Method and system for stabilizing the pointing of the optical axis of a space telescope

Abstract

This invention discloses a method and system for stabilizing the line-of-sight pointing of a space telescope. The method includes: acquiring the low-frequency attitude quaternions and high-frequency attitude angular velocities of the satellite; performing delay compensation on the low-frequency attitude quaternions; fusing the compensated attitude quaternions with the high-frequency attitude angular velocities using a data fusion algorithm to generate a high-frequency satellite attitude quaternion sequence consistent with the sampling rate of the servo control system; calculating the attitude transformation matrix based on this sequence; projecting the inertial frame pointing vector sequence between the target and the satellite position sequentially onto the satellite body coordinate system and the telescope base coordinate system to obtain a pointing vector sequence in the telescope base coordinate system; calculating the desired pointing angle of the telescope based on this sequence; and controlling the telescope to rotate so that the line-of-sight points towards the target. This invention solves the problems of insufficient pointing accuracy caused by low satellite attitude data sampling rate and delay in existing guidance pointing methods, effectively improving the line-of-sight pointing accuracy and stability of space telescopes.

Description

Technical Field

[0001] This invention relates to the field of space target observation technology, specifically to a method and system for stabilizing the line of sight of a space telescope. Background Technology

[0002] Space telescopes are widely used in fields such as situational awareness and laser communication, and line-of-sight pointing control is a key technology. Existing pointing control methods fall into two categories: optical closed-loop methods use image sensors to obtain high-frequency miss distances to form a control closed loop, which can adapt to high dynamic conditions, but rely on miss distance information and cannot track faint targets; guidance information-based methods use information such as the target, local orbit, and satellite attitude to guide pointing, which can achieve stable pointing for a long time without relying on miss distances, and are suitable for long-exposure conditions for faint targets, but are only applicable to low dynamic conditions.

[0003] With the increasing demand for detecting faint targets, the development of high-precision guidance and pointing technology has become an urgent problem to be solved. However, existing guidance and pointing methods typically only use low-frequency attitude quaternion information broadcast by the satellite's onboard computer, with a broadcast frequency of only 1-4 Hz and significant measurement delays. When the satellite is performing attitude maneuvers, the attitude measurement error increases sharply. Using low-frequency and delayed attitude information for pointing calculations leads to a significant decrease in the telescope's line-of-sight pointing accuracy, failing to meet the requirements for long-term stable exposure of faint targets, resulting in problems such as blurred imaging and target loss. Therefore, how to obtain a high-frequency, high-precision attitude reference based on low-frequency attitude information to improve pointing accuracy has become a pressing technical challenge in this field. Summary of the Invention

[0004] To address the problems existing in the prior art, this invention provides a method and system for stabilizing the line-of-sight pointing of a space telescope. This method solves the problems of low sampling rate of orbit prediction data and low sampling rate of satellite attitude data in existing guidance pointing methods, as well as the existence of delays, and can effectively improve the pointing accuracy and pointing stability of the line-of-sight pointing of a space telescope.

[0005] This invention is achieved through the following technical solution: A method for stabilizing the line-of-sight pointing of a space telescope includes the following steps: Obtain the low-frequency satellite attitude quaternion and the high-frequency satellite attitude angular velocity; Delay compensation is applied to the low-frequency satellite attitude quaternion to obtain the compensated attitude quaternion; A data fusion algorithm is used to fuse the compensated attitude quaternion with the high-frequency satellite attitude angular velocity to generate a high-frequency satellite attitude quaternion sequence that is consistent with the sampling rate of the servo control system. The attitude transformation matrix is ​​calculated based on the high-frequency satellite attitude quaternion sequence. The inertial pointing vector sequence between the target and the satellite position is then projected sequentially onto the satellite body coordinate system and the telescope base coordinate system to obtain the pointing vector sequence in the telescope base coordinate system. The desired pointing angle of the telescope is calculated based on the pointing vector sequence in the telescope base coordinate system, and then the telescope is rotated to make the line of sight point to the target.

[0006] Preferably, the delay compensation for the low-frequency satellite attitude quaternion specifically involves: Using the low-frequency satellite attitude quaternion received at the current moment as the attitude estimate at the historical moment, and using the high-frequency satellite attitude angular velocity for integral compensation, the low-frequency satellite attitude quaternion is extrapolated to the current moment to obtain the compensated attitude quaternion.

[0007] Preferably, the step of generating a high-frequency satellite attitude quaternion sequence using a data fusion algorithm specifically involves: Using the compensated attitude quaternion as the initial value, the high-frequency satellite attitude angular velocity is used to gradually deduce according to the attitude kinematic equation. Within one satellite attitude broadcasting cycle, multiple high-frequency satellite attitude quaternions with the same sampling rate as the servo control system are generated to form a high-frequency satellite attitude quaternion sequence.

[0008] Preferably, the inertial frame pointing vector sequence between the target and the satellite position is obtained through the following steps: Obtain the target position coordinates and satellite position coordinates broadcast by the satellite's satellite navigation computer; Based on the target position coordinates and satellite position coordinates, calculate the unit pointing vector of the satellite pointing towards the target in the inertial coordinate system; The unit pointing vector is interpolated to obtain an inertial frame pointing vector sequence that matches the sampling rate of the servo control system.

[0009] Preferably, the step of sequentially projecting the inertial frame pointing vector sequence onto the satellite body coordinate system and the telescope base coordinate system specifically includes: Calculate the attitude transformation matrix from the inertial coordinate system to the satellite body coordinate system based on the high-frequency satellite attitude quaternion sequence; Using the attitude transformation matrix, the inertial frame pointing vector sequence is projected onto the satellite body coordinate system to obtain the body coordinate system pointing vector sequence; Using a pre-calibrated installation matrix from the satellite body to the telescope base, the pointing vector sequence of the satellite body coordinate system is projected onto the telescope base coordinate system to obtain the pointing vector sequence of the base coordinate system.

[0010] Preferably, the step of calculating the desired pointing angle of the telescope based on the pointing vector sequence in the telescope base coordinate system specifically involves: Based on the components of each pointing vector in the pointing vector sequence of the base coordinate system on the three coordinate axes, the corresponding desired azimuth and desired pitch angles are calculated through spherical coordinate transformation, generating a desired pointing angle sequence consistent with the sampling rate of the servo control system.

[0011] Preferably, the data fusion algorithm includes any of the following: Direct integration method, Kalman filter algorithm, extended Kalman filter, unscented Kalman filter, complementary filter algorithm or neural network algorithm.

[0012] Preferably, the acquisition of the low-frequency satellite attitude quaternion specifically refers to: The satellite attitude quaternion is received from the satellite's satellite computer and is obtained by measuring a star sensor that is fixedly installed on the satellite body.

[0013] The specific steps for obtaining the high-frequency satellite attitude angular velocity are as follows: The system receives the three-axis attitude angular velocity output from a three-axis gyroscope mounted near the telescope base, and the sampling rate of the output data of the three-axis gyroscope is consistent with the sampling rate of the servo control system.

[0014] 9. A line-of-sight stabilizing pointing system for a space telescope, comprising: The data acquisition module is used to acquire the low-frequency satellite attitude quaternion and the high-frequency satellite attitude angular velocity. The delay compensation module is used to perform delay compensation on the low-frequency satellite attitude quaternion to obtain the compensated attitude quaternion. The data fusion module is used to fuse the compensated attitude quaternion with the high-frequency satellite attitude angular velocity using a data fusion algorithm, and generate a high-frequency satellite attitude quaternion sequence that is consistent with the sampling rate of the servo control system. The coordinate transformation module is used to calculate the attitude transformation matrix based on the high-frequency satellite attitude quaternion sequence, and to project the inertial pointing vector sequence between the target and the satellite position onto the satellite body coordinate system and the telescope base coordinate system in sequence to obtain the pointing vector sequence in the telescope base coordinate system. The pointing angle calculation module is used to calculate the desired pointing angle of the telescope based on the pointing vector sequence in the telescope base coordinate system, and then control the rotation of the telescope so that the line of sight points to the target.

[0015] A space telescope includes a line-of-sight stabilizing pointing system for the space telescope.

[0016] Compared with the prior art, the present invention has the following beneficial technical effects: This application proposes a line-of-sight stabilization pointing method for a space telescope. It acquires two types of satellite data: low-frequency attitude quaternions and high-frequency attitude angular velocities. First, delay compensation is applied to the low-frequency attitude quaternions to eliminate measurement transmission delay. Then, a data fusion algorithm is used to fuse the compensated attitude quaternions with the high-frequency angular velocities, generating a high-frequency satellite attitude quaternion sequence consistent with the sampling rate of the servo control system. This method uses high-frequency relative measurement data (gyro angular velocity) to interpolate and filter low-frequency absolute measurement data (star sensor attitude), upscaling the original 1-4Hz low-frequency attitude data to high-frequency data matching the servo control frequency (typically 50-200Hz). Simultaneously, delay compensation ensures that the attitude reference is aligned with the current time. Based on this, the method uses the fused high-frequency attitude quaternions for coordinate transformation, progressively projecting the target pointing vector in the inertial frame to the telescope base coordinate system, ultimately calculating the desired pointing angle and controlling the telescope rotation. This method fundamentally solves the problem of decreased line-of-sight pointing accuracy caused by low satellite attitude data sampling rate and time delay in traditional guidance and pointing methods. It enables the telescope to obtain continuous, smooth, and high-precision pointing commands under low dynamic conditions, meeting the stringent requirements for pointing stability during long-term stable exposure of faint targets, and significantly improving the observation capabilities of space telescopes.

[0017] This application also proposes a line-of-sight stabilization pointing system for a space telescope, an electronic device, and a computer storage medium, which possess all the advantages of the aforementioned line-of-sight stabilization pointing methods for space telescopes. Attached Figure Description

[0018] To more clearly illustrate the technical solutions of the embodiments of this application, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of this application and should not be regarded as a limitation of the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0019] Figure 1 This is a schematic diagram of the space telescope system of the present invention; Figure 2 This is a schematic diagram of the information flow of the space telescope system of the present invention; Figure 3 This is a block diagram of the space telescope servo control system of the present invention; Figure 4 This is a flowchart of the line-of-sight stabilization pointing method for the space telescope of the present invention.

[0020] In the image: 1. Satellite; 2. Star sensor; 3. Three-axis gyroscope; 4. Spaceborne telescope; 5. Line of sight; 6. Solar panel. Detailed Implementation

[0021] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. The components of the embodiments of this application described and shown in the accompanying drawings can generally be arranged and designed in various different configurations.

[0022] Therefore, the following detailed description of the embodiments of this application provided in the accompanying drawings is not intended to limit the scope of the claimed application, but merely to illustrate selected embodiments of the application. All other embodiments obtained by those skilled in the art based on the embodiments of this application without inventive effort are within the scope of protection of this application.

[0023] It should be noted that similar labels and letters in the following figures indicate similar items. Therefore, once an item is defined in one figure, it does not need to be further defined and explained in subsequent figures.

[0024] In the description of the embodiments of this application, it should be noted that if terms such as "upper," "lower," "horizontal," or "inner" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, or the orientation or positional relationship commonly used when the product of the invention is in use, they are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation on this application. In addition, terms such as "first" and "second" are only used to distinguish descriptions and should not be construed as indicating or implying relative importance.

[0025] Furthermore, the use of the term "horizontal" does not imply that the component must be absolutely horizontal, but rather that it can be slightly tilted. For example, "horizontal" simply means that its direction is more horizontal than "vertical," and does not mean that the structure must be completely horizontal, but can be slightly tilted.

[0026] In the description of the embodiments of this application, it should also be noted that, unless otherwise explicitly specified and limited, the terms "set," "install," "connect," and "link" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this application according to the specific circumstances.

[0027] See Figure 1The space telescope system of the present invention mainly includes a satellite 1, a star sensor 2, a three-axis gyroscope 3, and a spaceborne telescope 4.

[0028] Satellite 1 serves as the platform, providing the installation foundation and operating environment for all components. Solar panels 6 are installed on both sides of Satellite 1 to provide power for the entire system.

[0029] Star sensor 2 is fixedly mounted on satellite 1 and is used to measure the attitude information of satellite 1 in inertial space. Multiple star sensors 2 are typically equipped to achieve redundancy and information fusion. Their output is low-frequency satellite attitude quaternion data (typically 1~4Hz), which is broadcast to the telescope computer of the onboard telescope 4 via the satellite's onboard computer. Figure 1 The CCP has deployed three satellite sensors.

[0030] The three-axis gyroscope 3 is mounted near the base of the spaceborne telescope 4 and is used to sense the attitude angular velocity of satellite 1. The three-axis gyroscope 3 can output high-frequency attitude angular velocity information, and its sampling rate is consistent with the sampling rate of the telescope servo control system, providing a high-frequency reference for attitude data fusion.

[0031] The spaceborne telescope 4 is mounted on the satellite 1 platform and has two-dimensional rotation capability. Its line of sight 5 can be adjusted to point at the target. The spaceborne telescope 4 integrates a telescope computer and a servo control system: the telescope computer is connected to the satellite's onboard computer and the three-axis gyroscope 3, respectively, to receive low-frequency satellite attitude quaternions, high-frequency attitude angular velocities, and target and satellite position information, and to perform pointing calculations; the servo control system controls the telescope rotation according to the calculated desired pointing angle, so that the line of sight 5 is accurately pointed at the target.

[0032] When the system is working, the telescope computer receives low-frequency attitude quaternion and target position information broadcast by the satellite's onboard computer in real time. At the same time, it receives high-frequency attitude angular velocity output by the three-axis gyroscope 3. Through information fusion, it obtains a high-frequency, high-precision attitude reference. Combined with pointing vector interpolation and coordinate transformation, it generates the desired pointing angle that is consistent with the sampling rate of the servo control system. Finally, it drives the onboard telescope 4 to complete the stable and accurate pointing of the line of sight 5.

[0033] The satellite can be equipped with multiple star sensors for mutual backup. The telescope computer receives attitude data from multiple star sensors and performs fusion processing to further improve attitude measurement accuracy. In addition, the three-axis gyroscope can be replaced by a combination of three single-axis gyroscopes. The sensing axes of the three single-axis gyroscopes are orthogonal to each other and jointly output the three-axis attitude angular velocity.

[0034] Referring to 2-4, a method for stabilizing the line of sight of a space telescope includes the following steps: Step 1: The telescope computer calculates the unit pointing vector of the satellite pointing at the target in the inertial coordinate system based on the target and satellite position coordinates broadcast by the satellite's satellite computer, and converts the pointing vector into sequence data consistent with the sampling rate of the servo control system through an interpolation algorithm.

[0035] At time t, the satellite's onboard computer broadcasts the target's position coordinates in the inertial coordinate system. and satellite position coordinates ; The telescope computer calculates the unit pointing vector of the satellite towards the target in the inertial frame using the following formula. : Target location coordinates:

[0036] Satellite position coordinates:

[0037] Unit pointing vector:

[0038] The time interval between the satellite computer broadcasting the target's position coordinates and the satellite's position coordinates is... The sampling step size of the telescope servo control system is .because Usually greater than Furthermore, since the sampling rate is an integer multiple of the unit pointing vector, interpolation is required to obtain sequence data consistent with the sampling rate of the servo control system. An interpolation algorithm is used within one broadcast cycle. The pointing vector inside is interpolated to:

[0039] The broadcast frequency of orbit prediction data is typically low (0.5~2Hz), which cannot meet the high-frequency requirements of servo control systems. By interpolation, a continuous and smooth pointing vector sequence can be obtained, ensuring that the servo control system has accurate pointing target input in each control cycle, thus solving the problem of mismatch between the target and satellite position data sampling rate and the servo control frequency.

[0040] In some embodiments, the interpolation algorithm may employ methods such as linear interpolation, Lagrange interpolation, or spline interpolation.

[0041] In some embodiments, cubic spline interpolation can be used to obtain a smoother pointing vector change curve, reducing interpolation errors.

[0042] In some embodiments, if the motion law of the target is known, a prediction interpolation method based on a dynamic model can be used to extrapolate the position according to the target's orbital dynamic model to obtain a more accurate interpolation result.

[0043] Step 2: The telescope computer receives the low-frequency satellite attitude quaternion broadcast by the satellite's onboard computer and the high-frequency attitude angular velocity output by the three-axis gyroscope. It performs delay compensation on the low-frequency attitude quaternion and uses a data fusion algorithm to generate a high-frequency satellite attitude quaternion sequence that matches the sampling rate of the servo control system.

[0044] The telescope computer establishes a communication connection with the satellite's onboard computer via a data interface, receiving the satellite attitude quaternions broadcast by the onboard computer in real time. The satellite attitude quaternions are obtained by star sensors, processed by the onboard computer, and broadcast at a fixed frequency. This frequency is limited by the star sensor's measurement principle and data transmission bandwidth, and is usually 1~4Hz, which is considered low-frequency data.

[0045] Simultaneously, the telescope computer is connected to the three-axis gyroscope, receiving the three-axis attitude angular velocity output by the gyroscope in real time. The three-axis gyroscope, mounted near the spaceborne telescope base, is capable of high-frequency sensitivity to the satellite's angular motion. The sampling rate of its output data is consistent with the sampling rate of the telescope's servo control system to ensure the real-time requirements of the control system.

[0046] Specifically, it includes the following processes: S2.1, in t At any given moment, the satellite's onboard computer broadcasts the satellite's attitude quaternions. ,as follows:

[0047] in, As a scalar, The time delay between the satellite's attitude quaternion and the actual attitude quaternion at time t.

[0048] Let the mounting matrix from the three-axis gyroscope to the satellite body be... This matrix, obtained through ground calibration, is a 3×3 orthogonal matrix. The three-axis angular velocities output by the gyroscope are... The angular velocity of the satellite sensed by the gyroscope is:

[0049] It should be noted that the sampling rate of the gyroscope data is consistent with the sampling rate of the telescope servo control system.

[0050] S2.2, using the received attitude quaternion as... t - τ Attitude estimation at any given moment is performed by integrating the gyroscope angular velocity to extrapolate it to the current moment. t .

[0051] First, the rate of change of the satellite attitude quaternion can be obtained from the satellite attitude angular velocity: The rate of change of the satellite attitude quaternion can be obtained from the satellite attitude angular velocity. ,as follows:

[0052] right t The satellite attitude quaternions broadcast by the satellite's onboard computer at all times are used for delay compensation. Let the delay amount be... Delay compensation is achieved by integrating the gyroscope's angular velocity.

[0053] In practical engineering applications, due to the delay amount τ The values ​​are usually small and relatively fixed, and can be approximated by numerical integration methods, such as the trapezoidal rule or the Runge-Kutta method.

[0054] S2.3. Based on delay compensation, a data fusion algorithm is used to process one broadcast cycle. The attitude quaternions within the array are converted into high-frequency sequence data. Let the satellite attitude reporting period be... Then, within a broadcast period, the satellite attitude quaternion at any sampling time is:

[0055] Taking the direct integration method as an example, using the attitude quaternion after delay compensation as the initial value, the high-frequency attitude angular velocity output by the gyroscope is used to gradually deduce the high-frequency satellite attitude quaternion at each servo control sampling time within the broadcast period according to the attitude kinematic equation:

[0056] Here, we take the direct integration method as an example, within one broadcast cycle. M high-frequency attitude quaternions are obtained, forming a high-frequency attitude quaternion sequence consistent with the sampling rate of the servo control system:

[0057] When the next broadcast time arrives, the telescope computer receives new low-frequency attitude quaternions again, repeats the above delay compensation and recursive process, and generates the high-frequency attitude quaternion sequence for the next cycle. By repeating this cycle, a continuous stream of high-frequency attitude quaternions can be obtained.

[0058] The above recursive process is essentially a concrete implementation of the direct integration method, which is simple, efficient, and can quickly generate high-frequency attitude sequences. However, the direct integration method suffers from error accumulation; gyroscope drift and noise are amplified as time is integrated. To further improve the accuracy of attitude estimation, more complex data fusion algorithms can be employed.

[0059] Taking the Kalman filter algorithm as an example, the system's state equation and measurement equation are established. The state equation is the attitude kinematics equation, with the gyroscope angular velocity as input; the measurement equation is the relationship between the low-frequency attitude quaternions and the estimated values. Through the prediction-update iteration of the Kalman filter, state prediction is performed at each gyroscope sampling time, and state update is performed at each star sensor measurement time, thereby obtaining the optimal estimate of the high-frequency attitude quaternions. The Kalman filter can effectively suppress gyroscope drift and measurement noise, achieving higher accuracy attitude estimation than the direct integration method.

[0060] This step uses high-frequency relative measurement data (gyroscope angular velocity) to interpolate and filter low-frequency absolute measurement data (star sensor attitude quaternions). The direct integration method uses the low-frequency attitude quaternions as a reference and recursively applies high-frequency gyroscope angular velocity to upscale the low-frequency (1~4Hz) attitude data to a high-frequency range that matches the servo control frequency (typically 50~200Hz), providing a real-time attitude reference for high-precision pointing control. Delay compensation eliminates the transmission delay of the attitude data, aligning the attitude reference with the current moment. High-frequency satellite attitude quaternions are obtained through information fusion. This data combines absolute attitude reference (from the star sensor) and high-frequency characteristics (from the gyroscope), accurately reflecting the satellite's attitude state at any servo control moment and providing accurate attitude input for subsequent coordinate transformations.

[0061] In some embodiments, the data fusion algorithm may employ extended Kalman filtering (EKF) or unscented Kalman filtering (UKF) to handle the nonlinear characteristics of attitude quaternions.

[0062] In some embodiments, a neural network algorithm can be used to learn the mapping relationship between gyroscope angular velocity and attitude quaternion increment through offline training, and to quickly predict the attitude quaternion based on the gyroscope angular velocity during online operation.

[0063] In some embodiments, a complementary filtering algorithm can be used to fuse the low-frequency components of the low-frequency attitude quaternion with the high-frequency components of the gyro angular velocity integral, and balance the weights of the two types of data by adjusting the filtering parameters.

[0064] In some embodiments, if the gyroscope exhibits significant drift, a gyroscope drift estimation state can be introduced into the fusion algorithm to achieve online estimation and compensation of the gyroscope drift.

[0065] Step 3: The telescope computer calculates the attitude transformation matrix from the inertial coordinate system to the satellite body coordinate system based on the high-frequency satellite attitude quaternion obtained in Step 2, and projects the pointing vector obtained in Step 1 onto the satellite body coordinate system; then, based on the pre-calibrated installation matrix from the satellite body to the telescope base, the projected pointing vector is further transformed into the telescope base coordinate system to obtain the unit pointing vector in the telescope base coordinate system.

[0066] Specifically, it includes the following processes: S3.1 For any sampling time, the telescope computer calculates the attitude transformation matrix from the inertial coordinate system to the satellite body coordinate system based on the high-frequency satellite attitude quaternions at that time. The transformation relationship between the attitude quaternions and the attitude transformation matrix is ​​as follows:

[0067] in, This is the unit vector pointing from the satellite to the target in the satellite's body coordinate system, and it is a 3×1 orthogonal matrix. This is the attitude transformation matrix from the satellite body coordinate system to the inertial coordinate system. This matrix describes the orientation of each axis of the satellite body coordinate system in inertial space and serves as a bridge connecting inertial space and the satellite body.

[0068] The high-frequency satellite attitude quaternion sequence, with the same sampling rate as the servo control system, describes the satellite's real-time attitude at each control moment. The high-frequency pointing vector sequence, also with the same sampling rate, describes the satellite's unit direction of pointing towards the target in the inertial coordinate system. Both sets of data are strictly aligned in time and correspond to the same sampling moment.

[0069] S3.2 Using the attitude transformation matrix described above, convert the unit pointing vector in the inertial frame obtained in step 1 to... Pointing vector projection onto satellite body coordinate system: S3.3 A fixed installation relationship exists between the telescope base coordinate system and the satellite body coordinate system. Let the installation matrix from the satellite body to the telescope base be... This matrix, which can be obtained through precise ground calibration or in-orbit calibration, is a 3×3 orthogonal matrix that describes the fixed orientation of the telescope base relative to the satellite body.

[0070] Based on the pre-stored installation matrix S3.2, the telescope computer further projects the pointing vector in the satellite body coordinate system to the telescope base coordinate system:

[0071] in, The unit pointing vector in the telescope base coordinate system represents the direction of the target in the telescope base coordinate system, and is a 3×1 vector.

[0072] Coordinate transformation is the process of gradually converting the target's orientation from a unified inertial coordinate system to the telescope base coordinate system. It serves as a bridge connecting target motion, satellite attitude, and telescope pointing. The pointing vector in the inertial coordinate system describes the target's absolute orientation in space, but the telescope's rotation control needs to be described in the telescope base coordinate system. Through two coordinate transformations, the absolute orientation information is decoupled from the satellite attitude and telescope mounting orientation, allowing the telescope servo control system to directly control based on the pointing vector in the base coordinate system. The use of high-frequency attitude quaternions ensures the real-time performance and accuracy of the coordinate transformation.

[0073] In some embodiments, if there is flexible deformation in the installation of the satellite body to the telescope base, a dynamic correction model of the installation matrix can be established, and the installation matrix can be corrected in real time based on the on-board flexible measurement data to improve the coordinate transformation accuracy.

[0074] In some embodiments, if the telescope has multiple rotation axes and is non-orthogonally mounted, a more complex kinematic model can be introduced to map the pointing vector in the base coordinate system to the desired angle of each rotation axis.

[0075] Step 4: Based on the unit pointing vector in the telescope base coordinate system obtained in Step 3, the telescope computer calculates the desired azimuth and desired elevation angles of the telescope through spherical coordinate transformation, and generates the position command sequence required by the servo control system.

[0076] To clarify the geometric meaning of the pointing angle, the telescope base coordinate system is defined as follows: X-axis: points in the direction of satellite flight (along the orbit); Y-axis: Determined according to the right-hand rule, perpendicular to the X-axis (crossing the track direction); Z-axis: points towards the zenith (perpendicular to the orbital plane); Under this coordinate system, the direction of the telescope's line of sight is uniquely determined by two angles: Azimuth A: The angle between the projection of the line of sight onto the XY plane and the positive direction of the X-axis. Its value typically ranges from [-180°, 180°] to [0°, 360°]. Pitch angle E: The angle between the line of sight and the XY plane, i.e., the elevation angle of the line of sight relative to the horizontal plane, typically ranging from -90° to 90°. The unit pointing vector sequence in the telescope base coordinate system generated in step 3 is used as input data. It is consistent with the sampling rate of the servo control system and describes the direction of the target relative to the telescope base in each control cycle.

[0077] Based on the transformation relationship between spherical coordinates and rectangular coordinates, and based on the unit pointing vector in the telescope base coordinate system... Determine the desired azimuth angle of the telescope. Desired pitch angle ,as follows:

[0078] Furthermore, to improve the tracking performance of the servo control system, the calculated desired pointing angle can be post-processed as follows: Angle range normalization, angle continuity processing, and smoothing filtering.

[0079] For example, angle range normalization maps the azimuth and elevation angles to the effective range based on the actual mechanical limitations of the telescope. For instance, if the effective azimuth range is [0°, 360°), negative angles can be converted to this range by adding 360°; if mechanical limitations exist, it is necessary to check whether the angle exceeds the allowable range and take appropriate action.

[0080] Smoothing filtering involves applying a low-pass filter to the desired pointer angle sequence to eliminate high-frequency noise and obtain a smoother command trajectory. This can be achieved using a first-order low-pass filter or a moving average filter.

[0081] Pointing angle calculation transforms the target direction from a vector form into an executable rotation angle command for the telescope, serving as a crucial link between pointing vector calculation and servo control. Its mathematical essence is spherical coordinate transformation, decomposing the three-dimensional direction vector into two orthogonal rotation angles, corresponding to the telescope's azimuth and elevation axes, respectively. Through this transformation, the servo control system can point the line of sight towards the target direction via rotation in two degrees of freedom. The high frequency and high precision provided in step 3 ensure that the pointing angle command in each control cycle accurately reflects the target direction, while the precise calculation in step 4 guarantees an accurate mapping between the two. The post-processed desired pointing angle sequence is smooth, continuous, and controllable, providing high-quality position command input for the servo control system.

[0082] In some embodiments, the telescope base coordinate system may be defined in other ways, and the corresponding pointing angle calculation formula needs to be adjusted: If the Z-axis points in the direction of satellite flight and the X-axis points in the zenith, then the formula for calculating the pointing angle needs to be adjusted accordingly. If the northeast-sky coordinate system is used (X-axis points east, Y-axis points north, Z-axis points to the sky), the azimuth angle is usually defined as the angle of rotation clockwise or counterclockwise from north. The calculation formula needs to be adjusted according to the specific definition.

[0083] Step 5: The telescope computer sends the desired azimuth and desired elevation angles obtained in Step 4 to the servo control system. The servo control system drives the spaceborne telescope to rotate in two dimensions through a multi-closed-loop control structure of position loop, velocity loop and current loop, so that the telescope's line of sight is accurately pointed to the target, and stable tracking of the target is achieved.

[0084] Figure 3 The diagram shows the block diagram of the telescope servo control system. The system takes the desired azimuth / elevation angle of the telescope as the command input, calculates the deviation between the input and the actual angle fed back by the azimuth / elevation angle measurement sensor of the telescope, and outputs the deviation signal as a control voltage after processing by the telescope servo controller. The control voltage is then amplified by the telescope servo driver into a drive voltage, which drives the telescope motion actuator to complete the azimuth / elevation rotation. Finally, a closed-loop control is formed through angle feedback to achieve precise pointing of the telescope's line of sight.

[0085] This invention utilizes the fusion of low-frequency attitude quaternions and high-frequency gyro angular velocity information to obtain a high-frequency, high-precision attitude reference, solving the problems of low attitude data frequency and latency in traditional guidance and pointing schemes. By combining pointing vector interpolation and coordinate transformation, a high-precision desired pointing angle synchronized with the servo control frequency is generated. Finally, the servo control system drives the telescope to achieve precise pointing. This method effectively improves the pointing accuracy and stability of the space telescope's line-of-sight under low-dynamic conditions, meeting the requirements for long-term stable exposure and detection of faint targets, and achieving high-precision, stable pointing of the space telescope's line-of-sight.

[0086] Example 1 A line-of-sight stabilizing pointing system for a space telescope, comprising: The data acquisition module is used to acquire the low-frequency satellite attitude quaternion and the high-frequency satellite attitude angular velocity. The delay compensation module is used to perform delay compensation on the low-frequency satellite attitude quaternion to obtain the compensated attitude quaternion. The data fusion module is used to fuse the compensated attitude quaternion with the high-frequency satellite attitude angular velocity using a data fusion algorithm, and generate a high-frequency satellite attitude quaternion sequence that is consistent with the sampling rate of the servo control system. The coordinate transformation module is used to calculate the attitude transformation matrix based on the high-frequency satellite attitude quaternion sequence, and to project the inertial pointing vector sequence between the target and the satellite position onto the satellite body coordinate system and the telescope base coordinate system in sequence to obtain the pointing vector sequence in the telescope base coordinate system. The pointing angle calculation module is used to calculate the desired pointing angle of the telescope based on the pointing vector sequence in the telescope base coordinate system, and then control the rotation of the telescope so that the line of sight points to the target.

[0087] Example 2 A space telescope, comprising: Satellite platform; A star sensor, fixedly installed on the satellite platform, is used to measure the satellite attitude and output low-frequency satellite attitude quaternions; A three-axis gyroscope, mounted near the telescope base, is used to output high-frequency satellite attitude angular velocity; The line-of-sight stabilizing pointing system of the space telescope as described in Example 1 is installed on the satellite platform. The data acquisition module of the line-of-sight stabilizing pointing system is connected to the star sensor and the three-axis gyroscope signals respectively, and is used to receive the low-frequency satellite attitude quaternion and the high-frequency satellite attitude angular velocity. The telescope optical system, installed on the satellite platform, is driven and connected to the servo control module of the line-of-sight stabilization pointing system, and is used for target observation based on the line-of-sight pointing.

[0088] It should be noted that, in the several embodiments provided in this application, it should be understood that the disclosed apparatus and methods can be implemented in other ways. For example, the apparatus embodiments described above are merely illustrative; for instance, the division of modules is only a logical functional division, and in actual implementation, there may be other division methods. For example, multiple modules may be combined or integrated into another device, or some features may be ignored or not executed. The modules described as separate components may or may not be physically separated. The components shown as modules may be one or more physical units, that is, they may be located in one place or distributed in multiple different places. Some or all of the modules can be selected to achieve the purpose of the solution in this embodiment according to actual needs.

[0089] Furthermore, in the various embodiments of the present invention, the modules can be integrated into one processing unit, or each module can exist physically separately, or two or more modules can be integrated into one unit. The integrated unit described above can be implemented in hardware or as a software functional unit.

[0090] An electronic device provided in this application includes a memory and a processor. The memory stores a computer program, and when the processor executes the computer program, it implements the steps of the line-of-sight stabilization pointing method for a space telescope as described in any of the above embodiments.

[0091] Another electronic device provided in this application embodiment may further include: an input port connected to a processor for transmitting multimodal data collected by an external acquisition device to the processor; a display unit connected to the processor for displaying the processor's processing results to the outside world; and a communication module connected to the processor for enabling communication between the electronic device and the outside world. The display unit may be a display panel, a laser scanning display, etc.; the communication method adopted by the communication module includes, but is not limited to, Mobile High Definition Link (HML), Universal Serial Bus (USB), High Definition Multimedia Interface (HDMI), and wireless connection (including Wi-Fi, Bluetooth, Bluetooth Low Energy, and IEEE 802.11s-based communication technology).

[0092] This application provides a computer-readable storage medium storing a computer program. When the computer program is executed by a processor, it implements the steps of the line-of-sight stabilization pointing method for a space telescope as described in any of the above embodiments.

[0093] For descriptions of the relevant parts of the line-of-sight stabilization pointing system, electronic equipment, and computer-readable storage medium of the space telescope provided in this application, please refer to the detailed description of the corresponding parts in the line-of-sight stabilization pointing method of the space telescope provided in this application, which will not be repeated here. Furthermore, parts of the technical solutions provided in this application that are consistent with the implementation principles of corresponding technical solutions in the prior art have not been described in detail to avoid excessive elaboration.

[0094] The above content is only for illustrating the technical concept of the present invention and should not be construed as limiting the scope of protection of the present invention. Any modifications made to the technical solution based on the technical concept proposed in this invention shall fall within the scope of protection of the claims of this invention.

Claims

1. A method for stabilizing the line-of-sight pointing of a space telescope, characterized in that, Includes the following steps: Obtain the low-frequency satellite attitude quaternion and the high-frequency satellite attitude angular velocity; Delay compensation is applied to the low-frequency satellite attitude quaternion to obtain the compensated attitude quaternion; A data fusion algorithm is used to fuse the compensated attitude quaternion with the high-frequency satellite attitude angular velocity to generate a high-frequency satellite attitude quaternion sequence that is consistent with the sampling rate of the servo control system. The attitude transformation matrix is ​​calculated based on the high-frequency satellite attitude quaternion sequence. The inertial pointing vector sequence between the target and the satellite position is then projected sequentially onto the satellite body coordinate system and the telescope base coordinate system to obtain the pointing vector sequence in the telescope base coordinate system. The desired pointing angle of the telescope is calculated based on the pointing vector sequence in the telescope base coordinate system, and then the telescope is rotated to make the line of sight point to the target.

2. The method for stabilizing the line-of-sight pointing of a space telescope according to claim 1, characterized in that, The delay compensation for low-frequency satellite attitude quaternions is specifically as follows: Using the low-frequency satellite attitude quaternion received at the current moment as the attitude estimate at the historical moment, and using the high-frequency satellite attitude angular velocity for integral compensation, the low-frequency satellite attitude quaternion is extrapolated to the current moment to obtain the compensated attitude quaternion.

3. The method for stabilizing the line-of-sight pointing of a space telescope according to claim 1, characterized in that, The generation of high-frequency satellite attitude quaternion sequences using a data fusion algorithm is specifically as follows: Using the compensated attitude quaternion as the initial value, the high-frequency satellite attitude angular velocity is used to gradually deduce according to the attitude kinematic equation. Within one satellite attitude broadcasting cycle, multiple high-frequency satellite attitude quaternions with the same sampling rate as the servo control system are generated to form a high-frequency satellite attitude quaternion sequence.

4. The method for stabilizing the line-of-sight pointing of a space telescope according to claim 1, characterized in that, The inertial frame pointing vector sequence between the target and the satellite position is obtained through the following steps: Obtain the target position coordinates and satellite position coordinates broadcast by the satellite's satellite navigation computer; Based on the target position coordinates and satellite position coordinates, calculate the unit pointing vector of the satellite pointing towards the target in the inertial coordinate system; The unit pointing vector is interpolated to obtain an inertial frame pointing vector sequence that matches the sampling rate of the servo control system.

5. A method for stabilizing the line-of-sight pointing of a space telescope according to claim 1 or 4, characterized in that, The step of sequentially projecting the inertial frame pointing vector sequence onto the satellite body coordinate system and the telescope base coordinate system specifically includes: Calculate the attitude transformation matrix from the inertial coordinate system to the satellite body coordinate system based on the high-frequency satellite attitude quaternion sequence; Using the attitude transformation matrix, the inertial frame pointing vector sequence is projected onto the satellite body coordinate system to obtain the body coordinate system pointing vector sequence; Using a pre-calibrated installation matrix from the satellite body to the telescope base, the pointing vector sequence of the satellite body coordinate system is projected onto the telescope base coordinate system to obtain the pointing vector sequence of the base coordinate system.

6. The method for stabilizing the line-of-sight pointing of a space telescope according to claim 1, characterized in that, The calculation of the desired pointing angle of the telescope based on the pointing vector sequence in the telescope base coordinate system is specifically as follows: Based on the components of each pointing vector in the pointing vector sequence of the base coordinate system on the three coordinate axes, the corresponding desired azimuth and desired pitch angles are calculated through spherical coordinate transformation, generating a desired pointing angle sequence consistent with the sampling rate of the servo control system.

7. The method for stabilizing the line-of-sight pointing of a space telescope according to claim 1, characterized in that, The data fusion algorithm includes any of the following: Direct integration method, Kalman filter algorithm, extended Kalman filter, unscented Kalman filter, complementary filter algorithm or neural network algorithm.

8. The method for stabilizing the line-of-sight pointing of a space telescope according to claim 1, characterized in that, The specific details of obtaining the low-frequency satellite attitude quaternion are as follows: The satellite attitude quaternion is received from the satellite's satellite computer and is obtained by measuring a star sensor that is fixedly installed on the satellite body. The specific steps for obtaining the high-frequency satellite attitude angular velocity are as follows: The system receives the three-axis attitude angular velocity output from a three-axis gyroscope mounted near the telescope base, and the sampling rate of the output data of the three-axis gyroscope is consistent with the sampling rate of the servo control system.

9. A line-of-sight stabilizing pointing system for a space telescope, characterized in that, include: The data acquisition module is used to acquire the low-frequency satellite attitude quaternion and the high-frequency satellite attitude angular velocity. The delay compensation module is used to perform delay compensation on the low-frequency satellite attitude quaternion to obtain the compensated attitude quaternion. The data fusion module is used to fuse the compensated attitude quaternion with the high-frequency satellite attitude angular velocity using a data fusion algorithm, and generate a high-frequency satellite attitude quaternion sequence that is consistent with the sampling rate of the servo control system. The coordinate transformation module is used to calculate the attitude transformation matrix based on the high-frequency satellite attitude quaternion sequence, and to project the inertial pointing vector sequence between the target and the satellite position onto the satellite body coordinate system and the telescope base coordinate system in sequence to obtain the pointing vector sequence in the telescope base coordinate system. The pointing angle calculation module is used to calculate the desired pointing angle of the telescope based on the pointing vector sequence in the telescope base coordinate system, and then control the rotation of the telescope so that the line of sight points to the target.

10. A space telescope, characterized in that, Includes the line-of-sight stabilizing pointing system of the space telescope as described in claim 9.

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