Electromagnetic wave information processing apparatus and electromagnetic wave information processing method

Abstract

To provide an electromagnetic wave information processor for effectively and inexpensively projecting the measurement and estimation information of electromagnetic waves distributed in all the directions of the earth and cosmic space to the whole celestial sphere and the whole earth surface.SOLUTION: An input unit that inputs a measurement result from a measurement unit that measures electromagnetic waves incident on a spacecraft from substantially all directions, a calculation unit that performs calculation on the basis of information input to the input unit, and an output unit that outputs a calculation result in the calculation unit, the calculation section calculates, on the basis of the measurement result input to the input section, a local omnidirectional feature value that is a coefficient of a local basis function indicating a distribution of the electromagnetic wave input by the input section in a spacecraft coordinate system centered on the spacecraft at a predetermined position in space, and calculates, on the basis of a plurality of local omnidirectional feature values and information concerning a plurality of predetermined positions in space, a whole omnidirectional feature value that is a coefficient of a whole basis function to create a map indicating a distribution of a whole electromagnetic wave source including the earth's surface and the space.SELECTED DRAWING: Figure 5

Description

[Technical Field]

[0001] The present invention relates to a configuration of an electromagnetic wave information processing device and method, and more particularly to a technique that is effective when applied to processing electromagnetic wave information distributed in all directions on the earth and in outer space. [Background technology]

[0002] Methods have been proposed for determining the direction of arrival of electromagnetic waves by observing phase differences and other information through interference processing of signals received by multiple antennas. For example, there is radio astronomy observation, which observes radio sources in a specific, limited field of view using ground-based radio wave measurements or radio wave interferometry. There is also a method for observing radio wave sources on the Earth's surface using the arrival time difference and interference of radio waves received by multiple antennas on a single satellite or satellite flying in formation.

[0003] As background art in this technical field, for example, there is a technique such as that disclosed in Patent Document 1. Patent Document 1 discloses a "method for estimating the relative direction of arrival of a target signal by an antenna array of a spacecraft in Earth orbit." [Prior art documents] [Patent documents]

[0004] [Patent Document 1] US Patent Application Publication No. 2015 / 0355312 Summary of the Invention [Problem to be solved by the invention]

[0005] In the field of space situational awareness, an important issue is the rapid ascertainment and updating of radio source information in all directions, which is defined as any direction within the azimuth angle range of 0 degrees to 360 degrees and the elevation (or depression) angle range of -90 degrees to 90 degrees.

[0006] However, in the prior art including Patent Document 1, there is no known method for treating the electromagnetic wave source distribution in any direction measured from one point (for example, a terrestrial antenna or an artificial satellite) as local, omnidirectional feature quantity information, or for projecting or converting the distribution onto the entire celestial sphere centered on the Earth (i.e., the geocentric celestial sphere), effectively and at low cost.

[0007] For example, radio astronomy generally involves specific celestial directions that cannot be projected or transformed onto a celestial sphere centered on the Earth (i.e., a geocentric celestial sphere).

[0008] Furthermore, when observing radio wave sources on the Earth's surface near the satellites flying in formation, the measurement target is directly below the satellite, so it is not possible to estimate the electromagnetic wave distribution over the entire Earth's surface, and it is not possible to measure the electromagnetic wave distribution in the direction of the geocentric celestial sphere (space side).

[0009] Furthermore, even if projection and estimation were to be performed in all directions, the measurement time and amount of data would be enormous, making on-board processing difficult, and no such projection and estimation method is known.Furthermore, no method is known for performing global estimation from local measurement data.

[0010] Therefore, an object of the present invention is to provide an electromagnetic wave information processing device and an electromagnetic wave information processing method that can effectively and at low cost project measured and estimated information of electromagnetic waves distributed in all directions on the Earth and in outer space onto the celestial sphere or the entire earth's surface by acquiring omnidirectional feature amount information locally, and that can further estimate overall (celestial sphere and the entire earth's surface) data from local data. [Means for solving the problem]

[0011] In order to solve the above problems, the present invention provides a spacecraft system comprising an input unit that receives measurement results from a measurement unit that measures electromagnetic waves incident on a spacecraft from approximately all directions, a calculation unit that performs calculations based on the information input to the input unit, and an output unit that outputs the calculation results of the calculation unit, wherein the calculation unit calculates local omnidirectional feature values ​​that are coefficients of local basis functions that indicate the distribution of the electromagnetic waves input by the input unit in a spacecraft coordinate system centered on the spacecraft at a predetermined position in space, based on the measurement results input to the input unit, and calculates global omnidirectional feature values ​​that are coefficients of global basis functions, based on a plurality of the local omnidirectional feature values ​​and information on a plurality of the predetermined positions in space, thereby creating a map that indicates the overall distribution of electromagnetic wave sources including the Earth's surface and outer space, and the output unit outputs the map.

[0012] The present invention also provides an electromagnetic wave information processing device to be mounted on a spacecraft, the electromagnetic wave information processing device comprising: a measurement unit capable of measuring electromagnetic waves incident from approximately all directions; a calculation unit that performs calculations based on information measured by the measurement unit; and an output unit that outputs calculation results from the calculation unit, wherein the calculation unit calculates local omnidirectional feature values ​​that are coefficients of local basis functions that indicate the distribution of electromagnetic waves measured by the measurement unit in a spacecraft coordinate system centered on the spacecraft at a predetermined position in outer space, based on the electromagnetic wave measurement results measured by the measurement unit; and calculates global omnidirectional feature values ​​that are coefficients of global basis functions, based on a plurality of the local omnidirectional feature values ​​and information on a plurality of the predetermined positions in outer space, to create a map that indicates the overall distribution of electromagnetic wave sources including the Earth's surface and outer space, and the output unit outputs the map.

[0013] The present invention is also characterized by including the steps of: (a) calculating, by a calculation unit, local omnidirectional feature values, which are coefficients of local basis functions that indicate the distribution of electromagnetic waves measured by the measurement unit in a spacecraft coordinate system centered on the spacecraft at a predetermined position in space, based on electromagnetic wave measurement results measured by the measurement unit; (b) calculating, by a plurality of the local omnidirectional feature values ​​and information on a plurality of the predetermined positions in space, global omnidirectional feature values, which are coefficients of global basis functions, to create a map that indicates the overall distribution of electromagnetic wave sources including the Earth's surface and outer space; and (c) outputting, by an output unit, the map created in step (b). [Effects of the Invention]

[0014] According to the present invention, it is possible to effectively and at low cost project measured and estimated information of electromagnetic waves distributed in all directions on the Earth and in outer space onto the celestial sphere or the entire earth's surface by acquiring omnidirectional feature amount information locally, and further to realize an electromagnetic wave information processing device and an electromagnetic wave information processing method capable of estimating overall (celestial sphere and the entire earth's surface) data from local data.

[0015] Problems, configurations, and effects other than those described above will become apparent from the following description of the embodiments. [Brief explanation of the drawings]

[0016] [Figure 1] 1 is a flowchart showing the overall flow of an electromagnetic wave information processing method according to a first embodiment of the present invention. [Figure 2] FIG. 10 is a diagram illustrating a display example of local omnidirectional feature amounts. [Figure 3] FIG. 10 is a diagram showing an example of a display of omnidirectional feature quantities of the earth's surface and inertial space. [Figure 4] FIG. 10 is a diagram showing an example of displaying the earth's surface and geocentric celestial sphere omnidirectional feature quantities. [Figure 5] 1 is a block diagram showing a schematic configuration of an electromagnetic wave information processing device according to a first embodiment of the present invention. [Figure 6] FIG. 6 is a diagram schematically showing a processing flow (correlation method) of the calculation unit 2 in FIG. 5. [Figure 7] FIG. 7 is a diagram showing a modification of FIG. 6. [Figure 8] 10 is a flowchart showing details of the measurement processing performed by the arithmetic unit of the electromagnetic wave information processing device. [Figure 9] 10 is a flowchart showing the processing contents of a basis number and basis coefficient calculation unit. [Figure 10] 10 is a flowchart showing the processing content of an electromagnetic wave information conversion unit. [Figure 11] FIG. 10 is a diagram illustrating a processing flow in a learning phase and an operation phase. [Figure 12] 1A and 1B are diagrams illustrating examples of an Earth surface map and a space map display section. [Figure 13] 1A and 1B are diagrams illustrating examples of an Earth surface map and a space map display section. [Figure 14] 10 is a flowchart showing the processing flow for improving observation efficiency by the observation and satellite control task generation unit. [Figure 15] FIG. 2 is a block diagram showing an example of the configuration of an observation / satellite control task generation unit. [Figure 16] 10A and 10B are diagrams illustrating examples of an observation task list and a satellite control task list. [Figure 17] FIG. 10 is a diagram showing an example of a simulation result when an arbitrary radio wave source distribution is approximated by a spherical harmonic function. DETAILED DESCRIPTION OF THE INVENTION

[0017] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. In the drawings, the same components are designated by the same reference numerals, and detailed description of overlapping parts will be omitted.

[0018] In the following description, the term "local" refers to a location where a measurement signal input to an electromagnetic wave information processing device is acquired, that is, a location where a satellite is present.

[0019] The "spacecraft coordinate system" is a coordinate system based on axes fixed to the spacecraft, and is also called the body coordinate system. The "geocentric coordinate system" is a coordinate system with the Earth at its center, and is used to describe the motion of a satellite orbiting the Earth. [Example]

[0020] First Embodiment An electromagnetic wave information processing device and an electromagnetic wave information processing method according to a first embodiment of the present invention will be described with reference to FIGS.

[0021] FIG. 1 is a flowchart showing the overall flow of the electromagnetic wave information processing method of this embodiment.

[0022] As shown in FIG. 1, in the electromagnetic wave information processing method of this embodiment, when the electromagnetic wave information processing device starts processing, first, in step S101, electromagnetic wave information is acquired.

[0023] Next, in step S102, satellite-centered local omnidirectional feature quantities (coefficients) are calculated, and the data is compressed.

[0024] Next, in step S103, the electromagnetic wave information is converted into a ground surface map and an inertial space map.

[0025] Finally, in step S104, the database (DB) is updated, and a change in the entire area is detected (estimated) based on the difference with the data stored in the database (DB), and the process ends.

[0026] Figure 2 is a diagram showing an example of displaying local omnidirectional feature quantities. The satellite center is placed at the origin of xyz space, which can be considered as inertial space, and the spherical surface centered on the satellite position is displayed three-dimensionally. On the spherical surface, which corresponds to the azimuth angle and elevation angle (depression angle) when viewed from the satellite center, the strength of the electromagnetic wave source arriving from the corresponding direction is expressed on the spherical surface using shades of color. The scales of x, y, z and the electromagnetic wave source strength are in arbitrary units.

[0027] As mentioned above, a "local area" refers to a location where a measurement signal input to an electromagnetic wave information processing device is acquired. In a coordinate system centered on a local area (e.g., a satellite), a basis function (e.g., a spherical harmonic function) for expressing the distribution of an incoming electromagnetic wave source is referred to as a "local basis function." Furthermore, an omnidirectional feature (i.e., the coefficient of a local basis function) observed locally is referred to as a "local omnidirectional feature." In particular, when the "local area" refers to the location where a satellite is located, it is referred to as a "satellite-centered local omnidirectional feature." Omnidirectionality is defined as "any direction within the azimuth angle range of 0 to 360 degrees and the elevation (or depression) angle range of -90 to 90 degrees (corresponding to any point on a sphere)."

[0028] FIG. 3 is a diagram showing an example of displaying the omnidirectional feature quantities of the earth's surface and inertial space.

[0029] As shown in Figure 3, by using multiple channels (Ch) and triangulation to measure the distance to the object, it is possible to perform not only the celestial sphere (direction) but also three-dimensional mapping.

[0030] For example, by combining it with a satellite orbital information database (DB), it is effective in understanding the active status of radiation source satellites and debris situations. From local observations (local state quantities), it is possible to quickly estimate the overall state quantities by using the difference with the data stored in the database (DB) or by using a local-to-global learning device / model. Change detection has the advantage that it can be performed even with low resolution. In addition, after change detection (after extracting the area of ​​interest), it is also possible to generate a task to direct observation to the area of ​​interest.

[0031] FIG. 4 is a diagram showing an example of displaying the earth's surface and geocentric celestial sphere omnidirectional feature quantities.

[0032] As shown in Figure 4, by projecting the measured and estimated information of electromagnetic waves distributed in all directions on Earth and in outer space onto the Earth's surface or the inertial space on the geocentric celestial sphere, it is possible to quickly estimate the global state quantity from local observations (local state quantities) by using the difference with the data stored in the satellite orbit information database (DB) or by using a local-global learning device / model.

[0033] A specific example of the configuration of an electromagnetic wave information processing device and its method will be described below.

[0034] FIG. 5 is a block diagram showing a schematic configuration of an electromagnetic wave information processing device 100 according to this embodiment.

[0035] As shown in FIG. 5, the electromagnetic wave information processing device 100 of this embodiment includes, as its main components, a measurement unit 1, a calculation unit 2, an attitude detection device 9, a rotation control device 10, and an output unit 15.

[0036] The measurement unit 1 has a plurality of antennas 3, a plurality of amplifiers 4 corresponding to each of the antennas 3, a plurality of mixers 5 corresponding to each of the amplifiers 4, a plurality of intermediate frequency filters 6 corresponding to each of the mixers 5, a plurality of AD converters 7 corresponding to each of the intermediate frequency filters 6, and a local oscillator 8.

[0037] The calculation unit 2 has a storage device 11, an interference calculation unit 12, a spherical function coefficient calculation unit 13, and a radio wave source identification unit .

[0038] Similar to the principle used in FM receivers, the measurement unit 1 multiplies the target frequency by the frequency of a local oscillator 8 using a mixer 5, and then applies an intermediate frequency filter 6 to extract the difference frequency (intermediate frequency). This is converted to a low frequency to facilitate subsequent processing. The signal is then converted to analog by an AD converter 7 and input to the calculation unit 2, which is a calculation device.

[0039] Fig. 6 is a diagram schematically showing the processing flow (correlation method) of the calculation unit 2 in Fig. 5. Fig. 6 shows an example of processing for reconstructing the electromagnetic wave source in the radio wave source identification unit 14.

[0040] The processing unit in FIG. 6 is made up of a correlation calculation unit 51, an antenna pair addition unit 52, and an inter-axis addition unit 53.

[0041] Of these, the correlation calculation unit 51 is configured for each axial rotation and each antenna pair, and therefore processes all possible combinations of antenna pairs (for example, if the number of antennas is six, then 6C2 = 15 combinations) for one axial rotation. Here, one axial rotation is represented as 51-1, and the 15 possible antenna pair combinations are further represented as 51-1m to distinguish them. m is a maximum of 15. Note that N axial rotations are represented as 51-Na to 51-Nm.

[0042] 6 shows the process of 51-1a as a representative example. The process in the correlation calculation unit 51 ultimately executes the following equation (1). Here, the antenna electric field Ei(t,O) and the attitude information R PSij The reconstructed electromagnetic wave source direction is estimated as the product of (θ, φ, t, O).

[0043]

number

[0044] The antenna electric field Ei(t,O) is calculated as an interference waveform obtained by applying a low-pass filter (LPF) to the product of the antenna electric fields Ei(t,O), and the attitude information R PSij (θ,φ,t,O) can be calculated as interference fringes from a point radiation source. The direction of the reconstructed electromagnetic wave source is visualized by shading on the spherical surface, and the greater the difference in brightness between the bright and dark areas, the more reliable the information.

[0045] The reconstructed electromagnetic wave source direction calculated for each axis rotation and each antenna pair is calculated by averaging for each axis in the antenna pair adder 52 (52a-52n). This process is calculated using the following equation (2).

[0046]

number

[0047] Furthermore, the reconstructed electromagnetic wave source directions obtained by averaging for each axis are averaged by the inter-axis adder 53 to obtain a total result. This processing is performed using the following equation (3).

[0048]

number

[0049] The above processing will be described in detail below.

[0050] First, the electric field E measured by the ith antenna after the kth rotation is i is dependent on the attitude of the spacecraft due to the time t and the rotation operation k, and is obtained as time series data of voltage values ​​obtained by the analog-to-digital converter (AD converter 7) after the antenna.

[0051] Interference waveform R between the i-th and j-th antenna pairs ij is, for example, the electric field E i and the electric field E j The interference waveform can be obtained by arithmetic processing of the digital data after AD conversion, or by analog integration processing using a mixer in an electronic circuit, and then AD conversion processing can be performed after passing through a low-pass filter (LPF).

[0052] Next, theoretical interference fringes assuming a point radiation source are calculated from the relative positions of the antenna pair, which is determined from the attitude of the spacecraft, or the baseline vector, which is the vector connecting the antenna pair. By mapping the interference intensity when electromagnetic waves of a specified frequency arrive from a point radiation source located in each direction (azimuth angle, elevation angle) at infinity onto a spherical surface, theoretical interference fringes with a pattern that changes over time are obtained.

[0053] After the above processing, the electromagnetic wave source can be reconstructed by superimposing the theoretical interference fringes at each time using the change in interference intensity at each time as a weight.

[0054] The effect of the above process is that ghosts (artifacts) can be reduced by reconstructing electromagnetic wave sources using data acquired by multiple rotation operations. Furthermore, the use of rotation increases the number of resolvable electromagnetic wave sources, making it possible to reconstruct a large number of electromagnetic wave sources.

[0055] FIG. 7 is a diagram showing a modification of FIG. 6, and schematically shows the processing flow (spherical harmonics method) of the calculation unit 2 in FIG.

[0056] Here we describe the representation of omnidirectional radio wave sources using spherical harmonics.

[0057] In the spacecraft coordinate system centered on the spacecraft equipped with a three-dimensional array antenna, the radio wave source brightness of wave number k = |k| is defined as B(Ω k ) where k is the wave vector and Ω k =(θ k ,φ k ) is the solid angle, θ k is the elevation angle, φ k is the azimuth angle ( ● k is the spherical component of the wave vector). The visibility V, which is the wavenumber domain expression of the radio source brightness, is given by the following equation (4) when the phase reference is set as the origin of the spacecraft coordinate system (T. Carozzi, 2015, Monthly Notices of the Royal Astronomical Society: Letters 451).

[0058]

number

[0059] Here, r represents the position vector of the visibility region.

[0060] To express equation (4) using spherical harmonics, we use the visibility V(r,k) and the radio source brightness B(Ω k ) and the exponential function part exp(-ik·r) are expressed as the following equations (5) to (7), respectively.

[0061]

number

[0062]

number

[0063]

number

[0064] In equation (5), V lm is the expansion coefficient of the visibility, r = |r| is the radius, j l (kr) is the spherical Bessel function of the first kind, Y lm (Ω) is a spherical harmonic function (l and m are the azimuthal quantum number and magnetic quantum number, respectively), and the subscript ● r means the spherical coordinate representation of the position vector r. Also, in equation (6), b lm are the expansion coefficients of the radio source brightness, and equation (7) is obtained by expressing the electric field in plane wave expansion using spherical harmonics.

[0065] By substituting equations (5), (6), and (7) into equation (4), the relationship between visibility and radio source brightness can be expressed as the following equation (8) using the expansion coefficients of spherical harmonics.

[0066]

number

[0067] Furthermore, the expansion coefficients V of the spherical harmonics of the visibility obtained by the three-dimensional array antenna lm is expressed as the following equation (9) using the number of antenna channels N and the total number of minute rotation operations O.

[0068]

number

[0069] From this, by substituting equation (9) into equation (8), the expansion coefficient V of the spherical harmonic function of the visibility obtained by observation with a three-dimensional array antenna is obtained. lm From the above, the expansion coefficient b of the brightness of the omnidirectional radio source lm Finally, b lm By substituting into equation (6), the radio source brightness can be reconstructed.

[0070] Here, the first kind of spherical Bessel function j l (kr) is expressed by the following equation (10).

[0071]

number

[0072] Γ(z) is the gamma function and is expressed by the following equation (11), where e is the base of the natural logarithm.

[0073]

number

[0074] Spherical harmonic function Y lm (Ω)=Y l m (θ, φ) is expressed by the following equation (12).

[0075]

number

[0076] where m is an integer, k ≥ |m|, and Y * lm indicates the complex conjugate (the sign of the imaginary part is inverted), and P k m (t) is the associated Legendre polynomial shown in equation (13).

[0077]

number

[0078] That is, P k m (t) is the solution of the Legendre's associated differential equation shown in equation (14).

[0079]

number

[0080] It is known that the Legendre's associated differential equation has a solution when and only when equation (13) is satisfied. In equation (9), the orders of the spherical harmonic functions to be calculated (azimuthal quantum number, magnetic quantum number) can be changed depending on the distribution of the radio wave source to be measured and the required spatial resolution.

[0081] FIG. 8 is a flowchart showing the details of the measurement process performed by the arithmetic unit of the electromagnetic wave information processing device 100.

[0082] In the example of FIG. 8, when the arithmetic unit of the electromagnetic wave information processing device 100 starts processing, first, in steps S801 and S802, the arithmetic unit obtains the measurement content and the posture reference position (direction).

[0083] In FIG. 8, as the processing content of step S803, a series of procedures for executing rotation measurement are specifically described as steps S804 to S807.

[0084] In step S803, rotation control device 10 issues a command to rotation control device 10 using the attitude information acquired by attitude detection device 9, and rotation control device 10 controls rotation to the attitude reference position (direction), and then stops the rotation.

[0085] Next, in step S804, the calculation unit sets the rotation axis for one of the N iterations, and in step S805, the calculation unit synchronizes the timing of the start of rotation and the start of measurement for one of the N iterations. Under these conditions, in step S806, it is detected that the attitude detection device 9 has reached a predetermined rotation angle.

[0086] The processes from step S803 to step S806 are continued by changing the conditions in step S807 until measurements for all N rotation axes are completed.

[0087] Then, in step S808, the calculation unit associates each attitude and time information with the electric field waveform measured by each antenna, and performs a process of calculating an interference waveform by multiplying the signal for each antenna pair, and a process of calculating or reading a theoretical interference intensity change pattern from the attitude change, and at this time performs a process of reconstructing the electromagnetic wave source from the interference waveform obtained by multiplying the data of all antenna pairs for each rotation axis.

[0088] Furthermore, in step S809, the calculation unit multiplies the interference waveform at each time by the theoretical interference intensity change pattern corresponding to each time and integrates the results in the time direction to reconstruct the electromagnetic wave source, and also performs a process of integrating the electromagnetic wave source data for all rotation axes to reconstruct the electromagnetic wave source.

[0089] In the specific measurement process shown in Figure 8, the attitude detection device 9 recognizes the rotation angle, and then controls the start and stop of rotation around multiple axes in sequence.Furthermore, for each rotation axis, the electromagnetic wave source is reconstructed using the interference waveform of the antenna pair used for analysis, and the electromagnetic wave source is reconstructed by aligning all rotation axes.

[0090] Finally, in step S810, the omnidirectional feature amount (spherical coefficient) is calculated from the electromagnetic wave source distribution, and the process ends.

[0091] By approximating the omnidirectional distribution information using a basis of spherical functions, it is possible to effectively compress the amount of data.

[0092] FIG. 9 is a flowchart showing the processing contents of the basis number and basis coefficient calculation unit.

[0093] As shown in FIG. 9, when the basis number and basis coefficient calculation unit starts processing, first, in step S901, the complexity of the target environment, the required expression precision, and the allowable calculation time are defined.

[0094] Next, in step S902, an explanation and approximation function is defined and selected, such as a spherical function type, a plane function type, or an FFT (Fast Fourier Transform).

[0095] Next, in step S903, the basis number is calculated and determined.

[0096] Finally, in step S904, the coefficients of the basis are calculated, and the process ends.

[0097] The greater the complexity of the target environment, the higher the required representation accuracy, and the longer the allowable calculation time, the larger the order of the basis functions should be set. Explanation and approximation functions are set from spherical harmonic function coefficients, spherical Bessel function coefficients, spherical Neumann function coefficients, spherical Hankel function coefficients, spherical wavelet coefficients, spherical Haar bases, azimuth / elevation angle discretization coefficients, 1D to 3D FFT coefficients, and learners. Several orders are set, calculation time and error evaluations are performed, and the number of basis functions that meet the conditions is calculated and determined. Then, the basis coefficients are calculated based on the above conditions.

[0098] The complexity of the model can be adjusted depending on the scale and the time allowed, so if precision is not required, it can be made faster, and if precision is required, a model with higher expressive power can be used. A plane wave basis can also be used. If you want to speed up, you can use FFT processing. For things where the direction is determined to a certain extent, spherical coefficients are good. For a detailed look, a method of cutting with a plane is also good.

[0099] FIG. 10 is a flowchart showing the processing contents of the electromagnetic wave information conversion unit.

[0100] As shown in FIG. 10, when the electromagnetic wave information conversion unit starts processing, first, in step S1001, the local omnidirectional feature amount at the center of the satellite is acquired as the coefficient of a spherical function.

[0101] Next, in step S1002, the coefficients of the local spherical harmonic functions, orbital information, and positional relationship with the Earth are used to select only the coefficients that contribute most to a predetermined threshold, and then these are projected and converted as feature quantities on the Earth's surface and at a predetermined altitude (e.g., an altitude of 2,000 km).

[0102] Finally, in step S1003, coefficients are selected, and the projected and transformed features at the ground surface and at a predetermined altitude are added to calculate the coefficients of a spherical function, thereby obtaining and mapping the celestial sphere omnidirectional features, and the process ends.

[0103] By selecting coefficients with high contribution rates, the amount of data can be further compressed.In addition, by updating the database (DB) and comparing it with previously acquired databases (DB), changes can be quickly determined.

[0104] FIG. 11 is a diagram schematically illustrating the processing flow in the learning phase and the operation phase.

[0105] In the learning phase, spherical harmonic coefficients are calculated from orbital information and local observation results, or from the visibilities observed by each antenna pair, and then an overall map is created, which is then used as a database to hold the relationship (model) between the local observation results and the overall map.

[0106] During the operation phase, after calculating the spherical harmonic function coefficients from the orbital information and local observation results, the database can be used to estimate the overall result, enabling high-speed calculations. The overall estimation result can also be calculated using the difference with the database (DB). In this case, it is desirable to use the overall map that minimizes the difference. After the overall estimation, the overall basis function coefficients are calculated.

[0107] By using the coefficients of spherical functions, it is possible to compress electromagnetic wave information into a smaller amount of information. Furthermore, by efficiently creating a database (DB) and using the database (DB) to extract differences from local observation results and perform overall estimation, it is possible to perform overall estimation and detect changes and anomalies in a short time.

[0108] 12 and 13 are diagrams showing examples of the Earth surface map and the space map display section.

[0109] The earth surface map and outer space map of electromagnetic wave information are displayed, for example, in the formats shown in Figures 12 and 13. Maps for each frequency of electromagnetic waves may also be displayed.

[0110] The effect of displaying on a geocentric celestial sphere is that it is effective in extracting areas of interest from change points in Earth orbit missions. It is also effective in generating observation tasks and satellite control tasks. Displaying on a global scale also makes it possible to estimate the overall situation from local observations. It also allows for more accurate landing. It is also effective in determining whether a location is difficult to receive radio waves. This can be used to determine the communication area in advance.

[0111] FIG. 14 is a flowchart showing the processing flow for improving observation efficiency by the observation / satellite control task generation unit.

[0112] As shown in FIG. 14, when the observation / satellite control task generation unit of the electromagnetic wave information processing apparatus 100 starts processing, first, in step S1401, electromagnetic wave information is acquired.

[0113] Next, in step S1402, the calculation results in the calculation unit 2, that is, the data obtained by the coefficient calculation, are compressed.

[0114] Next, in step S1403, the electromagnetic wave information is converted into a ground surface map and a geocentric celestial sphere map.

[0115] Next, in step S1404, the earth's surface map and the geocentric celestial spherical map are output to update the database (DB), and differences from the data stored in the database (DB) are detected.

[0116] Finally, in step S1405, an observation task and a satellite control task are generated, and the process ends.

[0117] The processing flow shown in Figure 14 not only leads to a rapid understanding of the radio wave conditions of satellites and celestial bodies, but also enables the rapid switching of observations by generating new control tasks to improve the efficiency of observations. It is also expected that the radio wave conditions can be understood even more quickly.

[0118] FIG. 15 is a block diagram showing an example of the configuration of the observation and satellite control task generation unit 16. As shown in FIG.

[0119] As shown in FIG. 15, the observation / satellite control task generation unit 16 generates observation tasks and satellite control tasks based on information input from the earth's surface map and geocentric celestial sphere map output unit 17 .

[0120] The observation and satellite control task generation unit 16 is composed of an observation task input unit and satellite control task input unit 18, a task output model calculation unit 19, a database (DB) 20, a radio wave condition output unit 21, and an observation and satellite control task output unit 22.

[0121] The task output model calculation unit 19 calculates the difference between the satellite orbit information and celestial body position information data stored in the database (DB) 20 and the observed geocentric celestial spherical map, and further receives the observed earth's surface map, observation tasks, and satellite control tasks to calculate the radio wave conditions and satellite control tasks. This calculation may be performed using an input / output model previously obtained by machine learning, for example.

[0122] The database (DB) 20 stores, for example, satellite orbit information and celestial body position information from NORAD (North American Aerospace Defense Command), and other space object observation information.

[0123] The radio wave condition output unit 21 outputs the activity conditions of other satellites and celestial bodies.

[0124] The basic processing flow and its effects in the observation / satellite control task generation unit 16 have been explained using the flowchart in FIG.

[0125] FIG. 16 is a diagram showing an example of an observation task list and a satellite control task list.

[0126] The observation task list lists, for example, parameters such as axis 1 to axis 13, 0 to 0.1 rpm, integers, etc. for tasks such as changing the rotation axis, changing the rotation speed, and the number of observations.

[0127] In addition, the satellite control task list lists parameters such as thruster injection vector, ΔV, rotation speed (0-0.1 rpm), destination setting, receiving ground station setting, mission data (observation data), and HK (satellite status) data for tasks such as orbit change, attitude change, communication timing change, and communication content change.

[0128] Fig. 17 is a diagram showing an example of a simulation result when an arbitrary radio wave source distribution is approximated by a spherical harmonic function. Fig. 17 shows an example of approximating an arbitrary radio wave source distribution by a linear combination of spherical harmonic functions.

[0129] Dividing the azimuth angle and elevation angle (or depression angle) into 100 parts, the distribution of 10,000 variables is shown in Figure 17(a). This distribution is approximated using a total of 25 coefficients of spherical harmonics up to the fourth order as a basis, as shown in Figure 17(b). In this case, it is compressed to 0.25%, or 1 / 400.

[0130] Furthermore, for a more accurate approximation, a total of 64 coefficients up to the seventh order are used as a basis, resulting in the approximation shown in Figure 17(c). In this case, the data is compressed to 0.64%, or 1 / 150.

[0131] This ability to compress data reduces the amount of downlink data required for on-board calculations on a satellite, reduces the storage capacity required for data handling, and cuts costs.

[0132] As described above, the electromagnetic wave information processing device of this embodiment includes a measurement unit that measures electromagnetic waves incident on a spacecraft from approximately all directions, an input unit that receives the measurement results from the measurement unit, a calculation unit that performs calculations based on the information received from the input unit, and an output unit that outputs the calculation results from the calculation unit. Based on the measurement results received from the input unit, the calculation unit calculates local omnidirectional feature values, which are coefficients of local basis functions that represent the distribution of the electromagnetic waves received from the input unit in a spacecraft coordinate system centered on the spacecraft at a predetermined position in space. Based on the multiple local omnidirectional feature values ​​and information on multiple predetermined positions in space, the calculation unit calculates global omnidirectional feature values, which are coefficients of global basis functions, to create a map that represents the overall distribution of electromagnetic wave sources, including the Earth's surface and space. The output unit outputs the map. Here, basis functions (e.g., spherical harmonic functions) that represent the distribution of incoming electromagnetic wave sources or the distribution of radio wave sources on the Earth's surface in a coordinate system centered on the Earth (geocentric coordinate system) are referred to as "global basis functions."

[0133] Moreover, the electromagnetic wave information processing device of this embodiment is an electromagnetic wave information processing device to be mounted on a spacecraft, and includes a measurement unit capable of measuring electromagnetic waves incident from approximately all directions, a calculation unit that performs calculations based on information measured by the measurement unit, and an output unit that outputs the calculation results of the calculation unit, wherein the calculation unit calculates local omnidirectional feature amounts that are coefficients of local basis functions that indicate the distribution of electromagnetic waves measured by the measurement unit in a spacecraft coordinate system centered on the spacecraft at a predetermined position in space, based on the electromagnetic wave measurement results measured by the measurement unit, and calculates global omnidirectional feature amounts that are coefficients of global basis functions, based on the multiple local omnidirectional feature amounts and information on multiple predetermined positions in space, thereby creating a map that indicates the overall distribution of electromagnetic wave sources including the Earth's surface and outer space, and the output unit outputs the map.

[0134] The spacecraft further includes an overall estimation unit, wherein the calculation unit creates a database that stores the relationship between the local omnidirectional feature values ​​at a plurality of predetermined positions in space and the map, and the overall estimation unit calculates the local omnidirectional feature values ​​during operation in the new spacecraft coordinate system, and compares the local omnidirectional feature values ​​during operation with the database to detect a difference between the local omnidirectional feature values ​​and the local omnidirectional feature values ​​during operation, and estimates a change in the map.

[0135] The local omnidirectional feature amount is a spherical function coefficient.

[0136] The calculation unit also calculates observation tasks and satellite control tasks using the earth's surface map and the geocentric celestial sphere map of electromagnetic waves, and the output unit outputs the observation tasks and satellite control tasks calculated by the calculation unit.

[0137] By expressing omnidirectional features using coefficients of basis functions, the amount of data to be stored can be compressed, which reduces the amount of satellite communication required and allows downlinks over short paths or with short visibility times.

[0138] Furthermore, by accumulating and creating a database of the results of advance measurements of electromagnetic wave sources during the learning phase, it is possible to grasp the overall picture of radio wave information from local measurements, leading to a more rapid understanding of the overall picture.

[0139] In addition, by outputting observation tasks and satellite control tasks, it is possible to more efficiently and quickly grasp the distribution of electromagnetic wave sources in the area of ​​interest.

[0140] The present invention is not limited to the above-described embodiments and includes various modifications. For example, the above-described embodiments have been described in detail to clearly explain the present invention, and the present invention is not necessarily limited to those including all of the described configurations. Furthermore, it is possible to replace part of the configuration of one embodiment with the configuration of another embodiment, or to add the configuration of another embodiment to the configuration of one embodiment. Furthermore, it is possible to add, delete, or replace part of the configuration of each embodiment with other configurations.

[0141] Furthermore, the above-described configurations, functions, processing units, processing means, etc. may be partially or entirely implemented in hardware, for example, by designing them as integrated circuits. The above-described configurations, functions, etc. may also be implemented in software, with a processor interpreting and executing a program that implements each function. Information such as the programs, tables, and files that implement each function can be stored in a memory, a recording device such as a hard disk or SSD (Solid State Drive), or a recording medium such as an IC card, SD card, or DVD. [Explanation of symbols]

[0142] 1...Measuring unit 2...Arithmetic section 3...Antenna 4...Amplifier 5...Mixer 6...Intermediate frequency filter 7...AD converter 8...Local oscillator 9...Attitude detection device 10...Rotation control device 11...Storage device 12...Interference calculation unit 13...Spherical function coefficient calculation section 14...Radio source identification section 15...Output section 16...Observation and satellite control task generation unit 17...Earth surface map and geocentric celestial spherical map output section 18...Observation task input section and satellite control task input section 19...Task output model calculation unit 20...Database (DB) 21...Radio wave condition output section 22...Observation and satellite control task output section 30...Input section 51...Correlation calculation unit 52...Antenna pair adder 53...Inter-axis addition unit 100...Electromagnetic wave information processing device.

Claims

1. an input unit for inputting measurement results from a measurement unit that measures electromagnetic waves incident on the spacecraft from substantially all directions; a calculation unit that performs calculations based on information input to the input unit; an output unit that outputs the calculation result of the calculation unit, the calculation unit calculates, based on the measurement results input to the input unit, local omnidirectional feature values ​​which are coefficients of local basis functions that indicate the distribution of electromagnetic waves input by the input unit in a spacecraft coordinate system centered on the spacecraft at a predetermined position in space, and calculates global omnidirectional feature values ​​which are coefficients of global basis functions based on a plurality of the local omnidirectional feature values ​​and information on a plurality of the predetermined positions in space, thereby creating a map that indicates the distribution of electromagnetic wave sources overall, including the Earth's surface and outer space; The electromagnetic wave information processing apparatus is characterized in that the output unit outputs the map.

2. 2. The electromagnetic wave information processing device according to claim 1, Further comprising an overall estimation unit, the calculation unit creates a database that stores a relationship between the local omnidirectional feature amounts at a plurality of predetermined positions in the space and the map; the overall estimation unit calculates a local omnidirectional feature value during operation in a new spacecraft coordinate system, and compares the local omnidirectional feature value during operation with the database to detect a difference between the local omnidirectional feature value and the local omnidirectional feature value during operation, thereby estimating a change in the map.

3. 2. The electromagnetic wave information processing device according to claim 1, The electromagnetic wave information processing apparatus, wherein the local omnidirectional feature amount is a spherical function coefficient.

4. 2. The electromagnetic wave information processing device according to claim 1, the calculation unit calculates observation tasks and satellite control tasks using an earth surface map and a geocentric celestial sphere map of electromagnetic waves; The electromagnetic wave information processing apparatus is characterized in that the output unit outputs the observation task and the satellite control task calculated by the calculation unit.

5. An electromagnetic wave information processing device to be mounted on a spacecraft, a measurement unit capable of measuring electromagnetic waves incident from substantially all directions; a calculation unit that performs calculations based on the information measured by the measurement unit; an output unit that outputs the calculation result of the calculation unit, the calculation unit calculates, based on the electromagnetic wave measurement results measured by the measurement unit, local omnidirectional feature amounts which are coefficients of local basis functions that indicate the distribution of the electromagnetic waves measured by the measurement unit in a spacecraft coordinate system centered on the spacecraft at a predetermined position in space; creating a map showing the distribution of electromagnetic wave sources throughout the entire space, including the Earth's surface and outer space, by calculating global omnidirectional feature values ​​that are coefficients of global basis functions based on the local omnidirectional feature values ​​and information on the plurality of predetermined positions in outer space; The electromagnetic wave information processing apparatus is characterized in that the output unit outputs the map.

6. 6. The electromagnetic wave information processing device according to claim 5, Further comprising an overall estimation unit, the calculation unit creates a database that stores a relationship between the local omnidirectional feature amounts at a plurality of predetermined positions in the space and the map; the overall estimation unit calculates a local omnidirectional feature value during operation in a new spacecraft coordinate system, and compares the local omnidirectional feature value during operation with the database to detect a difference between the local omnidirectional feature value and the local omnidirectional feature value during operation, thereby estimating a change in the map.

7. 6. The electromagnetic wave information processing device according to claim 5, The electromagnetic wave information processing apparatus, wherein the local omnidirectional feature amount is a spherical function coefficient.

8. 6. The electromagnetic wave information processing device according to claim 5, the calculation unit calculates observation tasks and satellite control tasks using an earth surface map and a geocentric celestial sphere map of electromagnetic waves; The electromagnetic wave information processing apparatus is characterized in that the output unit outputs the observation task and the satellite control task calculated by the calculation unit.

9. An electromagnetic wave information processing method comprising the following steps: (a) a step in which a calculation unit calculates, based on the electromagnetic wave measurement results measured by the measurement unit, local omnidirectional feature quantities which are coefficients of local basis functions that indicate the distribution of the electromagnetic waves measured by the measurement unit in a spacecraft coordinate system centered on the spacecraft at a predetermined position in space; (b) calculating global omnidirectional feature values, which are coefficients of global basis functions, based on the plurality of local omnidirectional feature values ​​and information on the plurality of predetermined positions in space, to create a map showing the distribution of electromagnetic wave sources throughout the entire space, including the Earth's surface and space; (c) an output unit outputs the map created in the (b) step.

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