; The time corresponding to the imaging stage in motion is (T img_start , T img_end ], during which the satellite tracks the attitude trajectory required for satellite imaging in motion; The time corresponding to the preset stage after imaging is (T img_end , T img_end +t pre ], in this stage, the satellite starts to move from the attitude at the end of imaging and moves at time T img_end +t pre The post-preset attitude angle is reached, and the satellite angular velocity and angular acceleration both reach 0, where the post-preset attitude angle is set to: In the above formula, θ aft is the post-preset attitude angle, θ n ,ω n 、a n are respectively the imaging end time T img_end Satellite attitude angle, angular velocity vector, angular acceleration vector; The time corresponding to the post-imaging holding phase is (T img_end +t pre , T mission_end ], during this phase, the satellite will maintain a fixed post-preset attitude angle θ aft Unchanged, attitude angular velocity and angular acceleration are both 0; The instruction start time T in step 3 com The calculation method is: The time taken to start from digital transmission is t trans_on , the maximum time t required for the satellite to switch between any two possible attitudes man , and load startup time t pl_on Select the maximum value t max ; Remember and put the task start time T mission_start Forward max That is, the command start time T is obtained com ; Furthermore, for the phase obtained in step 3, the satellite starts from the command start time T com The attitude angle, angular velocity, and angular acceleration of the task start to move, and at the task start time T mission_start Reach the preset posture θ pre , at the same time, the angular velocity and angular acceleration reach 0, and a fifth-order polynomial curve is used to represent the posture trajectory of this stage.

2. The remote sensing satellite in-motion imaging and recording and releasing task control method according to claim 1, characterized in that: When the first or second condition is met, the imaging and recording task is not performed, where: Case 1: The interval between the imaging period in motion and the data transmission arc section is greater than the interval threshold; Case 2: The angular velocity of the posture required for imaging in motion is greater than the threshold.

3. The remote sensing satellite in-motion imaging and recording and releasing task control method according to claim 2, characterized in that: Situation 1 further includes: 1) When the imaging in motion comes first and the data transmission comes later, if the time interval between the start time of the data transmission arc segment and the end time of the imaging in motion is greater than the sum of the load shutdown time and the data transmission startup time, the imaging recording and releasing task will not be executed; 2) When the digital transmission is in front and the imaging in motion is in the back, if the time interval between the start time of the imaging in motion and the end time of the digital transmission arc is greater than the sum of the shutdown time of the digital transmission and the startup time of the load, the imaging recording and releasing task will not be executed; Case 2 further includes: if the satellite attitude maneuvering angular velocity during in-motion imaging is greater than 0.5 times the maximum rotation angular velocity of the data transmission antenna, there is a risk that the data transmission antenna will not be able to track the ground station and the imaging-while-recording-and-releasing task will not be performed.

4. The remote sensing satellite in-motion imaging and recording and releasing task control method according to claim 1, characterized in that: Step 4: The detailed action sequence is as follows: At the command start time, the data transmission subsystem and the payload subsystem are turned on, and the data transmission antenna begins to track the ground station; At the moment of command initiation, the attitude control subsystem starts to move according to the attitude trajectory of step 2 and step 3; At the start of imaging, the payload subsystem begins imaging; At the end of imaging, the payload subsystem ends imaging and enters standby mode; At the start of data transmission, the data transmission subsystem starts to transmit data to the ground; At the end of the data transmission, the data transmission subsystem stops transmitting data to the ground, and the data transmission antenna no longer tracks the ground station. At the end of the mission, the data transmission subsystem is shut down, the payload subsystem is shut down, and the attitude control subsystem enters the subsequent operation state.

Images