阅读说明：本技术 窄波束雷达捕获空间目标的等仰角搜索方法 (Equal elevation angle searching method for narrow-beam radar to capture space target ) 是由 徐劲 曹志斌 刘科君 杜建丽 杨冬 马剑波 于 2021-08-02 设计创作，主要内容包括：本发明提出了一种窄波束雷达捕获空间目标的等仰角搜索方法,采用了天体力学和天体测量学的基本方法,具体为基于空间目标的精密轨道参数,构建一种引导窄波束雷达发现和捕获目标的新方法,该方法为等仰角搜索方法,能够克服传统的点位预报搜索方法因预报沿迹误差扩散较快,雷达窄波束难以捕获目标的困难,显著提高窄波束雷达对空间目标的捕获成功率,是一种提升雷达应用效益的有效技术手段。(The invention provides an equal elevation search method for a narrow-beam radar to capture a space target, which adopts basic methods of celestial body mechanics and celestial body metrology, particularly a new method for guiding the narrow-beam radar to find and capture the target based on precise orbit parameters of the space target.)

1. The equal elevation searching method for the narrow beam radar to capture the space target is characterized in that radar guide data are generated based on target precision orbit parameters, the starting and stopping time of target crossing and the maximum orbit track error estimation during the target crossing so as to capture and track the corresponding target by the radar; the method specifically comprises the following steps:

step 1: calculating the intermediate time of the current transit of the target according to the starting and stopping time of the current transit of the target, taking the intermediate time as a reference time, and constructing an analysis perturbation model taking the reference time as an initial time by combining target precise track parameters;

step 2: calculating the theoretical station approaching moment of the target during the current transit period by combining the analysis perturbation model constructed in the step 1;

and step 3: discretizing the trace errors, and combining an analysis perturbation model to obtain a series of new perturbation models for describing the motion of each virtual target, wherein different visual tracks generated by each virtual target in the current transit period form a visual track cluster;

and 4, step 4: based on the theoretical station-approaching moment calculated in the step 2 and the solving process thereof, performing visibility confirmation on each visual track in the visual track cluster, and removing all invisible visual tracks;

and 5: removing the visual tracks with the detectable arc length not meeting the requirement in the visual track cluster;

step 6: determining the maximum detectable elevation angle and the minimum detectable elevation angle of each visual track in the visual track cluster, and further calculating to obtain the search elevation angle of the radar;

and 7: for each visual track in the visual track cluster, calculating observation characteristic parameters when all the virtual targets rise to a specified elevation angle based on the corresponding perturbation model;

and 8: carrying out continuous processing on azimuth angle values when the virtual target corresponding to each visual track in the visual track cluster rises to a specified elevation angle, so that the virtual target has a continuous change characteristic;

and step 9: and (4) further calculating and generating a series of guiding data for the radar to perform equal elevation searching and tracking according to the calculation results of the step 7 and the step 8.

2. Such asThe method of claim 1, wherein the narrow beam radar captures a spatial target at an equal elevation angle, and comprises: in the step 1, the intermediate time T of the current transit of the target is selected₀As reference time:

wherein T is_bAnd T_eRespectively serving as the starting time and the ending time of the current transit of the target;

defining the track tracing error of the target during the current transit period as the tracing error of a reference moment, and constructing an analysis perturbation model taking the reference moment as an initial moment by adopting the first-class singularity-free track root as a basic variable, wherein the construction process of the model is as follows:

a known set of target precision orbit parameters is t_q，E, where t_qFor the epoch time of the set of track parameters,andrespectively setting a position vector and a velocity vector of the target relative to an epoch geocentric inertia system, and setting an element as a target surface-to-quality ratio; based on known orbit parameters t_q，E, adopting a numerical method and a precise mechanical model to carry out perturbation extrapolation, and using t as the reference_qPush-out of time to T₀At that time, T is obtained₀Position vector of time target relative to epoch geocentric inertial systemSum velocity vectorAnd toAndconverting to obtain target T₀Initial pseudo-average number of times; based on the initial pseudo-average root number, an analytical perturbation model is constructed with a mathematical expression form as follows:

if a, i, Ω, ξ ω, η ω sin ω, λ ω + M is the number of osculating orbit of the first non-singular form of the target, where a is the radius of the orbit, i is the inclination of the orbit, Ω is the right ascension of the ascending intersection of the orbit, e is the eccentricity of the orbit, ω is the argument of the approach of the orbit, and M is the argument of the approach of the target, then:

the left end of the above formulas represents the number of kiss-cuts at time t,represents T₀The initial pseudo-average number of moments in time,is the angular velocity of the target translational motion, mu is the gravitational constant, omega₁，ω₁，λ₁The first order long term variation coefficient corresponding to the number,is a first-order short-period variation term of each number,the second-order short-period change term of each number is a reduced-order term related to the rotation of the earth.

3. The method of claim 2, wherein the narrow beam radar captures an elevation search of a spatial target at equal angles, and wherein: in the step 2, the calculation of the theoretical near-site time of the target transit period includes the following two steps:

first step to solve the approximate near-site timeThe formula is as follows:

wherein λ₀Is λ (T) at T₀The value of the moment is T₀The target weft straightening angle at the moment is calculated by the formula (6),is the long-term rate of change of λ (t), u_sAnd λ_sAre respectively T₀The true latitude angle projected by the measuring station on the track and the corresponding horizontal latitude angle,is the time rate of change of us;

the second step is firstly obtained by calculation of the formula (6)Target horizontal latitude angle of momentAnd utilizes the elliptic motion relationship ofIs calculated to obtainTarget true latitude angle of momentThen is provided withGiving the accurate near-station time by iterative solution as an initial valueCorresponding target true latitude angleThe equation for the iterative solution is as follows:

whereinAndis xi (t) and eta (t) respectivelyThe value of the time is calculated by the formula (4) and the formula (5), and theta isOpening angle theta of time target and survey station at geocentric₀Is composed ofThe orbit latitude of the time measuring station is rThe earth center distance of the target at the moment, R is the earth center distance of the survey station; finally, the elliptic motion relation is utilizedIs calculated to obtainTarget horizontal latitude angle of momentThe exact near-site time is given by:

4. the method of claim 3, wherein the narrow beam radar captures an elevation search of a spatial target at equal angles, and wherein: in step 3, the track tracing error of the target during the current transit period is considered as a random variable uniformly distributed in [ - τ, τ ], and the random variable is discretized to convert a probability problem into a certainty problem, which is defined as follows:

wherein, delta tau is a time increment, l is more than or equal to 1 and is a positive integer, and (l-1) delta tau is less than or equal to tau which is the maximum trace error estimation during the current border period of the target; in the constructed analytic perturbation model, the method is shown in the formula (6)Is replaced byKeeping other types unchanged to obtain a series of new perturbation models, wherein each new perturbation model corresponds to a virtual target on the theoretical orbit, and when k is 0, the corresponding virtual target is the theoretical target;

each virtual object forms a cluster of apparent trajectories during the current transit, the cluster of apparent trajectories being denoted as { Γ_k|l，-lR, each element of which is r_kAll correspond to a visual trackUniquely, k is decremented from l to l by 1 to form a view trace cluster.

5. The method of claim 4, wherein the narrow beam radar captures an elevation angle of a space target by an equal angle search method, and the method comprises: the specific process of the step 4 is as follows:

1) considering theoretical apparent trajectory gamma₀The visibility is determined by the transit forecast, and the corresponding station-near moment is calculated in the step 2;

2) considering two adjacent apparent trajectories Γ_kAnd Γ_k+1With Γ_kIs taken as the exact near-site time of r_k+1The approximate station-approaching moment of (2) is directly entered into the second solving process of the step (2), wherein the solving process adopts gamma_k+1The corresponding perturbation model performs a correlation calculation to give Γ_k+1The precise time of approaching the station; let k change continuously from 0 to l-1, and gradually obtain a series of visual trajectories gamma by adopting the above processing mode₁，Γ₂，...，Γ_lCorresponding station approaching time;

3) considering two adjacent apparent trajectories Γ_kAnd Γ_k-1With Γ_kIs taken as the exact near-site time of r_k-1The approximate station-approaching moment of (2) is directly entered into the second solving process of the step (2), wherein the solving process adopts gamma_k-1The corresponding perturbation model performs a correlation calculation to give Γ_k-1The precise time of approaching the station; let k change continuously from 0 to-l +1, and gradually obtain a series of visual trajectories gamma by adopting the above processing mode_-1，Γ_-2，...，Γ_-lCorresponding station approaching time;

thus completing the visual track cluster { gamma_k|l，-lCalculating the station-near time of all the visual tracks; when the station-approaching moment is known, respectively solving the distance and the elevation angle of each station-approaching point through track calculation and related coordinate conversion based on the perturbation model corresponding to each visual track, and matching the station-approaching points with detectable conditions of radar one by one to finish the confirmation of the visibility of each visual track; wherein the detectable conditions of the radar include thresholds for range and elevation;

from apparent track cluster { Γ_k|l，-lRemoving a plurality of invisible visual tracks, wherein the rest visual tracks still have continuity, and the formed visual track cluster is represented as { gamma_k|i，jAnd j is more than or equal to i and more than or equal to 0.

6. The method of claim 5, wherein the narrow beam radar captures an elevation search of a spatial target at equal angles, and wherein: the specific process of the step 5 is as follows: for apparent track cluster { Γ_k|i，jOne apparent track gamma in_kCombining the detectable condition of the radar and based on the corresponding perturbation model, carrying out searching calculation from the station-near moment to the back edge descending section with proper step length until the moment set by the threshold, and removing the visual track from the visual track cluster if an invisible target point is found in the searching process; repeating the above processing procedures for other visual tracks in the visual track cluster, removing a plurality of visual tracks with unsatisfactory detectable arc length, and keeping the rest visual tracks continuous, wherein the visual track cluster composed of the visual tracks is represented as { F_k|m，nAnd m is more than or equal to n.

7. The method of claim 6, wherein the method comprises: the specific process of the step 6 is as follows:

for apparent track cluster { Γ_k|m，nOne apparent track gamma in_kThe detectable elevation range is determined by the maximum detectable elevation and the minimum detectable elevation, wherein the maximum detectable elevation is the detected elevation at the near-station, and is calculated in step 4; for the minimum detectable elevation angle, searching and calculating by adopting a dichotomy method from the time to the leading edge rising section according to the corresponding near-station time given in the step 4 and based on the corresponding perturbation model, performing real-time judgment by combining the detectable condition of the radar in the calculating process, and finally giving the minimum detectable elevation angle meeting certain precision requirements;

repeating the above processing procedures on other visual tracks in the visual track cluster to obtain the maximum detectable elevation angle and the minimum detectable elevation angle corresponding to all the visual tracks; taking the minimum value of the maximum detectable elevation angles of all the visual tracks, and setting the minimum value as h_qTaking the maximum value of the minimum detectable elevation angles of all the visual tracks, and setting the quantity as h_pThen, the closed interval [ h ]_p，h_q]An elevation angle range suitable for radar to search for equal elevation angle is determined, where h_q≥h_p；

The calculation formula of the search elevation angle adopted when the radar works is as follows:

h＝h_p+β(h_q-h_p) (7)

where β is a search elevation adjustment factor, given in advance by the user.

8. The method of claim 7, wherein the narrow beam radar captures an elevation search of a spatial target at equal angles, and wherein: the specific process of the step 7 is as follows: for apparent track cluster { Γ_k|_m，nOne apparent track gamma in_kBased on a corresponding perturbation model, searching and calculating by adopting a bipartition method from a station-near moment to a leading-edge ascending section with a proper initial step length, generating a calculated elevation angle of a corresponding moment in each step in the calculation process, judging the proximity degree of the calculated elevation angle and a specified elevation angle, and finally providing observation characteristic parameters meeting certain precision requirements, wherein the observation characteristic parameters comprise time, an azimuth angle, a distance, an azimuth angle variability and an elevation angle variability when a target rises to the specified elevation angle, and the apparent movement speed and the flight direction of the target are determined by the azimuth angle variability and the elevation angle variability; repeating the above processing procedures on other visual tracks in the visual track cluster to obtain observation characteristic parameters corresponding to all virtual targets.

9. The method of claim 8, wherein the narrow beam radar captures an elevation search of a spatial target at equal angles, and wherein: the specific process of the step 8 is as follows:

for apparent track cluster { Γ_k|_m，nOne apparent track gamma in_kCorresponding to the azimuth angle A when the virtual target ascends to the specified elevation angle_kTo A, a_kRedefining the values to make them have continuously changing characteristics; setting A after redefinition_kValue is A'_kAnd considering that k varies continuously from m to n, then A'_kThe calculation process of (2) is as follows: first, take A'_m＝A_mFor the subsequent A_kLet Δ A_k＝A_k-A_k+1The subsequent A 'is calculated in three independent cases'_k：

1) If an integer p is present, m-1. gtoreq.p.gtoreq.n, such that Δ A_pIf < - π, then:

2) if an integer p is present, m-1. gtoreq.p.gtoreq.n, such that Δ A_pIf pi is greater, then:

3) if there is no integer p for the above two cases, then there are:

A′_k＝A_k m-1≥k≥n

a 'obtained above'_kThe continuity of the change was maintained as a whole, with A'_kSubstituted A_kAs the azimuth angle.

10. The method of claim 9, wherein the narrow beam radar captures an elevation search of a spatial target at equal angles, and wherein: the specific process of the step 9 is as follows:

for apparent track cluster { Γ_k|_m，nOne apparent track gamma in_kThe time, azimuth angle, distance, azimuth angle variability and elevation angle variability when the corresponding virtual target ascends to the specified elevation angle are respectively t_k，A′_k，ρ_k，Andwith t_kThe base point is a known parameter A 'on the base point'_k，ρ_k，Andrespectively constructing azimuth angle A', distance rho and azimuth angle variationRate of changeAnd elevation variabilityThe interpolation function of (a); and (3) adopting cubic natural spline interpolation, wherein the obtained interpolation functions are respectively as follows:

A′＝A′(t) (8)

ρ＝ρ(t) (9)

the interpolation functions above give different observed features that the real target may have in a continuous time range, and since a 'is a strictly monotonic function of t, a (t) has a unique inverse function, in terms of a'_kFor the base point, a cubic natural spline interpolation is still used to obtain the following equation:

t＝t(A′) (12)

t (a ') is also a strictly monotonic function with respect to a', giving different times at which a real object may appear in a continuous range of azimuth angles;

the time range of the real target rising to the designated elevation angle is a closed interval [ t_m，t_n]The corresponding azimuth angle range is a closed interval [ A'_m，A′_n]Or [ A'_n，A′_m]Corresponding to the azimuth interval, when the radar searches along the designated elevation angle, the beam direction also has a change interval marked as [ psi₁，ψ₂]；

The length Δ a of the azimuth angle change interval of the target at a specified elevation angle is as follows:

ΔA＝|A′_m-A′_n|

the length Δ ψ of the change interval of the corresponding beam pointing direction of the radar at a given elevation angle is as follows:

cosΔψ＝sin²h+cos²h cosΔA

let the effective beam diameter of the radar be w, determine [ psi₁，ψ₂]The number of evenly divided subintervals is as follows:

w^*＝(1-δ)w

where δ is a dimensionless scale factor and takes the value in the interval [0, 1], and N is [ ψ ]₁，ψ₂]Number of sub-intervals, [ psi ] divided by the above N₁，ψ₂]The sub-interval length does not exceed the effective beam diameter of the radar;

taking into account the azimuthal interval and [ psi₁，ψ₂]With the same division, the azimuth subinterval length is calculated as follows:

ΔA^*＝ΔA/N

defining a sign factor:

and each azimuth angle interval is sequentially set asTwo endpoint values of each azimuth subinterval are recurrently obtained by adopting the following mode:

is provided withIs a sub-interval of the azimuth angleAnd (3) calculating two endpoint values of the corresponding time subintervals by adopting an equation (12) respectively:

azimuth subintervalIs calculated by:

the center time corresponding to the center azimuth is calculated by equation (12):

the target distance, the azimuth angle variability and the elevation angle variability of the radar beam center pointing direction corresponding to the center azimuth angle are calculated by the following expressions (9), (10) and (11):

the azimuth angle of the radar beam center direction obtained by the calculationThe result of the continuous treatment is actually reduced to a normal representation method, and the corresponding value is set toThen there are:

this generates a series of sets of boot dataAndeach set of steering data corresponds to a dwell of the radar beam at a specified elevation angle, whereinThe bearing at which the center of the beam is pointed is determined,andthe start-stop time for beam dwell is determined,if a target is present in the beam, thenUsed for real-time discrimination of the target to determine whether the target is an observation target, if the target appears in the beam and is discriminated as the observation target, the method comprises the steps ofAndthe system is used for guiding the radar to perform tracking observation on the target for the next few seconds so as to enable the radar to lock the target and shift into self-tracking; when each group of guiding data changes from v to N, the corresponding wave beam sequentially resides at different directions on the designated elevation angle according to the time sequence, thereby forming the mode and process of searching the elevation angle of radar and the like, wherein the initial time of the first time of residing the wave beam isFor the rest of beams, the starting time of the beam residence at this time is the ending time of the beam residence at the last time, and the ending time of the beam residence at the last time is[t_m，t_n]Namely the effective working time period of the radar for implementing equal elevation search during the current transit of the target.

Technical Field

The invention belongs to the field of space detection, and particularly relates to an equal elevation search method for a narrow-beam radar to capture a space target.

Background

The precise tracking imaging radar is an important means for space target identification and precise orbit determination, can provide powerful technical support for space target collision early warning, motion situation perception and the like, and generally works in a high-frequency band and adopts a large-caliber antenna for realizing high resolution of imaging and high precision of point observation data, so that a detection beam is very narrow, and the effective beam diameter (half-power beam width) is usually less than 0.1 degree. In recent years, with the increase of information transmission rate of satellite-ground links of remote sensing satellites, broadband high-speed transmission has become a trend of satellite-ground data transmission, and a ground receiving system of the satellites also needs to adopt a high-frequency and large-aperture antenna, and the beam of the antenna is even narrower (non-patent document 1). The common problem of the two types of equipment in detecting the space target can be summarized as the problem of capturing and tracking the space target by the narrow-beam radar.

The precondition of data acquisition by the radar is that the space target can be captured and tracked, and the traditional capture and tracking mode is mainly search capture and tracking under the guidance of a program for predicting the target point, so that compared with a common radar, the narrow beam radar has great technical difficulty in capturing and tracking the space target, and taking the effective beam diameter of 0.1 degrees as an example, the deviation between the radar beam center pointing direction and the target direction is required to be less than 0.05 degrees to ensure the space target capture, thereby providing a very high requirement for the target point prediction precision. In order to overcome the adverse effect on space target capture and tracking of narrow-beam radar due to possible shortage of point location prediction accuracy, non-patent document 1 proposes two technical schemes, one is that a program guides a low-frequency wide beam coaxial with the radar to complete capture and tracking of a target first, and then the high-frequency narrow beam is switched to capture and track the target; the other method is to program guide radar narrow beams to search for a target, and the spiral scanning of the beams is overlapped in a small preset area while searching is carried out, so that the narrow beam radar can directly capture and track the target. However, both of these solutions have significant disadvantages, and the first solution will increase the difficulty and cost of radar manufacture; the second scheme has a large limitation, although the helical scanning is equivalent to widening the effective diameter of a beam to a certain extent, because the scanning range is small, the beam residence time in the scanning process is extremely short, the scanning direction change has certain blindness, the target leakage probability is still large, and in order to improve the capturing success rate, the point location prediction with high precision is still required, when the second scheme is adopted to capture the target, the track parameters which are close to the working day of the radar and have high precision are required to be selected for prediction, particularly for low-track high-dynamic targets, and in various situations faced by actual working, the condition is often difficult to be met, so that the effective use of the radar is limited.

The main factors influencing the target point prediction precision include track parameter errors, track mechanics model errors and prediction time length, and in addition, when the mechanics model of orbit determination is not matched with the predicted mechanics model, the prediction precision can also be obviously lost. In actual work, the conditions are limited, and people cannot expect to improve or change the above various established factors, and a new method is needed.

In the seventies of the last century, in order to meet the needs of observing laser geostationary satellites, researchers in astronomical circles in China have proposed an orbit interception method for capturing laser satellites (non-patent document 2), which uses an optical telescope mounted on a polar axis type tracking system to intercept and capture and track laser satellites and successfully capture targets based on orbital parameters one year and several years ago. The mechanism of the method is as follows: under the influence of various mechanical factors, although the satellite moves very quickly on the orbit, the change of the satellite orbit relative to the inertial space is very slow, and the precision loss of long-time prediction is not large, so that an interception point suitable for optical observation can be selected on the satellite orbit, the point is taken as an immobile point in the inertial space, and after an optical telescope is aligned with the interception point during observation, a driving clock is started to counteract the influence of the rotation of the earth, so that the telescope keeps staring at the interception point, and the interception and capture of the satellite are realized by early and late watching. The successful experience is mainly attributed to the change of the space target capturing strategy, although the processing of the above method on the track perturbation influence is still insufficient due to the difference of the detection mechanisms of the radar and the optical telescope, and the application requirements and the difference of the detection objects, the above method is not completely suitable for the capturing and tracking of the radar on the space target, especially the capturing and tracking of the narrow-beam radar on the low-track high-dynamic target, but the processing idea is worth reference.

Aiming at the problems and difficulties of the prior technical scheme for capturing the space target by the narrow-beam radar, the invention provides an equal elevation angle searching method suitable for finding and capturing the space target by the narrow-beam radar by adopting a related technical method adopted in the astronomical field during capturing the laser satellite, timely changing the thinking and combining the working mechanism of the radar, and the method corresponds to a brand new capturing strategy, is different from the existing searching, capturing and tracking mode based on point location prediction, has no over-high requirement on the accuracy of the point location prediction, does not increase the manufacturing cost and difficulty of the radar, has strong applicability, can realize higher capturing success rate, is favorable for the effective use of the radar, and is a key technology for capturing and tracking a low-orbit high dynamic target by the narrow-beam radar.

List of citation documents

Non-patent documents:

1. the dynamic tracking method comprises the steps of Wangmuyu, Wangyu, Maowei, He Yuanchun, narrow-beam high-dynamic-target high-precision tracking technology analysis, Internet of things technology, No.4 and 2018.

2. Chang Lin, niu Xiu lan, "a method of intercepting satellites", Shanghai astronomical Chapter, China academy of sciences, No.1, 1979.

3、Oliver Montenbruck，Eberhard Gill，Satellite Orbits，Models，Methods，and Applications，Springer-Verlag Berlin Heidelberg 2000.

4. Liulin, spacecraft orbits theory, defense industry press, 2000.

5. Wulianda, orbit and exploration of satellites and space debris, published by Chinese science and technology, 2011.

6、Press W.H.，Flannery B.P.，Teukolsky S.A.and Vetterling W.T.，Numerical Recipes-The Art of Scientific Computing，Cambridge University PRESS，Cambridge，New York，New Rochelle，Melbourne，Sydney，1989.

7、Michael A.Steindorfer，Georg Kirchner，Franz Koidl，Peiyuan Wang，Beatriz Jilete and Tim Flohrer，Day light space debris laser ranging，Nature communications，2020.

8、Felix R.Hoots and Ronald L.Roehrich，SPACETRACK REPORT N0.3，Models for Propagation of NORAD Element Sets，1980.

Disclosure of Invention

The narrow-beam radar has wide application in the aspects of space target imaging identification, precise orbit determination, high-speed satellite-ground link information transmission and the like, the acquisition and tracking of the space target are preconditions for successfully realizing various applications, and compared with a common radar with a wider effective beam diameter, the narrow-beam radar has great difficulty in acquiring and tracking the space target. Under the background, the invention provides a capturing and tracking strategy independent of target point position prediction, which is an equal elevation angle searching method and mainly aims to break through the technical bottleneck existing in the prior technical scheme and improve the application efficiency of the narrow beam radar.

In order to achieve the purpose, the invention adopts the following technical scheme:

the equal elevation searching method for the narrow beam radar to capture the space target is characterized in that radar guide data are generated based on target precision orbit parameters, the starting and stopping time of target crossing and the maximum orbit track error estimation during the target crossing so as to capture and track the corresponding target by the radar; the method specifically comprises the following steps:

step 1: calculating the intermediate time of the current transit of the target according to the starting and stopping time of the current transit of the target, taking the intermediate time as a reference time, and constructing an analysis perturbation model taking the reference time as an initial time by combining target precise track parameters;

step 2: calculating the theoretical station approaching moment of the target during the current transit period by combining the analysis perturbation model constructed in the step 1;

and step 3: discretizing the trace errors, and combining an analysis perturbation model to obtain a series of new perturbation models for describing the motion of each virtual target, wherein different visual tracks generated by each virtual target in the current transit period form a visual track cluster;

and 4, step 4: based on the theoretical station-approaching moment calculated in the step 2 and the solving process thereof, performing visibility confirmation on each visual track in the visual track cluster, and removing all invisible visual tracks;

and 5: removing the visual tracks with the detectable arc length not meeting the requirement in the visual track cluster;

step 6: determining the maximum detectable elevation angle and the minimum detectable elevation angle of each visual track in the visual track cluster, and further calculating to obtain the search elevation angle of the radar;

and 7: for each visual track in the visual track cluster, calculating observation characteristic parameters when all the virtual targets rise to a specified elevation angle based on the corresponding perturbation model;

and 8: carrying out continuous processing on azimuth angle values when the virtual target corresponding to each visual track in the visual track cluster rises to a specified elevation angle, so that the virtual target has a continuous change characteristic;

and step 9: and (4) further calculating and generating a series of guiding data for the radar to perform equal elevation searching and tracking according to the calculation results of the step 7 and the step 8.

In order to optimize the technical scheme, the specific measures adopted further comprise:

further, in step 1, the intermediate time T of the current transit of the target is selected₀As reference time:

wherein T is_bAnd T_eRespectively as the target of the current transitThe start time and the end time of (c);

defining the track tracing error of the target during the current transit period as the tracing error of a reference moment, and constructing an analysis perturbation model taking the reference moment as an initial moment by adopting the first-class singularity-free track root as a basic variable, wherein the construction process of the model is as follows:

a known set of target precision orbit parameters is t_q，E, where t_qFor the epoch time of the set of track parameters,andrespectively setting a position vector and a velocity vector of the target relative to an epoch geocentric inertia system, and setting an element as a target surface-to-quality ratio; based on known orbit parameters t_q，E, adopting a numerical method and a precise mechanical model to carry out perturbation extrapolation, and using t as the reference_qPush-out of time to T₀At that time, T is obtained₀Position vector of time target relative to epoch geocentric inertial systemSum velocity vectorAnd toAndconverting to obtain target T₀Initial pseudo-average number of times; based on the initial pseudo-average root number, an analytical perturbation model is constructed with a mathematical expression form as follows:

if a, i, Ω, ξ — e cos ω, η — e sin ω, λ ω + M are the number of osculating orbits of the first non-singular form of the target, where a is the orbit radius, i is the orbit inclination, Ω is the orbit ascent point right ascension, e is the orbit eccentricity, ω is the orbit perigee argument, and M is the target mean anomaly angle, then:

the left end of the above formulas represents the number of kiss-cuts at time t,represents T₀The initial pseudo-average number of moments in time,is the angular velocity of the target translational motion, mu is the gravitational constant, omega₁，ω₁，λ₁The first order long term variation coefficient corresponding to the number,is a first-order short-period variation term of each number,the second-order short-period change term of each number is a reduced-order term related to the rotation of the earth.

Further, in step 2, calculating the theoretical near-site time of the target during the current transit period includes the following two steps:

first step to solve the approximate near-site timeThe formula is as follows:

wherein λ₀Is λ (T) at T₀The value of the moment is T₀The target weft straightening angle at the moment is calculated by the formula (6),is the long-term rate of change of λ (t), u_sAnd λ_sAre respectively T₀The true latitude angle projected by the measuring station on the track and the corresponding horizontal latitude angle,is u_sThe time rate of change of (c);

the second step is firstly obtained by calculation of the formula (6)Target horizontal latitude angle of momentAnd utilizes the elliptic motion relationship ofIs calculated toToTarget true latitude angle of momentThen is provided withGiving the accurate near-station time by iterative solution as an initial valueCorresponding target true latitude angleThe equation for the iterative solution is as follows:

whereinAndis xi (t) and eta (t) respectivelyThe value of the time is calculated by the formula (4) and the formula (5), and theta isOpening angle theta of time target and survey station at geocentric₀Is composed ofThe orbit latitude of the time measuring station is rCenter-of-earth distance of time targetR is the earth center distance of the survey station; finally, the elliptic motion relation is utilizedIs calculated to obtainTarget horizontal latitude angle of momentThe exact near-site time is given by:

further, in step 3, the track tracing error of the target during the current transit period is considered as a random variable uniformly distributed in [ - τ, τ ], and the random variable is discretized to convert a probability problem into a certainty problem, which is defined as follows:

wherein, delta tau is a time increment, l is more than or equal to 1 and is a positive integer, and (l-1) delta tau is less than or equal to tau which is the maximum trace error estimation during the current border period of the target; in the constructed analytic perturbation model, the method is shown in the formula (6)Is replaced byKeeping other types unchanged to obtain a series of new perturbation models, wherein each new perturbation model corresponds to a virtual target on the theoretical orbit, and when k is 0, the corresponding virtual target is the theoretical target;

each virtual object forms a cluster of apparent trajectories during the current transit, the cluster of apparent trajectories being denoted as { Γ_k|_l，-lR, each element of which is r_kAll correspond to a visual trackUniquely, k is decremented from l to l by 1 to form a view trace cluster.

Further, the specific process of step 4 is as follows:

1) considering theoretical apparent trajectory gamma₀The visibility is determined by the transit forecast, and the corresponding station-near moment is calculated in the step 2;

2) considering two adjacent apparent trajectories Γ_kAnd Γ_k+1With Γ_kIs taken as the exact near-site time of r_k+1The approximate station-approaching moment of (2) is directly entered into the second solving process of the step (2), wherein the solving process adopts gamma_k+1The corresponding perturbation model performs a correlation calculation to give Γ_k+1The precise time of approaching the station; let k change continuously from 0 to l-1, and gradually obtain a series of visual trajectories gamma by adopting the above processing mode₁，Γ₂，...，Γ_lCorresponding station approaching time;

3) considering two adjacent apparent trajectories Γ_kAnd Γ_k-1With Γ_kIs taken as the exact near-site time of r_k-1The approximate station-approaching moment of (2) is directly entered into the second solving process of the step (2), wherein the solving process adopts gamma_k-1The corresponding perturbation model performs a correlation calculation to give Γ_k-1The precise time of approaching the station; let k change continuously from 0 to-l +1, and gradually obtain a series of visual trajectories gamma by adopting the above processing mode_-1，Γ_-2，...，Γ_-lCorresponding station approaching time;

thus completing the visual track cluster { gamma_k|_l，-lCalculating the station-near time of all the visual tracks; when the station-approaching moment is known, respectively solving the distance and the elevation angle of each station-approaching point through track calculation and related coordinate conversion based on the perturbation model corresponding to each visual track, and matching the station-approaching points with detectable conditions of radar one by one to finish the confirmation of the visibility of each visual track; wherein detectable conditions of the radarThresholds including range and elevation;

from apparent track cluster { Γ_k|_l，-lSeveral invisible visual tracks are removed, the rest visual tracks still have continuity, and the formed visual track cluster can be represented as { Γ_k|_i，jAnd j is more than or equal to i and more than or equal to 0.

Further, the specific process of step 5 is as follows: for apparent track cluster { Γ_k|_i，jOne apparent track gamma in_kCombining the detectable condition of the radar and based on the corresponding perturbation model, carrying out searching calculation from the station-near moment to the back edge descending section with proper step length until the moment set by the threshold, and removing the visual track from the visual track cluster if an invisible target point is found in the searching process; repeating the above processing procedure for other visual tracks in the visual track cluster to remove a plurality of visual tracks with unsatisfactory detectable arc length, wherein the rest visual tracks have continuity, and the visual track cluster composed of the visual tracks can be expressed as { F_k|_m，nAnd m is more than or equal to n.

Further, the specific process of step 6 is as follows:

for apparent track cluster { Γ_k|_m，nOne apparent track gamma in_kThe detectable elevation range is determined by the maximum detectable elevation and the minimum detectable elevation, wherein the maximum detectable elevation is the detected elevation at the near-station, and is calculated in step 4; for the minimum detectable elevation angle, searching and calculating by adopting a dichotomy method from the time to the leading edge rising section according to the corresponding near-station time given in the step 4 and based on the corresponding perturbation model, performing real-time judgment by combining the detectable condition of the radar in the calculating process, and finally giving the minimum detectable elevation angle meeting certain precision requirements;

repeating the above processing procedures on other visual tracks in the visual track cluster to obtain the maximum detectable elevation angle and the minimum detectable elevation angle corresponding to all the visual tracks; taking the minimum value of the maximum detectable elevation angles of all the visual tracks, and setting the minimum value as h_qAt the minimum detectable elevation angle of all visual tracksTaking the maximum value, and setting the amount as h_pThen, the closed interval [ h ]_p，h_q]An elevation angle range suitable for radar to search for equal elevation angle is determined, where h_q≥h_p；

The calculation formula of the search elevation angle adopted when the radar works is as follows:

h＝h_p+β(h_q-h_p) (7)

where β is a search elevation adjustment factor, given in advance by the user.

Further, the specific process of step 7 is as follows: for apparent track cluster { Γ_k|_m，nOne apparent track gamma in_kBased on a corresponding perturbation model, searching and calculating by adopting a bipartition method from a station-near moment to a leading-edge ascending section with a proper initial step length, generating a calculated elevation angle of a corresponding moment in each step in the calculation process, judging the proximity degree of the calculated elevation angle and a specified elevation angle, and finally providing observation characteristic parameters meeting certain precision requirements, wherein the observation characteristic parameters comprise time, an azimuth angle, a distance, an azimuth angle variability and an elevation angle variability when a target rises to the specified elevation angle, and the apparent movement speed and the flight direction of the target are determined by the azimuth angle variability and the elevation angle variability; repeating the above processing procedures on other visual tracks in the visual track cluster to obtain observation characteristic parameters corresponding to all virtual targets.

Further, the specific process of step 8 is as follows:

for apparent track cluster { Γ_k|_m，nOne apparent track gamma in_kCorresponding to the azimuth angle A when the virtual target ascends to the specified elevation angle_kTo A, a_kRedefining the values to make them have continuously changing characteristics; setting A after redefinition_kValue is A'_kAnd considering that k varies continuously from m to n, then A'_kThe calculation process of (2) is as follows: first, take A'_m＝A_mFor the subsequent A_kLet Δ A_k＝A_k-A_k+1The subsequent A 'is calculated in three independent cases'_k：

1) If an integer p, m-1. gtoreq.p.gtoreq.n is present, so thatTo obtain Delta A_pIf < - π, then:

2) if an integer p is present, m-1. gtoreq.p.gtoreq.n, such that Δ A_pIf pi is greater, then:

3) if there is no integer p for the above two cases, then there are:

A′_k＝A_k m-1≥k≥n

a 'obtained above'_kThe continuity of the change was maintained as a whole, with A'_kSubstituted A_kAs the azimuth angle.

Further, the specific process of step 9 is as follows:

for apparent track cluster { Γ_k|_m，nOne apparent track gamma in_kThe time, azimuth angle, distance, azimuth angle variability and elevation angle variability when the corresponding virtual target ascends to the specified elevation angle are respectively t_k，A′_k，ρ_k，Andwith t_kThe base point is a known parameter A 'on the base point'_k，ρ_k，Andconstruction of the azimuth A', the distance rho, the azimuth variabilityAnd elevation variabilityThe interpolation function of (a); and (3) adopting cubic natural spline interpolation, wherein the obtained interpolation functions are respectively as follows:

A′＝A′(t) (8)

ρ＝ρ(t) (9)

the interpolation functions give different observation characteristics that the real target may have in a continuous time range, and since A 'is a strictly monotonic function of t, A' (t) has a unique inverse function, with A_kFor the base point, a cubic natural spline interpolation is still used to obtain the following equation:

t＝t(A′) (12)

t (a ') is also a strictly monotonic function with respect to a', giving different times at which a real object may appear in a continuous range of azimuth angles;

the time range of the real target rising to the designated elevation angle is a closed interval [ t_m，t_n]The corresponding azimuth angle range is a closed interval [ A'_m，A′_n]Or [ A'_n，A′_m]Corresponding to the azimuth interval, when the radar searches along the designated elevation angle, the beam direction also has a change interval marked as [ psi₁，ψ₂]；

The length Δ a of the azimuth angle change interval of the target at a specified elevation angle is as follows:

ΔA＝|A′_m-A′_n|

the length Δ ψ of the change interval of the corresponding beam pointing direction of the radar at a given elevation angle is as follows:

cosΔψ＝sin²h+cos²hcosΔA

let the effective beam diameter of the radar be w, determine [ psi₁，ψ₂]The number of evenly divided subintervals is as follows:

w^*＝(1-δ)w

where δ is a dimensionless scale factor and takes the value in the interval [0, 1], and N is [ ψ ]₁，ψ₂]Number of sub-intervals, [ psi ] divided by the above N₁，ψ₂]The sub-interval length does not exceed the effective beam diameter of the radar;

taking into account the azimuthal interval and [ psi₁，ψ₂]With the same division, the azimuth subinterval length is calculated as follows:

ΔA^*＝ΔA/N

defining a sign factor:

and each azimuth angle interval is sequentially set asN, then the two endpoint values for each azimuth subinterval are recurved in the following manner:

is provided withIs a sub-interval of the azimuth angleAnd (3) calculating two endpoint values of the corresponding time subintervals by adopting an equation (12) respectively:

azimuth subintervalIs calculated by:

the center time corresponding to the center azimuth is calculated by equation (12):

the target distance, the azimuth angle variability and the elevation angle variability of the radar beam center pointing direction corresponding to the center azimuth angle are calculated by the following expressions (9), (10) and (11):

the azimuth angle of the radar beam center direction obtained by the calculationThe result of the continuous treatment is actually reduced to a normal representation method, and the corresponding value is set toThen there are:

this generates a series of sets of boot dataAndn, each set of guidance data corresponding to a dwell of the radar beam at a specified elevation angle, whereinThe bearing at which the center of the beam is pointed is determined,anddetermining the starting and stopping time of beam residence, if the target appears in the beamUsed for real-time discrimination of the target to determine whether the target is an observation target, if the target appears in the beam and is discriminated as the observation target, the method comprises the steps ofAndthe system is used for guiding the radar to perform tracking observation on the target for the next few seconds so as to enable the radar to lock the target and shift into self-tracking; when each group of guide data is changed from v-1 to v-N, the corresponding beams sequentially reside at different directions at a specified elevation angle according to the time sequence, thereby forming the mode and the process of searching the elevation angle of the radar and the like, wherein the starting time of the first beam residence isFor the rest of beams, the starting time of the beam residence at this time is the ending time of the beam residence at the last time, and the ending time of the beam residence at the last time is[t_m，t_n]Namely the effective working time period of the radar for implementing equal elevation search during the current transit of the target.

The invention has the beneficial effects that:

1) the invention does not depend on the target point location forecast, but is based on the conservative estimation of the target point location forecast trail error, and applies the orbit motion theory, and generates an equal elevation angle searching mode, the searching mode fully eliminates the influence of the point location forecast trail error on the target capture, the rest influence mainly comes from the errors of the point location forecast in other directions (normal direction and radial direction), because the errors in other directions increase slowly along with the forecast time, and the errors are small relative to the trail error, therefore, the equal elevation angle searching mode of the invention is adopted to capture and track the target, and the invention can be based on the target orbit parameter before longer time, and has no requirement on the adaptability of the orbit parameter, thereby widening the application condition of the radar, and the efficiency of the radar is obviously improved;

2) different from a capturing and tracking mode of point location guiding superposition spiral scanning, the guiding data of the method is completely obtained by track calculation, and the corresponding capturing and tracking mode has strict theoretical basis and no blindness, so that the method can obviously improve the capturing success rate of space targets, is particularly suitable for capturing and tracking low-orbit high-dynamic targets by narrow-beam radars, and obtains the evidence in the related checking result;

3) compared with a point location guide (or point location guide superposition spiral scanning) capturing and tracking mode, each beam based on the technical scheme of the invention generally has longer residence time, and when a target passes through the beam, the beam is generally in a waiting state, thereby being beneficial to radar detection and target discovery;

4) the implementation of the technical scheme of the invention can not increase the extra manufacturing cost and manufacturing difficulty of the radar, and for the horizontal radar, the target is captured and tracked according to the equal elevation searching mode of the invention, the operation is simple, the normal direction of the antenna is only required to be adjusted to the specified elevation in advance before observation, and the target can be searched only by rotating the azimuth axis of the radar gradually according to the preset angle in preset time during observation, but the invention is not limited to the horizontal radar;

5) the invention can also be applied to laser ranging observation of a space target in an attempt to get rid of the dependence of laser observation on optical guidance, so that the time window of laser observation of the low-orbit space target can be effectively expanded (non-patent document 7), and daytime laser observation of the space target can be possibly realized.

Drawings

Figure 1 is a schematic view of the geometrical relationship of azimuth interval and beam pointing interval.

FIG. 2 is a process flow diagram of the method of the present invention.

FIG. 3 is a graph showing the results of the prediction of 4 months by 169908 TLE.

FIG. 4 is a graph showing the results of alignment after about 4.5 days of prediction using 39452 TLE counts.

Detailed Description

The present invention will now be described in further detail with reference to the accompanying drawings.

The space target point position prediction error can be decomposed into an orbit tracing error, an orbit plane normal error and an orbit radial error, according to the artificial satellite dynamics theory, the position prediction error is mainly embodied as the tracing error which increases rapidly along with the prediction time, particularly for a low-orbit high-dynamic target, the error increases in a square mode along with the time and increases rapidly, and errors in other directions increase linearly along with the time and increase slowly and are mainly caused by perturbation change of the orbit ascent point right ascension. Therefore, how to effectively eliminate the adverse effect of the track tracing error on the radar discovery and target capture becomes the focus of the invention, and the theoretical starting point of the technical scheme of the invention is also the theoretical starting point, but the existing capture and tracking technology cannot effectively solve the problem.

Although the orbit tracing error of the target cannot be confirmed, a reliable and conservative estimation about the tracing error can be always given by experience as long as the forecasting time is not too long, and long-term practical experience shows that even if the orbit tracing error of 1 minute is limited, the allowable forecasting time duration can reach at least several days or even tens of days when the forecasting is carried out by adopting general precise orbit parameters. The actual work generally does not require longer forecast time, the actual working conditions are not so severe, and the overlong forecast time also causes the error in other directions to increase to be non-negligible, thereby affecting the effective implementation of the technical scheme of the invention, and therefore, the method is not suitable for being adopted.

The technical scheme of the invention corresponds to an equal elevation searching method, and the basic processing idea is as follows: due to the rotation of the earth, the time and the azimuth angle of a target reaching a certain specified elevation angle on different track positions on the same orbit are different, and the time and the azimuth angle are monotonously changed along with the front-back relation of the target along the track position, so that in a limited track error range, the time and the azimuth angle of a real target reaching the specified elevation angle have an ordered change range, the azimuth angle range and the corresponding time range can be orderly separated based on the effective beam diameter of the radar to generate a series of guide data of the radar, the radar searches the target according to the guide data, the effect is equivalent to performing traversal observation on all possible positions of the target on the specified elevation angle in the limited error range, and the real position of the target is located in the guide data. The technical scheme of the invention is implemented during a certain transit period of the target, the specific implementation needs to relate to the selection problem of the search elevation angle, the factors of target visibility, observation effectiveness and the like need to be considered when the search elevation angle is selected, the selection needs to be determined according to the current transit condition, due to the complexity of track calculation, a reasonable search elevation angle range can be provided firstly only by combining a program with relevant constraint conditions, and a user can only select and adjust the search elevation angle in a limited way in the range.

In summary, we set the input conditions of the technical solution as:

1) a known set of target precision orbit parameters may be orbit parameters before a plurality of days;

2) the starting and stopping time of a certain crossing of the target can be obtained in advance by carrying out crossing forecast on the known track parameters;

3) the conservative estimation of the track following error of the target during the current transit period by the user is an amount of time, which indicates that the target can reach the forecast position along the track at most possibly before or after the amount of time when passing the current transit period;

4) a dimensionless scale factor is taken from the closed interval [0, 1] to help the user select a reasonable search elevation.

The invention generates radar guide data based on the above input conditions to realize the capture and tracking of the radar to the corresponding target, and the technical scheme is described in detail as follows:

different types of target trajectory parameters may be interchanged, so that it is not assumed that a known set of target precision trajectory parameters is: t is t_q，E, where t_qFor the epoch time of the set of track parameters,respectively the position and the velocity vector of the target relative to the epoch geocentric inertial system, epsilon is the target surface-to-quality ratio, and T is set_bAnd T_eRespectively as the starting time and the ending time of the target current transit, and tau is the current estimated by the userDuring the transit period, the maximum track error of the target real position relative to the forecast position is one time quantum, beta is a scale factor with the value between 0 and 1, and the step processing is carried out as follows:

step 1: modeling of transit intermediate times

In order to facilitate the processing of track tracing errors, the invention selects the intermediate moment of the current transit of the target

And defining the track tracing error of the target transit period as the tracing error of the reference time, and constructing an analysis perturbation model taking the reference time as an initial time by adopting the first-class singularity-free track root as a basic variable so as to realize quantitative description of the influence of the tracing error.

The model construction process is as follows:

1) based on the known orbit parameter t_q，E, perturbation extrapolation from t using numerical method and high-precision mechanical model (non-patent document 3)_qPush-out of time to T₀At that time, T is obtained₀Position and velocity vectors of time targets relative to epoch geocentric inertial systemAndand toAndappropriate conversion is performed (non-patent document 4) to obtain a target T₀Initial pseudo-average number of moments. The treatment method has remarkable advantagesThe point is that the acquired model initial value can be ensured to have higher precision, the main significance of the method is that the increase of prediction errors in the normal direction and the radial direction of the orbit due to long-time perturbation extrapolation is fully reduced, and the method is of great importance to the effective implementation of the technical scheme of the invention.

2) Considering that the transit time of the target is short and the perturbation change in the period is small, the invention adopts a simplified analysis perturbation model, and the model only includes a first-order long-term, a first-order short-period term and a small amount of reduced-order terms (caused by earth rotation) in a second-order short-period term of the orbit perturbation change, wherein the reduced-order terms are carefully screened according to the perturbation change characteristics of the low-orbit high-dynamic target and the technical mechanism of the invention. The analysis perturbation model is applied to the special scene set by the invention, and has high calculation precision and is very simple.

The mathematical expression of the model is as follows:

if a, i, Ω, ξ — e cos ω, η — e sin ω, λ ω + M are the number of osculating orbits of the first non-singular form of the target, where a is the orbit radius, i is the orbit inclination, Ω is the orbit ascent point right ascension, e is the orbit eccentricity, ω is the orbit perigee argument, and M is the target mean anomaly angle, then:

the left end of the above forms is the number of kiss-cuts at time t,is T₀The initial pseudo-average number of moments in time,is the angular velocity of the target translational motion, mu is the gravitational constant, omega₁，ω₁，λ₁The first order long term variation coefficient corresponding to the number,is a first-order short-period variation term of each number,for the second-order short period variation terms of each number, the calculation of the first-order long term coefficient and the first-order short period term can be referred to non-patent document 4, which is not described herein again, and the following provides a calculation formula of the second-order short period term according to the present invention:

whereinThe quasi-average number at the time t can be obtained by removing the short-period terms from the formulas (1), (2) and (3),the ratio of the rotation speed of the earth to the angular speed of the target flat motion is shown as alpha < 10 for the low-orbit high-dynamic target^-1It is a small quantity, which is the cause of order reduction, and when S is greenwich fixed star in the orbital coordinate system at time t, its specific calculation is described in non-patent document 4, J₂₂，J₃₁，J₃₂，J₃₃，J₄₁，J₄₂，J₄₃，J₄₄And λ₂₂，λ₃₁，λ₃₂，λ₃₃，λ₄₁，λ₄₂，λ₄₃，λ₄₄The perturbation parameters of the earth's spherical shape are constants, and their values can be obtained by converting the earth's gravitational potential spherical harmonic coefficient, and the specific formula is shown in non-patent document 4.

By adopting the analysis perturbation model for calculation, the track tracing error of the target point prediction can be simply summarized into the calculation error of the sixth root lambda (t), and the complexity of subsequent technical processing is greatly reduced.

Step 2: calculation of theoretical near-site time

The near station of the target during the current transit corresponds to a certain point on a target track (or a view track), when the target runs to the point, the view elevation angle of the target is maximized, the distance of the target is generally minimized, the near station is a space point with the best radar detection condition because the detectable region of the radar generally only comprises two constraint conditions of action distance and view elevation angle, and the detectable arc sections of the current transit of the target are distributed around the near station. The invention utilizes the special properties of the near-site and performs step-by-step processing based on the determination of the near-site to generate reasonable and effective radar guide data.

A theoretical orbit of the target is determined by a known group of precise orbit parameters, a near station exists on the theoretical orbit corresponding to the current situation of the target, and the theoretical near station moment is determined firstly in the processing of the step, so that a foundation is laid for subsequent processing. Regarding the near-site time calculation, non-patent document 5 provides an effective method that solves the near-site time in two steps:

first step to solve the approximate near-site timeBriefly listed are the following formulas:

wherein λ₀Is λ (T) at T₀The value of the moment is T₀The target weft straightening angle at the moment can be calculated by the formula (6),is the long-term rate of change of λ (t), u_sAnd λ_sAre respectively T₀The true latitude angle projected by the measuring station on the track and the corresponding horizontal latitude angle,is u_sSee non-patent document 5 for a specific calculation formula thereof, which is not listed hereAnd (6) discharging.

The second step is firstly obtained by calculation of the formula (6)Target horizontal latitude angle of momentAnd utilizes the elliptic motion relationship ofIs calculated to obtainTarget true latitude angle of momentThen is provided withGiving the accurate near-station time by iterative solution as an initial valueCorresponding target true latitude angleBriefly listed are the equations to be solved iteratively as follows:

whereinAndis xi (t) and eta (t) respectivelyThe values of the moments can be respectively calculated byCalculated by the formulae (4) and (5) and theta isOpening angle theta of time target and survey station at geocentric₀Is composed ofThe orbit latitude of the time measuring station is rThe earth center distance of the time target, R, is the earth center distance of the survey station, and the calculation and detailed iterative process of the correlation quantity are described in non-patent document 5. Finally, the elliptic motion relation is utilizedIs calculated to obtainTarget horizontal latitude angle of momentThe exact near-site time is given by:

the method has the following necessities that the treatment is carried out in two steps: the first step of processing is direct solution, which always provides a better approximate value of the time close to the station, the second step of processing is iterative solution, which needs an initial value with certain precision to ensure the convergence of the iterative process, and the result of the first step of solution can be just used as the initial value of the second step of solution, so the two-step processing mode is indispensable to ensure the acquisition of the accurate time close to the station.

And step 3: discretization of tracing errors and generation of view clusters

Although the trace error of point location forecast during the target current transit period cannot be confirmed, a user provides an estimation range tau, so that the trace error can be considered to fall within a closed interval [ -tau, tau ], the invention considers the trace error as a random variable uniformly distributed within [ -tau, tau ], and discretizes the random variable in the step to convert a probability problem into a certainty problem, which is defined as follows:

where Δ τ is a time increment, l ≧ 1 is a positive integer, and (l-1) Δ τ ≦ τ, we actually take Δ τ to be 1 second in the present invention. In the constructed analytic perturbation model, we will refer to that in equation (6)Is replaced byAnd if the k is 0, the corresponding virtual target is the theoretical target.

The time difference distribution of each virtual target and the theoretical target on the track position just covers the trail error range of the target point forecast, and the definition of the trail errors shows that the real target can be between two adjacent virtual targets, so that the rule that the possible observation characteristics of the real target change along with the trail errors is searched through extracting the observation characteristics of each virtual target and based on the density of the track distribution of the virtual targets and the continuity of motion change, and the theoretical basis is provided for the formation of the target capture strategy.

As the earth rotates, from the ground observation station, the targets at different positions on the same orbit form different apparent motion trajectories during one transit, and as described above, each virtual target forms an apparent trajectory cluster during the current transit, and the apparent trajectory cluster can be expressed as { Γ_k|_l，-lR, each element of which is r_kAll correspond to a visual trackUniquely determined (corresponding to the perturbation model), k is decremented from l to 1 to l forming the apparent track cluster.

Based on the geometric characteristics of the target track, each visual track is always generated through a process of ascending the elevation angle and then descending the elevation angle, and the elevation angle on the visual track reaches the maximum at the near-station position. In addition, considering the rotation of the earth, when k is continuously changed from l to-l by 1, the corresponding apparent track gamma is_kHas the following three possible variation characteristics:

1) the visual track gradually approaches the zenith of the observation station, and the maximum elevation angle on the visual track gradually increases;

2) the visual track is gradually far away from the zenith of the observation station, and the maximum elevation angle on the visual track is gradually reduced;

3) the visual track gradually approaches the zenith of the observation station, the maximum elevation angle on the visual track gradually increases until the observation station passes through the target track surface, the maximum elevation angle on the visual track reaches the maximum at the moment, then the visual track gradually leaves the zenith of the observation station, and the maximum elevation angle on the visual track gradually decreases.

The above inherent characteristics of the visual track and the visual track cluster are the theoretical basis reasonably formed by the technical scheme of the invention, the introduction of the visual track cluster concept also provides an image and visual expression tool for subsequent processing, and the following method is based on the visual track cluster { gamma_k|_l，-lUnfold for further processing.

And 4, step 4: near site visibility constraints

Visual track cluster { gamma_k|_l，-lThe generation of the tracking error is only due to discretization of the tracking error and is not related to the detectable condition of the radar, so that the tracking error is called as a tracking cluster, the tracking cluster is used for representing the image and intuition and does not indicate that each tracking in the cluster is visible (detectable), and in order to form an effective technical scheme, the tracking in the cluster needs to be subjected to visibility judgment one by one, and the invisible tracking is removed.

Since the near-station is the spatial point with the best radar detection condition, for each visual track, if the near-station on the visual track is invisible, the whole visual track is invisible, and such visual track can not be considered naturally, otherwise, the visual track is considered to be visible, so that the near-station time corresponding to each visual track needs to be calculated firstly. In principle, the near-site time corresponding to each visual track can be calculated by adopting the method of the step 2 and based on the corresponding perturbation model, and the invention adopts a simpler and more effective method, and the specific calculation process is described as follows:

1) considering theoretical apparent trajectory gamma₀The visibility of the system is determined by the transit forecast, no judgment is needed, and the corresponding station-approaching moment is calculated in the step 2;

2) considering two adjacent apparent trajectories Γ_kAnd Γ_k+1Since the two corresponding virtual targets are very close in track position (the time difference Δ τ is 1 second), Γ may be used_kIs taken as the exact near-site time of r_k+1The approximate station-approaching moment of (2) is directly entered into the second solving process of step (2), wherein the solving process adopts gamma_k+1The corresponding perturbation model performs a correlation calculation to give Γ_k+1The exact near-site time. By continuously changing k from 0 to l-1, a series of visual trajectories gamma can be obtained step by adopting the above processing mode₁，Γ₂，...，Γ_lCorresponding station approaching time;

3) considering two adjacent apparent trajectories Γ_kAnd Γ_k-1Since the two corresponding virtual targets are very close in track position (the time difference Δ τ is 1 second), Γ may be used_kIs taken as the exact near-site time of r_k-1The approximate station-approaching moment of (2) is directly entered into the second solving process of step (2), wherein the solving process adopts gamma_k-1The corresponding perturbation model performs a correlation calculation to give Γ_k-1The exact near-site time. By continuously changing k from 0 to-l +1, a series of visual trajectories gamma can be obtained step by adopting the above processing mode_-1，Γ_-2，...，Γ_-lCorresponding to the time of the near site.

By this we have completed the view trajectory cluster { Γ_k|_l，-lCalculate the time of all the visual tracks at the near site, becauseThe first step solving process of the step 2 is skipped, and the calculating process is compact and smooth and is more effective.

Knowing the time of the near-station, the distance and the elevation angle of each near-station can be respectively solved through track calculation and related coordinate conversion based on the perturbation model corresponding to each visual track, and the distance and the elevation angle can be matched with detectable conditions (threshold values of action distance and elevation angle) of the radar one by one to finish the confirmation of the visibility of each visual track.

Through the above processing, we just look at the track cluster { Γ_k|_l，-lIn step 3, the continuous change characteristics of each visual track in the visual track cluster are described, so that it is easy to deduce that the removed visual tracks are necessarily positioned at two ends or one end of the visual track cluster and are continuous in pieces, so that the rest visual tracks still have continuity, and the visual track cluster formed by the visual tracks can still be expressed as { F_k|_i，jAnd j is more than or equal to i and more than or equal to 0.

And 5: detecting validity constraints

Practical operation often requires that the radar have a sufficient detectable arc length for two main reasons: firstly, when the detectable arc section is too short, the obtained observation data are few, and the use value of the observation data is possibly lost, so that the cost effectiveness of the radar is very low; secondly, the extremely short observable arc section generally occurs when the target track just exposes the ground, the elevation angle on the whole sight track is very small, the radar detection is seriously interfered by the atmosphere, the quality of observation data is reduced, and the use of the radar detection is also influenced. Therefore, the object-oriented track cluster { gamma } must be located_k|_i，jMake a further screen to remove those view tracks where the detectable arc is extremely short to ensure the effectiveness of radar detection.

According to the elevation angle change characteristic of the target moving along the visual track described in the step 3, the visual track near station is used as a boundary, the whole visual track is divided into two sections, one section is a front ascending section, the other section is a rear descending section, in order to enable the radar to have a longer detectable arc section after capturing the target, the technical scheme adopts an ascending section detection mode, and certain limit is made on the detectable time of the descending section, and the specific threshold is determined according to actual working requirements.

For apparent track cluster { Γ_k|_i，jOne apparent track gamma in_kThe method can combine the detectable condition of the radar and carry out searching calculation by proper step length from the time of the near-station based on the corresponding perturbation model till the time set by the threshold, and if an invisible target point is found in the searching process, the visual track is removed from the cluster. Repeating the above processing procedure for other visual tracks in the visual track cluster removes a plurality of visual tracks with unsatisfactory detectable arc length. It is not difficult to deduce based on the continuous change characteristics of each visual track in the visual track cluster, the removed visual tracks are necessarily positioned at two ends or one end of the visual track cluster and are continuous in pieces, so the rest visual tracks still have continuity, and the visual track cluster formed by the visual tracks can still be expressed as { F_k|_m，nAnd m is more than or equal to n.

Step 6: search elevation determination

Visual track cluster { gamma_k|_m，nEach visual track in the radar is possibly a route passed by a real target, and the detectable elevation angle ranges of the visual tracks are not consistent, so that the radar needs a proper search elevation angle to realize possible traversal detection of all the visual tracks at the specified elevation angle, and the capture success rate of the target is improved.

For apparent track cluster { Γ_k|_m，nOne apparent track gamma in_kThe detectable elevation range of the radar is determined by the maximum detectable elevation and the minimum detectable elevation, wherein the maximum detectable elevation is the detected elevation at the near-station, the detected elevation is calculated in step 4, in order to ensure that the radar can obtain effective observation data with enough duration, the minimum detectable elevation should be searched in the ascending section, the corresponding near-station time is given in step 4, the search calculation can be carried out by adopting a dichotomy from the time forward by an appropriate initial step size based on the corresponding perturbation model,in the calculation process, the real-time judgment needs to be carried out by combining the detectable conditions of the radar, and finally the minimum detectable elevation angle meeting certain precision requirements is given.

Repeating the above processing procedures for other visual tracks in the visual track cluster to obtain the maximum detectable elevation angle and the minimum detectable elevation angle corresponding to all the visual tracks. Taking the minimum value of the maximum detectable elevation angles of all the visual tracks, and setting the minimum value as h_qTaking the maximum value of the minimum detectable elevation angles of all the visual tracks, and setting the quantity as h_pThen, the closed interval [ h ]_p，h_q]An elevation angle range suitable for the radar to perform equal elevation angle search is determined, and the radar performs equal elevation angle search at any elevation angle in the range, so that traversal detection of all the visual tracks can be realized. The minimum detectable elevation angle of the visual track is also certain to be maximum by combining action distance constraint conditions detected by radar, so that the elevation angle h can be considered to be the elevation angle h_qAnd h_pCorresponding to the same apparent trajectory, then: h is_q≥h_pI.e. the elevation angle range determined above is always valid.

The specific search elevation angle adopted by the radar during working is determined by the relevant input conditions of the technical scheme, and a calculation formula is given as follows:

h＝h_p+β(h_q-h_p) (7)

beta is a search elevation angle adjustment factor, and the search elevation angle h is always within the elevation angle range [ h ] according to the definition of beta_p，h_q]An internal value. When the value of beta is 0, the radar is shown to search according to the minimum elevation framed by the program; when the value of beta is 1, the radar is shown to search according to the maximum elevation angle framed by the program.

And 7: calculation of characteristic parameters at a specified elevation angle

The virtual target moves along the corresponding visual track, the time, the azimuth angle, the distance, the visual movement speed and the flight direction of the virtual target rising to the designated elevation angle collectively reflect the observation characteristics of the target at the position, and are target observation characteristic parameters in the radar and other elevation angle search modes. In the step of processing, observation characteristic parameters corresponding to each virtual target are extracted and used as a basis for equal elevation angle searching, capturing and distinguishing of the real target by the radar.

For apparent track cluster { Γ_k|_m，nOne apparent track gamma in_kBased on a corresponding perturbation model, searching and calculating by adopting a bipartition method from the near-station time forward by using a proper initial step length, generating a calculated elevation angle of the corresponding time in each step in the calculation process, judging the proximity degree of the calculated elevation angle and a specified elevation angle, and finally providing observation characteristic parameters meeting certain precision requirements, including time, azimuth angle, distance, azimuth angle variability and elevation angle variability of a target reaching the specified elevation angle, wherein the apparent movement speed and the flight direction of the target are determined by the azimuth angle variability and the elevation angle variability. Repeating the above processing procedures on other visual tracks in the visual track cluster to obtain observation characteristic parameters corresponding to all the virtual targets.

And 8: continuous processing of azimuth

For apparent track cluster { Γ_k|_m，nOne apparent track gamma in_kSetting the azimuth angle of the corresponding virtual target rising to the designated elevation angle as A_kWhen k is continuously changed from m to n, the corresponding visual track in the visual track cluster is also continuously changed, and the continuous change is reflected as A when being projected to a specified elevation angle_kIn principle A_kShould be continuous to visually reflect the continuous change process of the corresponding visual track, but due to the numerical expression of the azimuth, A_kThe change of (a) is generally not continuous, and there may be problems: azimuth in the general sense (e.g. A)_k) All take values in the interval [0, 2 π), with the north direction being 0, and count clockwise up to 2 π, when k varies continuously from m to n, if A_kThe change of (A) passes through the north direction_kThe change of (2) is not continuous, and there is a jump from near 0 to near 2 pi, or from near 2 pi to near 0 in the middle.

As is clear from the above problems, A_kThe discontinuity of the change is caused by the numerical expression of the azimuth angle, and the corresponding azimuth change has no discontinuity from the physical process, so the discontinuity of the A must be caused_kRedefines them to have continuously changing characteristics to adapt to the subsequent correlation processing. Setting A after redefinition_kValue is A'_kAnd considering that k varies continuously from m to n, then A'_kThe calculation process of (2) is as follows: first, take A'_m＝A_mFor the subsequent A_kLet Δ A_k＝A_k-A_k+1The subsequent A 'is calculated in three independent cases'_k：

1) If an integer p is present, m-1. gtoreq.p.gtoreq.n, such that Δ A_pIf < - π, then:

2) if an integer p is present, m-1. gtoreq.p.gtoreq.n, such that Δ A_pIf pi is greater, then:

3) if there is no integer p for the above two cases, then there are:

A′_k＝A_k m-1≥k≥n

the above calculation process needs to be gradually adjusted to Δ A_kThe determination is made until one of the situations occurs.

A 'obtained above'_kIs no longer limited to values taken within [0, 2 π), thus maintaining the continuity of the change as a whole, but A'_kAnd A_kThere is no essential difference, both correspond to the same physical orientation, so for convenience of subsequent processing we will use A'_kSubstituted A_kIt is also called the azimuth.

And step 9: generation of boot data

For apparent track cluster { Γ_k|_m，nOne apparent track gamma in_kSetting the time, azimuth angle, distance, azimuth angle variability and elevation angle variability of the corresponding virtual target rising to the specified elevation angle as t_k，A′_k，ρ_k，Andwhich have been calculated in step 7 and step 8, the position of the virtual object on the track being determined by the position of the virtual object in relation to the known parametersIs determined byAs can be seen from the definition of (a), when k varies continuously from m to n,gradually becomes smaller, so that the time for each virtual target to reach a certain fixed point on the orbit becomes larger in sequence, and considering that the angular velocity of the target motion is far greater than the earth rotation velocity, t can be judged_kAlso successively larger, i.e. when k varies continuously from m to n, t_kIs a strictly monotonically ascending sequence, and can be further inferred based on earth rotation, A'_kThe change with k is also a monotonous sequence, or monotonous ascending, or monotonous descending, which is related to the position of the target on the track near the station when the target passes the current situation.

Due to t_kAnd A'_kThe above variation characteristics, and considering the continuity of the general trajectory along with the change of the trajectory error, may consider that there is a monotonic function relationship between the possible azimuth angle a 'of the real target rising to the specified elevation angle and the corresponding time t, where a' is a strict monotonic function of t, and they are in one-to-one correspondence, or may be expressed in another way: although we do not know in which bearing a real target will appear when it rises to a specified elevation angle, if it appears in one bearing, it may only appear in one unique bearingA time of one. The space-time relation characteristics enable the radar to traverse all possible directions of a real target according to the time-sequence equal elevation searching process, and are key factors for effectively forming the capturing strategy.

Due to t_kIs a strictly monotonically rising sequence, and is therefore given by t_kThe base point is a known parameter A 'on the base point'_k，ρ_k，Andthe data relating to azimuth A', distance ρ, and azimuth variability can be constructed separatelyAnd elevation variabilityIn consideration of the smoothness of the general apparent trajectory varying with the trajectory error, the present invention actually employs cubic natural spline interpolation (non-patent document 6), and the interpolation functions obtained thereby are given as follows:

A′＝A′(t) (8)

ρ＝ρ(t) (9)

the interpolation functions above give different observation characteristics that the real target may have in a continuous time range, and since A ' is a strictly monotonic function of t, A ' (t) has a unique inverse function, which may be A '_kFor the base point, it is still obtained using cubic natural spline interpolation, given as follows:

t＝t(A′) (12)

t (a ') is also a strictly monotonic function on a' that gives different times at which a real object may appear in a continuous range of azimuth angles.

The time range of the real target rising to the designated elevation angle is a closed interval [ t_m，t_n]The corresponding azimuth angle range is a closed interval [ A'_m，A′_n]Or [ A'_n，A′_m]Depending on the monotonically varying nature of the function a' (t). As shown in fig. 1, when the radar searches along a specific elevation angle corresponding to the azimuth interval, there is also a variation interval, which is marked as [ psi ], in the beam direction₁，ψ₂]If will [ psi₁，ψ₂]Is divided into several sub-intervals, the corresponding azimuth angle interval is also divided into the same sub-intervals for a certain [ psi₁，ψ₂]Sub-interval having a corresponding azimuth sub-interval, wherein the two endpoint times of the azimuth sub-interval are calculated respectively by using equation (12), and a time sub-interval is determined from the two endpoint times, such that the time sub-interval is equal to the [ psi ]₁，ψ₂]The time sub-intervals corresponding to the sub-intervals, such that each [ psi₁，ψ₂]The subintervals each have a corresponding time subinterval. Based on the monotonicity of A' (t), the radar beams can be sequentially arranged in the corresponding [ psi ] according to the time sequence₁，ψ2]In the center direction of the subinterval, each placement corresponds to one beam dwell, the starting time and the ending time of each beam dwell are respectively the head time and the tail time of the subinterval corresponding to the time, the search mode and the search process of the radar on the designated elevation angle are formed through each beam dwell, and because only the track error predicted by the target point is concerned in the related step processing, only the track error is considered, as long as the effective beam diameter of the radar is not less than [ psi ]₁，ψ₂]Subinterval length, based on the above equal elevation search method, can achieve missing-free detection of real target, but errors in other directions (normal and radial) are generally present, even though they are in phaseFor small amounts of tracking errors, proper consideration is still required.

Suppose that the real target rises to a specified elevation angle at a certain time and that this time is at a certain [ psi₁，ψ₂]If only the tracking error exists in the time subinterval corresponding to the subinterval, the real target direction of the time is always within the [ psi ]₁，ψ₂]In the subinterval, the real target direction at that time may deviate from the [ ψ ] due to errors in other directions₁，ψ₂]Sub-interval if the radar effective beam diameter and [ psi ]₁，ψ₂]If the sub-intervals are equal in length, the radar may miss the target in the detection process, and in order to improve the capture success rate of the target, the effective beam diameter of the radar should be larger than [ psi ]₁，ψ₂]The sub-interval length, since the radar effective beam diameter belongs to the limited working parameters, we cannot change, and the only alternative method is to reduce [ psi₁，ψ₂]Length of subintervals for which the pair [ psi ] is required₁，ψ₂]A finer division is performed.

The length of the azimuth change interval for a target at a given elevation angle is given as follows:

ΔA＝|A′_m-A′_n|

as shown in fig. 1, according to the spherical geometry, the length of the corresponding beam pointing variation interval of the radar at a given elevation angle can be calculated as follows:

cosΔψ＝sin²h+cos²hcosΔA

wherein the delta psi is psi₂-ψ₁It can be obtained by inverting the function values of the other chords. Let the effective beam diameter of the radar be w, determine [ psi₁，ψ₂]The number of evenly divided subintervals is as follows:

w^*＝(1-δ)w

wherein δ is dimensionlessThe scale factor can be selected in the interval [0, 1], and N is [ psi₁，ψ₂]The number of sub-intervals, [ psi ] divided by N above can be strictly proven mathematically₁，ψ₂]The sub-interval length does not exceed the effective beam diameter of the radar, the larger the delta, the larger [ psi₁，ψ₂]The smaller the subinterval length, the more δ is approaching 1, [ ψ ]₁，ψ₂]The subinterval length will tend to 0, which if the target is still not captured, indicates that the error in the other direction has grown too much beyond the effective beam radius of the radar, which generally results from the long extrapolation time for the target trajectory perturbation. Although theoretically, the capturing success rate of the target gradually increases with the gradual increase of the delta, the residence time of each sub-beam of the radar is gradually shortened, so that the dynamic stability of a radar servo system and the signal processing of the radar are adversely affected, therefore, the selection of the delta value in the actual work needs to be balanced by combining various factors, and the delta is less than or equal to 0.5 according to the existing practical experience, so that the general application requirements can be met.

Known interval [ psi₁，ψ₂]The method can generate the guiding data required by the radar, and the guiding data respectively give the starting time, the ending time and the center pointing azimuth angle of each sub-beam residence when the radar performs equal elevation search, and the target distance, the azimuth variability and the elevation variability of each sub-beam center pointing. Taking into account the azimuthal interval and [ psi₁，ψ₂]With the same division, the azimuth subinterval length can be calculated as follows:

ΔA^*＝ΔA/N

defining a sign factor:

and each azimuth angle interval is sequentially set as1, 2, N, thenTwo endpoint values of each azimuth subinterval can be recurrently obtained by adopting the following modes:

is provided withIs a sub-interval of the azimuth angleThe corresponding time subinterval, its two endpoint values can be calculated by using equation (12):

azimuth subintervalThe central azimuth of (c) can then be calculated by:

the center time corresponding to the center azimuth can be calculated by equation (12):

the target distance, the azimuth angle variability and the elevation angle variability of the radar beam center pointing direction corresponding to the center azimuth angle are calculated by the following expressions (9), (10) and (11):

the azimuth angle of the radar beam center direction obtained by the calculationActually, the result is the result after the continuous processing, and in order to meet the working habit of the radar, the result is finally reduced to the common representation method, and the corresponding value is set asThen there are:

by this time, we complete the generation of all the boot data, and the process ends.

The above processing procedure is only described for the general case, and there are two special cases in the processing procedure, and although these two special cases are unlikely to occur, they should be explained for the completeness of the technical solution:

special example 1: after the processing of step 5, if looking at the track cluster { Γ_k|_m，nIf the rate is null, the radar cannot acquire effective observation data meeting the working requirements in the current transit of the target, and the subsequent processing process is terminated;

special example 2: at the point of step 5If the trajectory cluster { gamma is looked at_k|_m，nIf there is only one visual track, only the processing of step 6 and step 7 is continued, after the processing is finished, the time when the virtual target on the visual track ascends to the designated elevation angle is taken as the central time, the central time is respectively decreased and increased by delta tau/2 to be taken as the starting time and the ending time of beam residence, a primary beam residence is shared, the azimuth angle, the target distance, the azimuth angle variability and the elevation angle variability pointed by the beam center are respectively taken as corresponding observation characteristic parameters of the virtual target on the visual track, and the characteristic parameters are obtained by calculation in step 7.

Through the processing of the steps, a reasonable designated elevation angle h is obtained, and a series of groups of guide data are generatedAndn, each set of guidance data corresponding to a dwell of the radar beam at a specified elevation angle, whereinThe bearing at which the center of the beam is pointed is determined,anddetermining the starting and stopping time of beam residence, if the target appears in the beamCan be used for real-time discrimination of the target to determine whether the target is an observation target (due to the narrow wave beam, the distance between the observation target and the target is equal toVery close, an appropriate discrimination threshold can be set accordingly), if a target is present in the beamAnd is judged as the observation target, thenAndcan be used for guiding the radar to carry out tracking observation on the target for the following seconds, so that the radar can lock the target and shift into self-tracking. When each group of guide data is changed from v-1 to v-N, the corresponding beams sequentially reside at different directions at a specified elevation angle according to the time sequence, thereby forming a mode and a process of searching for the elevation angle of radar and the like, wherein the starting time of the first beam residence isFor the rest of beams, the starting time of the beam residence at this time is the ending time of the beam residence at the last time, and the ending time of the beam residence at the last time is[t_m，t_n]Namely the effective working time period of the radar for implementing equal elevation search during the current transit of the target.

The detailed processing flow of the technical scheme of the invention is shown in figure 2.

In order to make the technical scheme of the present invention better understood and understood by those skilled in the relevant art, the theoretical starting point of the technical scheme will be analyzed and explained below, and the implementation of the technical scheme will be clearly and completely described by combining two specific examples, so that the application effect of the present invention will be embodied in the two examples.

First, error analysis and description

The point location prediction error of the spatial target is mainly an extrapolation error of perturbation calculation thereof, and the perturbation calculation of the spatial target already has a relatively mature analysis motion theory (non-patent document 4). Assuming a, e, i, Ω, ω, and M as the number of osculating tracks in the original form of the target, where a is the track radius, e is the track eccentricity, i is the track inclination, Ω is the track ascent point right ascension, ω is the track perigee argument, and M is the target mean angle, based on the first-order perturbation analysis theory in the form of pseudo-average number of roots proposed in non-patent document 4, and considering the pseudo-average number of roots, the first-order long-period perturbation term of the space target appears in a differential form, which can be approximately equal to the second-order long-term, so a related perturbation analysis formula is given as follows:

the left end of the above forms is the number of osculating roots at the target time t,are respectively epoch t_qThe corresponding quasi-average number of the time can be obtained by precise orbit determination,is an epoch t_qThe angular velocity of the target translational motion at a time (pseudo-average),is an epoch t_qThe time rate of change, omega, of the angular velocity of the time-of-day translational movement₁，ω₁，M₁Respectively, the first-order long-term perturbation term coefficient, a₂，e₂，i₂，Ω₂，ω₂，M₂Respectively are second-order long-term perturbation term coefficients corresponding to the number of the elements,respectively, the first-order short-period perturbation items corresponding to the number of the elements. Although the expressions (13) - (18) only correspond to the first-order analysis perturbation solution of the target, the change rule for describing the point location prediction error is enough, and we analyze the error change characteristics of each item at the right end of the expressions, and further extract the main rule that each root calculation error changes along with the prediction time.

The calculation error of the first-order short period term still shows short period change and is small, and has no substantial contribution to the error of each number and error increase, so that the calculation error of each-order long term is linearly increased along with the time, but the high-order long term error is small relative to the low-order long term error, therefore if the perturbation formula of a certain number contains a plurality of long term terms with different orders, when the long term change of the calculation error of the number is considered, only the lowest-order long term error is considered, and in addition, a time square increase term is also present, and the time square increase term appears in the perturbation formula of the mean-approximate-point angle M, and the coefficient of the term containsThe definition of the elliptical motion relationship and the pseudo-average number is given easily:

is a second order small quantity, although the coefficient of the term is small, is composed ofThe calculation error in this term increases quadratically with time and the long-term perturbation variation of the orbit's radius is mainly caused by atmospheric resistance, a₂In relation to the target face value ratio, the atmospheric resistance perturbation is very significant for low orbit satellites with large face values, so the calculation error of the term is generally not negligible, and even after long-time perturbation extrapolation, the term may rise to be a main error. Based on the above analysis and consideration, we give the following main calculation errors for each number:

wherein, the delta a, the delta e, the delta i, the delta omega and the delta M are respectively calculation errors of corresponding numbers, are respectively epoch t_qThe corresponding pseudo-average root error of the time can be understoodFor a target tracking error, Δ Ω₁And Δ ω₁Respectively, the first-order long-term coefficient error, Δ a, of the corresponding root₂，Δe₂And Δ i₂Respectively, the second-order long term coefficient errors corresponding to the root numbers,andare respectively asAndthe error in the determination of (a) is,contains the determination error of the target face value ratio e.

Based on equations (19) to (24), it can be seen that the point location prediction error of the spatial target is caused by its orbit determination error (precision orbit parameter error used as prediction) and perturbation extrapolation error, due to the zeroth-order long-term coefficientIs composed ofEach first-order long-term coefficient isEach second-order long-term coefficient and the square term coefficientAre all made ofE (non-patent document 4), the tracking error also indirectly causes a perturbation extrapolation error. Due to the fact thatM and omega are position parameters of the target on the track, so the calculation error of the M and the omega corresponds to the locus error of point location prediction, wherein the calculation error of the M not only contains a zero-order long-term perturbation term error, but also contains a second-order square perturbation term error, so the locus error is increased very rapidly along with the prediction time; the calculation errors of other numbers are mainly embodied as errors of point location forecast in other directions (normal direction and radial direction), wherein the maximum error is derived from the calculation error of the right ascension channel omega of the orbit intersection point, the error contains a first-order long-term perturbation term error, and the corresponding error term coefficient is delta omega₁The magnitude of the coefficient is omega₁The product of the self magnitude and the orbit determination error magnitude can reach 10 for general precise orbit determination of a space target^-7～10^-8Therefore, errors in point location prediction in other directions grow very slowly.

From the above analysis, the following basic conclusions can be made: the spatial target point location prediction error can be decomposed into a locus error and errors in other directions, the locus error is a main error of location prediction due to high growth speed, and the errors in other directions grow slowly and are secondary errors of location prediction. The above conclusion is that the invention forms the theoretical basis of an effective technical scheme, and since the effective beam diameter of a narrow beam radar is very small, how to eliminate the influence of a point location prediction locus error becomes a key problem to be solved in order to capture a spatial target, and because of uncertainty of the locus error, if the target is still captured and tracked by guidance of point location prediction, the problem cannot be solved, which is a technical bottleneck generally existing in various existing technical schemes. The technical scheme of the invention is that the processing of the tracking error is simplified on one hand, the precision of the perturbation calculation model is reasonably improved on the other hand, the error increase of the point location forecast in other directions is effectively inhibited, the target orbit determination precision depends on the selection of a user for the track parameter, the existing experience shows that the two-line root number and the domestic common cataloging root number can meet the general application requirements, and under the specific condition, the track parameter with higher precision is required for laser ranging observation, the orbit parameters can be obtained from the outside, and can also be obtained by adopting observation data of domestic precision tracking equipment and orbit determination by a high-precision numerical method, and the orbit parameters with which precision should be adopted in specific work need to be determined through experiments.

Errors in other directions of the point location prediction are mainly caused by perturbation extrapolation errors of the right ascension of the orbit intersection point, which can be given according to non-patent document 4:

wherein J₂Are the main band harmonic coefficients of the earth,is the track radius (pseudo-average), Ω₁The smaller is Δ Ω₁The smaller the target orbit is, the slower the error of the point location forecast in other directions grows, which shows that the technical scheme of the invention is more effective when applied to the target with higher orbit.

Second, combine the example to explain the technical scheme

The technical scheme of the invention is described in detail by two examples, wherein the examples use the variables and symbols defined in the technical scheme, and obtain corresponding results by giving specific values to the variables.

Example 1:

in this example we chose AJISAI (NASA catalog No. 169908) as the experimental target, which is the target trackThe road height is 1400 kilometers, the road height is a laser calibration star, high-precision standard ephemeris data can be compared, a certain radar in China is selected as an experimental radar in the experiment, the effective beam diameter of the radar is assumed to be 0.05 degrees, when a target enters the effective beam of the radar, the included angle between the beam center pointing direction and the target direction is smaller than 0.025 degrees, a group of double-row cataloging root numbers of the target is firstly obtained from a NASA (www.space-track. org), and the root epoch time t_qCorresponding to the conditions of 10, 16, 05, 25 min 16.146 s (Beijing), 2020, 25 min 16.146 s (non-patent document 8), the position and velocity vector of the target relative to the J2000 geocentric inertial system at the same epoch time is generated by defining the number of double-row elements (non-patent document 3) and performing corresponding coordinate transformation (non-patent document 8)Andand the target face value is more than e and is determined by the target track parameter t_q，E, and based on the detectable conditions (action distance and elevation angle constraint conditions) of the radar, adopting a numerical method and a high-precision mechanical model to carry out transit forecasting to generate a series of target transit periods (determined by a transit starting time and a transit ending time), selecting one of the transit periods, wherein the starting time T of the transit period_bCorresponding to 23 hours 01 and 47 minutes (Beijing hours) of 03 and 01 of 2021, and ending time T_eCorresponding to 03, 02, 00, 08 minutes (Beijing time) in 2021, searching and capturing experiments of targets are carried out in the transit time, and a known group of target precise orbit parameters are t_q，E, which is the orbit parameter four and a half months ago relative to the transit time period, the maximum trail error tau of the forecast of the orbit parameter point location of the group is estimated to be 100 seconds, the scaling factor beta is taken to be 0.3511597, the searching elevation angle of the radar is determined, in the transit forecast calculation,the adopted high-precision mechanical model comprises earth central gravity and shape perturbation, atmospheric resistance perturbation and daily and monthly gravity perturbation, wherein the harmonic series of the earth gravity potential sphere is truncated to 20 multiplied by 20. After the preparation of the data and the setting of the input conditions are completed, the following experimental steps are carried out:

step 1: modeling of transit intermediate times

Will t_q，T_b，T_eRespectively expressed by reduced julian days, and converting corresponding Beijing time into earth dynamics time (TDT), and calculating intermediate time T of the current transit of the target₀＝(T_b+T_e) 2, based on the known orbit parameter t_q，E, adopting a numerical method and a mechanical model same with the calculation of the transit forecast to carry out perturbation extrapolation, and calculating the mean value from t_qPush-out of time to T₀At that time, T is obtained₀Position and velocity vectors of a time target relative to the J2000 Earth-centered inertial SystemAndfurther will beAndconversion to target T₀Initial pseudo-average number of momentsWith the initial pseudo-average number, an analysis perturbation model expressed by the formulas (1) to (6) can be constructed, and the analysis perturbation model describes the theoretical orbital motion of the target during the current transit period.

Step 2: calculation of theoretical near-site time

Based on radarThe coordinates of the station can always obtain the geocentric distance and the geocentric latitude and longitude of the survey station, and the analysis perturbation model established in the step 1 is adopted to calculate in two steps according to the method of the non-patent document 5, wherein the first step is T₀Calculating to obtain the approximate near-site timeThe second step is composed ofObtaining the accurate near-station time by iterative computationThe accurate near-site time is the theoretical near-site time of the target transit period.

And step 3: discretization of tracing errors and generation of view clusters

Taking Δ τ as 1 second, yieldk 101, 100, 0, 100, -101, used in sequence in the analytical perturbation model of step 1SubstitutionA series of new perturbation models are formed, each new perturbation model describes the motion of a virtual target, when k is 0, the corresponding virtual target is a theoretical target, each virtual target moves along the same orbit in an inertial space, only the positions on the orbit are different, due to the rotation of the earth, the virtual targets generate different visual tracks in the transit period from a ground radar station, and the visual tracks form a visual track cluster which can be expressed as { gamma_k|_101，-101}。

And 4, step 4: near site visibility constraints

Theoretical apparent trajectory gamma₀Time of near siteAlready given in step 2; considering two adjacent apparent trajectories Γ_kAnd Γ_k+1With Γ_kTime of near siteAs r_k+1Approximate near-site time ofNamely haveAnd based on gamma_k+1The perturbation model directly enters the second step iteration solving process of the step 2, and gamma is obtained through calculation_k+1Time of near siteBy continuously changing k from 0 to 100, the visual trace gamma can be obtained gradually by the above processing method₁，Γ₂，...，Γ₁₀₁Corresponding station approaching time; considering two adjacent apparent trajectories Γ_kAnd Γ_k-1With Γ_kTime of near siteAs r_k-1Approximate near-site time ofNamely haveAnd based on gamma_k-1The perturbation model directly enters the second step iteration solving process of the step 2, and gamma is obtained through calculation_k-1Time of near siteThe visual trace gamma can be obtained gradually by continuously changing k from 0 to-100 by adopting the above processing mode_-1，Γ_-2，...，Γ_-101Corresponding to the time of the near site.

Known apparent track cluster { gamma_k|_101，-101The near-station time of each visual track can be respectively solved for the near-station distance and the elevation angle of each visual track through track calculation and related coordinate conversion based on the perturbation model corresponding to each visual track, and the near-station distance and the elevation angle are matched with the detectable conditions of the radar one by one to finish the confirmation of the visibility of each visual track, wherein the visual track gamma is₀Is determined by the context forecast, without re-confirmation, from the apparent trajectory cluster { Γ_k|_101，-101After all invisible visual tracks are removed, the rest visual tracks form a continuous visual track cluster { gamma }_k|_i，j}，i≥0≥j。

And 5: detecting validity constraints

For apparent track cluster { Γ_k|_i，jOne apparent track gamma in_kThe whole visual track is divided into two sections by taking a near station as a boundary, one section is a front ascending section, the other section is a rear descending section, the detectable time of the descending section is limited to be not less than 10 seconds in the step, based on the limited condition, a corresponding perturbation model is adopted, searching calculation is carried out backward from the near station moment by the step length of 10 seconds, only one step is needed to be calculated, the target distance and the elevation angle on the corresponding step point are obtained, the target distance and the elevation angle are matched with the detectable condition of the radar, if the matching is unsuccessful, the visual track is removed from the visual track cluster, and otherwise, the visual track is reserved. Paired eye trajectory cluster { gamma_k|_i，jRepeating the above processing procedures for other visual tracks to remove a plurality of visual tracks with unsatisfactory detectable arc length, wherein the rest visual tracks form a continuous visual track cluster { Γ_k|_m，n}，m≥n。

Step 6: search elevation determination

For apparent track cluster { Γ_k|_m，nOne apparent track gamma in_kThe maximum detectable elevation angle is the detection elevation angle at the near-station, which is given in step 4, the minimum detectable elevation angle should be found in the ascending section, and two perturbation models can be adopted based on the corresponding perturbation modelsThe method comprises the steps of carrying out search calculation from the time close to a station forward by a proper initial step length, matching the target distance and the elevation angle obtained in each step with detectable conditions of the radar in the calculation process, determining the search direction of the next step according to the matching result, determining whether to terminate the search according to the current step length, and finally giving out the minimum detectable elevation angle meeting certain precision. Paired eye trajectory cluster { gamma_k|_m，nRepeating the above processing procedures for other visual tracks to obtain the maximum detectable elevation angle and the minimum detectable elevation angle of all the visual tracks respectively. In the step, the initial step length of the dichotomy search calculation is selected to be 30 seconds, and the convergence precision of the dichotomy is 0.1 second.

Taking the minimum value h from the maximum detectable elevation angles of all the visual tracks_qThen obtain h_q53.22026944 degrees, the maximum h is taken from the smallest detectable elevation angle of all the view tracks_pThen obtain h_p5.50316638 degrees, and a search elevation angle h of the radar 22.259 degrees is calculated from equation (7) according to a specified β value.

And 7: calculation of characteristic parameters at a specified elevation angle

For apparent track cluster { Γ_k|_m，nOne apparent track gamma in_kBased on the corresponding perturbation model, adopting a dichotomy method to search and calculate from the time close to the station forward by a proper initial step length, subtracting a specified elevation from the target elevation obtained in each step in the calculation process, determining the search direction of the next step according to the positive and negative of the difference, determining whether to terminate the search according to the absolute value of the difference, and finally providing observation characteristic parameters meeting certain precision, including the time t when the target reaches the specified elevation_kAzimuth angle A_kDistance rho_kAzimuthal angle variabilityAnd elevation variabilityPaired eye trajectory cluster { gamma_k|_m，nRepeat the above process for other visual tracks to obtain the resultThere is an observed characteristic parameter of the virtual target at a specified elevation angle. In the step, the initial step length of the dichotomy search calculation is selected to be 30 seconds, and the convergence precision of the dichotomy is 10^-4And (4) degree.

And 8: continuous processing of azimuth

Visual track cluster { gamma_k|_m，nOne apparent track gamma in_kCorresponding to a virtual target whose azimuth angle at which it rises to a specified elevation angle takes the value A in the usual way_kWhen k is continuously changed from m to n, in order to ensure continuity of corresponding azimuth angle values, redefining the azimuth angle values is required, and the redefined azimuth angle value is set to be A'_kAnd then A'_kThe calculation process of (2) is as follows: first, take A'_m＝A_mLet Δ A_k＝A_k-A_k+1The subsequent A 'is calculated in three independent cases'_k：

1) If an integer p is present, m-1. gtoreq.p.gtoreq.n, such that Δ A_pIf < - π, then:

2) if an integer p is present, m-1. gtoreq.p.gtoreq.n, such that Δ A_pIf pi is greater, then:

3) if there is no integer p for the above two cases, then there are:

A′_k＝A_k m-1≥k≥n

for Δ A stepwise in the above calculation_kThe determination is made until one of the situations occurs.

And step 9: generation of boot data

For apparent track cluster { Γ_k|_m，nAny one of the apparent tracks F_kCorresponding to the time t when the virtual target rises to the specified elevation angle_kAnd direction of theAngle A'_kDistance rho_kAzimuthal angle variabilityAnd elevation variabilityGiven in step 7 and step 8, may be t_kIs a base point, ρ_k，Andfor function values on the base points, an interpolation function rho (t) is respectively constructed by adopting a cubic natural spline interpolation method,andfrom A'_kIs a base point, t_kAnd (5) constructing an interpolation function t (A') by adopting a cubic natural spline interpolation method as a function value on the base point.

The length of the azimuth angle change interval of the target at the specified elevation angle is calculated as follows:

ΔA＝|A′_m-A′_n|

the beam pointing change interval length when the radar searches along the designated elevation angle is calculated as follows:

cosΔψ＝sin²h+cos²h cosΔA

Δψ＝cos^-1(cosΔψ)

the effective beam diameter of the radar is 0.05 degrees, the value of the effective beam diameter is w after radian conversion, in the step, a scaling factor delta is taken to be 0.2, and the number of subintervals of the azimuth angle interval after uniform division is determined as follows:

w^*＝(1-δ)w

the azimuth subinterval length is then calculated as:

ΔA^*＝ΔA/N

defining a sign factor:

and each azimuth angle interval is sequentially set asN, two endpoint values of each azimuth subinterval are recurrently obtained by the following method:

is provided withIs a sub-interval of the azimuth angleThe corresponding time subinterval, its two endpoint values are calculated as follows:

azimuth subintervalIs calculated by:

the corresponding time of the center azimuth is calculated by the following formula:

the target distance, the azimuth variability and the elevation variability corresponding to the central azimuth angle are respectively calculated by the following formulas:

will center the azimuthReducing to a normal representation form, and setting the corresponding value asThe calculation is as follows:

this completes the generation of the entire boot data.

Through the processing of the steps, the search elevation h of the radar is determined, and a series of groups of guidance are generatedData ofAndn, table 1 intercepts 7 sets of guidance data for performing an equal elevation search on AJISAI by the radar, and the guidance data sets are arranged row by row from top to bottom in time sequence, and each row is from left to right, the first column is a start time of beam dwell, the second column is an end time of beam dwell, the third column is an azimuth angle pointed by a beam center, the fourth column is a target distance pointed by the beam center, the fifth column is an azimuth angle variability pointed by the beam center, and the sixth column is an elevation angle variability pointed by the beam center.

TABLE 1 partial pilot data for radar search AJISAI (search elevation 22.259 degrees)

In the experiment we also base on the known precise orbit parameter t_q，E, point location prediction is carried out by adopting a numerical method and a mechanical model which is the same as that of transit prediction calculation, point location guiding data on a time sequence in the transit period of the target is generated through the point location prediction, the point location guiding data are called as forecast point locations, the point location guiding data on the same time sequence are generated based on standard ephemeris interpolation, the point location guiding data are called as standard point locations, and the standard point locations can be used for checking the target capturing effect of the equal elevation angle searching method and the point location prediction guiding method provided by the invention by considering the standard point locations as real point locations of the target. Table 2 captures 7 groups of standard point data and corresponding forecast point data in the time sequence, and gives the comparison result of the forecast point data and the standard point data, each group of point data is arranged line by line from top to bottom in the time sequence, and each line is the first line from left to rightThe column is the point location corresponding time, the second column is the azimuth of the standard point location, the third column is the elevation of the standard point location, the fourth column is the distance of the standard point location, the fifth column is the azimuth of the forecast point location, the sixth column is the elevation of the forecast point location, the seventh column is the distance of the forecast point location, the eighth column is the included angle between the forecast point location and the standard point location, and the ninth column is the absolute value of the difference between the distance of the forecast point location and the distance of the standard point location. The results in table 2 show that the included angles between each group of forecast point locations and the standard point locations are greater than 2 degrees and exceed the effective beam radius of the radar by 0.025 degrees, which indicates that the radar cannot capture the target under guidance of point location forecast, and the distances between each group of forecast point locations and the standard point locations are also greatly different by more than 110 kilometers.

TABLE 2 comparison of AJISAI Standard and forecast Point locations

Tables 1 and 2 are marked with an underlined part, the marked part in table 1 corresponds to a beam dwell at the time when the radar searches at an elevation angle of 22.259 degrees, the marked part in table 2 corresponds to a standard point of a target at a certain time, the target elevation angle at the time is 22.259 degrees, namely the target appears at the search elevation angle, therefore, whether the radar performs the equal elevation search can capture the target depends on whether the standard point enters the effective detection range of the beam during the certain dwell period of the beam or not, it can be known by comparing the related data of the marked parts in tables 1 and 2 that the corresponding time of the standard point falls within the starting and stopping time range of the beam dwell at the time, the included angle between the standard point and the beam center is 0.00619 degrees and is smaller than the effective beam radius of the radar, the distance between the standard point and the target distance pointed by the beam center is also very small and is only 291.304 meters, which indicates that the radar can capture the target according to the equal elevation search method of the invention, and the target can be accurately judged in real time.

After the radar detects the target, the target needs to be continuously tracked for a period of time so as to lock the target and switch into self-tracking, and therefore, a plurality of subsequent moments need to be generatedThe point location tracking data of (1, 2), k, we refer to as tracking point locations, and each corresponding standard point location can be obtained by standard ephemeris interpolation, which is not assumed to be the caseFor a monotonically rising sequence, considering that the radar has a function of automatically correcting the "miss amount", it is possible toThe standard point location of the moment is the corrected point location, and the corresponding azimuth angle is set asElevation angle ofAzimuthal variability shown in the labeled portion of Table 1And elevation variabilityFor constant variability, the radar is given by linear extrapolationThe tracking point location of the moment is calculated according to the following formula:

in the formulaAndazimuth and elevation angles, respectively, of the tracking points, from which the determination can be madeThe included angle between the time tracking point location and the standard point location is increased by 1 from 1, and the processing modes are adopted to respectively giveWhen the included angle between the tracking point location and the standard point location at each moment is 1, the calculation needs to be carried outAndthey are respectively the corresponding time, azimuth and elevation of the initial standard point location, and can be found from the standard point data shown in the labeled part of table 2. Fig. 3 shows the angle between the forecast point location and the standard point location and the change of the angle between the tracking point location and the standard point location with time within a period of the transit of the target, the dotted line in the graph is the change curve of the angle between the forecast point location and the standard point location, the solid line is the change curve of the angle between the tracking point location and the standard point location, and the dotted line is the separation line taking the effective beam radius of the radar as the threshold, as can be seen from fig. 3, the radar can not capture the target according to the guidance of the forecast point location, but the equal elevation angle searching and tracking method of the invention can capture the target, and can keep tracking the target for about 70 seconds after capturing the target, so the radar has enough time to lock the target and turn into self-tracking.

Example 2:

in this example, we select SWARM a (NASA catalog number 39452) as the experimental target, the target track height is 420 km, it is a laser calibration star, it has high precision standard ephemeris data for comparison, the radar and its effective beam diameter selected in the experiment are the same as in example 1, first, a group of double-row catalog root number of the target is obtained from NASA website, the root epoch time corresponds to 20 minutes at 03 month and 09 days in 2021 and 48.430 seconds (beijing time), the group of double-row root number is converted to generate the position vector, velocity vector and target surface value ratio of the target relative to J2000 geocentric inertial system at the same epoch time, based on the converted target track parameters, the transit forecast is performed by using the same numerical method and mechanical model as in example 1 to generate a series of target transit time, we select one of the transit time, the start time of the transit time corresponds to 35 minutes at 03 days 14 days 03 and 14 days in 2021 (beijing time), the ending time corresponds to 03, 14, 03 and 44 minutes (Beijing time) in 2021, searching and capturing the target in the transit time period, a known group of target track parameters are track parameters relative to the transit time period before four and a half days, the maximum trail error of point location forecast of the group of track parameters is estimated to be 10 seconds, a scaling factor beta is 0.49181314 to determine the search elevation angle of the radar, and after the data preparation and input conditions are set, the same experiment steps as the example 1 are carried out, and the steps are not repeated.

Through the above experimental processing, we determine that the search elevation angle of the radar is 25.592 degrees, and the detailed experimental results are shown in table 3, table 4 and fig. 4, wherein table 3 has the same meaning as table 1, table 4 has the same generating way and meaning as table 2, and fig. 4 has the same generating way and meaning as fig. 3.

TABLE 3 Radar search SWARM A partial steering data (search elevation 25.592 degrees)

TABLE 4 comparison of SWARM A Standard and forecast Point locations

From the results in table 4, the included angles between each group of forecast point locations and the standard point locations are all larger than 1 degree and exceed the effective beam radius of the radar by 0.025 degree, which indicates that the radar cannot capture the target under guidance of point location forecast, and the distance between each group of forecast point locations and the distance between the standard point locations are also greatly different by more than 17 kilometers.

The labeled part of table 3 corresponds to a beam dwell when the radar searches at an elevation angle of 25.592 degrees, the labeled part of table 4 corresponds to a standard point location at a certain time of the target, the target elevation angle at the time is 25.592 degrees, that is, the target appears at the search elevation angle, therefore, whether the target can be captured by the radar when the radar performs the equal elevation angle search depends on whether the standard point enters the effective detection range of the beam during the certain dwell period of the beam or not, it can be known by comparing the relevant data of the labeled parts of table 3 and table 4 that the corresponding time of the standard point falls within the start-stop time range of the beam dwell of the sub-time, and the included angle between the standard point location and the beam center direction obtained by calculation is 0.0243 degrees, which is smaller than the effective beam radius of the radar by 0.025 degrees, the distance between the standard point and the target distance pointed by the beam center is also very small, which is only 65.183 meters, which indicates that the radar can capture the target according to the equal elevation angle search method of the invention, and the target can be accurately judged in real time.

It can be seen from fig. 4 that the radar cannot capture the target according to the guidance of the forecast point location, but the equal elevation search and tracking method of the invention can capture the target and keep tracking the target for about 5 seconds after capturing the target, so that the radar has enough time to lock the target and switch into self-tracking.

The above is only a preferred embodiment of the present invention, and the protection scope of the present invention is not limited to the above-mentioned embodiments, and all technical solutions belonging to the idea of the present invention belong to the protection scope of the present invention. It should be noted that modifications and embellishments within the scope of the invention may be made by those skilled in the art without departing from the principle of the invention.