Signal processing system, signal processing method, and program

Abstract

To provide a signal processing system, signal processing method and program, which offer enhanced signal identification capability.SOLUTION: A signal processing system according to an embodiment is configured to form beam-forming based on different frequency transitions occurring at each mobile body observation point while performing cooperative observation using multiple mobile body observation points having no orderly movement paths, so as to separate observation signals observed by the multiple mobile body observation points.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a signal processing system, a signal processing method, and a program.

Background Art

[0002] In the satellite industry that has entered the era of megaconstellations, due to the comprehensiveness covering the entire world, not only communication and sensing by individual satellites, but also overall resource optimization and cooperative systems are actively discussed. For example, by measuring radar waves, signal waves, or various propagation characteristics derived from the earth by each satellite included in a megaconstellation (a group of satellites), it is expected to expand the observation functions and performance of the satellites (see, for example, Patent Document 1).

[0003] For example, there is a method of grasping the three-dimensional and wide-range atmospheric conditions by using signals such as GNSS (Global Navigation Satellite System) from satellites to grasp the propagation characteristics between each GNSS satellite and each satellite included in the megaconstellation. In addition, there is a method of identifying the position of the interference radio wave source by receiving it with a plurality of satellite groups flying in formation or a megaconstellation against interference radio waves from the ground surface or outer space. Both methods are possible by accurately grasping the position, time, orbit, received signal, and frequency offset of the signal source at each observation point, and there are practical problems due to the accuracy limits caused by each accuracy, the frequency to be handled, or the reception time.

[0004] To address such problems, there is a method of improving accuracy by increasing the observation frequency of the same observation target. By observing the same observation target several times using a group of artificial satellites that continuously change their positions relative to each other, errors are mitigated through integration processing, averaging processing, etc. For example, GNSS satellites and a mega-constellation are used to make multiple evaluations based on combinations of propagation paths by different transmitting and receiving satellites passing through the same space. Additionally, for radio waves from the observation target, by continuously receiving them with a time difference using the same group of observation satellites, multiple evaluations are made using different estimation information for the same observation target based on relatively changing position and velocity relationships.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0006] In cases where identification can be made in advance for each signal wave like GNSS, or in cases where signals are constantly transmitted with special specifications from special ships and there are limited similar transmission sources in the vicinity, various estimations are relatively easy. However, in cases where there are multiple transmission sources whose signals cannot be identified and the signal transmission timings overlap at the same time, or where each transmission source switches within a short time, these methods may significantly degrade performance. In particular, in an unorganized and uncontrollable group of observation points, since each frequency transition is different for each observation target, when the difference is large, cooperative processing does not hold in a jamming state.

[0007] The present invention has been made in consideration of such circumstances, and in a situation where signals transmitted from each of a plurality of moving body observation points may be jammed, one of the objectives is to provide a signal processing system, a signal processing method, and a program that can improve the signal identification ability by performing cooperative observation considering different frequency transitions for the plurality of moving body observation points.

Means for Solving the Problem

[0008] One aspect of the present invention is a signal processing system that separates observation signals, which are signals observed by each of a plurality of mobile object observation points, by forming beamforming based on different frequency transitions occurring at each mobile object observation point in cooperative observation by a plurality of mobile object observation points having no order in the movement path.

Advantages of the Invention

[0009] According to one aspect of the present invention, the discrimination ability of the observation signal can be improved by performing cooperative observation at a plurality of mobile object observation points.

Brief Description of the Drawings

[0010]

Figure 1

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Embodiments for Carrying Out the Invention

[0011] Hereinafter, with reference to the drawings, embodiments of the signal processing system, signal processing method, and program of the present invention will be described.

[0012] [Configuration of Signal Processing System] FIG. 1 is a conceptual diagram of a signal processing system 1 according to an embodiment. As shown in the figure, the signal processing system 1 includes, for example, a ground station 10, a plurality of artificial satellites 20 (two in the illustrated example, 20-A and 20-B), a space agency 30, and the like.

[0013] The ground station 10 is a radio station installed on the ground. The ground station 10 receives signals from the artificial satellites 20 or transmits commands regarding observations (for example, instructions such as the timing to be observed and the location to be observed) to the artificial satellites 20. If the artificial satellites 20 described later have an autonomous function and a control function for other observation systems or the like, the ground station 10 may be omitted.

[0014] The plurality of artificial satellites 20 form a satellite constellation, a cluster of satellite groups, or the like. These artificial satellites 20 may have different orbits from each other, and furthermore, the orbits of each artificial satellite 20 may not be orderly (that is, they may be disorderly). An artificial satellite 20 existing in space and serving as a receiving point for electromagnetic waves is an example of a "mobile observation point".

[0015] For example, while navigating along a predetermined orbit, the artificial satellite 20 observes the ground (including the ocean) and transmits a signal representing the observation result (hereinafter referred to as an observation signal) to the ground station 10, other artificial satellites 20, the space agency 30, and the like. The orbit is, for example, an earth orbit. The orbit of the artificial satellite 20 is an example of a "travel path".

[0016] For example, while navigating along its orbit, the artificial satellite 20 receives signals transmitted from the observation target area R (signals transmitted from objects existing in the observation target area R). The observation target area R is, for example, the ocean. In this case, the signals transmitted from the observation target area R may include signals transmitted from the AIS (Automatic Identification System) of ships existing on the ocean (hereinafter referred to as AIS signals).

[0017] Note that the observation target area R is not limited to the ocean and may be on land. Furthermore, the observation target area R may be in outer space. In this case, the artificial satellite 20 may receive signals transmitted from objects existing on land (such as vehicles) or signals transmitted from objects existing in outer space (such as other artificial satellites 20).

[0018] A plurality of artificial satellites 20 may observe the same observation target area R at a specified simultaneous time while cooperating with each other according to a predetermined observation plan.

[0019] For example, the ground station 10 may periodically update the observation plan based on the position information of the artificial satellite 20. Furthermore, the ground station 10 may analyze in advance the conditions for the orbits of the plurality of artificial satellites 20 to intersect, and when the timing (time) for the orbits of the artificial satellites 20 to intersect arrives, it may uplink the observation plan to each artificial satellite 20 as an observation request command. When receiving such an observation plan, the plurality of artificial satellites 20 will observe the same observation target area R while cooperating with each other at the timing (time) when their orbits intersect.

[0020] The conditions for the orbits to intersect may be determined using a dedicated system for managing and avoiding collisions of objects existing in outer space, such as artificial satellites 20 and space debris. Furthermore, the conditions for the orbits to intersect may be determined by each artificial satellite 20 based on inter-satellite communication and on-orbit conditions. For example, the on-orbit conditions may include conditions related to position information or conditions for detecting beneficial implementation timings by monitoring changes in the electromagnetic environment.

[0021] Note that the artificial satellite 20 included in the signal processing system 1 may be another moving body that moves in outer space such as a space probe, or may be an aircraft or a drone that navigates in the airspace above the ground. Further, the artificial satellite 20 may be a moving body that moves on land such as a vehicle, for example. Space probes, aircraft, drones, vehicles, etc. are other examples of "mobile observation points".

[0022] The space agency 30 is a radio station existing in outer space. The space agency 30 may be one of the artificial satellites 20, or may be a geostationary satellite or the like in a medium to high orbit with respect to a low orbit satellite. By transmitting and receiving signals with the artificial satellite 20, the space agency 30 may perform command transmission for observation instructions and collection of observation data, etc. on behalf of the ground station 10, or may be used in combination with the ground station 10.

[0023] [Configuration of Signal Processing Device] FIG. 2 is a configuration diagram of the signal processing device 100 according to the embodiment. For example, it includes a communication device 110, an observation sensor 120, a storage unit 130, and a processing unit 140.

[0024] The communication device 110 includes, for example, an antenna and a transceiver, and is composed of analog devices and digital devices. The antenna may be, for example, a parabolic antenna or a phased array antenna. Depending on the frequency of the electromagnetic wave to be handled, these antennas may be composed of lenses or mirrors, or mechanical operations such as semiconductor elements and MEMS (Micro Electro Mechanical Systems) may also be used. The transceiver irradiates or receives electromagnetic waves toward the ground station 10, the artificial satellite 20, or the space agency 30 via an antenna or the like. Also, with respect to the electromagnetic waves from the observation target area R, reception and observation may be performed on signal waves and radar waves, or the functions may be shared with the observation sensor 120, or they may be integrated with the communication device 110 if they are in the same frequency band.

[0025] Observation sensor 120 is a sensor for observing the observation target area R, and is, for example, an optical sensor, a radio wave sensor, or the like. The optical sensor includes, for example, a multi-spectral scanner, an imaging spectrometer, a lidar, and the like. The radio wave sensor includes, for example, a microwave scatterometer, a synthetic aperture radar, a microwave radiometer, a microwave altimeter, and the like. These optical sensors and radio wave sensors may be active sensors or passive sensors. The radio wave sensor may be a multi-antenna capable of transmitting, receiving, or both of a plurality of types of radio waves.

[0026] The storage unit 130 is realized by, for example, an HDD (Hard Disc Drive), a flash memory, an EEPROM (Electrically Erasable Programmable Read Only Memory), a ROM (Read Only Memory), a RAM (Random Access Memory), or the like. The storage unit 130 stores, for example, a program executed by a processor.

[0027] The processing unit 140 includes, for example, a cooperative control unit 142 and an orbit calculation unit 144. These components are realized, for example, by a processor such as a CPU (Central Processing Unit) or a GPU (Graphics Processing Unit) executing a program stored in the storage unit 130. Further, the processing unit 140 may be realized by hardware (circuit) such as an LSI (Large Scale Integration), an ASIC (Application Specific Integrated Circuit), an FPGA (Field-Programmable Gate Array), or an SOC (System On Chip), or may be a digital annealer device excellent in combinatorial optimization problems. Further, it may be realized by the cooperation of software and hardware. Also, the program referred to by the processor may be stored in the storage unit 130 in advance, or may be stored in a removable storage medium such as a DVD or a CD-ROM, and installed from the storage medium to the storage unit 130.

[0028] The cooperative control unit 142 uses the observation sensor 120 to observe the same observation target area R while cooperating with other artificial satellites 20.

[0029] The orbit calculation unit 144 calculates, for example, the orbit of the artificial satellite 20 (i.e., the self-artificial satellite) on which the signal processing device 100 is mounted, or calculates the orbits of other artificial satellites 20. The orbit calculation unit 144 may be provided in the space agency 30 or the ground station 10. In this case, the orbit calculation unit 144 provided in the space agency 30 or the ground station 10 may calculate the content of the observation plan for the artificial satellite 20 and generate necessary commands. Further, the orbit calculation unit 144 may be provided in the artificial satellite 20 itself and calculate the content of the observation plan by itself from the surrounding environment.

[0030] [Details of the method for separating observation signals] Hereinafter, the details of the method for separating the observation signals in the signal processing system 1 according to the present embodiment will be described. In the present embodiment, attention is paid to the fact that the spatial frequency shifts (Doppler shifts) fd of a plurality of artificial satellites 20 with different orbits are different from each other, and the observation signals are separated using these frequency shifts fd.

[0031] FIG. 4 is a diagram showing the concept of frequency shift. In the illustrated example, it represents the footprint (spatial distribution of the frequency shift fd when projected onto the ground surface or the like) FP of the frequency shift fd of a certain artificial satellite 20. As shown in the figure, in the footprint FP of the frequency shift fd, the magnitude of the frequency shift fd changes according to the vector V representing the moving direction of the artificial satellite 20, such as from -fd to +fd.

[0032] FIGS. 5 and 6 are diagrams showing an example of the frequency shift fd when two artificial satellites 20 perform cooperative observation. In the figure, FP_a represents the footprint of the frequency shift fd_a of the artificial satellite 20-A moving along the vector V_a representing the moving direction. FP_b represents the footprint of the frequency shift fd_b of the artificial satellite 20-B moving along V_b representing the moving direction.

[0033] First, assume the condition that artificial satellites 20-A and 20-B having different moving vectors V exist in the vicinity where their orbits intersect. In the vicinity where the orbits intersect, it becomes possible for artificial satellites 20-A and 20-B to simultaneously observe a plurality of objects S1 to Sn (n is an arbitrary natural number, and in the example of FIG. 5, n = 5) existing in the observation target area R. That is, in the vicinity where the orbits intersect, artificial satellites 20-A and 20-B can perform cooperative observation.

[0034] Under the conditions where such cooperative observations can be carried out, it is assumed that electromagnetic waves are transmitted from each of a plurality of objects S1 to Sn with different positions from each other at approximately the same timing (approximately the same time). In such a case, as shown in FIG. 6, in the artificial satellite 20-A, the electromagnetic wave of the object S1 is received causing a frequency shift Δfs1A, the electromagnetic wave of the object S2 is received causing a frequency shift Δfs2A, the electromagnetic wave of the object S3 is received causing a frequency shift Δfs3A, and the electromagnetic wave of the object Sn is received causing a frequency shift ΔfsnA.

[0035] Similarly, in the artificial satellite 20-B, the electromagnetic wave of the object S1 is received causing a frequency shift Δfs1B, the electromagnetic wave of the object S2 is received causing a frequency shift Δfs2B, the electromagnetic wave of the object S3 is received causing a frequency shift Δfs3B, and the electromagnetic wave of the object Sn is received causing a frequency shift ΔfsnB.

[0036] Thus, the electromagnetic waves transmitted from each of the plurality of objects S1 to Sn are received with different values of frequency shifts Δfs1A to ΔfsnA in the artificial satellite 20-A and frequency shifts Δfs1B to ΔfsnB in the artificial satellite 20-B, respectively.

[0037] The frequency shift is determined by the relative positional relationship between the movement vectors Va of the artificial satellite 20-A and Vb of the artificial satellite 20-B and each of the plurality of objects S1 to Sn.

[0038] Therefore, the processing unit 140 of the signal processing apparatus 100 estimates an area (hereinafter referred to as the target area P) where the frequency transitions are relatively the same from the footprint FP_a of the frequency transition fd_a of the artificial satellite 20-A and the footprint FP_b of the frequency transition fd_b of the artificial satellite 20-B. In this case, when the object S to be observed is also a moving object, the frequency transition also changes according to the movement vector. Therefore, the processing unit 140 may estimate the target area P in consideration of the movement vector of the object S that is a moving object. Hereinafter, as an example, it is assumed that the object S has a negligible movement vector and the artificial satellite 20 which is a movement observation point has a non-negligible speed with respect to the frequency band of the target electromagnetic wave.

[0039] [Processing Flow of Signal Processing System] FIG. 7 is an example of a flowchart showing a series of processing flows of the signal processing system 1 according to the embodiment. Each process in the flowchart may be sequential or partially omitted. Also, each process in the flowchart may be executed by any one of the artificial satellite 20, the space agency 30, and the ground station 10, or may be executed simultaneously by a plurality of them. In the description of this flowchart, as an example, it is described that cooperative observation is performed by the artificial satellites 20-A and 20-B.

[0040] First, the artificial satellites 20 each perform observation and collect data (step S100). The collected data is recorded, and for example, overwriting is performed when recording reaches the limit of the capacity (step S101). When there is an instruction for cooperative observation (step S102), downlink data is generated from the recorded data and transmitted to the ground station (step S104). The instruction for cooperative observation (step S102) may be internally held by the artificial satellite itself as an observation pattern (step S103), or may be determined and performed by external cooperative observation by command reception (step S109) (step S108). Also, for example, when a group of artificial satellites plans independently, communication and the like may be exchanged with surrounding artificial satellites (step S105), and the opportunity for cooperative observation may be determined (steps S106 and S107).

[0041] After each artificial satellite has downlinked (step S104) data for cooperative observation to the ground station, each data is extracted (steps S111, S112, and S113) by the ground equipment and cooperative processing is started. Alternatively, instead of the ground station, a space agency such as a geostationary satellite that can simultaneously view the artificial satellite group may collect data by inter-satellite communication and implement it.

[0042] After preparing the data necessary for the cooperative observation process from each satellite (step S113), the observation direction for each observation point is calculated (step S117) from the frequency transition distribution (step S116) of each artificial satellite calculated from the orbital information (step S115). When the direction is calculated, the beamforming conditions for each artificial satellite or the whole can be obtained and implemented (step S118). In other words, that is, the target area P is calculated, and the observation signal of the object S existing in the target area P, which is a partial area of the observation target area R, is extracted from the observation signals received from each of the plurality of objects S1 to Sn existing in the observation target area R. With the obtained data group composed of relatively close frequency transitions, high-precision signal separation processing becomes possible by the cooperative observation process (step S119).

[0043] When the signal separation process (step S119) is performed and the signal information and position information are correctly extracted (step S120), the actual relative position and frequency transition can be obtained from the results, so calibration becomes possible in the calculation of the frequency transition distribution (step S116) (step S121). Also, by grasping the information of interest (step S122) from the correctly obtained signal information and position information, the requirements for a new observation target area R are sorted out (step S123), which becomes the required conditions for the orbit calculation (step S115).

[0044] Beamforming may be realized either by digital processing or analogically in terms of antenna directivity and satellite attitude. Alternatively, when having multi-antenna data for every 20 different artificial satellites, after collecting all of them, signal extraction processing such as digital beamforming may be performed overall. When performing overall processing, the observation data for each antenna for each artificial satellite may use the condition that the frequency transition is uniform as a constraint condition for the processing. Also, regarding the assumed distribution of the frequency transition according to the movement vector in each artificial satellite 20, for example, when the object S is a ship and the received signal from the ship contains position information such as an AIS signal, it may be corrected by deriving the actual frequency transition from the ship's position information obtainable from the AIS signal that can be extracted independently by each artificial satellite 20 and the relationship between the relative position and relative speed of each artificial satellite 20. This may be done multiple times to improve the accuracy further.

[0045] According to the embodiment described above, the signal processing system 1 causes a plurality of artificial satellites 20 with different orbits to observe the same observation target area R while cooperating with each other, and based on the cooperative observation, each artificial satellite 20 forms analog beamforming or digital beamforming, or the artificial satellite group as a whole forms digital beamforming. As a result, it is possible to perform the difficult signal separation processing (the processing of S119 described above) on the signals observed by each of the plurality of artificial satellites 20. As a result, the discrimination ability of the observation signals by the signal processing system 1 can be improved.

[0046] (Other Embodiments) The following other embodiments will be described. The processing unit 140 of the signal processing device 100 described above may provide the observation signal to an external device via the communication unit 110 only when it becomes possible to observe the same observation target area R simultaneously. The external devices include the above-described ground station 10, other artificial satellites 20, space agencies 30, and further aviation agencies, maritime agencies, etc.

[0047] The processing unit 140 of the signal processing device 100 records only the observation signals observed by the observation sensor 120 over a certain period in the storage unit 130 by means of a shift register or data overwrite, and provides the observation signals recorded in the storage unit 130 over a certain period to an external device via the communication device 110 only when the same observation target area R can be observed simultaneously during the certain period in which the observation signals are recorded in the storage unit 130.

[0048] The certain period during which the observation signals are recorded is optimized based on the frequency or interval at which cooperative observation is performed. This optimization may be executed, for example, by the processing unit 140 of the signal processing device 100.

[0049] The condition that the movement vectors V cross each other may be obtained from the prediction of the movement vectors V. In this case, the processing unit 140 of the signal processing device 100 mounted on the artificial satellite 20 may plan to observe the observation target area R when receiving a command from an external device, or may plan to observe the observation target area R by the processing unit 140 itself obtaining necessary information.

[0050] The prediction of the movement vectors V may be performed based on simulation results such as communication with the surroundings or path analysis of other artificial satellites 20 that can cooperate during cooperative observation and the observation target area R.

[0051] The content of the observation request command, which is a command for requesting each artificial satellite 20 to perform cooperative observation, may be determined, for example, by the signal processing device 100 of the ground station 10.

[0052] The observation request command is an observation request at a timing when cooperative observation is possible, and may also include content for requesting and controlling each artificial satellite 20 to observe the target area P where the frequency transition fd matches.

[0053] The processing unit 140 of the signal processing device 100 evaluates the electromagnetic wave environment constantly or periodically by means of the electromagnetic wave monitoring function of the artificial satellite 20, determines whether the electromagnetic wave environment is a specific environment from the evaluation, and observes the observation target area R when the electromagnetic wave environment is a specific environment.

[0054] Until the processing unit 140 of the signal processing device 100 determines that the electromagnetic wave environment is a specific environment, although it performs the observation and evaluation of the observation target area R, it does not record the observation signals observed in that environment in the storage unit 130. On the other hand, when the processing unit 140 determines that the electromagnetic wave environment is a specific environment, it records the observation signals observed in that environment in the storage unit 130.

[0055] The processing unit 140 of the signal processing device 100 spatially divides and observes the observation target area R according to the distribution of the frequency transition fd, that is, the footprint FP of the frequency transition fd, by means of analog beamforming or digital beamforming, and compensates the frequency transition fd for each of the observation signals in the divided areas.

[0056] The footprint FP of the frequency transition fd is calibrated once or multiple times using a signal source including position information detectable by the observation sensor 120.

[0057] The processing unit 140 of the signal processing device 100 aggregates and optimizes some or all of the observation signals received by the multi-antennas included in the respective observation sensors 120 of the plurality of artificial satellites 20. Then, the processing unit 140 performs digital beamforming based on the aggregated observation signals, or performs arrival direction estimation and signal separation processing.

[0058] The optimization processing of the observation signals makes it a constraint condition that the frequency transitions of the sets of observation signals are equal for each artificial satellite 20.

[0059] Figs. 7 and 8 are diagrams showing an observation target area R and a peripheral area D when a plurality of artificial satellites 20 perform cooperative observation. Fig. 7 shows an observation target area R1 where cooperative observation is possible by artificial satellites 20-A and 20-B, and its peripheral area D1. In the peripheral area D1, although the observation fields from the respective artificial satellites overlap, the satellite-to-satellite distance is very far with respect to the observation frequency, and there is a possibility of being affected by grating lobes or the like. Therefore, the effects described in the above-described embodiments may be limited.

[0060] However, since it is possible to estimate the arrival direction by the conventional frequency transition and reception time difference, when implementing the observation plan in the observation target area R1, it is possible to set the observation of the peripheral area D1 at the time before and after. Furthermore, in the observation plan in the observation target area R1, for the processing according to the above-described embodiment, sampling data of the time waveform is simultaneously acquired by each artificial satellite, and in the observation plan of the peripheral area D1, only the spectrum time transition data after Fourier transform may be acquired. That is, the command for causing the artificial satellite 20, which is a moving object observation point, to observe the observation target area R1 may include several instructions such as causing the artificial satellite 20 to acquire sampling data of the time waveform in the observation target area R1, and acquiring the spectrum time transition data after Fourier transform for the peripheral area D1 at the time before and after acquiring the sampling data. The command for causing the artificial satellite 20 to observe the observation target area R1 may be generated by the processing unit 140 of the artificial satellite 20, or may be generated by an external device (for example, the ground station 10, another artificial satellite 20, the space agency 30, etc.). By implementing the observation plan based on such a command, the total data amount can be saved, and at the time before and after the peripheral area D1, each artificial satellite can perform its original mission. In other words, it enables the conventional arrival direction estimation and enables more efficient long-term cooperative observation with an efficient data amount.

[0061] FIG. 8 shows observation areas R1 to R9 and peripheral areas D1 to D9 when a plurality of artificial satellites 20-A to 20-G have respective movement vectors V_a to V_g and cooperate. For example, coordinated observation may be performed by three or more of the artificial satellites 20-E, 20-F, and 20-G, such as the observation area R9 and the peripheral area D9.

[0062] As described above, the embodiments for carrying out the present invention have been described using the embodiments. However, the present invention is not limited to such embodiments, and various modifications and substitutions can be made without departing from the gist of the present invention.

Explanation of Reference Numerals

[0063] 1... signal processing system, 10... ground station, 20... artificial satellite, 30... space agency, 100... signal processing device, 110... communication device, 120... observation sensor, 130... storage unit, 140... processing unit

Claims

1. In cooperative observation by a plurality of mobile object observation points having no order in the movement path, by forming beamforming based on different frequency transitions occurring at each mobile object observation point, separating an observation signal which is a signal observed by each of the plurality of mobile object observation points. A signal processing system.

2. The plurality of mobile object observation points are a plurality of artificial satellites having different orbits from each other. The signal processing system according to Claim 1.

3. The plurality of mobile object observation points perform the cooperative observation when they can simultaneously observe the same observation target area. The signal processing system according to Claim 1.

4. The plurality of mobile object observation points perform the cooperative observation when they can simultaneously observe the same observation target area and the movement paths cross each other. The signal processing system according to Claim 1.

5. The plurality of mobile object observation points provide the observation signal only when they can simultaneously observe the same observation target area. The signal processing system according to Claim 1.

6. The plurality of mobile object observation points record only the observation signals for a certain period by a shift register or data overwriting, and provide the observation signals recorded in the certain period only when they can simultaneously observe the same observation target area during the certain period in which the observation signals are being recorded. The signal processing system according to Claim 1 or Claim 5.

7. The certain period during which the observation signal is recorded is optimized based on the frequency or interval at which the cooperative observation is performed. The signal processing system according to Claim 6.

8. The condition that the movement paths cross each other is obtained from the prediction of the movement paths. The mobile object observation point plans to observe the observation target area when receiving a command from the outside, or plans to autonomously observe the observation target area by obtaining necessary information by itself from a previous mobile object observation point. The signal processing system according to Claim 4.

9. The prediction of the movement paths is performed based on simulation results such as communication with the surroundings or path analysis of the mobile object observation points that can be coordinated and the observation target area. The signal processing system of Claim 8.

10. The command is transmitted from a ground station, an aviation station, a maritime station, or a space agency. The content of the command is determined on the earth or in outer space. The signal processing system according to Claim 8.

11. The observation of the observation target area autonomously planned by the mobile observation point determines whether the electromagnetic wave environment is a specific environment at all times or periodically by means of the electromagnetic wave monitoring function of the mobile observation point, and is carried out when it is determined that the electromagnetic wave environment is the specific environment. The signal processing system according to claim 8.

12. As the electromagnetic wave monitoring function, the mobile observation point does not record the observation and evaluation of the observation target area until it is determined that the electromagnetic wave environment is the specific environment, and records only when it is determined that the electromagnetic wave environment is the specific environment. The signal processing system according to claim 11.

13. The cooperative observation is to control the plurality of mobile observation points to observe an area where the frequency transition coincides based on the spatial frequency transition distribution obtained from the movement vector of the mobile observation point. The signal processing system of claim 1.

14. The mobile observation point spatially divides and observes the observation target area according to the frequency transition distribution by means of the analog or digital beamforming, and compensates the frequency transition for each observation signal of the divided area. The signal processing system according to claim 13.

15. The frequency transition distribution is calibrated once or a plurality of times using a signal source including position information detectable at the mobile observation point. The signal processing system according to claim 13.

16. The beamforming is performed by aggregating and optimizing some or all of the observation signals received by the multi-antenna of the mobile observation point, or the arrival direction estimation and signal separation processing are performed. The signal processing system according to claim 13.

17. The optimization process makes it a constraint condition that the frequency transitions of the set of observation signals are equal for each mobile observation point. The signal processing system according to claim 16.

18. The command for causing the mobile observation point to observe the observation target area instructs to acquire sampling data of the time waveform in the observation target area, and to acquire time transition data of the spectrum after Fourier transform for the peripheral area at the time before and after that, enabling conventional arrival direction estimation and enabling more efficient long-term cooperative observation with an efficient data volume. The signal processing system according to claim 4.

19. In cooperative observation by a plurality of mobile object observation points without order in a movement path, by forming beamforming based on different frequency transitions occurring at each mobile object observation point, an observation signal, which is a signal observed by each of the plurality of mobile object observation points, is separated. Signal processing method.

20. On a computer, In cooperative observation by a plurality of mobile object observation points without order in a movement path, by forming beamforming based on different frequency transitions occurring at each mobile object observation point, separating an observation signal, which is a signal observed by each of the plurality of mobile object observation points. Program for causing execution.

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