Satellite formation interferometric imaging detection method and system for spatial reverse formation flying

Abstract

The application discloses a kind of space reverse satellite formation interference imaging detection method and system of accompanying flight, the method comprises: setting center satellite or virtual center satellite and the initial parameter of N satellite formation satellite of reverse accompanying flight;The relative orbit element of N satellite formation satellite of accompanying flight is calculated;Absolute orbit element is calculated according to relative orbit element;According to absolute orbit element, the position of each satellite of accompanying flight is forecasted, and the detection baseline formed by every two satellite of accompanying flight is calculated;Baseline distribution uniformity measure function is calculated according to detection baseline, as objective function, optimization algorithm is used to explore optimization, and optimal solution is obtained;Based on optimal solution, the above steps are repeated, and the detection baseline with continuity and uniformity in radial and circumferential direction is obtained;According to the detection baseline obtained, imaging inversion is carried out based on interference imaging principle.The application effectively improves the rapid coverage of long-short baseline, and short baseline is more dense.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of passive microwave interferometric imaging based on satellite formation, and particularly relates to a satellite formation interferometric imaging detection method and system for space reverse flying. BACKGROUND

[0002] Interferometric imaging detection using multiple satellite formation flight is an important means to improve spatial resolution. Each satellite carries a microwave radiometer, and interferometric imaging is performed based on the principle of interferometric imaging using multiple satellite formation flight to form an interference baseline.

[0003] With the center satellite or virtual satellite as the center, the satellite performs circumnavigational flying. According to the relative motion position equation, when there is no long-term relative drift, the relative motion trajectory of the flying satellite with respect to the center satellite is a spatial ellipse, and the flying period is equal to the orbit period of the center satellite. The sub-satellite point circular flying means that the sub-satellite point projection plane is a circle. A plurality of satellites are distributed at different radii and different initial phases, and the relative motion directions of the flying satellites are different, that is, counterclockwise and clockwise rotation exist at the same time.

[0004] According to the principle of interferometric imaging, the relative position vectors of each two satellites form a detection baseline in the spatial frequency domain. The projection vector of the relative position vector in the sub-satellite point direction is the projection detection baseline (referred to as "baseline" for short). The relative motion of the flying satellite with respect to the center satellite is a projection circle, different satellites are distributed at different radii, the angular velocity is the same, and the rotation is reverse. According to the baseline analysis, the formed detection baseline is an ellipse, the long axis and the short axis are determined by the inner and outer ring radii, and the ellipse rotation angle is determined by the initial phase difference of the inner and outer ring satellites. With the satellite flying around for one week, the baseline direction rotates for one week.

[0005] For satellite formation, it is very easy to realize long baseline, but due to the consideration of satellite safety distance, short baseline is often sparse. The conventional interferometric imaging satellite formation configuration is usually multiple satellites flying in the same direction, and the formed detection baseline is uniformly distributed in long and short baselines, and the angle changes uniformly with time. The effect is not ideal for the case of fast sampling of long and short baselines in different directions and more dense short baselines. SUMMARY

[0006] In order to realize fast long and short baseline coverage and more dense short baseline, the purpose of the present application is to overcome the defects of the prior art, and a satellite formation interferometric imaging detection method and system for space reverse flying are provided. The detection baseline formed by the inner and outer ring reverse flying satellites is an ellipse, the long axis and the short axis are determined by the inner and outer ring radii, the ellipse rotation angle is determined by the initial phase difference of the inner and outer ring satellites, and the short baseline is more densely distributed, which can meet the requirement of fast sampling of long and short baselines in different directions and more dense short baselines.

[0007] In order to achieve the above object, the application provides a satellite formation interferometric imaging detection method based on space reverse flying, which comprises the following steps:

[0008] Step 1) setting initial parameters of a central satellite or a virtual central satellite and N formation satellites for reverse flying;

[0009] Step 2) calculating relative orbit elements of the N formation satellites for flying;

[0010] Step 3) calculating absolute orbit elements according to the relative orbit elements obtained in step 2);

[0011] Step 4) forecasting the position of each flying satellite according to the absolute orbit elements obtained in step 3), and calculating a detection baseline formed by each two flying satellites;

[0012] Step 5) calculating a baseline distribution uniformity measurement function according to the detection baseline obtained in step 4) as a target function, and using an optimization algorithm to search and explore an optimal solution;

[0013] Step 6) repeating steps 2) to 4) based on the optimal solution to obtain a detection baseline with continuity and uniformity in radial and circumferential directions;

[0014] Step 7) performing imaging inversion based on the detection baseline obtained in step 6) according to the principle of interferometric imaging.

[0015] As an improvement of the above method, the initial parameters in step 1) comprise:

[0016] six orbit elements of the central satellite or the virtual central satellite: semi-major axis a0, eccentricity e0, orbit inclination i0, perihelion argument ω0, ascending node right ascension Ω0, and mean anomaly M0;

[0017] the N satellites are distributed on K circular rings, each circular ring has N k satellites, the initial value of the radius of the kth circular ring is r k , k = 1, 2,..., K, the maximum ring radius is R, and the initial phase angle of the jth flying satellite is

[0018] As an improvement of the above method, step 2) specifically comprises:

[0019] the formation mode of the flying satellites is a subsatellite point circle, and the space multi-ring reverse flying, the relative orbit elements of the jth flying satellite satisfy the following formula:

[0020]

[0021] wherein, Δa j , Δe xj , Δeyj , Δi xj , Δi yj , ΔM j respectively represent the relative semi-major axis, the relative eccentricity in x direction, the relative eccentricity in y direction, the relative inclination in x direction, the relative inclination in y direction and the relative argument of periapsis.

[0022] As an improvement of the above method, the step 3) specifically comprises:

[0023] The absolute orbit elements of the jth satellite are obtained by the following formula:

[0024]

[0025] wherein a j , e j , i j , ω j , Ω j and M j respectively represent the semi-major axis, the eccentricity, the inclination, the argument of periapsis, the longitude of ascending node and the argument of periapsis of the jth satellite.

[0026] As an improvement of the above method, the step 4) specifically comprises:

[0027] According to the absolute orbit elements of the satellites obtained in step 3), the position r j (x, y, z) of the jth satellite, the position r i (x, y, z) of the ith satellite, i, j = 1,..., N are calculated, and the detection baseline Δr i,j (u, v, w) formed by each two satellites is calculated, denoted as b(u, v, w).

[0028] As an improvement of the above method, the step 5) specifically comprises:

[0029] According to the detection baseline obtained in step 4), the distribution uniformity measure function Cornwell index M cs (b1, b2,..., b s ) is calculated:

[0030]

[0031] wherein s is the number of detection baselines formed by the N satellites, s = N × (N-1) / 2, b1, b2,..., b s represent the s detection baselines at a certain time;

[0032] Taking the Cornwell index as a target function, each annular radius, the number of satellites on each annular, and the initial phase angle of each satellite distribution as optimization variables, an optimal solution is obtained through optimization search.

[0033] As an improvement of the above method, the step 6) specifically comprises:

[0034] The detection baseline formed by the coplanar and co-rotating formation satellites is circularly distributed, satisfying the following formula:

[0035]

[0036] Wherein, (u, v) represents the projection of any point on the detection baseline formed by the i-th companion satellite and the j-th companion satellite;

[0037] The baseline formed by the satellites between different rings is elliptically distributed, the long axis is |r i +r j |, the short axis is |r i -r j |, and the elliptical rotation angle is determined by the initial phase difference between the inner and outer ring satellites , satisfying the following formula:

[0038]

[0039] Wherein, is a phase angle varying with time.

[0040] As an improvement of the above method, the step 7) specifically comprises:

[0041] According to (u, v) obtained in step 6), the corresponding visibility function Viss(u, v) is calculated by the following formula:

[0042]

[0043] According to the basic principle of interferometric imaging, the inversion image T B (ξ,η) is obtained by the following formula:

[0044]

[0045] Wherein, (ξ,η) is the position coordinates of each point of the image.

[0046] On the other hand, the present application proposes a satellite formation interferometric imaging detection system for space reverse companion flying, which comprises:

[0047] An initial parameter setting module is used to set the initial parameters of the central satellite or virtual central satellite and N reverse companion flying formation satellites.

[0048] A relative orbit element calculation module is configured to calculate relative orbit elements of the N formation flying satellites;

[0049] An absolute orbit element calculation module is configured to calculate absolute orbit elements according to the relative orbit elements obtained by the relative orbit element calculation module;

[0050] A baseline detection calculation module is configured to obtain the absolute orbit elements, predict the positions of each formation flying satellite, and calculate a baseline formed by each two formation flying satellites;

[0051] An optimization module is configured to calculate a baseline distribution uniformity measure function as a target function according to the baseline obtained by the baseline detection calculation module, and perform optimization exploration by using an optimization algorithm to obtain an optimal solution;

[0052] A baseline detection calculation module based on the optimal solution is configured to obtain a baseline with continuity and uniformity in the radial direction and the circumferential direction based on the optimal solution obtained by the optimization module; and

[0053] An imaging inversion module is configured to perform imaging inversion based on the baseline detection calculation module based on the optimal solution to obtain a baseline according to the baseline obtained by the baseline detection calculation module based on the optimal solution

[0054] Compared with the prior art, the present application has the following advantages:

[0055] The satellite formation interferometric imaging detection method of the present application has the following advantages: BRIEF DESCRIPTION OF DRAWINGS

[0056] Figure 1 is a flow chart of the satellite formation interferometric imaging detection method of the present application;

[0057] Figure 2 is a schematic diagram of a multi-satellite multi-ring reverse subsatellite point circle configuration;

[0058] Figure 3 is a schematic diagram of a relative trajectory of a subsatellite point projection plane (XY plane);

[0059] Figure 4 is a schematic diagram of baseline distribution in a period of time;

[0060] Figure 5 is a schematic diagram of baseline distribution in an orbit period;

[0061] Figure 6 is a simulation original image;

[0062] Figure 7 is an interference inversion diagram. DETAILED DESCRIPTION

[0063] The present application provides a satellite formation interferometric imaging detection method of space reverse flying. The flying mode is a multi-layer circle of subsatellite point, and the relative motion directions of the flying satellites are different, being counterclockwise and clockwise rotation at the same time. The characteristics are that the detection baseline formed by the inner and outer ring reverse flying satellites is an ellipse, the long axis and the short axis are determined by the inner and outer ring radii, and the ellipse rotation angle is determined by the initial phase difference of the inner and outer ring satellites. With the satellite flying around for one circle, the baseline direction rotates for one circle. The satellite formation of the inner and outer ring reverse flying satellites has the continuous change characteristics of the baseline length, which can meet the rapid sampling demand of different length baselines. At the same time, compared with the deployment of multiple satellites on a single radius circle, the deployment difficulty is reduced.

[0064] The technical solutions of the present application will be described in detail below in combination with the drawings and embodiments.

[0065] Embodiment 1

[0066] As shown in the drawings, the embodiment 1 of the present application provides a satellite formation interferometric imaging detection method of space reverse flying. The specific description is as follows: Figure 1

[0067] Step 1), set the orbit parameters (a0, e0, i0, ω0, Ω0, M0) of the central satellite (or virtual central satellite). It is assumed that there are N satellites for formation flying, which are distributed on K circles, and there are N k satellites on each ring. The initial value of the radius of each circle is r k (j = 1, 2,..., K), and the initial value of the initial phase angle of each satellite is The maximum ring radius is R. As shown in the drawings, it is a multi-satellite multi-ring reverse subsatellite circle configuration diagram. Figure 2

[0068] Step 2), according to the flying radius r k , the initial phase k of the N satellites on the K circles obtained in step 1), calculate the relative orbit elements (Δa j , Δe xj , Δe yj , Δi xj , Δi yj , ΔM j ) of all satellites. The formation mode is a subsatellite circle, and the space is multi-ring reverse flying.

[0069] The relative orbit elements of the jth satellite are: (Δa j , Δe xj , Δe yj , Δi xj , Δi yj ​​ΔM j ).

[0070] where j = 1,2,...,m k .(1)

[0071] Step 3) Calculate the absolute orbital elements (a, e, i, Ω, ω, M) from the relative orbital elements (Δa j , Δe xj , Δe yj , Δi xj , Δi yj , ΔM j ) of all satellites.

[0072] Calculate the absolute orbital elements from the relative orbital elements of the satellites:

[0073]

[0074] Step 4) Calculate the satellite positions r j (x, y, z) from the absolute orbital elements of the surrounding satellites obtained in Step 3), and calculate the detection baseline Δr i,j (u, v, w) formed by each pair of satellites. The spatial frequency baseline is Δr i,j = r i - r j , where i, j = 1,...,N, denoted as b(u, v, w).

[0075] Step 5) Calculate the uniformity distribution measure function Cornwell index based on the baseline. Take the Cornwell index as the objective function, and the initial phase angle of each satellite distribution, the number of satellites on each ring, and the radius of each ring as the optimization variables to perform optimization search. Further, the optimal solution is obtained.

[0076] The total number of baselines formed by N satellites is s = N × (N-1) / 2. For s baselines at a certain time, M cs (b1, b2,..., b s ), the uniformity distribution measure function is calculated as follows:

[0077]

[0078] Step 6) According to the optimal solution, repeat steps 2), 3), and 4). The detection baseline has continuity and uniformity in both radial and circumferential directions.

[0079] The baseline characteristics are analyzed as follows:

[0080] (1) Baselines formed by the same ring

[0081] Assume that the circular ring radius of the first ring is r1, and both satellites are deployed on the ring, and the initial phases of the two satellites are The same ring can only rotate in the same direction. Then the projection positions of the two satellites are:

[0082]

[0083] Since the two satellites have the same angular velocity around the fly, the angles changing with time are the same. The baseline formed by the two satellites is:

[0084]

[0085] From the above formula, it can be seen that

[0086]

[0087] As can be seen, the satellites rotating in the same direction on the same ring have a circularly distributed baseline.

[0088] (2) Baseline formed between different rings

[0089] Assume that the circular ring radius of the first ring is r1, and the circular ring radius of the second ring is r2, and the initial phases of the two satellites are The two space rings rotate in opposite directions. Then the projection position of the satellite located in the first ring is:

[0090]

[0091] Due to the opposite rotation, the projection position of the satellite located in the second ring is:

[0092]

[0093] Since the two satellites have the same angular velocity around the fly, the angles changing with time are the same. The baseline formed by the two satellites is:

[0094]

[0095] From the above formula, it can be seen that

[0096]

[0097] As can be seen, the baseline formed by the satellites between different rings is elliptically distributed. The long axis is |r1+r2|, and the short axis is |r1-r2|. The rotation angle of the ellipse is determined by the initial phase difference of the inner and outer ring satellites.

[0098] Step 7), according to the interference baseline obtained in step 6), imaging inversion can be carried out based on the interference imaging principle.

[0099] T B ​​where T is the two-dimensional simulated image brightness temperature, (ξ,η) is the position coordinate of each point of the image. The projection detection baseline is (u,v), and the visibility function Viss corresponding to (u,v) is calculated according to the following formula:

[0100]

[0101] According to the basic principle of interferometric imaging, the inversion image is obtained by the following formula:

[0102]

[0103] Embodiment 2

[0104] Based on the above system, embodiment 2 of the present application proposes a satellite formation interferometric imaging detection system for spatial reverse companion flight, which is realized based on the method of embodiment 1. The system comprises:

[0105] An initial parameter setting module is configured to set initial parameters of a central satellite or a virtual central satellite and N formation satellites for reverse companion flight;

[0106] A relative orbit element calculation module is configured to calculate relative orbit elements of the N formation satellites for companion flight;

[0107] An absolute orbit element calculation module is configured to calculate absolute orbit elements according to the relative orbit elements obtained by the relative orbit element calculation module;

[0108] A detection baseline calculation module is configured to obtain the absolute orbit elements, predict the position of each satellite for companion flight, and calculate the detection baseline formed by each two satellites for companion flight;

[0109] An optimization module is configured to calculate a baseline distribution uniformity measure function according to the detection baseline obtained by the detection baseline calculation module, as a target function, and perform optimization exploration by using an optimization algorithm to obtain an optimal solution;

[0110] A detection baseline calculation module based on the optimal solution is configured to obtain a detection baseline with continuity and uniformity in the radial direction and the circumferential direction based on the optimal solution obtained by the optimization module;

[0111] An imaging inversion module is configured to perform imaging inversion based on the principle of interferometric imaging according to the detection baseline obtained by the detection baseline calculation module based on the optimal solution.

[0112] Simulation example:

[0113] Taking a 9-satellite subsatellite point circular formation as an example, the simulation process is as follows:

[0114] 1) An example of 9 satellites distributed on 3 rings, as shown in FIG. 1, is a subsatellite projection plane (XY plane) relative trajectory diagram; Figure 3

[0115] ​2) a baseline distribution diagram for a period of time, as shown in Figure 4

[0116] 3) a baseline distribution diagram for an orbital period, as shown in Figure 5

[0117] 4) a simulation original drawing, as shown in Figure 6

[0118] 5) an interference imaging inversion diagram, as shown in Figure 7

[0119] Finally, it should be noted that the above examples are only used to illustrate the technical solutions of the present application and are not limiting. Although the present application has been described in detail with reference to the examples, those skilled in the art should understand that modifications or equivalent replacements to the technical solutions of the present application do not deviate from the spirit and scope of the present application, and they should be covered in the scope of the claims of the present application.​​​​

Claims

1. A satellite formation interferometric imaging detection method based on space reverse formation flying, the method comprising: Step 1) setting initial parameters of a central satellite or a virtual central satellite and N reverse formation flying satellites; Step 2) calculating relative orbit elements of the N formation flying satellites; Step 3) calculating absolute orbit elements according to the relative orbit elements obtained in Step 2); Step 4) predicting the position of each flying satellite according to the absolute orbit elements obtained in Step 3), and calculating a detection baseline formed by each two flying satellites; Step 5) calculating a baseline distribution uniformity metric function according to the detection baseline obtained in Step 4) as a target function, and performing optimization exploration by using an optimization algorithm to obtain an optimal solution; Step 6) repeating Steps 2) to 4) based on the optimal solution to obtain a detection baseline having continuity and uniformity in both radial and circumferential directions; Step 7) performing imaging inversion based on the detection baseline obtained in Step 6) according to an interferometric imaging principle; the Step 6) specifically comprising: the detection baseline formed by the formation satellites rotating in the same direction on the same ring is circularly distributed, satisfying the following formula: wherein (u, v) represents a projection of any point on the detection baseline formed by the i th flying satellite and the j th flying satellite; The baselines formed by satellites in different rings are elliptical, with a major axis of |r|. i +r j |, minor axis is |r i -r j The elliptical rotation angle is determined by the initial phase difference between the inner and outer ring satellites. The following equation is determined: wherein is the phase angle as a function of time.

2. The method of claim 1, wherein the space reverse formation flying satellite interferometric imaging probe is characterized by, the initial parameters of the Step 1) comprising: six orbit elements of the central satellite or the virtual central satellite: semi-major axis a 0, eccentricity e 0, orbit inclination i 0, perihelion argument ω 0, ascending node right ascension Ω 0, and mean anomaly M 0; N satellites are distributed on K annular rings, each annular ring has N k satellites, the initial value of the radius of the kth annular ring is r k ,k = 1, 2,..., K, the maximum ring radius is R, and the initial phase angle of the initial value of the jth companion satellite is 3. The method of claim 2, wherein the space reverse formation flying satellite interferometric imaging probe is characterized by, the Step 2) specifically comprising: the formation mode of the flying satellites is a space multi-ring reverse flying around a subsatellite point circle, and the relative orbit elements of the j th flying satellite satisfy the following formula: wherein Δa j , Δe xj , Δe yj , Δi xj , Δi yj , ΔM j denote the relative semi-major axis, the relative eccentricity in the x direction, the relative eccentricity in the y direction, the relative inclination in the x direction, the relative inclination in the y direction and the relative mean anomaly, respectively.

4. The method of claim 3, wherein the space reverse formation flying satellite interferometric imaging probe is characterized by, the Step 3) specifically comprising: the absolute orbit elements of the j th flying satellite are obtained by the following formula: where a j , e j , i j , ω j , Ω j and M j represent the semi-major axis, eccentricity, inclination, argument of perigee, longitude of the ascending node and mean anomaly of the jth co-orbital satellite, respectively.

5. The method of claim 4, wherein the space reverse formation flying satellite interferometric imaging probe is characterized by, the Step 4) specifically comprising: From the absolute orbital elements of the formation satellite obtained in step 3), the position r j (x,y,z) of the jth formation satellite is calculated i (x,y,z) of the ith formation satellite is calculated, i,j = 1,...,N, and the probe baseline Δr i,j (u,v,w) formed by each pair of satellites is calculated, denoted as b(u,v,w).

6. The method of claim 5, wherein the space reverse formation flying satellite interferometric imaging probe is characterized by, the Step 5) specifically comprising: The Cornwell indicator M is calculated from the probe baseline obtained according to step 4) as a measure of the uniformity of the distribution cs (b1,b2,...,b s ) Wherein, s is the number of detection baselines formed by N chaser satellites, s=N×(N-1) / 2, b1, b2,..., bs represent s detection baselines at a certain moment. s s detection baselines at a certain moment the Cornwell index is taken as the target function, each ring radius, the number of satellites on each ring, and the initial phase angle of each satellite distribution are taken as optimization variables, and optimization search is performed to obtain an optimal solution.

7. The method of claim 1, wherein the space reverse formation flying satellite interferometric imaging probe is characterized by, the Step 7) specifically comprising: according to (u, v) obtained in Step 6), a corresponding visibility function Viss (u, v) is calculated by the following formula: where T B (ξ,η) two-dimensional simulated image brightness temperature; According to the basic principle of interferometric imaging, the inversion image T is obtained by the following formula B '(ξ,η): wherein (ξ, η) is a position coordinate of each point of an image.

8. A system for interferometric imaging detection of a satellite formation based on the spatial retro-formation flying of claim 1, characterized in that, the system comprising: an initial parameter setting module configured to set initial parameters of a central satellite or a virtual central satellite and N reverse formation flying satellites; a relative orbit element calculation module configured to calculate relative orbit elements of the N formation flying satellites; an absolute orbit element calculation module configured to calculate absolute orbit elements according to the relative orbit elements obtained by the relative orbit element calculation module; a detection baseline calculation module configured to predict the position of each flying satellite according to the absolute orbit elements obtained by the absolute orbit element calculation module, and calculate a detection baseline formed by each two flying satellites; an optimization module configured to calculate a baseline distribution uniformity metric function according to the detection baseline obtained by the detection baseline calculation module as a target function, and perform optimization exploration by using an optimization algorithm to obtain an optimal solution; a detection baseline calculation module based on the optimal solution, configured to obtain a detection baseline having continuity and uniformity in both radial and circumferential directions based on the optimization module; and An imaging inversion module is configured to perform imaging inversion based on the interferometric imaging principle according to the detection baselines obtained by the detection baseline calculation module based on the optimal solution.

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