Drift angle compensation method for pitch maneuver of sweep imaging satellite

Abstract

The invention provides a drift angle compensation method for pitching maneuver of a swing-broom imaging satellite. The drift angle compensation method comprises the following steps: step 1, designing a track of swing-broom maneuver; 2, solving a drift angle according to an image motion speed model on a focal plane; 3, designing a pitching maneuvering compensation drift angle track; 4, determining an initial value of a drift angle compensation track parameter; and 5, adjusting drift angle compensation track parameters by using an iteration method. According to the method, main causes of the drift angle in load swing-scan imaging are analyzed, and the ground image motion speed caused by the satellite moving along an orbit is counteracted by utilizing the angular speed of a satellite platform in the pitching direction, so that compensation of the drift angle of the swing-scan imaging satellite is realized, and the imaging quality of the wide swing-scan imaging satellite is improved.

Description

Technical Field

[0001] The invention provides a drift angle compensation method realized by satellite body maneuvering for a wide-band sweep imaging satellite adopting a TDICCD optical payload, and belongs to the field of spacecraft attitude control. Background Art

[0002] With the progress of social economy and the evolution of modern combat strategies, people have an increasing demand for improving the coverage of high-resolution images and the ability to quickly perceive battlefields on a national or even global scale. It is particularly urgent to improve the imaging coverage width of optical remote sensing satellites. Traditional optical remote sensing satellites usually use push-broom imaging, and when the push-broom speed is fixed, there is a mutually restrictive relationship between the imaging coverage width and the resolution. In order to resolve the contradiction between the two, some scholars have proposed an imaging method that allows the camera to swing and scan along the vertical track direction, which greatly increases the width of ground imaging.

[0003] Swing-scan wide-band imaging satellites generally use a time-delay integration CDCD (TDICCD) camera as the imaging optical payload. According to the imaging principle of TDICCD, in theory, the image motion direction and magnitude of each image point on the focal plane must match the integral rotation direction and integration time of TDICCD. However, due to the influence of factors such as attitude maneuvers, orbital motion, and earth rotation during the swing-scan imaging process, the image of the ground target on the image plane will produce image motion, which greatly affects the imaging quality. The error in the image motion velocity direction is called the drift angle.

[0004] For general push-broom, staring and other imaging methods, there are two main ways to compensate for the drift angle: the first is the drift mechanism matching, that is, installing a focal plane drift mechanism on the satellite to match the drift angle. This method has high real-time performance, but the mechanical structure installed on the focal plane will reduce the reliability of the drift angle matching, and at the same time increase the total weight of the imaging satellite and improve the control requirements of the platform; the second is the attitude yaw matching method, which rotates the satellite platform around the yaw axis by a certain angle so that the integral direction of TDICCD is consistent with the image motion velocity direction, thereby achieving drift angle matching. This method has higher reliability, and with the continuous improvement of the attitude control accuracy and flexibility of agile imaging satellites, the attitude yaw drift angle matching method is gradually being adopted by more agile satellites.

[0005] However, due to the vertical orbit swing imaging method, the TDICCD installation direction is perpendicular to the orbit direction. During the optical payload swing imaging process, the image motion speed caused by the swing maneuver is along the integration direction of the TDICCD, and the ground image motion speed caused by the satellite motion along the orbit is perpendicular to the integration direction of the TDICCD. The ground image motion speed caused by the satellite motion along the orbit is the main factor causing the drift angle. The drift angle compensation problem in the swing imaging case cannot be solved by only the above-mentioned attitude yaw method. Summary of the invention

[0006] (I) Purpose of the invention

[0007] The purpose of the present invention is to solve the problem that the traditional attitude yaw method cannot achieve the compensation of the drift angle of the optical payload swing imaging method, and propose a method for achieving the drift angle compensation of the optical payload swing imaging satellite through the pitch attitude maneuver of the central platform. The method analyzes the main causes of the drift angle in the payload swing imaging, and uses the angular velocity of the satellite platform in the pitch direction to offset the ground image motion velocity caused by the satellite's orbital motion, thereby achieving compensation for the drift angle of the swing imaging satellite and improving the imaging quality of the wide-band swing imaging satellite.

[0008] (II) Technical solution

[0009] In order to achieve the above-mentioned purpose, the present invention first gives the angular velocity curve of the payload sweep imaging, and then calculates the curve of the drift angle changing with time under the sweep imaging mode through the image motion velocity model on the focal plane. According to the analysis results of the characteristics of the drift angle curve, combined with the given angular velocity curve of the optical payload sweep imaging, a satellite platform pitch maneuvering angular velocity curve is designed. When the optical payload scans the ground according to the sweep imaging angular velocity curve, the satellite platform can maneuver according to the designed pitch maneuvering angular velocity curve to achieve compensation for the drift angle.

[0010] The present invention relates to a method for compensating a drift angle of a sweep imaging satellite pitch maneuver, and the steps are as follows:

[0011] Step 1: Design the trajectory of the sweeping maneuver

[0012] The payload swing imaging satellite runs on a fixed orbit. By controlling the payload to swing along the orbital velocity, the TDICCD camera installed on it can scan the ground for imaging. The schematic diagram of the uniform speed phase of the scanning imaging is shown in the figure. Figure 1 As shown in the figure, the ground is imaged in the forward scanning phase, and no imaging is performed in the retracement phase. The angles of the forward swing and the retracement in one cycle are the same. The corresponding scanning angular velocity curve is shown in Figure 2 As shown, the angular velocity curve is divided into two parts: forward swing and reverse swing. The forward swing includes a forward acceleration stage, a uniform scanning stage (imaging stage), and a forward deceleration stage. The reverse swing stage is a continuous sine curve. The curve design process of the angular velocity trajectory is as follows:

[0013] The forward acceleration phase is a quarter-cycle sine curve, and the corresponding angular velocity is:

[0014]

[0015] Among them, t 0is the starting time of the payload scanning imaging mission, t is the current time, and f 1 is the sinusoidal angular frequency during the acceleration phase, α max is the maximum angular acceleration of the load in the sweeping trajectory.

[0016] The angular velocity during the uniform scanning phase is a constant, and the corresponding angular velocity is:

[0017] ω r2 =ω uni (2)

[0018] Among them, ω uni is the angular velocity of the uniform scanning stage, and the starting time of the uniform scanning stage is

[0019] The positive deceleration stage is a quarter-cycle sine curve symmetrical to the positive acceleration stage, and the corresponding angular velocity is:

[0020]

[0021] Among them, t 2 =t 1 +t uni is the start time of the forward acceleration phase, t uni is the duration of the uniform scanning phase, which is determined according to the specific imaging task. The amplitude and frequency of the forward deceleration phase and the forward acceleration phase are the same.

[0022] The reverse retrace stage is a sine function of one-half cycle, and the total angle rotated in the forward swing stage is equal to the total angle rotated in the reverse retrace stage. The corresponding angular velocity is:

[0023]

[0024] Among them, f 2 is the angular frequency of the reverse sweep phase, which is determined based on the fact that the forward swing and the reverse swing have the same rotation angle. is the start time of the reverse retrace phase, and the end time of the reverse retrace phase is

[0025] The load sweep angular velocity of a whole cycle can be expressed as:

[0026]

[0027] Formula (5) is the angular velocity curve of the load sweep in one cycle. The trajectory satisfies that the load rotates at the same angle in the forward sweep phase and the reverse sweep phase. The load performs ground scanning imaging in the uniform speed phase of each cycle, and the imaging strips in adjacent cycles can be completely overlapped to complete the wide-width ground imaging task.

[0028] Step 2: Solve the deviation angle based on the image motion velocity model on the focal plane

[0029] When the payload sweeps around the orbital velocity direction according to the angular velocity curve described by equation (5), the TDICCD integrates the image of the ground along the direction perpendicular to the orbital velocity. At this time, the image motion velocity caused by the orbital velocity will be perpendicular to the integration direction of the TDICCD, and this image motion velocity will cause a drift angle. The principle of the generation of the drift angle is as follows: Figure 3 As shown in the figure, the image motion velocity caused by the payload sweep angular velocity is along the integral direction of TDICCD, and the image motion velocity direction caused by the satellite's orbital angular velocity is perpendicular to the integral direction of TDICCD. The image motion in this direction will cause the camera imaging quality to deteriorate, and the angle β is the drift angle.

[0030] In order to accurately solve the drift angle, the image velocity model on the focal plane is used to calculate the drift angle. First, the image point p on the focal plane is taken as 1 ,p 2 ) to calculate the corresponding ground target position vector

[0031]

[0032] in, is the component array of the vector from the center of the earth to the ground target corresponding to the image point in the geocentric inertial coordinate system, is the coordinate transformation matrix from the geocentric orbital coordinate system to the geocentric inertial coordinate system, is the coordinate transformation matrix from the satellite payload coordinate system to the geocentric orbit coordinate system, is the installation matrix of the camera relative to the satellite payload coordinate system, is the component array of the vector from the camera to the corresponding ground target point in the camera coordinate system, is the component array of the vector from the satellite platform center of mass to the camera in the satellite payload coordinate system, It is the component array of the vector from the center of the earth to the center of mass of the satellite in the geocentric orbital coordinate system.

[0033] Then the ground target position vector By bringing in the image motion velocity field model and the corresponding attitude and orbit parameters, the image motion velocity on the focal plane can be obtained:

[0034]

[0035] Among them, f is the focal length of the camera combination, H is the track height, that is, the distance between the center of mass of the central platform and the ground target point projected onto the optical axis, is the component array of the vector from the satellite's center of mass to the ground target point in the satellite payload coordinate system, It is the component array of the vector pointing from the satellite's center of mass to the ground target point in the geocentric orbit coordinate system.

[0036] Pick The two components in the focal plane are the forward image velocity V of the target image point q p1 and the lateral image motion velocity V p2 , then the calculation formula of the deflection angle β at the focal plane target image point is:

[0037] β=arctan(V p2 / V p1 ) (8)

[0038] The index to measure the effect of the bias angle on the image quality is the modulation transfer function of the camera corresponding to the bias angle, which is expressed as follows:

[0039]

[0040] Where n is the integration series of TDICCD, MTF D is the camera modulation transfer function corresponding to the deviation angle, which is used to characterize the influence of the deviation angle on the image quality. For this indicator, in engineering, as long as the value is greater than a certain value, the imaging quality requirement can be met, which is generally 0.98. Therefore, the compensation of the deviation angle does not need to be completely compensated to zero.

[0041] In the complete simulation system, the satellite payload is controlled to maneuver according to the payload angular velocity curve given in step 1, and the drift angle within an imaging cycle is calculated based on the image motion velocity model.

[0042] Step 3: Design of pitch maneuver compensation drift angle trajectory

[0043] According to the principle of the drift angle of the payload sweep imaging satellite, it can be seen that the main cause of the drift angle is the image motion speed in the vertical focal surface integral direction caused by the orbital angular velocity. In order to offset the influence of the image motion speed, it is hoped to generate an opposite image motion speed. Therefore, by controlling the angular velocity of the satellite platform in the pitch axis direction, an image motion speed opposite to the image motion speed caused by the orbital angle can be generated, thereby achieving compensation for the drift angle. The schematic diagram of the compensation principle is shown in Figure 4 shown.

[0044] If the pitch axis is maneuvered at the same angular velocity, the optical payload's line of sight axis will deviate from the sub-satellite point at an increasingly larger angle, and the final imaging strip will not be able to be spliced. Therefore, the trajectory of the satellite platform's pitch maneuver to compensate for the drift angle needs to be designed so that the total angle around the pitch axis in one cycle is 0. According to the analysis of the drift angle without bias compensation, the drift angle is approximately symmetrical during the uniform sweep imaging stage, and the drift angle is the largest when the line of sight axis points to the ground. Therefore, the angular velocity curve for the drift angle compensation is designed based on the payload sweep image, such as Figure 5 As shown, the acceleration and deceleration stages and the reverse retrace stage are all sinusoidal curves, and the compensation curve corresponding to the uniform ground scanning stage is a half-cycle with an amplitude of ω a The sine curve plus a constant value ω f , the angles of rotation in the forward and reverse stages are the same, and the key parameters include the constant ω f The size of and the amplitude of the sine function corresponding to the sweeping stage ω a The time of each stage of the trajectory is consistent with the load sweep angular velocity curve in step 1, and the specific expression is as follows:

[0045] Angular velocity during forward acceleration:

[0046]

[0047] Among them, ω f is the amplitude of the angular velocity trajectory during the acceleration phase.

[0048] The angular velocity of the bias angle compensation corresponding to the load uniform speed scanning stage is:

[0049] ω by2 =ω f +ω a sin(f 3 (tt 1 )) (11)

[0050] Among them, ω a is the amplitude of the corresponding sine function, is the corresponding angular frequency.

[0051] Angular velocity during the forward deceleration phase:

[0052]

[0053] Among them, t 2 is the start time of the positive deceleration phase. The angular velocities in the positive deceleration phase and the positive acceleration phase are both sinusoidal functions with the same amplitude and frequency.

[0054] Angular velocity in reverse phase:

[0055] ω by4 =-ωd sin(f 2 (tt 3 )) (13)

[0056] Among them, ω d is the amplitude of the sine curve in the reverse phase, f 2 is the angular frequency of the reverse phase, t 3 is the start time of the reverse phase. d This can be solved based on the condition that the sum of the total angles rotated in the forward and reverse phases is zero.

[0057] The designed pitch maneuver compensation drift angle trajectory, that is, the pitch angular velocity curve of the satellite platform in one sweep cycle can be expressed as:

[0058]

[0059] From the above designed pitch velocity drift angle compensation trajectory, it can be seen that the only variable that determines the trajectory is ω f and ω a Only these two values ​​need to be determined to find the deviation angle compensation trajectory.

[0060] Step 4: Determine the initial value of the deviation angle compensation trajectory parameters

[0061] Let the orbit height be h and the radius of the earth be R e , the orbital angular velocity is ω o According to the principle of pitch axis maneuver to compensate for the drift angle, the ground image motion velocity caused by the orbital angular velocity is:

[0062] V ωo =ω o R e (15)

[0063] The ground image motion velocity caused by the angular velocity of the satellite platform's pitch axis is:

[0064] V ωby =ω by h (16)

[0065] Among them, ω by is the angular velocity of the satellite along the pitch axis, corresponding to the angular velocity of the pitch maneuver to compensate for the drift angle designed in step 3.

[0066] Since only in ω by2 In the stage, the camera performs ground scanning imaging, so it is necessary to consider this stage ω f and ω a Effect on angular velocity, ω fThe corresponding initial value is solved according to the relationship between the ground image motion velocity caused by the orbital angular velocity and the ground image motion velocity caused by the satellite platform pitch axis angular velocity, ω f The initial value can be expressed as:

[0067]

[0068] ω a The existence of is to compensate for the slight difference in the ground image velocity of the load under different swing angles. Its amplitude can be solved in proportion to the difference between the maximum and minimum values ​​of the drift angle, ω a The initial value of can be expressed as:

[0069] ω a0 =α(β max -β min ) (18)

[0070] Among them, α is the setting coefficient.

[0071] Step 5: Iteratively adjust the deviation angle compensation trajectory parameters

[0072] Substitute the initial parameters of the drift angle compensation trajectory obtained in step 4 into equation (14) in step 3 to obtain the pitch angular velocity curve of the satellite platform, and then bring it into the complete simulation system to solve the residual drift angle β' after the initial compensation. The difference between the maximum and minimum values ​​of the drift angle is recorded as Δβ. The maximum value β' of the residual drift angle in one cycle is max As a benchmark, adjust ω appropriately f The size of (according to the residual deviation angle multiplied by a coefficient), β' max If it is greater than zero, it increases ω f The absolute value of is, otherwise it decreases; according to formula (18), adjust ω a The newly obtained drift angle compensation trajectory parameters are substituted into equation (14) in step 3 to obtain the pitch angular velocity curve of the satellite platform, which is then substituted into the complete simulation system and the residual drift angle and its corresponding MTF are solved according to the image motion velocity model in step 2. D Parameters, MTF D If the parameter requirements are not met, the above method is repeated to adjust the deviation angle compensation trajectory parameters until the modulation transfer function corresponding to the deviation angle meets the requirements. Generally, after two or three iterations, the size of the remaining deviation angle can meet the requirements.

[0073] In summary, the drift angle compensation method for the pitch maneuver of the sweep imaging satellite is obtained by designing the payload sweep trajectory and establishing the image motion velocity model, and a drift angle compensation trajectory for the satellite pitch maneuver is designed. The parameters of the compensation trajectory are adjusted through an iterative method, and finally the compensation of the drift angle is achieved to improve the imaging quality.

[0074] (III) Advantages

[0075] The advantages of the drift angle compensation method for the pitch maneuver of a sweep imaging satellite provided by the present invention are:

[0076] ① The present invention adopts the satellite attitude maneuvering method to perform drift angle compensation. Compared with the drift angle compensation method using the drift angle compensation mechanism, it has higher reliability and can reduce the satellite mass, and is suitable for agile imaging satellites.

[0077] ② The present invention designs a drift angle compensation method for satellite pitch maneuvers for the swing-scan wide-band imaging method, while the traditional satellite attitude yaw drift angle compensation method cannot achieve drift angle compensation for swing-scan imaging. BRIEF DESCRIPTION OF THE DRAWINGS

[0078] Figure 1 Schematic diagram of the payload sweeping ground imaging area.

[0079] Figure 2 Schematic diagram of the load sweep angular velocity trajectory.

[0080] Figure 3 Schematic diagram of the principle of generating the drift angle in the swing scanning imaging method.

[0081] Figure 4 Schematic diagram of the principle of drift angle compensation for satellite pitch maneuvers.

[0082] Figure 5 This is the designed drift angle compensation trajectory for the pitch maneuver.

[0083] Figure 6 This is the front bias angle compensation curve in the simulation example.

[0084] Figure 7 MTF before compensation in the simulation example Dx Numerical curve.

[0085] Figure 8 This is the deviation angle curve after compensation in the simulation example.

[0086] Fig. 9 MTF after compensation in the simulation example Dx Numerical curve. DETAILED DESCRIPTION

[0087] Following the previous steps, the drift angle compensation method is verified in combination with a specific satellite scanning imaging mission. The selected parameters are as follows:

[0088] Earth radius R e =6738.14Km, orbital height h = 798.12Km, orbital angular velocity is ω o=0.00104rad / s, the maximum angular acceleration of the load sweep α max =0.157rad / s 2 , uniform angular velocity ω uni =0.128rad / s, combined focal length f=0.5m, TDICCD camera integration number n=96.

[0089] The present invention relates to a method for compensating a drift angle of a sweep imaging satellite pitch maneuver, and the specific implementation steps are as follows:

[0090] Step 1: Design the trajectory of the sweeping maneuver

[0091] According to the specific satellite sweep imaging mission, the specific expression of the designed payload sweep maneuver angular velocity can be obtained as:

[0092]

[0093] Among them, α max =0.157rad / s 2 ,ω uni =0.128rad / s, f 1 =1.2323, f 2 =0.5, t 0 =0,t 1 =1.274,t 2 =9.458, t 3 =10.733, t 4 =17.

[0094] Step 2: Solve the deviation angle based on the image motion velocity model on the focal plane

[0095] According to the imaging principle of the TDICCD camera and the load sweep imaging trajectory designed in step 1, it is not difficult to see that there will be a drift angle in the optical load sweep imaging method. In order to accurately solve the drift angle, the image motion velocity model on the focal plane is used to calculate the drift angle.

[0096] The load sweep angular velocity obtained by equation (19) is brought into the simulation system, and the load is controlled to track the sweep trajectory. The coordinate transformation matrices required by the image motion velocity model can be obtained. The image point p = (0, 0) on the focal plane can be obtained according to equations (6) and (7). The two components in the focal plane are the forward image velocity V of the target image point q p1 and the lateral image motion velocity V p2 , then the calculation formula of the deflection angle β at the focal plane target image point is:

[0097] β=arctan(V p2 / Vp1 ) (20)

[0098] The index to measure the effect of the bias angle on the image quality is the modulation transfer function of the camera corresponding to the bias angle, which is expressed as follows:

[0099]

[0100] When the deviation angle compensation is not performed, the deviation angle and MTF obtained by solving the above steps are Dx The results are as follows Figure 6 and Figure 7 As shown, it can be seen that the maximum deviation angle is about 3.7°, at which time the MTF Dx The value of is close to 0, which is far from meeting the imaging quality requirements.

[0101] Step 3: Design of pitch maneuver compensation drift angle trajectory

[0102] The trajectory of the pitch maneuver to compensate for the drift angle is the angular velocity of the satellite platform maneuvering around the pitch axis, and its expression is as follows:

[0103]

[0104] The time and angular frequency parameters are the same as those of the sweeping maneuver trajectory, ω f and ω a Determined in the next step.

[0105] Step 4: Determine the initial value of the deviation angle compensation trajectory parameters

[0106] Solve ω according to equations (17) and (18) in step 4 f and ω a The initial value of α is 0.002, and the initial values ​​of the two parameters are ω f0 =0.008rad / s,ω a0 =0.001rad / s. Substituting this parameter into equation (22) can obtain the pitch maneuver compensation drift angle trajectory. Substituting this trajectory into the complete simulation system, the satellite platform is controlled to track the pitch angular velocity trajectory, and then the drift angle and MTF are solved according to step 2. Dx , the residual deviation angle after preliminary compensation can be obtained.

[0107] Step 5: Iteratively adjust the deviation angle compensation trajectory parameters

[0108] The residual drift angle β' after the initial compensation is solved in step 4. The difference between the maximum and minimum values ​​of the drift angle is recorded as Δβ. The minimum value β of the residual drift angle in one cycle is min As a benchmark, adjust ω appropriately f The size of β min If it is greater than zero, it increases ωf The absolute value of Δβ is reduced; adjust ω appropriately according to the size of Δβ a Substitute the newly obtained drift angle compensation trajectory into the model of step one and step two. If there is still a drift angle, repeat the above method to adjust the parameters until the modulation transfer function corresponding to the drift angle meets the requirements.

[0109] In this simulation example, a compensation trajectory that meets the requirements is obtained after one iteration, and its corresponding drift angle curve and MTF are Dx Curve like Figure 8 and Fig. 9 As shown, it can be seen that the deviation angle is less than 0.04° after compensation, and the corresponding MTF Dx The value is greater than 0.998, which can meet the imaging quality requirements.

Claims

1. A method for compensating drift angle of a sweep imaging satellite pitch maneuver, characterized in that: The steps include: Step 1: Design the trajectory of the sweeping maneuver The payload swing imaging satellite runs on a fixed orbit. The TDICCD camera installed on it scans the earth by controlling the payload to swing in the direction of the orbital velocity. When scanning the earth in the uniform speed stage, the earth is imaged in the forward scanning stage, and no imaging is performed in the retracement stage. The angles of the forward swing and the retracement in one cycle are the same. The corresponding scanning angular velocity curve is divided into two parts: the forward swing and the reverse swing. The forward swing includes the forward acceleration stage, the uniform speed scanning stage, and the forward deceleration stage, and the reverse swing stage is a continuous sine curve. Step 2: Solve the deviation angle based on the image motion velocity model on the focal plane When the payload sweeps along the orbital velocity direction according to the angular velocity curve, TDICCD integrates the image of the earth along the direction perpendicular to the orbital velocity. At this time, the image motion velocity caused by the orbital velocity will be perpendicular to the integral direction of TDICCD, and this image motion velocity will cause a drift angle; the image motion velocity caused by the angular velocity of the payload sweep is along the integral direction of TDICCD, and the image motion velocity direction caused by the orbital angular velocity of the satellite is perpendicular to the integral direction of TDICCD; Step 3: Design a pitch maneuver trajectory to compensate for drift angle By controlling the angular velocity of the satellite platform in the pitch axis direction, an image shift velocity opposite to the image shift velocity caused by the orbit angle is generated to achieve compensation for the drift angle; The trajectory of the satellite platform's pitch maneuver to compensate for the drift angle needs to be designed so that the total angle around the pitch axis in one cycle is 0; according to the analysis of the drift angle when there is no bias compensation, in the uniform sweep imaging stage, the drift angle is approximately symmetrical, and the drift angle is the largest when the line of sight axis points to the ground; therefore, the angular velocity curve for the drift angle compensation is designed based on the load sweep image; the acceleration and deceleration sections and the reverse retrace stage are all sinusoidal curves, and the compensation curve corresponding to the uniform ground scanning stage has an amplitude of half a cycle of ω a The sine curve plus a constant value ω f , the angles of rotation in the forward and reverse stages are the same, and the key parameters include the constant ω f The size of and the amplitude of the sine function corresponding to the sweeping stage ω a ; The time of each stage of the trajectory is consistent with the load sweep angular velocity curve in step 1; Step 4: Determine the initial value of the deviation angle compensation trajectory parameter; Step 5: Use the iterative method to adjust the deviation angle compensation trajectory parameters.

2. The method for compensating drift angle of a sweep imaging satellite pitch maneuver according to claim 1, characterized in that: In step 1, the curve design process of the angular velocity trajectory is as follows: The forward acceleration phase is a quarter-cycle sine curve, and the corresponding angular velocity is: Among them, t0 is the starting time of the payload scanning imaging task, t is the current time, f1 is the sinusoidal angular frequency in the acceleration phase, α max is the maximum angular acceleration of the load in the sweeping trajectory; The angular velocity during the uniform scanning phase is a constant, and the corresponding angular velocity is: oh r2 =ω uni (2) Among them, ω uni is the angular velocity of the uniform scanning stage, and the starting time of the uniform scanning stage is The positive deceleration stage is a quarter-cycle sine curve symmetrical to the positive acceleration stage, and the corresponding angular velocity is: Where t2 = t1 + t uni is the start time of the forward acceleration phase, t uni is the duration of the uniform scanning phase, which is determined according to the specific imaging task. The amplitude and frequency of the forward deceleration phase and the forward acceleration phase are the same; The reverse retrace stage is a sine function of one-half cycle, and the total angle rotated in the forward swing stage is equal to the total angle rotated in the reverse retrace stage. The corresponding angular velocity is: Where f2 is the angular frequency of the reverse sweep phase, which is determined based on the fact that the forward swing and the reverse swing have the same rotation angle. is the start time of the reverse retrace phase, and the end time of the reverse retrace phase is 3. The method for compensating drift angle of a sweep imaging satellite pitch maneuver according to claim 2, characterized in that: The load sweep angular velocity of a whole cycle is expressed as: Formula (5) is the angular velocity curve of the load sweep in one cycle. The trajectory satisfies that the load rotates at the same angle in the forward sweep phase and the reverse sweep phase. The load performs ground scanning imaging in the uniform speed phase of each cycle, and the imaging strips in adjacent cycles can be completely overlapped to complete the wide-width ground imaging task.

4. The method for compensating drift angle of a sweep imaging satellite pitch maneuver according to claim 1, characterized in that: In step 2, in order to accurately solve the drift angle, the image velocity model on the focal plane is used to calculate the drift angle, and the image point p = (p1, p2) on the focal plane is taken to calculate the corresponding ground target position vector in, is the component array of the vector from the center of the earth to the ground target corresponding to the image point in the geocentric inertial coordinate system, is the coordinate transformation matrix from the geocentric orbital coordinate system to the geocentric inertial coordinate system, is the coordinate transformation matrix from the satellite payload coordinate system to the geocentric orbit coordinate system, is the installation matrix of the camera relative to the satellite payload coordinate system, is the component array of the vector from the camera to the corresponding ground target point in the camera coordinate system, is the component array of the vector from the satellite platform center of mass to the camera in the satellite payload coordinate system, It is the component array of the vector from the center of the earth to the center of mass of the satellite in the geocentric orbital coordinate system.

5. The method for compensating drift angle of a sweep imaging satellite pitch maneuver according to claim 4, characterized in that: The ground target position vector Substitute the image motion velocity field model and the corresponding attitude and orbit parameters into the image motion velocity on the focal plane. for: Among them, f is the focal length of the camera combination, H is the track height, that is, the distance between the center of mass of the central platform and the ground target point projected onto the optical axis, is the component array of the vector from the satellite's center of mass to the ground target point in the satellite payload coordinate system, It is the component array of the vector pointing from the satellite's center of mass to the ground target point in the geocentric orbit coordinate system.

6. The method for compensating drift angle of a sweep imaging satellite pitch maneuver according to claim 5, characterized in that: Pick The two components in the focal plane are the forward image velocity V of the target image point q. p1 and the lateral image motion velocity V p2 , then the calculation formula of the deflection angle β at the focal plane target image point is: β=arctan(V p2 / V p1 ) (8) The index to measure the effect of the bias angle on the image quality is the modulation transfer function of the camera corresponding to the bias angle, which is expressed as follows: Where n is the integration series of TDICCD, MTF D is the camera modulation transfer function corresponding to the bias angle, which is used to characterize the influence of the bias angle on the imaging quality.

7. The method for compensating drift angle of a sweep imaging satellite pitch maneuver according to claim 1, characterized in that: In step 3, the angular velocity during the forward acceleration phase is: oh by1 =ω f sin(f1(t-t0)) (10) Among them, ω f is the amplitude of the angular velocity trajectory during the acceleration phase; The angular velocity of the bias angle compensation corresponding to the load uniform speed scanning stage is: oh by2 =ω f +oh a sin(f3(t-t1)) (11) Among them, ω a is the amplitude of the corresponding sine function, is the corresponding angular frequency; ω a The magnitude of is calculated in proportion to the difference between the maximum and minimum values ​​of the drift angle, ω a The initial value of is expressed as: oh a0 =α(β max -b min ) Among them, α is the setting coefficient; Angular velocity during the forward deceleration phase: Wherein, t2 is the start time of the forward deceleration phase, and the angular velocities of the forward deceleration phase and the forward acceleration phase are both sinusoidal functions with the same amplitude and frequency; Angular velocity in reverse phase: oh by4 =-ω d sin(f2(t-t3)) (13) Among them, ω d is the amplitude of the sine curve in the reverse phase, f2 is the angular frequency in the reverse phase, and t3 is the start time of the reverse phase; ω d It is solved based on the condition that the sum of the total angles rotated in the forward and reverse phases is zero.

8. The method for compensating drift angle of a sweep imaging satellite pitch maneuver according to claim 7, characterized in that: The designed pitch maneuver compensation drift angle trajectory, that is, the pitch angular velocity curve of the satellite platform within one sweep cycle is expressed as:

9. The method for compensating drift angle of a sweep imaging satellite pitch maneuver according to claim 1, characterized in that: In step 4, let the orbit height be h and the radius of the earth be R e , the orbital angular velocity is ω o According to the principle of pitch axis maneuver to compensate for the drift angle, the ground image motion velocity caused by the orbital angular velocity is: The ground image motion velocity caused by the angular velocity of the satellite platform's pitch axis is: Among them, ω by is the angular velocity of the satellite along the pitch axis; ω f The corresponding initial value is solved according to the relationship between the ground image motion velocity caused by the orbital angular velocity and the ground image motion velocity caused by the satellite platform pitch axis angular velocity, ω f The initial value is expressed as:

10. The method for compensating drift angle of a sweep imaging satellite pitch maneuver according to claim 8, characterized in that: In step 5, the initial parameters of the drift angle compensation trajectory are substituted into equation (14) in step 3 to obtain the pitch angular velocity curve of the satellite platform, and then substituted into the complete simulation system to solve the residual drift angle β' after the initial compensation. The difference between the maximum and minimum values ​​of the drift angle is recorded as Δβ, and the maximum value β′ of the residual drift angle in one cycle is taken as max As a benchmark, adjust ω f The size of β′ max If it is greater than zero, it increases ω f The absolute value of ω, otherwise it decreases; adjust ω a The size of the drift angle compensation trajectory parameters is substituted into the equation (14) in step 3 to obtain the pitch angular velocity curve of the satellite platform, which is then substituted into the complete simulation system and the residual drift angle and its corresponding MTF are solved according to the image motion velocity model. D Parameters, MTF D If the parameter requirements are not met, the above method is repeated to adjust the deviation angle compensation trajectory parameters until the modulation transfer function corresponding to the deviation angle meets the requirements.

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