CN-122026996-A - Coarse-fine switching method and device in satellite overhead tracking

CN122026996ACN 122026996 ACN122026996 ACN 122026996ACN-122026996-A

Abstract

The application provides a coarse-fine switching method and equipment in satellite overhead tracking, wherein the method comprises the steps of carrying out state estimation and uncertainty quantification based on instantaneous pointing errors of a satellite overhead tracking system in the satellite overhead stage, generating and dynamically updating two-dimensional probability density distribution describing light spot positions, fusing the two-dimensional probability density distribution with a light intensity distribution map influenced by atmospheric turbulence to obtain effective receiving indexes, determining a region of interest in fine tracking detection from the probability distribution, carrying out space-time clustering analysis on multi-frame detection data continuously collected by fine tracking equipment, calculating fine tracking point coordinates and identification confidence thereof, carrying out judgment based on atmospheric turbulence prediction data and probability distribution prediction tracking interruption probability, and combining the confidence, if the judgment passes, switching a control system into a fine tracking closed loop tracking mode. The application can realize the automatic switching from coarse aiming to fine aiming with high speed, reliability and anti-interference under the high dynamic scene of satellite fast overhead so as to ensure the fast establishment and stable maintenance of the free space optical communication link.

Inventors

FENG JIAOYANG
GAO RAN
WANG FEI
XU QI
ZHANG HONGYUAN
ZHU LEI
LIU BO
TIAN QINGHUA
REN JIANXIN
CHEN SHUAIDONG
HU SHANTING
ZHAO JIANYE
ZHONG QING

Assignees

北京邮电大学

Dates

Publication Date: 20260512
Application Date: 20260213

Claims (10)

1. The coarse-fine switching method in satellite overhead tracking is characterized by comprising the following steps: in the satellite overhead stage, carrying out state estimation and uncertainty quantization on the instantaneous pointing error of a satellite overhead tracking system in a coarse aiming open-loop mode, and generating and dynamically updating two-dimensional probability density distribution for describing the occurrence position of a satellite light spot; The two-dimensional probability density distribution is fused with a light intensity distribution map influenced by atmospheric turbulence, and an effective receiving index is calculated; In the interested region, carrying out space-time clustering analysis on multi-frame detection data continuously collected by a fine sight detection device to extract a signal cluster; And carrying out mode switching judgment based on the identification confidence and the tracking interruption probability, and controlling the satellite overhead tracking system to switch from a coarse aiming open loop mode to a fine aiming closed loop tracking mode if the judgment passes.
2. The method for coarse-fine switching in satellite overhead tracking according to claim 1, wherein in the stage of satellite overhead, the state estimation and uncertainty quantization are performed on the instantaneous pointing error of the satellite overhead tracking system currently in the coarse-overhead open-loop mode, and a two-dimensional probability density distribution for describing the occurrence position of a satellite light spot is generated and dynamically updated, and the method comprises the following steps: Acquiring a theoretical pointing angle of a satellite relative to a ground station, which is output by a satellite ephemeris prediction unit in a satellite overhead tracking system currently in a coarse aiming open-loop mode, and a current actual pointing angle of the satellite, which is fed back by a mechanical turntable encoder in the satellite overhead tracking system, and calculating a difference value between the theoretical pointing angle and the actual pointing angle to serve as a current instantaneous pointing error, wherein the instantaneous pointing error comprises an azimuth pointing error and a pitch angle pointing error; inputting the instantaneous pointing error into a Kalman filter, so that the Kalman filter takes the instantaneous pointing error of the satellite overhead tracking system and the angular velocity corresponding to the instantaneous pointing error as state variables, and recursively estimates the state variables to enable the Kalman filter to output a state estimation value and a posterior estimation error covariance matrix; And determining the shape and the diffusion range of the two-dimensional probability density distribution based on the posterior estimation error covariance matrix, thereby generating and continuously updating the two-dimensional probability density distribution.
3. The coarse-fine switching method in satellite overhead tracking according to claim 2, wherein the two-dimensional probability density distribution is a two-dimensional gaussian distribution taking a position error component in the state estimation value as a mean value and a submatrix for describing position uncertainty in the posterior estimation error covariance matrix as a covariance matrix; Or the two-dimensional probability density distribution is a Gaussian mixture model formed by weighted mixing of a plurality of two-dimensional Gaussian distributions; correspondingly, the determining the shape and the diffusion range of the two-dimensional probability density distribution based on the posterior estimation error covariance matrix comprises: And decomposing eigenvalues of submatrices used for describing the position uncertainty in the posterior estimation error covariance matrix, and determining an error ellipse used for representing the shape and the diffusion range of the two-dimensional probability density distribution based on the eigenvalues and eigenvectors obtained by decomposition.
4. The method for coarse-fine switching in satellite overhead tracking according to claim 1, wherein the fusing the two-dimensional probability density distribution with a light intensity distribution affected by atmospheric turbulence calculates an effective receiving index, and determining a region of interest for fine-focus detection from the two-dimensional probability density distribution based on the effective receiving index comprises: simulating to generate a light intensity distribution map influenced by turbulence based on the atmospheric turbulence prediction data; Spatially aligning the two-dimensional probability density distribution with the light intensity distribution map, and spatially convoluting the two-dimensional probability density distribution with the light intensity distribution map to obtain a spatial two-dimensional numerical distribution of the effective receiving index; Based on the two-dimensional numerical distribution of the effective receiving index, calculating to obtain an effective receiving index value, judging whether the index value is equal to or larger than a preset starting threshold value, if so, intercepting a sub-area from the two-dimensional probability density distribution according to the two-dimensional numerical distribution of the effective receiving index value, and taking the sub-area as a region of interest for fine aiming detection.
5. The coarse-fine switching method in satellite overhead tracking according to claim 4, wherein said capturing a sub-region from said two-dimensional probability density distribution according to said two-dimensional numerical distribution of effective reception index comprises: intercepting a subarea of pixel points, which are in the two-dimensional probability density distribution, of which the probability integral value exceeds a first preset threshold value and the value is higher than a second preset threshold value in the two-dimensional numerical value distribution covering the effective receiving index, from the two-dimensional probability density distribution, wherein the subarea is a rectangular area or a circular area.
6. The method for coarse and fine switching in satellite overhead tracking according to claim 1, wherein the performing space-time clustering analysis on multi-frame detection data continuously collected by the fine detection device in the region of interest to extract a signal cluster, calculating fine tracking point coordinates and identification confidence of the fine tracking point coordinates based on the signal cluster comprises: In the region of interest, controlling a fine-aiming detection device to continuously acquire multi-frame detection data at a frame rate higher than a preset frame rate threshold, wherein the fine-aiming detection device is a fine-aiming imaging camera, and the detection data is digital image data; Carrying out dark current deduction and flat field correction pretreatment operation on the digital image data of each frame in sequence; Threshold segmentation is carried out on each frame of preprocessed image data, pixel points with signal strength exceeding a background noise threshold value are marked as candidate bright points, and the space coordinates and the optical signal strength value of each candidate bright point are recorded; Constructing a three-dimensional data set according to the space coordinates of each candidate bright spot and the sequence number of the acquisition time frame, and performing space-time density clustering analysis on the three-dimensional data set based on a space-time density clustering algorithm to obtain at least one cluster, wherein the value of the space neighborhood radius of the space-time density clustering algorithm is positively correlated with the average noise level of multi-frame digital image data; And calculating weighted centroids of all the candidate bright spots in the signal clusters in the space dimension by taking the optical signal intensity values of the candidate bright spots in the signal clusters as weights, taking the space coordinates of the weighted centroids as fine aiming tracking point coordinates, and calculating the identification confidence of the fine aiming tracking point coordinates according to the signal clusters.
7. The coarse-fine switching method in satellite overhead tracking according to claim 6, wherein the calculating according to the signal cluster obtains the identification confidence of the fine tracking point coordinates, and the method comprises the following steps: calculating a spatial aggregation index of the signal clusters according to the spatial distribution of the candidate bright points in the signal clusters; calculating a time continuity index of the signal cluster based on the distribution of the candidate bright spots in the signal cluster on a time frame; and calculating a signal-to-noise ratio index of the signal cluster according to the comparison of the total optical signal intensity value of the signal cluster and the background noise intensity; and carrying out weighted fusion calculation on the space concentration index, the time continuity index and the signal to noise ratio index to obtain the identification confidence coefficient of the coordinate of the fine aiming tracking point.
8. The method for coarse and fine switching in satellite overhead tracking according to claim 1, wherein the predicting tracking interruption probability based on residual uncertainty characterized by the atmospheric turbulence prediction data and the two-dimensional probability density distribution, performing mode switching decision based on the identification confidence and the tracking interruption probability, and controlling the satellite overhead tracking system to switch from a coarse aiming open loop mode to a fine aiming closed loop tracking mode if the decision passes, comprises: Based on the atmospheric turbulence prediction data, predicting the change trend of at least one parameter of atmospheric coherence length, isochrone angle and flicker index in a preset time period in the future, and estimating the probability that the received signal strength at the fine sight tracking point in the preset time period is lower than a signal-to-noise ratio threshold required for maintaining closed-loop tracking in the future by combining the residual uncertainty parameter extracted from the two-dimensional probability density distribution, so as to take the probability as the tracking interruption probability; comparing the identification confidence coefficient with a preset confidence coefficient judgment threshold, and comparing the tracking interruption probability with a preset interruption probability judgment threshold; if the identification confidence coefficient is equal to or greater than the confidence coefficient judgment threshold and the tracking interruption probability is smaller than or equal to the interruption probability judgment threshold, judging that the mode switching judgment is passed; setting the coordinate of the fine aiming tracking point as an initial target of fine aiming closed-loop tracking, starting a quick reflector of a fine aiming module in the satellite overhead tracking system to perform closed-loop feedback control, and simultaneously switching a coarse aiming module in the satellite overhead tracking system into a follow-up compensation mode, so that the satellite overhead tracking system is switched from a coarse aiming open-loop mode to a fine aiming closed-loop tracking mode.
9. An electronic device comprising a memory, a processor and a computer program stored on the memory and executable on the processor, wherein the processor implements a coarse-fine handoff method in satellite overhead tracking as claimed in any one of claims 1 to 8 when the computer program is executed by the processor.
10. A computer readable storage medium having stored thereon a computer program, which when executed by a processor implements a coarse-fine handover method in satellite overhead tracking according to any of claims 1 to 8.

Description

Coarse-fine switching method and device in satellite overhead tracking Technical Field The application relates to the technical field of satellite optical communication, in particular to a coarse-fine switching method and equipment in satellite overhead tracking. Background In low orbit satellite communication systems, satellite overhead is the most challenging stage in the overall communication link. As satellites pass through the zenith vicinity from the ground station observer's perspective, their azimuth angle relative to the ground station can change drastically over a very short period of time, with angular velocities of tens of degrees per second or even higher. In this highly dynamic process, if the system needs to switch between different beacon sources or communication terminals, it is often difficult for the conventional tracking method to ensure the continuity and stability of the link. The conventional satellite optical communication tracking and aiming system generally adopts a coarse aiming and fine aiming two-stage structure. The coarse aiming module drives the mechanical turntable to approximately point the optical antenna to the satellite direction according to satellite ephemeris prediction, but the pointing error is influenced by ephemeris, machinery, atmosphere and other factors, and typical values are in the order of hundreds of micro radians. The fine sighting module realizes micro radian level accurate tracking through closed loop feedback by utilizing devices such as a quick reflector, a wavefront sensor and the like, but has a limited effective working range (usually a few milliradians). At present, a rough and fine switching strategy commonly adopted in engineering is a scanning capture mode, wherein after a rough aiming system points an antenna to a predicted position, a fine aiming sensor performs spiral or raster scanning in a preset uncertain area, and when the intensity of an output signal of a detector exceeds a certain fixed or self-adaptive threshold value, the acquisition is judged to be successful, and the acquisition is immediately switched to fine aiming closed loop tracking. The method essentially searches for uniform traversal of an uncertainty region, but its core logic is unchanged, although it can be optimized by demarcating the region, multiple detectors, or adjusting the threshold. The wavefront sensor (Wavefront Sensor, WFS) is a photoelectric detection device for detecting the phase distortion of the optical wavefront, and can measure the wavefront error caused by the atmospheric turbulence in real time. However, the prior art scheme has three outstanding technical problems, namely, the first step of severely restricting the performance of a link in the satellite overhead stage is that the acquisition efficiency is low, the method regards an uncertain region as uniform distribution, ignores the statistical rule of coarse sighting errors (such as systematic deviation or disturbance aggregation), causes a large number of invalid scans in a low probability region, prolongs the acquisition time, and is difficult to meet the requirement of an overhead short time window. Secondly, the anti-interference capability is weak, light spots can split, flicker and mix noise under strong atmospheric turbulence or background light interference, and the traditional single-frame and single-threshold-based judgment mechanism is extremely easy to generate false alarm (the noise is judged as a target) or miss alarm (the real signal is lost), so that the reliability is poor. Third, the switching decision mechanism is coarse, namely the switching is only dependent on a single condition of whether the instantaneous signal strength exceeds a threshold value, and the comprehensive evaluation of signal continuity and future stability of a link is lacked, so that the lock is immediately lost due to signal quality critical or instantaneous disturbance after the switching, frequency is heavy to capture, and the link continuity is seriously affected. The invention aims to provide a brand new coarse-fine switching method aiming at the problems. Disclosure of Invention In view of this, embodiments of the present application provide a coarse-fine handoff method and apparatus in satellite overhead tracking to obviate or mitigate one or more disadvantages in the prior art. The application provides a coarse-fine switching method in satellite overhead tracking, which comprises the following steps: in the satellite overhead stage, carrying out state estimation and uncertainty quantization on the instantaneous pointing error of a satellite overhead tracking system in a coarse aiming open-loop mode, and generating and dynamically updating two-dimensional probability density distribution for describing the occurrence position of a satellite light spot; The two-dimensional probability density distribution is fused with a light intensity distribution map influenced by atmospheric turbulence, and an effe