CN112162158B - Method and device for evaluating pointing mismatch of antenna of on-orbit terahertz detector - Google Patents
Method and device for evaluating pointing mismatch of antenna of on-orbit terahertz detector Download PDFInfo
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Abstract
The invention discloses an on-orbit terahertz detector antenna pointing mismatching evaluation method and device. In the evaluation method, firstly, an ideal target azimuth of a radio star in a directional diagram of an ideal terahertz detection antenna and a deviation between an actual observation position and the ideal target azimuth caused by a thermal deformation effect are obtained; establishing an influence model of thermal deformation deviation on position deviation in an antenna directional diagram; equating the phase corresponding to the actually observed peak value to be an actual observation vector in an ideal coordinate system, and obtaining the pointing deviation of the radio star according to the ideal observation vector of the direction vector of the antenna pointing to the position of the radio star in the ideal coordinate system under the actual observation moment corresponding to the actually observed peak value; repeating the steps, solving the pointing deviation of each radio star one by one, and establishing a deviation equation of the antenna thermal deformation; and solving a deviation equation to obtain the deviation amount of the antenna electric axis direction. By using the method and the device, the positioning and registration accuracy of the on-orbit terahertz detector can be improved.
Description
Technical Field
The invention relates to an evaluation method for antenna pointing mismatch of an on-orbit terahertz detector, and also relates to a corresponding evaluation device, belonging to the technical field of satellite remote sensing.
Background
When the effective load carried by the remote sensing satellite of the static orbit works in the orbit, the satellite body and the load can generate thermal deformation. According to the on-orbit data analysis of the optical star loads of the U.S. GOES series satellite and the Chinese Fengyun A star, the deformation quantity is not negligible for remote sensing. The change of the optical sight line caused by deformation can reach 1000 micro-arc magnitude, and the on-orbit observation pointing accuracy of the remote sensing load and the positioning accuracy of the remote sensing data are directly influenced.
For an on-orbit terahertz detector, the antenna can be influenced by the outside after being normally unfolded. Due to the change of solar illumination on the in-orbit terahertz detector, the satellite platform and the antenna can deform in orbit, the parameters such as the antenna pointing direction, the antenna directional diagram and the like of the terahertz detector obviously deviate from the original design and ground measurement parameters due to thermal deformation, and the positioning and registration accuracy of detection data can be directly influenced due to the change of the equivalent electric axis of the in-orbit antenna caused by the deformation.
Since the deformation quantity is closely related to time (the motion between the satellite and the sun), the deformation quantity is not a stable deviation and shows a typical time-varying characteristic. The thermal deformation deviations need to be monitored, evaluated and corrected continuously. A mathematical model capable of accurately describing the thermal deformation deviation of the on-orbit terahertz detector is established, and is the basis and key for solving the time-varying deviation.
Because the static track on-orbit terahertz detector has large volume, complex structure, and more components and influencing factors which generate thermal deformation, the modeling and solving of the thermal deformation deviation of the on-orbit terahertz detector are complex, and the technical difficulty is high.
At present, the thermal deformation research in the field of geostationary orbit satellites at home and abroad mainly focuses on the research on the in-orbit thermal deformation rule of the optical remote sensing load consisting of the optical scanning mirror. For satellite-borne optical imaging loads, an optical target can be selected from an optical remote sensing image, and deviation can be evaluated in an image matching mode.
However, for the terahertz microwave detection type load, the obtained detection data is target object radiation information, not a directly visualized optical image, and therefore, the deviation estimation cannot be performed by an image matching method. In addition, the overall dimension of the terahertz detection antenna is generally larger than that of a common optical load, and the exposed surface of an antenna system is more than that of the common optical load, so that the comprehensive deformation degree of the terahertz detection antenna is larger than that of the common optical load, and the influence factors are more complex.
Disclosure of Invention
The invention aims to solve the primary technical problem of providing an evaluation method for misdirection of an antenna of an on-orbit terahertz detector.
The invention aims to solve another technical problem of providing an evaluation device for misdirection of an antenna of an on-orbit terahertz detector.
In order to achieve the purpose, the invention adopts the following technical scheme:
according to a first aspect of the embodiments of the present invention, there is provided an evaluation method for pointing mismatch of an on-orbit terahertz detector antenna, including the following steps:
obtaining an ideal target azimuth of the radio star in a directional diagram of the ideal terahertz detection antenna and deviation between an actual observation position and the ideal target azimuth caused by a thermal deformation effect;
establishing an influence model of thermal deformation deviation on position deviation in an antenna directional diagram by utilizing the influence relation of the thermal deformation effect on the position;
equating the phase corresponding to the actually observed peak value as an actual observation vector under an antenna ideal coordinate system, and obtaining the pointing deviation of the radio star according to the ideal observation vector of the direction vector of the antenna pointing to the position of the radio star under the antenna ideal coordinate system under the actual observation moment corresponding to the actually observed peak value;
repeating the steps, solving the pointing deviation of each radio star one by one, and establishing a deviation equation of the antenna thermal deformation;
and solving the deviation equation to obtain the deviation amount of the antenna electric axis direction.
Preferably, the method comprises the following steps:
s1: performing resident observation around each radio star and recording observation data;
s2: according to the geometrical information of the satellite, the radio stars and the antenna, the ideal target position of the radio stars in the antenna coordinate system during each step of residence is calculated in sequence;
s3: drawing a discrete observation energy intensity antenna distribution diagram according to the corresponding relation between the actual detection data and the observation phase, and further fitting to obtain an actual detection antenna directional diagram;
s4: comparing the actual detection antenna pattern with the ideal design antenna pattern;
s5: calculating a phase corresponding to an actually observed peak value according to an actually detected antenna directional diagram, and extracting an actual observation time;
s6: the phase corresponding to the actually observed peak value is equivalent to an actual observation vector under an antenna ideal coordinate system;
s7: calculating an ideal observation vector of a direction vector of the antenna pointing to the position of the radio star at the actual detection moment under an antenna ideal coordinate system;
s8: constructing an equivalent relation between an actual observation vector and an ideal observation vector through a thermal deformation deviation matrix;
s9: constructing an equivalent transformation relation equation set with the pointing deviation as an unknown quantity by using all the radio star observation data;
s10: and calculating to obtain the directional mismatch angle component of the terahertz detector antenna, and obtaining a directional deviation matrix of the corresponding time period.
Preferably, the same radio star is observed for multiple times in a time period and a frequency band under the same antenna space reference condition;
calculating an ideal target direction of the radio star relative to a main beam of the terahertz detection antenna at the mth resident observation center moment;
and calculating the ideal target azimuth of the radio satellite under an inertial system according to the observation time of the radio satellite, the space-time information of the observation satellite, the design parameters of the observation antenna and the antenna pointing data.
Preferably, the position coordinates and attitude angles of the satellite are acquired at the moment of the mth resident observation center;
and converting an ideal target vector under an inertial system into a target vector of an antenna coordinate system according to the position coordinates and the attitude angle of the satellite.
According to the target vector of the antenna coordinate system, uniquely determining a group of E, H-direction observation azimuth angles as a main beam ideal observation azimuth angle of the mth resident observation center moment;
and calculating an ideal target position of the radio satellite relative to the main beam of the terahertz detection antenna at the mth resident observation center moment according to the ideal observation azimuth angle of the radio satellite at the mth resident observation center moment, a preset observation azimuth angle and the ideal observation azimuth angle of the main beam.
Preferably, the fitting to obtain the actual probing antenna pattern comprises the steps of:
the DN values of the digital energy signals correspond to the observation phases one by one to obtain a discrete sampling antenna directional diagram;
and solving the optimal fitting coefficient according to the discrete sampling antenna directional diagram and a fitting function solving method, and fitting to obtain the actually measured antenna directional diagram.
Preferably, the equivalent transformation relationship between the ideal observation direction vector and the actual direction vector satisfies: AU (AU) k ＝V k Wherein, U k Is an ideal direction vector of observation, V k Is the actual direction vector;
to make AU k -V k ＝ε k The thermal deformation deviation matrix is obtained in a mode of minimum error,
wherein epsilon k For the k-th star, at the strongest peak of the measured signal, the ideal observation vector U is subjected to mismatch angle k Corrected and actual observation vector V k The residual error between (k is 1,2, …, N), N is the effective observation radio starThe number of the cells.
Preferably, the step of constructing an equivalent transformation relation equation set with the pointing deviation as an unknown quantity by using all the radio satellite observation data comprises the following steps:
the actual observation vector of the radio star is compared with the ideal observation vector so as to make AU k -V k ＝ε k Solving a thermal deformation deviation matrix in a mode of minimum error, and constructing a plurality of equivalent equations;
and solving the equivalent equation set to obtain a pointing mismatch angle deviation component of the terahertz detector antenna based on the radio stars.
Preferably, the actual observation vector of the radio satellite position is converted into an ideal observation vector under an antenna ideal coordinate system at the radio satellite position, the satellite attitude and the antenna spatial relationship at the mth resident observation center moment.
According to a second aspect of the embodiments of the present invention, there is provided an apparatus for evaluating pointing mismatch of an on-orbit terahertz detector antenna, including a processor and a memory, wherein the processor reads a computer program in the memory, and is configured to perform the following operations:
obtaining an ideal target azimuth of the radio star in a directional diagram of the ideal terahertz detection antenna and deviation between an actual observation position and the ideal target azimuth caused by a thermal deformation effect;
establishing an influence model of thermal deformation deviation on position deviation in an antenna directional diagram by utilizing the influence relation of the thermal deformation effect on the position;
equating the phase corresponding to the actually observed peak value as an actual observation vector under an antenna ideal coordinate system, and obtaining the pointing deviation of the radio star according to the ideal observation vector of the direction vector of the antenna pointing to the position of the radio star under the antenna ideal coordinate system under the actual observation moment corresponding to the actually observed peak value;
repeating the steps, solving the pointing deviation of each radio star one by one, and establishing a deviation equation of the antenna thermal deformation;
and solving the deviation equation to obtain the deviation amount of the antenna electric axis direction.
Compared with the prior art, the invention provides a method for modeling the deviation of the pointing direction of an antenna electric axis caused by thermal deformation by taking a radio star as a spatial reference, taking the equivalent deviation of a terahertz detection antenna in the pointing direction of a three-dimensional space caused by the thermal deformation effect as a to-be-evaluated quantity, and further solving the deviation of the pointing direction of the antenna electric axis, thereby eliminating the thermal deformation deviation of the terahertz detection instrument in the orbit and improving the positioning and registering precision.
Drawings
FIG. 1 is a schematic view of step-wise dwell observation around a radio star in an embodiment of the present invention;
FIG. 2 is a schematic diagram illustrating a relationship between an inertial system and an antenna coordinate system according to an embodiment of the present invention;
FIG. 3 is a discretely sampled antenna pattern in an embodiment of the present invention;
FIG. 4 is a flow chart of an evaluation method provided by an embodiment of the present invention;
fig. 5 is a schematic structural diagram of an evaluation apparatus according to an embodiment of the present invention.
Detailed Description
The technical contents of the invention are described in detail below with reference to the accompanying drawings and specific embodiments.
For convenience of understanding, an interferometric atmospheric vertical detector (abbreviated as a detector or GIIRS) on a wind cloud star a is taken as an example to simply illustrate the operation of the detector. The main function of the detector is to realize the vertical structure observation of the atmospheric temperature and humidity parameters. On a static orbit of the earth, the detector performs infrared spectrum distribution detection on a required area, provides input data for numerical weather forecast, provides detection service for disastrous weather monitoring and atmospheric chemical components, and realizes the observation of visible light on cloud. During detection, cold space background sampling is performed at predetermined time intervals, followed by black body scaling and star sensitivity. The task content of the known area observation comprises cold space calibration, black body calibration, star sensitivity and area detection. In the process of regional observation, 1 cold space calibration, 1 black body calibration, 1 star sensitivity at 15 positions (5 stars each of which is observed at 3 positions) and regional detection are set to be carried out every 15 minutes.
According to the demand of weather forecast, the GIIRS area survey is currently mainly to observe clear sky. Firstly, the longitude and latitude of an area needing to be observed are converted into row and column numbers in a nominal grid, so that each clear sky point is converted into a point represented by the row and column numbers. Then, screening out all grid points with cloud cover values smaller than the specified clear sky coefficient, namely, screening out all points represented by row and column numbers. And after clear sky screening, segmenting clear sky grids according to the detector residence point range (namely the size of the detector area array), and counting the clear sky quantity in each residence point range. The residence point with a high clear-to-air ratio is preferably selected, for example, the ratio is 100% or 90%. The preferred residence points are merged (distributed residence) on the principle of 20 residence points per 15 minute time period. For more than 20 laterally consecutive dwell points, a split is required. And calculating the number of the resident points according to the starting and stopping column numbers of the continuous resident points, and performing up-compensation on less than 20 resident points. And in each 15-minute time period, arranging the continuous residence points into a task, and calculating the task time according to the number of the residence points. Meanwhile, the running time of each task of cold space scaling, black body scaling and star sensitivity as well as the fast pointing and command interval time are accurately calculated. Therefore, each task is reasonably arranged in time to generate a task schedule, and an instruction is generated according to the task schedule and is injected into the satellite.
The main thought of the thermal deformation time-varying mathematical model provided by the embodiment of the invention is as follows: observing the radio star by using a terahertz detector with the radio star as a reference, and acquiring the difference between the E surface and the H surface of the main lobe of the actual directional diagram of the detection antenna and the E surface and the H surface of the ideal design directional diagram according to the actual measurement data; by constructing a mathematical relationship between the deviation of a main lobe directional diagram of the antenna of the terahertz detector and the equivalent detection direction of the load in the three-dimensional space, the equivalent deviation of the equivalent thermal deformation effect of the antenna of the terahertz detector in the three-dimensional space can be described; and finally, by observing a plurality of groups of radio satellite data and taking equivalent deviation in a thermal deformation three-dimensional space as an unknown quantity, a corresponding thermal deformation deviation equation set can be constructed, and the solution of the antenna pointing mismatch can be realized through optimal solution.
The antenna of the on-orbit terahertz detector generally comprises an antenna main reflecting surface, a multi-stage auxiliary reflecting surface, an antenna feed source, various rotating parts and the like, and the detector antenna comprises more components, so that the thermal deformation influence factors are very complex. After the satellite is in orbit, if no engineering feasible method is available, the deviation of the direction of the antenna of the detector cannot be obtained with high precision.
Based on an identifiable reference target space position (astronomical ephemeris), a directional offset model of the terahertz detection antenna thermal deformation effect in a three-dimensional space is directly constructed and solved, so that the directional offset of the terahertz detection antenna can be effectively identified, and the output antenna directional offset can be directly applied to geographic positioning of terahertz detection data.
The invention utilizes the on-orbit terahertz detector to carry out discrete distributed observation data of the radio star in two directions of the main surface (E surface and H surface) of the antenna, thereby calculating the quantitative difference between the ideal phase of the radio star in an ideal antenna directional diagram and the discrete phase in an actual on-orbit observation directional diagram. And then, according to an equivalent deviation influence model of the thermal deformation of the terahertz detection antenna on a three-dimensional space, correlating the ideal phase with the actual phase to form the difference of discrete directional diagrams observed by the same radio star, and further constructing a corresponding deviation equation. Finally, under a certain optimization standard, the deviation equation set is solved in a numerical mode, and the deviation amount of the antenna pointing to each direction in the three-dimensional space can be obtained.
The following describes in detail an evaluation method for the pointing mismatch of the antenna of the on-orbit terahertz detector provided by the present invention with reference to fig. 1 to 4. In the following steps, M, K, M, N, and the like are positive integers.
A plurality of frequency bands to be evaluated (detection frequency bands) and time periods to be evaluated (detection time periods) of the thermal deformation amount are preset. In practical application, a frequency band to be evaluated is selected from a band list of a load detection band according to application requirements, and then mismatch evaluation is performed on a certain specific frequency band. If the multiple frequency bands need to be evaluated, the single frequency band is evaluated one by one, and then the results of the multiple frequency bands are summarized and analyzed to obtain the relative difference among the multiple frequency bands. For the evaluation time period, the evaluation time period is usually set in a relatively fixed time interval manner to improve the convenience of the design of the observation scheme. The time interval duration of the evaluation period is mainly determined by the minimum evaluation interval of the application demand research target, for example, the evaluation period can be selected at intervals of 15 minutes and half an hour. Whether the spectral bands are overlapped or not is determined by the payload design spectral bands, and the overlapping is not generally carried out. However, whether or not the spectral bands overlap, the assessment can be performed using the present method. And selecting a certain number of radio stars in each corresponding frequency band and corresponding time period, and establishing a corresponding relation of frequency band-time period-radio stars.
It is assumed that the number of the radio satellites observed at each time is N in each frequency band-time period-radio satellite correspondence. Namely, for a detection frequency band, in a detection time period corresponding to the detection frequency band, the selected N radio stars are observed.
As shown in fig. 4, the method for evaluating the pointing mismatch of the antenna of the on-orbit terahertz detector provided by the invention mainly comprises the following steps: firstly, the radio star has an ideal position in the directional diagram of the ideal terahertz detection antenna, and the actual observation position deviates from the ideal position due to the thermal deformation effect, and the deviation can be described by two orthogonal coordinates. Then, by using the influence relation of the thermal deformation effect on the position, an influence model of the thermal deformation deviation on the position deviation in the antenna directional diagram can be abstracted and established. And finally, correlating the deviation in actual detection with the deviation in the model to complete the construction of the mathematical model of the antenna thermal deformation deviation equation. The concrete description is as follows:
s1: and performing resident observation around each radio star and recording observation data.
In actual observation, it is assumed that N radio stars are observed within a specific detection frequency band and detection time period. For each radio star, the k-th radio star is not usedFor example (k ═ 1,2, …, N), assume that at the central instant T of the acquisition period kC The ideal radio star position is S k With S k Centering, the main beam of the antenna array is directed to the radio satellite S k The antenna E, H can correspond to a unique observation direction in two directions, which is not marked as (E) kC ,H kC ). As shown in fig. 1, the main beam of the antenna array 2 is directed to the radio star 1.
To observe the azimuth (E) kC ，H kC ) And step-by-step resident pointing design of the antenna orientation is carried out at fixed intervals delta alpha in two directions E, H of the antenna as a reference center, and grid coverage type step-by-step resident observation is carried out around the center of an ideal radio star. Assuming that the parking positions are divided into 2K +1 in the direction E, H, a mesh parking grid of (2K +1) rows and (2K +1) columns is formed (see fig. 1), and M ═ 2K +1 is performed in total 2 Sub-step dwell observation. For example, at the first row and first column, the design's dwell observation azimuth is (DE) 1,1 ,DH 1,1 ) Can be expressed as
DE 1,1 ＝E kC -KΔα,DH 1,1 ＝H kC -KΔα；
At row i and column j, the designed dwell observation azimuth is (DE) i,j ,DH i,j ) Wherein
DE i,j ＝E kC +(i-1-K)Δα,
DH i,j ＝H kC +(i-1-K)Δα,
(i ═ 1,2, …, K; j ═ 1,2, …, K), and a detailed schematic diagram is shown in fig. 1.
For convenience of description, the numbering sequence (i, j) of the 2-dimensional space residence is described by a 1-dimensional serial number m, wherein the relation between m and the step residence observation row number is (i-1) × (2K +1) + j.
Therefore, the designed dwell observation azimuth angle at ith row and jth column is (DE) i,j ,DH i,j ) Equivalently, the designed dwell observation azimuth at the mth dwell position is (DE) m ,DH m ) (ii) a Further for more accurate representation, the method is used for designing an observer of the kth star at the mth dwell positionAzimuth angle, which is denoted as (DE) k,m ,DH k,m )。
Similarly, sequentially observing the N radio stars, and sequentially recording original radiation digital signal values, namely original DN values, of loads when the radio stars are observed; and simultaneously recording the number of the radio satellite, the observation time, the observation direction, and the satellite orbit position and attitude at the corresponding time.
S2: and according to the geometric information of the satellite, the radio star and the antenna, sequentially calculating the ideal target position of the radio star in the antenna coordinate system when the radio star resides in each step.
For the observation result in step S1, the same radio star S is subjected to observation for one observation period k In total, M observations were made, where M is (2K +1) 2 . Multiple observations over a period of time, specifically m observations residing step by step. In a complete experiment, the frequency band is fixed.
Because the radio satellites are respectively positioned at different azimuths of the antenna at different observation moments and the attitude and orbit states of the satellite are changed at the moments, the ideal target azimuth (E) of the radio satellites relative to the main beam of the terahertz detection antenna at the mth resident observation center moment needs to be calculated under the same antenna space reference condition under the inertial system k,m ,H k,m )。
According to space information such as the observation time, the satellite attitude, the satellite position and the satellite velocity of the radio satellite, the ideal target azimuth (E) can be calculated based on the design parameters of the antenna and the antenna pointing data k,m ,H k,m ). The method mainly comprises the following steps:
1) at the mth resident observation center time T m The satellite position coordinate P at the moment can be obtained according to the telemetering information downloaded by the satellite and the terahertz detector m Attitude angle Att m (ii) a Meanwhile, according to the star motion rule, the star position coordinate S can be obtained km 。
For the convenience of calculation, the position coordinates are all the international universal geocentric inertial coordinate system-J2000-ECI coordinate system.
Observation azimuth angle (theta) of antenna in direction E, H E ,θ H ) Uniquely determining a three-dimensional antenna pointing vector V of an antenna main beam under an instrument reference coordinate system ante ＝g(θ E ,θ H ) (ii) a For a certain three-dimensional target vector V ante The observed azimuth angles (theta) of a group of E, H directions can be uniquely determined E ,θ H ) So that the main beam of the antenna points to a target vector V ant 。
2) From the satellite position coordinates P m And attitude angle Att m An ideal target vector V under the inertial system can be obtained SC2Star,m Target vector V converted to antenna coordinate system ante,m 。
At the mth resident observation center time T m Under inertial system, pointing from satellite to star S k Can be represented as V SC2Star,m ＝S km -P m ；
The definition of the antenna coordinate system can be described as that the main beam direction of the ideal antenna is the + Z-axis direction, the E-plane direction is the + X-axis direction, and the H-plane direction is the + Y-axis direction. Fig. 2 shows the relationship of the inertial system to the antenna coordinate system.
3) According to the derivation of steps 1) and 2), from V ante,m The observed azimuth angles (theta) of a group of E, H directions can be uniquely determined E,m ,θ H,m ) I.e. is T m The main beam ideal observation azimuth angle at the moment.
4) Comprehensively utilizing the ideal observation azimuth angle (E) of the radio satellite at the central moment of the detection period kC ,H kC ) Azimuth of observation (DE) designed for step-wise dwell observation m ,DH m ) And the main beam ideal observation azimuth angle (theta) calculated at the time of actual observation E,m ,θ H,m ) Calculating the ideal target direction (E) of the radio satellite relative to the main beam of the terahertz detection antenna at the mth resident observation center moment k,m ,H k,m ) Specifically, it can be expressed as:
E k,m ＝DE m +θ E,m -E kC ；
H k,m ＝DH m +θ H,m -H kC
s3: and drawing a discrete observation energy intensity antenna distribution diagram according to the corresponding relation between the actual detection data and the observation phase, and further fitting to obtain an actual detection antenna directional diagram.
This step comprises two substeps:
31) and (4) enabling the DN value of the digital energy signal to correspond to the observation phases one by one to obtain a discrete sampling antenna directional diagram.
For the same star, with the antenna design zero phase as a reference, the DN value (digital signal formed by the response of the instrument to the radiation of the radio star and capable of representing the radiation signal intensity) of the actually measured radio star acquired by the step-by-step residence of M times and the observation direction (E) of the ideal target of the antenna obtained in the step S2 are compared k,m ,H k,m ) One by one, discrete sampling antenna patterns formed by M times of stepped resident mesh coverage observation can be quantitatively described (see fig. 3). FIG. 3 is a view of the observation direction (E) k,m ,H k,m ) And the measured digital signals of the radiation response of the planets are formed in a one-to-one correspondence mode.
32) And fitting to obtain an actually measured antenna directional diagram according to the discrete sampling antenna directional diagram.
According to the discrete sampling antenna directional diagram of the radio stars and the overall characteristics of the curved surface of the antenna directional diagram, the basic type of the fitted curved surface can be determined, then, according to a fitting function solving method, the optimal fitting coefficient is solved, and the actually measured antenna directional diagram based on actual detection data can be obtained.
S4: the actual detected antenna pattern is compared to the ideal designed antenna pattern.
Comparing the fitted actual observation antenna directional diagram with the ideal design antenna directional diagram, and if the similarity beta of the two is greater than a set threshold beta 0 If so, the observation data of the radio star is considered to be effective to enter the subsequent steps; otherwise, the observation is invalid, and the step S1 is returned to process the detection data of the next radio star.
S5: according to the actual detection antenna directional diagram, calculating the phase corresponding to the actually observed peak value, and extracting the actual observation time (Tf) k )。
Based on the fitted actual detected antenna patterns, in the E, H direction of the antenna, respectivelyAnd calculating the phase of the actually observed peak in the graph according to the observed phase value corresponding to the vertex in the graph and the corresponding time sequence. The phase corresponding to the actually observed peak is not recorded as (Ef) k ，Hf k ) (ii) a And extracting (Ef) k ，Hf k ) At the actual detection instant Tf k 。
S6: and (4) equating the phase corresponding to the actually observed peak value to be an actual observation vector under an antenna ideal coordinate system.
Will actually detect the peak phase (Ef) k ，Hf k ) Equivalent to actual detection vector V under the ideal coordinate system of the antenna k ＝(Xf k ，Yf k ，Zf k ) T Wherein Xf k ，Yf k ，Zf k T represents a vector transposition, and a column vector is transposed into a column direction, respectively, for coordinate values on the X, Y, Z axes in the ideal antenna coordinate system.
S7: the calculation is carried out at the actual detection instant (Tf) k Time of day), the direction vector of the antenna pointing to the position of the radio star is an ideal observation vector in an ideal coordinate system of the antenna.
Based on the motion law of the radio stars, the Tf is calculated k Radio star position P of time k And integrating the satellite position, attitude and antenna spatial relationship to point the antenna to the radio satellite position P k Is converted into an ideal observation vector U under an antenna ideal coordinate system k ＝(Xd k ，Yd k ，Zd k ) T 。
S8: and constructing an equivalent relation between the actual observation vector and the ideal observation vector through the thermal deformation deviation matrix.
Assuming that the synthetic observation direction deflects due to the deformation caused by the thermal deformation effect in the ideal coordinate system of the antenna, and the formed deviation matrix is A, an equivalent transformation relation AU between the ideal observation direction vector U and the actual direction vector V can be constructed k ＝V k 。
In the ideal coordinate system of the antenna, the pointing deviation caused by thermal deformation can be generally expressed by a thermal deformation deviation matrix A with 3 × 3 dimensions as follows
Considering that the coordinate system in practical application is considered as a rigid orthogonal coordinate system, the coordinate system transformation matrix a of the antenna usually only includes the rolling, pitching and yawing direction generation θ,
The conversion matrix a for mismatch angles of size ψ is a (θ, Φ, ψ).
S9: and constructing an equivalent transformation relation equation set by using the pointing deviation as an unknown quantity by using all the radio star observation data.
Repeating the steps S1 to S4, and obtaining the actual observation vectors V of the N radio stars k And ideal observation vector U k By substituting the equivalence conversion relations in step S8, a plurality of equivalence equation sets of corresponding types can be constructed.
S10: and calculating to obtain the directional mismatch angle component of the terahertz detector antenna, and obtaining a directional deviation matrix of the corresponding time period.
To solve the system of equivalent equations in step S9, it can be converted to a deviation in mismatching angle θ,
Psi is unknown quantity, so that the comprehensive evaluation equation set AU k -V k ＝ε k Optimization problem with minimum error, where k For the k-th star, at the strongest peak of the measured signal, the ideal observation vector U is subjected to mismatch angle k Corrected and actual observation vector V k The residual error between (k is 1,2, …, N), and N is the number of valid observed stars. And solving the optimization problem through a numerical solving algorithm to obtain a thermal deformation deviation matrix A.
In practical solutions, it is usually only necessary to solve for the roll, pitch and yaw direction bias components (θ, g, b, c, g, b, c, g, b, c, and c,
ψ)，And solving of the directional mismatch angle deviation component of the terahertz detector antenna based on the radio stars can be completed.
In order to realize the method for evaluating the pointing mismatching of the antenna of the on-orbit terahertz detector, the invention also provides a device for evaluating the pointing mismatching of the antenna of the on-orbit terahertz detector. As shown in fig. 5, the evaluation device includes a memory 31 and a processor 32, and may further include a communication component, a sensor component, a power component, and an input/output interface according to actual needs. The memory 31, the communication module, the sensor module, the power module, and the input/output interface are all connected to the processor 32. The memory 31 may be a Static Random Access Memory (SRAM), an Electrically Erasable Programmable Read Only Memory (EEPROM), an Erasable Programmable Read Only Memory (EPROM), a Programmable Read Only Memory (PROM), a Read Only Memory (ROM), a magnetic memory, a flash memory, etc., and the processor 32 may be a Central Processing Unit (CPU), a Graphic Processing Unit (GPU), a Field Programmable Gate Array (FPGA), an Application Specific Integrated Circuit (ASIC), a Digital Signal Processing (DSP) chip, etc. Other communication components, sensor components, power components, etc. may be implemented using common components found in existing smart devices and are not specifically described herein.
On the other hand, in the evaluation apparatus, the processor 32 reads the computer program in the memory 31 for performing the following operations:
obtaining an ideal target azimuth of the radio star in a directional diagram of the ideal terahertz detection antenna and deviation between an actual observation position and the ideal target azimuth caused by a thermal deformation effect;
establishing an influence model of thermal deformation deviation on position deviation in an antenna directional diagram by utilizing the influence relation of the thermal deformation effect on the position;
equating the phase corresponding to the actually observed peak value as an actual observation vector under an antenna ideal coordinate system, and obtaining the pointing deviation of the radio star according to the ideal observation vector of the direction vector of the antenna pointing to the position of the radio star under the antenna ideal coordinate system under the actual observation moment corresponding to the actually observed peak value;
repeating the steps, solving the pointing deviation of each radio star one by one, and establishing a deviation equation of the antenna thermal deformation;
and solving the deviation equation to obtain the deviation amount of the antenna electric axis direction.
Compared with the prior art, the invention provides a method for modeling the deviation of the pointing direction of an antenna electric axis caused by thermal deformation by taking a radio star as a spatial reference, taking the equivalent deviation of a terahertz detection antenna in the pointing direction of a three-dimensional space caused by the thermal deformation effect as a to-be-evaluated quantity, and further solving the deviation of the pointing direction of the antenna electric axis, thereby eliminating the thermal deformation deviation of the terahertz detection instrument in the orbit and improving the positioning and registering precision.
The present invention has been described in detail. It will be apparent to those skilled in the art that any obvious modifications thereof can be made without departing from the spirit of the invention, which infringes the patent right of the invention and bears the corresponding legal responsibility.
Claims (8)
1. An on-orbit terahertz detector antenna pointing mismatch assessment method is characterized by comprising the following steps:
s1: performing resident observation around each radio star and recording observation data;
s2: sequentially calculating the ideal target orientation of the radio stars in the antenna coordinate system when the radio stars reside step by step according to the geometrical information of the observation satellite, the radio stars and the antenna;
s3: according to the corresponding relation between the actual detection data and the observation phase, drawing a discrete observation energy intensity antenna distribution diagram, and further fitting to obtain an actual detection antenna directional diagram;
s4: comparing the actual detection antenna pattern with the ideal design antenna pattern;
s5: calculating a phase corresponding to an actually observed peak value according to an actually detected antenna directional diagram, and extracting an actual observation time;
s6: equating the phase corresponding to the actually observed peak value as an actual observation vector under an antenna coordinate system;
s7: calculating an ideal observation vector of a direction vector of the antenna pointing to the position of the radio star at the actual detection moment under an antenna coordinate system;
s8: constructing an equivalent relation between an actual observation vector and an ideal observation vector through a thermal deformation deviation matrix;
s9: constructing an equivalent transformation relation equation set with pointing deviation as an unknown quantity by using all the radio star observation data;
s10: and calculating to obtain the directional mismatch angle component of the terahertz detector antenna, and obtaining a directional deviation matrix of the corresponding time period.
2. The evaluation method of claim 1, wherein:
the step S2 includes the steps of:
observing the same radio star for multiple times in a time period and a frequency band under the same antenna space reference condition;
calculating an ideal target direction of the radio satellite relative to a main beam of the terahertz detection antenna at the mth resident observation center moment, wherein m is a positive integer;
and calculating the ideal target azimuth of the radio satellite under an inertial system according to the observation time of the radio satellite, the space-time information of the observation satellite, the design parameters of the observation antenna and the antenna pointing data.
3. The evaluation method according to claim 2, wherein
The step of calculating the ideal target position of the radio satellite relative to the main beam of the terahertz detection antenna at the mth resident observation center time comprises the following steps:
acquiring the position coordinate and the attitude angle of the satellite at the mth resident observation center moment;
converting an ideal target vector under an inertial system into a target vector of an antenna coordinate system according to the position coordinates and the attitude angles of the satellite;
according to the target vector of the antenna coordinate system, uniquely determining a group of E, H-direction observation azimuth angles as a main beam ideal observation azimuth angle of the mth resident observation center moment;
and calculating an ideal target position of the radio satellite relative to the main beam of the terahertz detection antenna at the mth resident observation center moment according to the ideal observation azimuth angle of the radio satellite at the mth resident observation center moment, a preset observation azimuth angle and the ideal observation azimuth angle of the main beam.
4. The evaluation method according to claim 3, wherein:
the step S3 of fitting to obtain an actual detection antenna pattern includes the following steps:
the DN values of the digital energy signals correspond to the observation phases one by one to obtain a discrete sampling antenna directional diagram;
and solving the optimal fitting coefficient according to the discrete sampling antenna directional diagram and a fitting function solving method, and fitting to obtain the actually measured antenna directional diagram.
5. The evaluation method of claim 1, wherein:
the equivalent relation between the actual observation vector and the ideal observation vector satisfies the following conditions: AU (AU) k ＝V k Wherein, U k Is an ideal observation vector, V k Is the actual observation vector;
to make AU k -V k ＝ε k The thermal deformation deviation matrix A is obtained in a mode of minimum error,
wherein epsilon k For the k-th star, at the strongest peak of the measured signal, the ideal observation vector U is subjected to mismatch angle k Corrected and actual observation vector V k The residual error between k and k is 1,2, …, and N is the number of effective observation stars.
6. The evaluation method of claim 5, wherein:
the step S9 includes:
the actual observation vector and the ideal observation vector of the radio star are combined to make AU k -V k ＝ε k Solving a thermal deformation deviation matrix in a mode of minimum error, and constructing a plurality of equivalent equations;
and solving the equivalent equation set to obtain a pointing mismatch angle deviation component of the terahertz detector antenna based on the radio stars.
7. The evaluation method of claim 5, wherein:
in step S7, the actual observation vector of the radio satellite position is converted into an ideal observation vector in the antenna coordinate system based on the radio satellite position at the mth resident observation center time and by integrating the position of the observation satellite, the attitude of the observation satellite, and the spatial relationship of the antenna.
8. An evaluation device for on-orbit terahertz detector antenna pointing mismatch is characterized by comprising a processor and a memory, wherein the processor reads a computer program in the memory and is used for executing the following operations:
the on-orbit terahertz detector antenna pointing mismatch evaluation method according to any one of claims 1 to 7.
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