Acquisition and tracking system, artificial satellite, control device, acquisition and tracking method, and program

Abstract

To detect a direction of an object from an artificial satellite for controlling a direction of a device.SOLUTION: A capture tracking system comprises: wave acquiring means for acquiring a wave from an object and being mounted on an artificial satellite; drive means for rotating the wave acquiring means for changing an orientation direction of the wave acquiring means; direction calculating means for calculating a direction of the object, from the wave acquired by the wave acquiring means; and control means for, on the basis of a relative orbit motion model of the object to the artificial satellite, a posture rate of the artificial satellite, and a state shift model indicating variation of a direction of the object in a visual field of the wave acquiring means when the drive means rotates the wave acquiring means, calculating a rotation angle of the drive means so that, a magnitude of deviation indicated by an evaluation function value of a magnitude of a deviation between, a visual field center direction of the wave acquiring means and a direction of the object viewed from the wave acquiring means, becomes small as much as possible and operating the drive means by the calculated rotation angle.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present invention relates to an acquisition and tracking system, an artificial satellite, a control device, an acquisition and tracking method, and a program. [Background technology]

[0002] 2. Description of the Related Art In some cases, a method of acquiring light or the like from an object and detecting the direction from which the light or the like is emitted is used to detect the direction of an object for communication or the like. For example, Patent Document 1 describes that a position detection unit placed on the ceiling of a factory or the like detects the position or displacement of a mobile device by receiving light emitted by the mobile device moving within the factory, or by the position detection unit emitting light and receiving the light reflected by the mobile device. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 2019-117993 Summary of the Invention [Problem to be solved by the invention]

[0004] When photographing an object from a satellite, the direction of the object may be detected from the satellite and the orientation of a device such as a camera may be controlled.

[0005] An example of an object of the present invention is to provide an acquisition and tracking system, an artificial satellite, a control device, an acquisition and tracking method, and a program that can solve the above-mentioned problems. [Means for solving the problem]

[0006] According to a first aspect of the present invention, an acquisition and tracking system is mounted on a satellite and comprises: electromagnetic wave acquisition means for acquiring electromagnetic waves from an object; drive means for changing the orientation direction of the electromagnetic wave acquisition means by rotating the electromagnetic wave acquisition means; direction calculation means for calculating the direction of the object from the electromagnetic waves acquired by the electromagnetic wave acquisition means; and control means for calculating a rotation angle of the drive means so as to minimize the magnitude of the deviation indicated by an evaluation function value of the magnitude of the deviation between the direction of the center of the field of view of the electromagnetic wave acquisition means and the direction of the object as seen from the electromagnetic wave acquisition means, based on a relative orbital motion model of the object with respect to the satellite, an attitude rate of the satellite, and a state transition model indicating the fluctuation of the direction of the object within the field of view of the electromagnetic wave acquisition means due to the drive means rotating the electromagnetic wave acquisition means, and for operating the drive means at the calculated rotation angle.

[0007] According to a second aspect of the present invention, a satellite includes electromagnetic wave acquiring means for acquiring electromagnetic waves from an object, driving means for changing the orientation direction of the electromagnetic wave acquiring means by rotating the electromagnetic wave acquiring means, direction calculating means for calculating the direction of the object from the electromagnetic waves acquired by the electromagnetic wave acquiring means, and control means for calculating a rotation angle of the driving means so as to minimize the magnitude of the deviation indicated by an evaluation function value of the magnitude of the deviation between the direction of the center of the field of view of the electromagnetic wave acquiring means and the direction of the object as seen from the electromagnetic wave acquiring means, based on a relative orbital motion model of the object with respect to the satellite, an attitude rate of the satellite, and a state transition model indicating the fluctuation of the direction of the object within the field of view of the electromagnetic wave acquiring means due to the driving means rotating the electromagnetic wave acquiring means, and for operating the driving means at the calculated rotation angle.

[0008] According to a third aspect of the present invention, the control device includes a control means for calculating a rotation angle of the drive means based on a relative orbital motion model of the object with respect to the satellite, an attitude rate of the satellite, and a state transition model showing fluctuations in the direction of the object within the field of view of the electromagnetic wave acquisition means due to the drive means rotating the electromagnetic wave acquisition means that acquires electromagnetic waves from the object, so that the magnitude of the deviation indicated by an evaluation function value of the magnitude of the deviation between the center direction of the field of view of the electromagnetic wave acquisition means and the direction of the object as seen from the electromagnetic wave acquisition means is as small as possible, and for operating the drive means at the calculated rotation angle.

[0009] According to a fourth aspect of the present invention, an acquisition and tracking method includes a computer acquiring electromagnetic waves from an object via an electromagnetic wave acquiring means mounted on a satellite, calculating a direction of the object from the electromagnetic waves, calculating a rotation angle of the driving means so as to minimize a magnitude of deviation indicated by an evaluation function value of the magnitude of deviation between the direction of the center of the field of view of the electromagnetic wave acquiring means and the direction of the object as seen from the electromagnetic wave acquiring means, based on a relative orbital motion model of the object with respect to the satellite, an attitude rate of the satellite, and a state transition model indicating a fluctuation in the direction of the object within the field of view of the electromagnetic wave acquiring means due to the driving means rotating the electromagnetic wave acquiring means, and operating the driving means at the calculated rotation angle.

[0010] According to a fifth aspect of the present invention, a program causes a computer to execute the following steps: acquire electromagnetic waves from an object via an electromagnetic wave acquiring means mounted on a satellite; calculate the direction of the object from the electromagnetic waves; calculate a rotation angle of the driving means so as to minimize the magnitude of the deviation indicated by an evaluation function value of the magnitude of the deviation between the center direction of the field of view of the electromagnetic wave acquiring means and the direction of the object as seen from the electromagnetic wave acquiring means, based on a relative orbital motion model of the object with respect to the satellite, an attitude rate of the satellite, and a state transition model indicating a change in the direction of the object within the field of view of the electromagnetic wave acquiring means due to the driving means rotating the electromagnetic wave acquiring means; and operate the driving means at the calculated rotation angle. [Effects of the Invention]

[0011] According to the present invention, the direction of the object can be detected from the satellite and the orientation of the device can be controlled. [Brief explanation of the drawings]

[0012] [Figure 1] FIG. 2 is a diagram illustrating an example of an operating environment of the satellite according to the first embodiment. [Figure 2] FIG. 1 is a diagram illustrating an example of the configuration of an artificial satellite according to a first embodiment. [Figure 3] 4 is a diagram showing an example of a data flow when the control system according to the first embodiment calculates a command value for the rotation angle of the motor. FIG. [Figure 4] FIG. 2 is a diagram illustrating an example of a definition of a coordinate system in the first embodiment. [Figure 5] FIG. 2 is a diagram showing an example of the positional relationship between an artificial satellite and an object at time k in the first embodiment. [Figure 6] FIG. 2 is a diagram showing an example of the positional relationship between an artificial satellite and an object when viewed from the positive direction of the Z axis at time k in the first embodiment. [Figure 7] FIG. 2 is a diagram showing an example of the positional relationship between a satellite and an object when viewed from the negative direction of the Y axis at time k in the first embodiment. [Figure 8] FIG. 10 is a diagram showing an example of the positional relationship between an artificial satellite and an object when viewed from the positive direction of the Z axis at time k+1 in the first embodiment. [Figure 9] FIG. 10 is a diagram showing an example of the positional relationship between a satellite and an object when viewed from the negative direction of the Y axis at time k+1 in the first embodiment. [Figure 10] 4 is a diagram showing a signal flow from when the camera acquires an image to when the motor operates according to the first embodiment. FIG. [Figure 11] FIG. 10 is a diagram illustrating an example of an operating environment of a satellite according to a second embodiment. [Figure 12] FIG. 10 is a diagram illustrating an example of a definition of a coordinate system in the second embodiment. [Figure 13] FIG. 11 is a diagram illustrating an example of an operating environment of a satellite according to a third embodiment. [Figure 14] FIG. 10 is a diagram illustrating an example of an operating environment of a satellite according to a fourth embodiment. [Figure 15] FIG. 10 is a diagram illustrating an example of the configuration of an artificial satellite according to a fourth embodiment. [Figure 16] FIG. 2 is a diagram showing orbit and attitude conditions of an artificial satellite in an analysis according to the first embodiment. [Figure 17] FIG. 4 is a diagram showing setting of a signal processing time within a satellite in the analysis according to the first embodiment. [Figure 18] FIG. 10 is a diagram showing setting of an error in analysis according to the first embodiment. [Figure 19] FIG. 10 is a diagram showing the setting of the image center error of the object captured by the camera in the analysis according to the first embodiment. [Figure 20] FIG. 4 is a diagram showing an analysis result of the pointing accuracy of the artificial satellite according to the first embodiment. [Figure 21] FIG. 13 is a diagram illustrating an example of the configuration of an acquisition and tracking system according to a fifth embodiment. [Figure 22] FIG. 13 is a diagram illustrating an example of the configuration of an artificial satellite according to a sixth embodiment. [Figure 23] FIG. 13 is a diagram illustrating an example of the configuration of a control device according to a seventh embodiment. [Figure 24]FIG. 19 is a diagram showing an example of a processing procedure in an acquisition and tracking method according to the eighth embodiment. [Figure 25] FIG. 1 is a schematic block diagram illustrating the configuration of a computer according to at least one embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0013] The following describes embodiments of the present invention, but the following embodiments do not limit the scope of the invention as claimed. Furthermore, not all of the combinations of features described in the embodiments are necessarily essential to the solution of the invention.

[0014] The acquisition and tracking system according to the embodiment includes a receiver mounted on a satellite that receives electromagnetic waves from an object, a motor that is mounted on the receiver and that changes the direction of orientation of the receiver by rotating (rotating) the motor around one axis or two axes, a processing unit that calculates the direction of the object from the electromagnetic waves received by the receiver, and a control unit that calculates the rotation angle of the motor and instructs the motor.

[0015] In addition, the acquisition and tracking system according to the embodiment includes a receiver mounted on a satellite and receiving electromagnetic waves from an object, a transmitter that transmits electromagnetic waves to the object, a motor that is mounted with the receiver and transmitter and rotates around one axis or two axes to change the direction of the transmitter, a processing unit that calculates the direction of the object from the electromagnetic waves received by the receiver, and a control unit that calculates the rotation angle of the motor and instructs the motor.

[0016] In particular, the control unit of the acquisition and tracking system according to the embodiment is equipped with a state transition model that reflects the relative orbital motion of the object with respect to the satellite, the attitude rate of the satellite, and fluctuations in the direction of the object within the field of view of the receiver due to the rotational drive of the motor. This state transition model is used to predict the future direction of the object from the current direction of the object, construct an evaluation function from the predicted results of the future direction of the object, and by minimizing this evaluation function, the optimal motor rotation angle for receiving electromagnetic waves from the object or transmitting electromagnetic waves to the object is calculated.

[0017] By being configured as described above, the acquisition and tracking system according to the embodiment is mounted on a satellite and can acquire and track electromagnetic waves from an object moving at high speed in space with high accuracy, and can also transmit electromagnetic waves to the object. The acquisition and tracking system according to the embodiment can be said to be a fine acquisition and tracking system.

[0018] First Embodiment Fig. 1 is a diagram showing an example of the operating environment of a satellite according to the first embodiment. In the example of Fig. 1, the satellite 1 moves at a relative velocity v with respect to the target object 2 and passes near the target object 2. An arrow R111 indicates the direction of the target object 2 as seen from the satellite 1 in the example of Fig. 1. An arrow R121 indicates the direction of the relative motion of the satellite 1 with respect to the target object 2 in the example of Fig. 1. In the example of FIG. 1, the artificial satellite 1 is shown approaching the target object 2. The artificial satellite 1 is equipped with a camera 3, and controls the pointing direction of the camera 3 in the azimuth (AZ) direction and elevation (EL) direction to capture an image of the target object 2. The camera 3 corresponds to an example of an electromagnetic wave acquiring means. The camera 3 also corresponds to an example of a receiver that receives electromagnetic waves. Alternatively, the artificial satellite 1 may be equipped with a receiver that receives radio waves in addition to or instead of the camera 3.

[0019] The azimuth direction here refers to a direction in a reference plane that is virtually set for the satellite 1. The azimuth direction can be expressed by an azimuth angle (azimuth angle). The azimuth angle is the angle of the azimuth direction with respect to a reference direction included in the reference plane. For example, a plane parallel to the direction of travel of the satellite 1 may be used as the reference plane, and the direction of travel of the satellite 1 may be used as the reference direction. In this case, the azimuth angle is the angle of the azimuth direction when the direction of travel of the satellite 1 is used as the reference. The axis of rotation of the azimuth angle is also called the azimuth axis. The azimuth axis is expressed as the axis of rotation perpendicular to the reference plane. The azimuth direction can be said to be the direction of rotation around the azimuth axis. The axis XAZ in FIG. 1 shows an example of an azimuth axis.

[0020] The elevation direction here is the direction relative to the reference plane. The elevation direction can be expressed as an elevation angle. The elevation angle is the angle of the elevation direction relative to the reference plane. The axis of rotation of the elevation angle is also called the elevation axis. The elevation axis is expressed as a rotation axis parallel to the reference plane. The elevation direction can be said to be the direction of rotation around the elevation axis. The axis XEL in FIG. 1 is an example of an elevation axis.

[0021] In the first embodiment, the attitude rate of the satellite 1 is assumed to be constant. In addition, in the first embodiment, the orbital motion of the satellite 1 and the orbital motion of the target object 2 are both assumed to be uniform linear motion due to inertia. Therefore, when the satellite 1 is used as a reference, the target object 2 moves relatively at a uniform linear motion. In addition, when the target object 2 is used as a reference, the satellite 1 moves relatively at a uniform linear motion.

[0022] Fig. 2 is a diagram showing an example of the configuration of a satellite 1 according to the first embodiment. In addition to the camera 3 shown in Fig. 1, the configuration of the satellite 1 shown in Fig. 2 further includes an object direction calculation system 4, a control system 5, a motor 6, and a satellite bus system 7. Fig. 2 also shows an object 2 and a ground system 8.

[0023] The target object 2 can be any of a variety of objects that can be imaged from the artificial satellite 1, and is not limited to a specific object. For example, the target object 2 may be a celestial body such as an asteroid. Alternatively, the target object 2 may be an artificial object such as another artificial satellite. In the first embodiment, it is assumed that the gravitational force between the artificial satellite 1 and the target object 2 is negligible.

[0024] The camera 3 captures an image of the object 2 and outputs the captured image of the object 2 to an object direction calculation system 4. The motor 6 rotates the camera 3 in the azimuth direction and elevation direction, thereby changing the pointing direction (direction of the center of the field of view) of the camera 3. The motor 6 is an example of a driving means. The object direction calculation system 4 calculates the direction of the object 2 relative to the pointing direction of the camera 3 based on the image of the object 2, and outputs the calculated direction to the control system 5. The object direction calculation system 4 corresponds to an example of a direction calculation means. Also, the object direction calculation system 4 corresponds to an example of a processing unit.

[0025] The control system 5 calculates the drive angles (rotation angles) of the motor 6 in the azimuth and elevation directions to position the image of the object 2 in the center of the field of view of the camera 3, and outputs these to the motor 6. In this way, the control system 5 controls the operation of the motor 6. The control system 5 receives inputs of attitude information and relative orbit information of the satellite 1 from the satellite bus system 7, and command parameters from the ground system 8. The control system 5 calculates the rotation angle of the motor 6 based on the attitude information and relative orbit information of the satellite 1, the command parameters, and the direction of the object 2 calculated by the object direction calculation system 4.

[0026] The control system 5 corresponds to an example of a control means. The control system 5 also corresponds to an example of a control unit. The combination of the camera 3, the object direction calculation system 4, the control system 5, and the motor 6 corresponds to an example of an acquisition and tracking system. The satellite 1, which includes the control system 5, corresponds to an example of a control device. The control system 5 controls the rotation of the motor 6, thereby controlling the orientation of the camera 3. The control performed by the control system 5 is also referred to as control of the rotation of the motor 6, and also as control of the orientation of the camera 3.

[0027] The satellite bus system 7 is a satellite bus in the satellite 1. The satellite bus is a combination of equipment for the basic functions and operations of the satellite. It is called a satellite bus or bus equipment to distinguish it from mission equipment for performing the satellite's purpose. For example, equipment for a power system, thermal control, attitude control, orbital control, and communications may be included in the satellite bus.

[0028] The attitude information is information that indicates the attitude of the satellite 1. For example, the satellite bus system 7 may be equipped with an attitude sensor such as a mechanical or non-mechanical gyro sensor, which measures the attitude of the satellite 1 and outputs it as attitude information. The attitude information may include information that represents the attitude rate of the satellite 1 as a rotational angular velocity around each axis of a three-dimensional Cartesian coordinate system.

[0029] The relative orbit information is information that indicates the relative orbit of the object 2 with respect to the satellite 1. For example, the satellite bus system 7 may use a motion model to simulate the motion of the satellite 1 and the motion of the object 2, calculate the relative orbit of the object 2 with respect to the satellite 1, and output the calculated relative orbit information. Alternatively, the satellite bus system 7 may store pre-calculated relative orbit information. Alternatively, the satellite bus system 7 may receive the relative orbit information from the ground system 8.

[0030] The ground system 8 is a control system for the artificial satellite, installed on the ground (on the Earth) such as a ground station. In particular, the ground system 8 transmits command parameters to the artificial satellite 1. The command parameters here are control commands for the artificial satellite. The command parameters may include control command values. In this case, the control command values ​​are also referred to as parameters or parameter values.

[0031] The ground system 8 also receives various types of status information of the satellite 1, such as attitude information of the satellite 1, and various types of observation data from the satellite 1, such as images of the target object 2 captured by the satellite 1. The ground system 8 may calculate command parameters using the various types of information received from the satellite 1.

[0032] The object orientation calculation system 4 may be configured using a computer, or may be configured using dedicated hardware such as an ASIC (Application Specific Integrated Circuit) or an FPGA (Field-Programmable Gate Array).

[0033] The control system 5 may be configured using a computer, or may be configured using dedicated hardware such as an ASIC or FPGA. The satellite bus system 7 may be configured to include a computer, and various information such as attitude information may be calculated using the computer. Alternatively, the satellite bus system 7 may be configured to include dedicated hardware for calculating various information.

[0034] 3 is a diagram showing an example of the flow of data when the control system 5 calculates a command value for the rotation angle of the motor 6. In the example of FIG. 3, the control system 5 includes a state transition model 9 and an evaluation function 10. The state transition model 9 calculates the change in the direction of the object 2 within the field of view of the camera 3. Specifically, the state transition model 9 receives inputs of the direction of the object 2 up to now, the attitude rate of the satellite 1, relative orbit information of the object 2 with respect to the satellite 1, and the rotation angle of the motor 6, and outputs the direction of the object 2 in the future. The present here is the timing at which the control system 5 calculates the command value for the rotation angle of the motor 6. The future here is, for example, the imaging timing from the present to the immediate future among the timings at which the camera 3 repeatedly images the object 2.

[0035] The evaluation function 10 receives the input of the direction of the future object 2 output by the state transition model 9, and outputs an evaluation value for that direction. The closer the direction of the future object 2 is to the direction of the center of the field of view of the camera 3, the higher the evaluation value that the evaluation function 10 outputs. Here, an example will be described in which the evaluation function 10 outputs an evaluation value that decreases as the evaluation becomes higher. For example, the evaluation function 10 may output the square of the angle of the direction of the future object 2 relative to the direction of the center of the field of view of the camera 3 as the evaluation value. However, the evaluation function 10 may also output an evaluation value that increases as the evaluation becomes higher.

[0036] The control system 5 calculates the motor rotation angle that will give the highest possible evaluation by the evaluation function 10, and adopts this as the command value for the motor rotation angle. For example, the control system 5 may solve an optimization problem that searches for a motor rotation angle that minimizes the evaluation value of the evaluation function 10 under the constraints indicated by the state transition model 9.

[0037] The relative orbital motion model in the first embodiment will be described below. The relative orbital motion model is a model used by the satellite bus system 7 to calculate relative orbital information. Fig. 4 is a diagram showing an example of the definition of a coordinate system in the first embodiment. In the example of Fig. 4, the center of mass of the satellite 1 is set as the origin, and the direction from the center of mass of the satellite 1 to the target object 2 at the time of closest approach between the satellite 1 and the target object 2 is set as the positive direction of the X axis. Furthermore, the direction of relative movement of the target object 2 as seen from the satellite 1 at the time of closest approach is set as the negative direction of the Y axis. In this case, the X axis and the Y axis are perpendicular to each other.

[0038] The Z axis is set to a direction perpendicular to both the X axis and the Y axis. In the example of Fig. 4, the positive direction of the Z axis is determined so that the coordinate system is a right-handed system, but this is not limiting. In the first embodiment, the coordinate system illustrated in FIG. 4 is also referred to as the main coordinate system. In the following, the time is referred to as the sampling time T s Let k be an integer, and time step k (the kth time step) will also be expressed as time k.

[0039] The relative position of the object 2 in this coordinate system is represented by a vector r, which is also written as r(x, y, z) or (x, y, z). The relative velocity of the object 2 is represented by a vector v, which is written as v(v x ,v y ,v z ) or (v x ,v y ,v z ) is also written as As described above, in the first embodiment, both the artificial satellite 1 and the target object 2 perform uniform linear motion, and therefore the relative motion of the target object 2 with respect to the artificial satellite 1 is also uniform linear motion.

[0040] The relative position and velocity of object 2 with respect to satellite 1 at time k is (x k ,y k ,z k ,v x,k ,v y,k ,v z,k ) from time k to sampling time T s The x-coordinate of the position of object 2 at time k+1 after the lapse of time k+1 is expressed as in equation (1).

[0041]

number

[0042] The y-coordinate of the position of object 2 at time k+1 k+1 is expressed as equation (2).

[0043]

number

[0044] z coordinate of the position of object 2 at time k+1 k+1 is expressed as in equation (3).

[0045]

number

[0046] The x-coordinate v of the velocity of object 2 at time k+1 x,k+1 is expressed as in equation (4).

[0047]

number

[0048] The y-coordinate v of the velocity of object 2 at time k+1 y,k+1 is expressed as in equation (5).

[0049]

number

[0050] z-coordinate v of the velocity of object 2 at time k+1 z,k+1 is expressed as in equation (6).

[0051]

number

[0052] Equations (1) to (6) can be summarized in matrix form as shown in equation (7).

[0053]

number

[0054] Equation (7) is an example of a relative orbital motion model. The vector (x k ,y k ,z k ,v x,k ,v y,k ,v z,k ) is an example of relative orbit information. The control system 5 receives relative orbit information (x0, y0, z0, v x,0 ,v y,0 ,v z,0) as an initial value and repeatedly applying the calculation using the matrix of equation (7), it is possible to obtain relative trajectory information of the object 2 at a desired time k.

[0055] The state transition model 9 in the first embodiment will be described. FIG. 5 is a diagram showing an example of the positional relationship between the artificial satellite 1 and the target object 2 at time k. As mentioned above, the position and velocity of object 2 at time k are (x k ,y k ,z k ,v x,k ,v y,k ,v z,k ) is expressed as follows. As mentioned above, the attitude rate of the satellite 1 is assumed to be constant, and the attitude rate is expressed as (ω x ,ω y ,ω z ) that is, the satellite 1 rotates around the X axis at an angle ω x and rotates around the Y axis by an angle ω per unit time. y and rotates around the Z axis by an angle ω per unit time. z Only rotates.

[0056] The rotation angle of the motor 6 in the azimuth direction and elevation direction at time k is (θ AZ (k),θ EL At time k, the position of the object 2 in the camera's field of view converted into an angle is (φ AZ (k),φ EL That is, the direction of the object 2 as seen from the satellite 1 is at an angle φ AZ (k) and an angle φ EL It is assumed that the difference is (k).

[0057] The orientation vector of the camera 3 when not driven is set to (1,0,0). That is, the positive direction of the X axis is used as the reference for the orientation of the camera 3, and the rotation angle of the motor 6 when the camera 3 is facing in the positive direction of the X axis is set to (0,0). In addition, the elevation axis motor of the motor 6 is assumed to be equipped with an azimuth axis motor. In other words, when the motor 6 is rotated around the elevation axis, the azimuth axis also rotates in response to the rotation.

[0058] The position vector of object 2 at time k is normalized to a unit vector and is defined as (ex(k),ey(k),ez(k)). AZ (k),θ EL (k)) and (φ AZ (k),φ EL To do this, imagine changing the orientation of camera 3 from the orientation (1,0,0) to the orientation (ex(k),ey(k),ez(k)).

[0059] As described above, since the elevation axis motor is equipped with an azimuth axis motor, the pointing direction vector of the camera 3 is first rotated around the elevation axis from the pointing direction vector (1,0,0) of the camera 3 when not driven. EL (k)+φ EL (k)) and then rotate it around the azimuth axis (θ AZ (k)+φ AZ (k)) is rotated. This rotation is expressed as in equation (8).

[0060]

number

[0061] The two-axis rotation equation (equation (8)) can be summarized as equation (9).

[0062]

number

[0063] From equation (9), equation (10) holds for rotation around the azimuth axis.

[0064]

number

[0065] atan represents the arc tangent. Furthermore, equation (11) holds for rotation around the elevation axis.

[0066]

number

[0067] asin represents the arc sine.

[0068] FIG. 6 is a diagram showing an example of the positional relationship between the artificial satellite 1 and the target object 2 when viewed from the positive direction of the Z axis at time k. Vector (x k ,y k ) is the position vector (x k ,y k ,z k ) onto the XY plane. k ,y k ) can be said to be the position vector of object 2 at time k on the XY plane. Vector (v x,k ,v y,k ) is the velocity vector (v x,k ,v y,k ,v z,k ) onto the XY plane. x,k ,v y,k ) can be said to be the velocity vector of object 2 at time k on the XY plane.

[0069] Moreover, an arrow R211 indicates the direction of the camera 3 at time k projected onto the XY plane. Angle θ AZ (k) represents the angle formed by the arrow R211 when the positive direction of the x-axis at time k is used as the reference. AZ(k) can be said to be the rotation angle of the motor 6 in the azimuth direction (the rotation angle of the motor 6 around the azimuth axis) when the pointing direction vector of the camera 3 is hypothetically changed from (1,0,0) by driving the motor 6 without taking into account the attitude rate of the satellite 1.

[0070] Arrow R211 and vector (x k ,y k ) is the angle (φ AZ (k),φ EL (k)) the angular component φ around the azimuth axis AZ Represents (k). Arrow R221 indicates that satellite 1 is moving at a constant attitude rate (ω x ,ω y ,ω z ) and is shown as a symbol representing rotation.

[0071] FIG. 7 is a diagram showing an example of the positional relationship between the artificial satellite 1 and the target object 2 when viewed from the negative direction of the Y axis at time k. Vector (x k ,z k ) is the position vector (x k ,y k ,z k ) onto the XZ plane. k ,z k ) can be said to be the position vector of object 2 at time k on the XZ plane. Vector (v x,k ,v z,k ) is the velocity vector (v x,k ,v y,k ,v z,k ) onto the XZ plane. x,k ,v z,k ) can be said to be the velocity vector of object 2 at time k on the XZ plane.

[0072] Moreover, an arrow R311 indicates the direction of the camera 3 at time k projected onto the XZ plane. Angle θ EL(k) represents the angle formed by the arrow R311 when the positive direction of the x-axis at time k is used as a reference. EL (k) can be said to be the rotation angle of motor 6 in the elevation direction (the rotation angle of motor 6 around the elevation axis) when the pointing direction vector of camera 3 is hypothetically changed from (1,0,0) by driving motor 6 without taking into account the attitude rate of satellite 1.

[0073] Arrow R311 and vector (x k ,z k ) is the angle (φ AZ (k),φ EL (k)) the angle component φ around the elevation axis EL Represents (k). Arrow R321 indicates that satellite 1 is moving at a constant attitude rate (ω x ,ω y ,ω z ) and is shown as a symbol representing rotation.

[0074] FIG. 8 is a diagram showing an example of the positional relationship between the artificial satellite 1 and the target object 2 when viewed from the positive direction of the Z axis at time k+1. Vector (x k+1 ,y k+1 ) is the position vector (x k+1 ,y k+1 ,z k+1 ) onto the XY plane. k+1 ,y k+1 ) can be said to be the position vector of object 2 at time k+1 on the XY plane. Vector (v x,k+1 ,v y,k+1 ) is the velocity vector (v x,k+1 ,v y,k+1 ,v z,k+1 ) onto the XY plane. x,k+1 ,v y,k+1 ) can be said to be the velocity vector of object 2 at time k+1 on the XY plane.

[0075] Moreover, an arrow R411 indicates the direction of the camera 3 at time k+1 projected onto the XY plane. The rotation angle of the motor 6 in the azimuth direction from time k to k+1 is Δθ AZ (k), the angle formed by the arrow R411 when the positive direction of the x-axis at time k is used as the reference is θ AZ (k)+Δθ AZ It is expressed as (k). Also, the rotation angle of the satellite 1 around the azimuth axis from time k to k+1 is ω z T s It is expressed as:

[0076] Arrow R411 and vector (x k+1 ,y k+1 ) is the angle (φ AZ (k+1),φ EL (k+1)) of the angle component φ around the azimuth axis AZ Represents (k+1). Arrow R421 indicates that satellite 1 is moving at a constant attitude rate (ω x ,ω y ,ω z ) and is shown as a symbol representing rotation.

[0077] FIG. 9 is a diagram showing an example of the positional relationship between the artificial satellite 1 and the target object 2 when viewed from the negative direction of the Y axis at time k+1. Vector (x k+1 ,z k+1 ) is the position vector (x k+1 ,y k+1 ,z k+1 ) onto the XZ plane. k+1 ,z k+1 ) can be said to be the position vector of object 2 at time k+1 on the XZ plane. Vector (v x,k+1 ,v z,k+1 ) is the velocity vector (v x,k+1 ,v y,k+1 ,vz,k+1 ) onto the XZ plane. x,k+1 ,v z,k+1 ) can be said to be the velocity vector of object 2 at time k+1 on the XZ plane.

[0078] Moreover, an arrow R511 indicates the direction of the pointing direction of the camera 3 at time k+1 projected onto the XZ plane. The rotation angle of the motor 6 in the elevation direction from time k to k+1 is Δθ EL (k), the angle formed by the arrow R511 when the positive direction of the x-axis at time k is used as the reference is θ EL (k)+Δθ EL It is expressed as (k). Also, the rotation angle of the satellite 1 around the elevation axis from time k to k+1 is ω y T s It is expressed as:

[0079] Arrow R511 and vector (x k+1 ,z k+1 ) is the angle (φ AZ (k+1),φ EL (k+1)) the angle component φ around the elevation axis EL Represents (k+1). Arrow R521 indicates that satellite 1 is moving at a constant attitude rate (ω x ,ω y ,ω z ) and is shown as a symbol representing rotation.

[0080] The position and velocity of object 2 at time k (X k ,Y k ,Z k ,V x,k ,V y,k ,V z,k ) and the position and velocity of object 2 at time k+1 (X k+1 ,Y k+1 ,Z k+1 ,V x,k+1 ,V y,k+1 ,V z,k+1) is expressed by the above formula (7). Also, as described above, the rotation angle of the motor 6 from time k to time k+1 is expressed as (Δθ AZ (k),Δθ EL As mentioned above, the angle of the position of the object 2 in the camera field of view at time k+1 is expressed as (φ AZ (k+1),φ EL (k+1)). Furthermore, the vector obtained by normalizing the position vector of the object 2 at time k+1 to a unit vector is expressed as (ex(k+1),ey(k+1),ez(k+1)).

[0081] From FIG. 8 and the equation obtained by substituting time k+1 into equation (10), equation (12) can be obtained about the azimuth axis at time k+1.

[0082]

number

[0083] Furthermore, from FIG. 9 and an equation obtained by substituting time k+1 into equation (11), equation (13) can be obtained about the elevation axis at time k+1.

number

[0084] By subtracting each side of equation (10) from each side of equation (12) and rearranging, we obtain equation (14).

[0085]

number

[0086] By subtracting each side of equation (11) from each side of equation (13) and rearranging, we obtain equation (15).

[0087]

number

[0088] The combination of equation (14) and equation (15) gives (φ AZ (k),φ EL This corresponds to an example of state transition model 9 for (k). Equations (14) and (15) are rearranged. τ AZ (k) is defined as in equation (16).

[0089]

number

[0090] τ EL (k) is defined as in equation (17).

[0091]

number

[0092] φ AZ '(k) is defined as in equation (18).

[0093]

number

[0094] φ EL '(k) is defined as in equation (19).

[0095]

number

[0096] Δθ AZ '(k) is defined as in equation (20).

[0097]

number

[0098] Δθ EL'(k) is defined as in equation (21).

[0099]

number

[0100] Using equations (16), (18) and (20), equation (14) can be expressed as equation (22).

[0101]

number

[0102]

number

[0103] Equations (22) and (23) correspond to an example of the state transition model 9. The evaluation function in the first embodiment will be described. 10 is a diagram showing the flow of signals from when the camera 3 captures an image until the motor 6 starts operating. Each part shown in FIG. 10 is a signal flow diagram showing the flow of signals from when the camera 3 captures an image until the motor 6 starts operating. s The operation is sequential with unit time being

[0104] The time when the image is acquired by the camera 3 is designated as t0. The time from time t0 until the motor 6 starts to operate is designated as Hw. The time Hw includes the time required for image processing in the object direction calculation system 4, the time required for rotation angle calculation in the control system 5, and the time required for data transmission between each component. The time from time t0 until the operation of the motor 6 controlled based on the image information obtained at time t0 is designated as Hp. The time during which the motor 6 is operated based on the image information obtained at time t0 is referred to as the control target period.

[0105] Next, the evaluation function is defined. Evaluation function J AZ(t0) is defined as in equation (24).

[0106]

number

[0107] Evaluation function J EL (t0) is defined as in equation (25).

[0108]

number

[0109] "φ" in equation (24) AZ '(k+t0)-τ AZ (k+t0)" and "φ" in Eq. (25) EL '(k+t0)-τ EL (k+t0)” is the direction (φ AZ (k+t0),φ EL (k+t0)) and "Q AZ "," "R AZ "," "P AZ "," Q EL "," "R EL " and "P EL " are all weighting coefficients.

[0110] Evaluation function J AZ (t0), J EL (t0) is the angle (φ AZ (k),φ EL (k)), that is, to place the object 2 in the center of the field of view of the camera 3 (Δθ' AZ (k),Δθ' EL This means calculating (k). The control system 5 is, for example, AZ (t0), J EL (t0) Solve the optimization problem to minimize each value of the evaluation function J AZ (t0), J EL(t0) The rotation angle (Δθ' of the motor 6 is adjusted so that each value is as small as possible. AZ (k),Δθ' EL (k)) is calculated.

[0111] Q AZ The value of and Q EL The value of each is usually set to 1. AZ , R EL are Δθ', respectively. AZ (k), Δθ' EL (k) is a parameter that constrains R AZ The value of and R EL The value of can be determined based on the control response and controllability. In equation (24), the weight for time Hp+t0 is the weight Q from time Hw+t0 to time Hp-1+t0. AZ weight P different from AZ In addition, in equation (25), the weight Q for the time period from Hw+t0 to Hp-1+t0 is used as the weight for the time period Hp+t0. EL weight P different from EL By assigning the value, the stability of the control is guaranteed. P AZ The value of and P EL The value of Q AZ The value of R AZ The value of Q EL The value of R EL The value of φ' can be calculated by solving the Riccati algebraic equation based on the coefficients of the state transition equations (equations (22) and (23)). AZ The coefficient of the term "(k)" is 1, and "-Δθ AZ The coefficient of the '(k)' term is -1. In equation (23), 'φ' EL The coefficient of the term "(k)" is 1, and "-Δθ EL The coefficient of the '(k)' term is -1.

[0112] The evaluation function shown in Equation (24) and Equation (25) and the state transition model 9 are used to calculate the rotation angle (Δθ AZ (k),Δθ ELThe calculation process of (k) will be explained. The control period using the image captured by camera 3 at time t0 is from time k=t0+Hw to t0+Hp. The state transition around the azimuth axis during this period is expressed as follows by repeatedly using equations (22) and (23): The rotation angle around the azimuth axis at time t0+Hw+1 is expressed as in equation (26).

[0113]

number

[0114] The rotation angle around the azimuth axis at time t0+Hw+2 is expressed as in equation (27).

[0115]

number

[0116] The rotation angle around the azimuth axis at each time from time t0+Hw+1 to time t0+Hp is expressed as in equation (28).

[0117]

number

[0118] Equation (28) can be expressed as equation (29).

[0119]

number

[0120] X AZ (t0) is expressed as in equation (30).

[0121]

number

[0122] L is expressed as in equation (31).

[0123]

number

[0124] M is expressed as in equation (32).

[0125]

number

[0126] u AZ (t0) is expressed as in equation (33).

[0127]

number

[0128] The evaluation function J in Eq. (24) AZ (t0) can be expressed as in equation (34).

[0129]

number

[0130] A superscript T on a matrix or vector denotes the transpose of that matrix or vector. Q ’~ is expressed as in equation (35).

[0131]

number

[0132] R ’~ is expressed as in equation (36).

[0133]

number

[0134] T AZ (T0) is expressed as equation (37).

[0135]

number

[0136] T AZ (t0) is a vector indicating the angle change due to the relative motion of the object 2 with respect to the satellite 1. The control system 5 obtains the relative orbit information (X k ,Y k ,Z k ,V x,k ,V y,k ,V z,k ) as the initial value, calculate the relative orbit information at the desired time using equation (7), and use equation (16) to calculate T AZ (t0) may be calculated.

[0137] The evaluation function J in Eq. (24) AZ When (t0) takes the minimum value, u AZ The derivative with respect to (t0) is 0. This can be shown as in equation (38).

[0138]

number

[0139] Here, δ is the symbol for differentiation. Substituting the state transition equation of equation (29) into equation (34) and rearranging it, the evaluation function J AZ u when (t0) takes the minimum value AZ (t0) is derived as shown in equation (39).

[0140]

number

[0141] G is expressed as in equation (40).

[0142]

number

[0143] W AZ is expressed as in equation (41).

[0144]

number

[0145] Δθ AZ (k) is expressed as equation (42) by reflecting the influence of the attitude rate based on equation (20).

[0146]

number

[0147] The control system 5 calculates Δθ in equation (42) between time t0+Hw and time t0+Hp. AZ The motor 6 is controlled based on the above. For the elevation direction, Equation (43) can be obtained in the same way as Equation (41).

[0148]

number

[0149] G is the same as shown in equation (40). W EL is expressed as equation (44).

[0150]

number

[0151] T EL (T0) is expressed as equation (45).

[0152]

number

[0153] Δθ EL (k) is expressed as equation (46) by reflecting the influence of the attitude rate based on equation (21).

[0154]

number

[0155] The control system 5 calculates Δθ in equation (46) between time t0+Hw and time t0+Hp. EL The motor 6 is controlled based on the above.

[0156] As described above, the camera 3 is mounted on the artificial satellite 1 and acquires electromagnetic waves from the target object 2. The motor 6 rotates the camera 3 to change the pointing direction of the camera 3. The object direction calculation system 4 calculates the direction of the object 2 from the electromagnetic waves acquired by the camera 3 . Based on a relative orbital motion model of the object 2 relative to the satellite 1, the attitude rate of the satellite 1, and a state transition model showing the fluctuation in the direction of the object 2 within the field of view of the camera 3 due to the motor 6 rotating the camera 3, the control system 5 calculates the rotation angle of the motor 6 so that the magnitude of the deviation indicated by the evaluation function value of the magnitude of the deviation between the center direction of the field of view of the camera 3 and the direction of the object 2 as seen from the camera 3 is as small as possible, and operates the motor 6 at the calculated rotation angle.

[0157] The artificial satellite 1 can detect the direction of the object 2 from the artificial satellite 1 and control the orientation of the camera 3. In particular, the artificial satellite 1 can control the orientation of the camera 3 itself, so that the orientation of the camera 3 can be controlled even when real-time control is not possible from the ground due to communication delays or the like. Furthermore, the artificial satellite 1 can reflect the relative orbital motion of the object 2 and the attitude data of the artificial satellite 1 in the control of the orientation of the camera 3, and in this respect, the orientation of the camera 3 can be controlled with high precision.

[0158] Furthermore, both the target object 2 and the artificial satellite 1 move at a constant speed in a straight line due to inertia. The control system 5 uses a relative orbital motion model that indicates that both the object 2 and the satellite 1 are moving at a constant speed in a straight line due to inertia in a three-dimensional Cartesian coordinate system with the center of mass of the satellite 1 as the origin, the X axis in the direction from the center of mass of the satellite 1 to the center of mass of the object 2 at the time when the satellite 1 comes closest to the object, the Y axis in the direction of the satellite 1's movement at that time, and the Z axis in a direction perpendicular to these two directions. With the artificial satellite 1, it is possible to control the orientation of the camera 3 in an environment where both the target object 2 and the artificial satellite 1 are moving at a constant speed in a straight line due to inertia. In particular, with the artificial satellite 1, the coordinate axes are set in the direction from the center of mass of the artificial satellite 1 to the center of mass of the target object 2 when the artificial satellite 1 is closest to the target object, and in the direction of travel of the artificial satellite 1 at that time, so that it is possible to control the orientation of the camera 3 with a relatively simple calculation.

[0159] The motor 6 rotates around the elevation axis (Y axis) and the azimuth axis (Z axis), and is disposed so that the rotation around the elevation axis also rotates the azimuth axis. The direction of the center of the field of view of the camera 3 changes according to the rotation of the motor 6 around the elevation axis and the rotation of the motor 6 around the azimuth axis. The control system 5 uses a state transition model that indicates the change in the deviation between the direction of the object 2 as seen from the camera 3 and the direction of the center of the field of view of the camera 3, based on the amount of rotation of the motor 6, the attitude rate of the satellite 1, and the relative orbital motion of the object 2, for each of the azimuth and elevation directions. According to the artificial satellite 1, the azimuth axis and elevation axis are aligned with the coordinate axes, so that the orientation of the camera 3 can be controlled with relatively simple calculations.

[0160] In addition, the control system 5 uses an evaluation function value based on the sum of the magnitude of the deviation between the direction of the center of the field of view of the camera 3 and the direction of the object 2 as seen from the camera 3 for each time step included in the time from the start to the end of control of the motor 6 based on the electromagnetic waves acquired by the camera 3. It is expected that the satellite 1 can move the direction of the center of the field of view of the camera 3 closer to the direction of the object 2 as seen from the camera 3 throughout the period of control of the motor 6 .

[0161] Furthermore, the control system 5 uses an evaluation function in which the part indicating the amount of rotation of the motor 6 per time step is weighted based on the control response and control accuracy of the motor 6. According to the artificial satellite 1, the control response and control accuracy of the motor 6 can be reflected in the control of the orientation of the camera 3, and in this respect, it is expected that the orientation of the camera 3 can be controlled with high precision.

[0162] In addition, the control system 5 uses an evaluation function in which the part indicating the magnitude of the deviation between the direction of the center of the field of view of the camera 3 and the direction of the object 2 as seen from the camera 3 at the last time step among the time steps included in the time from the start to the end of control of the motor 6 based on the electromagnetic waves acquired by the camera 3 is weighted by a weight calculated by solving a Riccati algebraic equation. In this regard, it is expected that the satellite 1 will be able to stably control the orientation of the camera 3.

[0163] Second Embodiment 11 is a diagram showing an example of the operating environment of a satellite according to the second embodiment. In the second embodiment, a case will be described in which both the satellite 1 and the target object 2 move under the influence of gravity of the Earth 11. In other respects, the second embodiment is similar to the first embodiment.

[0164] The second embodiment will also be described with reference to Figures 2 and 3. The configuration of the satellite 1 according to the second embodiment is the same as that of the first embodiment described with reference to Figure 2. In the second embodiment, the configuration of the control system 5 and the data flow when calculating the command value for the rotation angle of the motor 6 are the same as those of the first embodiment described with reference to Figure 3. As in the first embodiment, the artificial satellite 1 is equipped with a camera 3, and the pointing direction of the camera 3 is controlled in the azimuth direction and elevation direction to capture an image of the target object 2.

[0165] As in Figure 1, the axis XAZ in Figure 11 indicates the azimuth axis, and the axis XEL indicates the elevation axis. An arrow R611 indicates the direction of the target object 2 as seen from the artificial satellite 1 in the example of Fig. 11. An arrow R621 indicates the direction of travel of the artificial satellite 1 in the example of Fig. 11. An arrow R622 indicates the direction of travel of the target object 2 in the example of Fig. 11.

[0166] The relative orbital motion model in the second embodiment will be described. Fig. 12 is a diagram showing an example of the definition of a coordinate system in the second embodiment. In the example of Fig. 12, the center of mass of the satellite 1 is set as the origin, and the direction from the center of mass of the Earth 11 to the center of mass of the satellite 1 is set as the positive direction of the X axis. The direction of travel of the satellite 1 is set as the positive direction of the Y axis. The Z axis is set as a direction perpendicular to both the X axis and the Y axis. In the example of Fig. 12, the positive direction of the Z axis is defined so that the coordinate system is a right-handed system, but this is not limiting.

[0167] In the second embodiment, the coordinate system illustrated in FIG. 12 is also referred to as the main coordinate system. In the second embodiment, the time is set as the sampling time T s The time step k (the kth time step) is also expressed as time k, where k is an integer.

[0168] The relative position of the object 2 in this coordinate system is represented by a vector r, which is also written as r(x, y, z) or (x, y, z). The relative velocity of the object 2 is represented by a vector v, which is written as v(vx ,v y ,v z ) or (v x ,v y ,v z ) is also written as In the second embodiment, the distance from the center of mass of the Earth 11 to the center of mass of the artificial satellite 1 is set to R0. The relative position and velocity of the object 2 with respect to the artificial satellite 1 at time k are (x k ,y k ,z k ,v x,k ,v y,k ,v z,k ), the relative acceleration of object 2 at time k (a x,k ,a y,k ,a z,k ) X coordinate component a x,k is expressed as equation (47) from Hill's equation.

[0169]

number

[0170] n is expressed as in equation (48).

[0171]

number

[0172] μ0 is expressed as in equation (49).

[0173]

number

[0174] G is the gravitational constant. M is the mass of the Earth. The relative acceleration of object 2 at time k (a x,k ,a y,k ,a z,k ) Y coordinate component a y,k is expressed as equation (50).

[0175]

number

[0176] The relative acceleration of object 2 at time k (a x,k ,a y,k ,a z,k ) Z coordinate component a z,k is expressed as in equation (51).

[0177]

number

[0178] The relative position of object 2 at time k+1 (x k+1 ,y k+1 ,z k+1 )'s X coordinate component x k+1 is expressed as in equation (52).

[0179]

number

[0180] The relative position of object 2 at time k+1 (x k+1 ,y k+1 ,z k+1 ) Y coordinate component y k+1 is expressed as in equation (53).

[0181]

number

[0182] The relative position of object 2 at time k+1 (x k+1 ,y k+1 ,z k+1 ) Z coordinate component z k+1 is expressed as in equation (54).

[0183]

number

[0184] The relative velocity of object 2 at time k+1 (v x,k+1 ,v y,k+1 ,v z,k+1 )'s X coordinate component v x,k+1 is expressed as equation (55).

[0185]

number

[0186] The relative velocity of object 2 at time k+1 (v x,k+1 ,v y,k+1 ,v z,k+1 ) Y coordinate component v y,k+1 is expressed as in equation (56).

[0187]

number

[0188] The relative velocity of object 2 at time k+1 (v x,k+1 ,v y,k+1 ,v z,k+1 ) Z coordinate component v z,k+1 is expressed as equation (57).

[0189]

number

[0190] Equations (52) to (57) are expressed as equation (58) based on equations (47), (50) and (51).

[0191]

number

[0192] Equation (58) corresponds to an example of the relative orbital motion model in the second embodiment. Hereinafter, as in the first embodiment, Δθ AZ (t0+Hw), , Δθ AZ(t0+Hp) and Δθ EL (t0+Hw), , Δθ EL (t0+Hp). The control system 5 calculates Δθ AZ (t0+Hw), , Δθ AZ (t0+Hp) and Δθ EL (t0+Hw), , Δθ EL The motor 6 can be controlled based on (t0+Hp).

[0193] As described above, both the target object 2 and the artificial satellite 1 are affected by the gravity of a celestial body other than the target object 2. The control system 5 uses a relative orbital motion model that indicates that both the object 2 and the satellite 1 are affected by the gravity of a celestial body other than the object 2 in a three-dimensional Cartesian coordinate system with the center of mass of the satellite 1 as the origin, the X axis in the direction from the center of mass of the celestial body to the center of mass of the satellite 1, the Y axis in the direction of the satellite's movement, and the Z axis in a direction perpendicular to these two directions. With the artificial satellite 1, the orientation of the camera 3 can be controlled in an environment where both the target object 2 and the artificial satellite 1 are affected by the gravity of a celestial body other than the target object 2. In particular, with the artificial satellite 1, the coordinate axes are set in the direction from the center of mass of the celestial body to the center of mass of the artificial satellite 1 and in the direction of travel of the artificial satellite, so that the orientation of the camera 3 can be controlled with relatively simple calculations.

[0194] Third Embodiment FIG. 13 is a diagram illustrating an example of an operating environment of the satellite according to the third embodiment. In the third embodiment, a case will be described in which the mass of the target object 12 is large and the satellite 1 moves under the influence of the target object 12. In other respects, the third embodiment is similar to the first embodiment. Examples of a case in which the mass of the target object 12 is large include, but are not limited to, a case in which the target object 12 is a satellite, a planet, or a star.

[0195] The third embodiment will also be described with reference to Figures 2 and 3. The configuration of the satellite 1 according to the third embodiment is the same as that of the first embodiment described with reference to Figure 2. In the third embodiment, the configuration of the control system 5 and the data flow when calculating the command value for the rotation angle of the motor 6 are the same as those of the first embodiment described with reference to Figure 3. As in the first embodiment, the artificial satellite 1 is equipped with a camera 3, and the pointing direction of the camera 3 is controlled in the azimuth direction and elevation direction to capture an image of the target object 12.

[0196] A relative orbital motion model in the third embodiment will be described. As a coordinate system in the third embodiment, the same coordinate system as in the first embodiment described with reference to Fig. 4 can be used. In the third embodiment, this coordinate system is also referred to as the main coordinate system. In the third embodiment, the time is set as the sampling time T s The time step k (the kth time step) is also expressed as time k, where k is an integer.

[0197] The relative position of the object 12 in this coordinate system is represented by a vector r, which is also written as r(x, y, z) or (x, y, z). The relative velocity of the object 12 is represented by a vector v, which is also written as v(v x ,v y ,v z ) or (v x ,v y ,v z ) is also written as In the third embodiment, the distance from the center of mass of the satellite 1 to the center of mass of the object 12 when the satellite 1 is closest to the object 12 is defined as R0. The relative position and velocity of the object 12 with respect to the satellite 1 at time k are defined as (x k ,y k ,z k ,v x,k ,v y,k ,v z,k ), the relative acceleration (a x,k ,a y,k ,a z,k ) X coordinate component a x,kis expressed as equation (59).

[0198]

number

[0199] n is the same as shown in equation (48). The relative acceleration (a x,k ,a y,k ,a z,k ) Y coordinate component a y,k is expressed as in equation (60).

[0200]

number

[0201] The relative acceleration (a x,k ,a y,k ,a z,k ) Z coordinate component a z,k is the same as shown in equation (51). n is the same as shown in equation (48). The relative position (x k+1 ,y k+1 ,z k+1 )'s X coordinate component x k+1 , Y coordinate component y k+1 , Z coordinate component z k+1 are similar to those shown in equations (52), (53), and (54). The relative velocity (v x,k+1 ,v y,k+1 ,v z,k+1 )'s X coordinate component v x,k+1 , Y coordinate component v y,k+1 , Z coordinate component v z,k+1 are similar to those shown in equations (55), (56), and (57).

[0202] Equations (52) to (57) are expressed as equation (61) based on equations (59), (60) and (51).

[0203]

number

[0204] Equation (61) corresponds to an example of the relative orbital motion model in the third embodiment. Hereinafter, as in the first embodiment, Δθ AZ (t0+Hw), , Δθ AZ (t0+Hp) and Δθ EL (t0+Hw), , Δθ EL (t0+Hp). The control system 5 calculates Δθ AZ (t0+Hw), , Δθ AZ (t0+Hp) and Δθ EL (t0+Hw), , Δθ EL Based on (t0+Hp), the motor 6 can be controlled.

[0205] As described above, the satellite 1 is affected by the gravity of the target object 12. The control system 5 uses a relative orbital motion model that indicates that the satellite 1 is affected by the gravity of the object 12 in a three-dimensional Cartesian coordinate system with the center of mass of the satellite 1 as the origin, the X axis in the direction from the center of mass of the satellite 1 to the center of mass of the object 12 at the time when the satellite 1 and the object 12 are closest to each other, the Y axis in the direction of the satellite 1's movement at that time, and the Z axis in a direction perpendicular to these two directions. With the artificial satellite 1, it is possible to control the orientation of the camera 3 in an environment where the artificial satellite 1 is affected by the gravity of the target object 12. In particular, with the artificial satellite 1, the coordinate axes are set in the direction from the center of mass of the artificial satellite 1 to the center of mass of the target object 12 when the artificial satellite 1 and the target object 12 are closest to each other, and in the direction of travel of the artificial satellite 1, so that it is possible to control the orientation of the camera 3 with a relatively simple calculation.

[0206] <Modifications of the First, Second, or Third Embodiments> In the first, second, and third embodiments, examples have been shown in which an image of an object is observed by the camera 3, but the object observed by the satellite 1 is not limited to visible light from the object. For example, the object may be electromagnetic waves in a broad sense, such as microwaves, infrared rays, ultraviolet rays, X-rays, or gamma rays. Furthermore, in addition to or instead of the camera 3, the satellite 1 may be equipped with an electromagnetic wave detection sensor, such as an antenna, a photodiode, or a scintillation detector, that is responsive to the frequency of the electromagnetic waves of the object to be observed.

[0207] <Fourth embodiment> 14 is a diagram showing an example of an operating environment of an artificial satellite according to the fourth embodiment. In the fourth embodiment, an example will be described in which two artificial satellites moving under the influence of gravity of the Earth 11 communicate with each other using microwaves. In the example of FIG. 14 , the artificial satellite 1 transmits microwaves to the artificial satellite 13. To do this, the artificial satellite 1 includes a microwave transmitter 15 in addition to the components of the first to third embodiments. The microwave transmitter 15 is provided so that its pointing direction is the same as that of the camera 3. The artificial satellite 1 controls the pointing direction of the camera 3 in the azimuth direction and elevation direction so that the artificial satellite 13 is captured at or near the center of the field of view of the camera 3. As a result, the pointing direction of the microwave transmitter 15 also faces the artificial satellite 13, and the artificial satellite 1 can transmit microwaves toward the artificial satellite 13.

[0208] Instead of capturing an image of an object, the satellite 1 according to the fourth embodiment captures an image of the satellite 13 with the camera 3 in order to adjust the orientation of the microwave transmitter 15, and transmits microwaves toward the satellite 13. In other respects, the satellite 1 according to the fourth embodiment is the same as that of the second embodiment. The satellite 13 is equipped with a microwave receiver 16 and receives microwaves transmitted by the microwave transmitter 15 of the satellite 1 .

[0209] 11, the axis XAZ indicates the azimuth axis, and the axis XEL indicates the elevation axis. An arrow R811 indicates the direction of the artificial satellite 13 as seen from the artificial satellite 1 in the example of Fig. 14. An arrow R821 indicates the direction of travel of the artificial satellite 1 in the example of Fig. 14. An arrow R822 indicates the direction of travel of the artificial satellite 13 in the example of Fig. 14.

[0210] Fig. 15 is a diagram showing an example of the configuration of a satellite 1 according to the fourth embodiment. As described above, the satellite 1 according to the fourth embodiment shown in Fig. 15 further includes a microwave transmitter 15 in addition to the configuration of the satellite 1 according to the first to third embodiments shown in Fig. 2. The microwave transmitter 15 is provided so that its pointing direction is the same as that of the camera 3, and the motor 6 rotates the camera 3 and the microwave transmitter 15 in the azimuth direction and the elevation direction. 15, an artificial satellite 13 is shown in place of the target object 2 in FIG. 2. The artificial satellite 13 includes a microwave receiver 16, and receives microwaves transmitted by the microwave transmitter 15 of the artificial satellite 1.

[0211] In other respects, the configuration of FIG. 15 is the same as that of FIG. The microwave transmitter 15 is an example of a transmitting means. The combination of the camera 3, the object direction calculation system 4, the control system 5, the motor 6, and the microwave transmitter 15 is an example of an acquisition and tracking system.

[0212] In the fourth embodiment, the configuration of the control system 5 and the data flow when calculating the command value for the rotation angle of the motor 6 are the same as those in the first to third embodiments described with reference to Figure 3. The relative orbital motion model in the fourth embodiment can be the same as that in the second embodiment. For example, in the fourth embodiment, the control system 5 can use the relative orbital motion model shown in equation (58). Hereinafter, as in the first embodiment, Δθ AZ (t0+Hw), , Δθ AZ (t0+Hp) and Δθ EL (t0+Hw), , Δθ EL(t0+Hp). The control system 5 calculates Δθ AZ (t0+Hw), , Δθ AZ (t0+Hp) and Δθ EL (t0+Hw), , Δθ EL The motor 6 can be controlled based on (t0+Hp).

[0213] As described above, microwave transmitter 15 is installed so as to face in the same direction as camera 3, and transmits electromagnetic waves to artificial satellite 13, which is an example of a target object. The artificial satellite 1 can communicate with the artificial satellite 13 .

[0214] <Modification of the Fourth Embodiment> In the fourth embodiment, the case where the artificial satellite 1 and the artificial satellite 13 move under the influence of gravity of the Earth 11 has been described as an example, but similar to the first embodiment, the artificial satellite 13 may move at a constant speed in a straight line relative to the artificial satellite 1. In this case, the same relative orbital motion model as in the first embodiment can be used, and similar to the first embodiment, Δθ AZ (t0+Hw), , Δθ AZ (t0+Hp) and Δθ EL (t0+Hw), , Δθ EL (t0+Hp). The control system 5 calculates Δθ AZ (t0+Hw), , Δθ AZ (t0+Hp) and Δθ EL (t0+Hw), , Δθ EL The motor 6 can be controlled based on (t0+Hp).

[0215] Furthermore, in the fourth embodiment, an example has been shown in which an image of the satellite 13 is observed by the camera 3, but the object of observation by the satellite 13 is not limited to visible light from the satellite 13. For example, the object of observation may be electromagnetic waves in a broad sense, such as microwaves, infrared rays, ultraviolet rays, X-rays, or gamma rays. Furthermore, in addition to or instead of the camera 3, the satellite 1 may be provided with an electromagnetic wave detection sensor, such as an antenna, a photodiode, or a scintillation detector, that is responsive to the frequency of the electromagnetic waves to be observed.

[0216] The analysis results of the pointing accuracy of the artificial satellite 1 according to the first embodiment will be described. Figure 16 is a diagram showing the orbit and attitude conditions of the artificial satellite 1 used in the analysis. In the analysis, the relative speed of the target object 2 to the artificial satellite 1 was set to 35 kilometers per second (km / s), and the closest distance between the target object 2 and the artificial satellite 1 was set to 510 kilometers (km). The orbital motion of the target object 2 relative to the artificial satellite 1 was set to uniform linear motion. The attitude of the artificial satellite 1 was set to inertial motion due to a fixed position.

[0217] Figure 17 is a diagram showing the settings of signal processing time within the satellite 1 in the analysis. In the analysis, the processing time in the object direction calculation system 4 was set to 0.15 seconds, and the processing time in the control system 5 was set to 0.5 seconds. Furthermore, each part of the satellite 1 was configured as a separate device, and the communication time between each part was set to 0.05 seconds. The Hw time in Figure 10, which is the sum of the processing time in the object direction calculation system 4, the processing time in the control system 5, and the communication time, is 0.75 seconds. 10, the control period is set to 1 second, and the camera 3 captures an image of the object 2 every second.

[0218] Figure 18 shows the error settings used in the analysis. In the analysis, the trajectory error in the X-axis direction was set to 10 kilometers, and the trajectory error in the Y-axis direction was set to 3 seconds (105 kilometers). Furthermore, the noise in the image of the object 2 acquired by the camera 3 was set to within 0.003 degrees in the 3σ range in terms of angle.

[0219] 19 is a diagram showing the setting of the image center error of the object 2 captured by the camera 3 in the analysis. The horizontal axis of the graph in FIG. 19 represents time, and the vertical axis represents the angle of blur in the image captured by the camera 3. Assuming that there will be a discrepancy between the control of the camera 3 by the motor 6 and the actual orientation of the camera 3, the shake angle shown in FIG. 19 was added to the angle calculated from the image of the camera 3. For comparison, the camera pointing accuracy was analyzed not only for the satellite 1 according to the first embodiment, but also for the feedback method and the combination of the feedback method and the feedforward method.

[0220] Here, the feedback method and the feedforward method will be explained. One method of observing targets such as asteroids using artificial satellites is for the satellite to fly by the target and take photographs of the target with a camera during this time. For example, by taking and analyzing images of the surface of the parent body of a meteor shower that collided with the Earth during its formation, it is possible to elucidate the origin of life on Earth.

[0221] When photographing an object during a flyby observation in space exploration, the probe (artificial satellite) and the object are moving at high speed and the observation time is short, so a precision capture and tracking system technology is required that can capture light from the object with high accuracy and track it in accordance with the relative movement of the object. The observation targets of this precision acquisition and tracking system technology are not limited to asteroids, but can also be celestial bodies with high gravity, malfunctioning satellites and space debris that move under the influence of the Earth's gravity. This will contribute not only to space science but also to the field of national security. Furthermore, if it is possible to not only acquire and track light from the target but also to transmit electromagnetic waves to the target and establish a communication link, it will also be useful in the field of communications.

[0222] In precision acquisition and tracking system technology, the motor angle control method for pointing the camera's field of view center (photography direction) toward the observed object can be either the feedback method, the feedforward method, or a combination of the feedforward and feedback methods. With the feedback method, the motor is operated in accordance with the center direction of the observed object obtained from the image processing system. With the feedforward method, the satellite stores a profile of angle change in the direction of the observed object in advance, and operates the motor in accordance with that profile.

[0223] However, there is a possibility that sufficient observation accuracy cannot be obtained by the feedback method, the feedforward method, or a combination of the feedforward method and the feedback method. With the feedback method, the length of time between when the camera captures an image of the observed object and when the motor starts operating is affected by the processing time in the image processing system, the processing time in the control system to calculate the motor rotation amount, and the communication time between devices. These processing and communication times are long due to the constraints of the onboard capability of spacecraft, which require high reliability, and can take several seconds in some cases. During this time, the observation satellite and the observed object are moving at high speeds of several km / s (kilometers per second). Therefore, with the feedback method, which operates the motor in accordance with the movement of the observed object, it is thought that control cannot keep up, resulting in a deterioration in observation accuracy.

[0224] On the other hand, the feedforward method uses a pre-stored angle change profile of the object being observed, which may result in a prediction error between the angle change profile and the actual profile, resulting in a deterioration in the accuracy of the observed position. In contrast, analysis results showed that the acquisition and tracking method for the satellite 1 according to the first embodiment can achieve higher pointing accuracy than when using the feedback method or when using a combination of the feedback method and the feedforward method.

[0225] Fig. 20 is a diagram showing the analysis results of the pointing accuracy of the satellite 1 according to the first embodiment. The horizontal axis of the graph in Fig. 20 represents time. The timing when the satellite 1 comes closest to the target object 2 is set to 0 seconds. The vertical axis represents the error angle between the pointing direction of the camera 3 and the direction of the target object 2. Line L11 shows the pointing accuracy of the camera 3 when the artificial satellite 1 according to the first embodiment is used. Line L12 shows the pointing accuracy of the camera when the feedback method is used. Line L13 shows the pointing accuracy of the camera when the feedback method and the feedforward method are combined. In the example of Figure 20, it can be seen that the pointing accuracy of the satellite 1 according to the first embodiment is improved by more than one-tenth compared to the pointing accuracy achieved by the feedback method or a combination of the feedback method and the feedforward method.

[0226] Fifth Embodiment Fig. 21 is a diagram showing an example of the configuration of an acquisition and tracking system according to the fifth embodiment. In the configuration shown in Fig. 21, an acquisition and tracking system 610 includes an electromagnetic wave acquisition unit 611, a drive unit 612, a direction calculation unit 613, and a control unit 614. With this configuration, the electromagnetic wave acquisition unit 611 is mounted on a satellite and acquires electromagnetic waves from an object. The drive unit 612 changes the orientation direction of the electromagnetic wave acquisition unit 611 by rotating the electromagnetic wave acquisition unit 611. The direction calculation unit 613 calculates the direction of the object from the electromagnetic waves acquired by the electromagnetic wave acquisition unit 611. The control unit 614 calculates a rotation angle of the drive unit 612 so as to minimize the magnitude of the deviation indicated by an evaluation function value of the magnitude of the deviation between the direction of the center of the field of view of the electromagnetic wave acquisition unit 611 and the direction of the object as seen from the electromagnetic wave acquisition unit 611, based on a relative orbital motion model of the object with respect to the satellite, the attitude rate of the satellite, and a state transition model indicating the fluctuation of the direction of the object within the field of view of the electromagnetic wave acquisition unit 611 due to the drive unit 612 rotating the electromagnetic wave acquisition unit 611, and operates the drive unit 612 at the calculated rotation angle. The electromagnetic wave acquiring unit 611 is an example of an electromagnetic wave acquiring means. The driving unit 612 is an example of a driving means. The direction calculating unit 613 is an example of a direction calculating means. The control unit 614 is an example of a control means.

[0227] The acquisition and tracking system 610 can detect the direction of the target object from the satellite and control the orientation of the electromagnetic wave acquiring unit 611. In particular, the acquisition and tracking system 610 can control the orientation of the electromagnetic wave acquiring unit 611 from the satellite, so that the orientation of the electromagnetic wave acquiring unit 611 can be controlled even when real-time control cannot be performed from the ground due to communication delays or the like. Furthermore, the acquisition and tracking system 610 can reflect the relative orbital motion of the target object and the attitude data of the satellite in the control of the orientation of the electromagnetic wave acquiring unit 611, and in this respect, the orientation of the electromagnetic wave acquiring unit 611 can be controlled with high precision.

[0228] Sixth Embodiment Fig. 22 is a diagram showing an example of the configuration of a satellite according to the sixth embodiment. In the configuration shown in Fig. 22, a satellite 620 includes an electromagnetic wave acquiring unit 621, a driving unit 622, a direction calculating unit 623, and a control unit 624. In this configuration, the electromagnetic wave acquisition unit 621 is mounted on a satellite and acquires electromagnetic waves from an object. The drive unit 622 changes the orientation direction of the electromagnetic wave acquisition unit 621 by rotating the electromagnetic wave acquisition unit 621. The direction calculation unit 623 calculates the direction of the object from the electromagnetic waves acquired by the electromagnetic wave acquisition unit 621. The control unit 624 calculates a rotation angle of the drive unit 622 so as to minimize the magnitude of the deviation indicated by an evaluation function value of the magnitude of the deviation between the direction of the center of the field of view of the electromagnetic wave acquisition unit 621 and the direction of the object as seen from the electromagnetic wave acquisition unit 621, based on a relative orbital motion model of the object with respect to the satellite, the attitude rate of the satellite, and a state transition model indicating the fluctuation of the direction of the object within the field of view of the electromagnetic wave acquisition unit 621 due to the drive unit 622 rotating the electromagnetic wave acquisition unit 621, and operates the drive unit 622 at the calculated rotation angle. The electromagnetic wave acquiring unit 621 corresponds to an example of electromagnetic wave acquiring means. The driving unit 622 corresponds to an example of driving means. The direction calculating unit 623 corresponds to an example of direction calculating means. The control unit 624 corresponds to an example of control means.

[0229] The artificial satellite 620 can detect the direction of the target object from the artificial satellite 620 and control the orientation of the electromagnetic wave acquiring unit 621. In particular, the artificial satellite 620 can control the orientation of the electromagnetic wave acquiring unit 621, so that even when real-time control cannot be performed from the ground due to communication delays or the like, the orientation of the electromagnetic wave acquiring unit 621 can be controlled. Furthermore, the artificial satellite 620 can reflect the relative orbital motion of the target object and attitude data of the artificial satellite 620 in the control of the orientation of the electromagnetic wave acquiring unit 621, and in this respect, the orientation of the electromagnetic wave acquiring unit 621 can be controlled with high precision.

[0230] Seventh Embodiment 23 is a diagram showing an example of the configuration of a control device according to the seventh embodiment. In the configuration shown in FIG. With this configuration, the control unit 631 calculates the rotation angle of the drive unit so that the magnitude of the deviation indicated by the evaluation function value of the magnitude of the deviation between the center direction of the field of view of the electromagnetic wave acquisition unit and the direction of the object as seen from the electromagnetic wave acquisition unit is as small as possible, based on a relative orbital motion model of the object with respect to the satellite, the attitude rate of the satellite, and a state transition model showing the fluctuation of the direction of the object within the field of view of the electromagnetic wave acquisition unit due to the drive unit rotating the electromagnetic wave acquisition unit that acquires electromagnetic waves from the object, and operates the drive unit at the calculated rotation angle. The control unit 631 corresponds to an example of a control means.

[0231] The control device 630 can detect the direction of the target object from the satellite and control the orientation of the electromagnetic wave acquisition unit. In particular, the control device 630 can control the orientation of the electromagnetic wave acquisition unit from the satellite, so it can control the orientation of the electromagnetic wave acquisition unit even when real-time control is not possible from the ground due to communication delays, etc. Furthermore, the control device 630 can reflect the relative orbital motion of the target object and the attitude data of the satellite in the control of the orientation of the electromagnetic wave acquisition unit, and in this respect, it is possible to control the orientation of the electromagnetic wave acquisition unit with high precision.

[0232] Eighth Embodiment FIG. 24 is a diagram showing an example of a processing procedure in the acquisition and tracking method according to the eighth embodiment. The acquisition and tracking method shown in FIG. 24 includes acquiring electromagnetic waves (step S611), calculating a direction (step S612), and performing control (step S613). In acquiring electromagnetic waves (step S611), the computer acquires electromagnetic waves from the target object via an electromagnetic wave acquisition unit mounted on the satellite. In calculating the direction (step S612), the computer calculates the direction of the object from the obtained electromagnetic waves. In performing control (step S613), the computer calculates the rotation angle of the drive unit so that the magnitude of the deviation indicated by the evaluation function value of the magnitude of the deviation between the center direction of the field of view of the electromagnetic wave acquisition unit and the direction of the object as seen from the electromagnetic wave acquisition unit is as small as possible, based on the relative orbital motion model of the object with respect to the satellite, the attitude rate of the satellite, and a state transition model showing the change in the direction of the object within the field of view of the electromagnetic wave acquisition unit due to the drive unit rotating the electromagnetic wave acquisition unit, and operates the drive unit at the calculated rotation angle.

[0233] According to the acquisition and tracking method shown in Fig. 24, the direction of the target object can be detected from the satellite and the orientation of the electromagnetic wave acquiring unit can be controlled. In particular, according to the acquisition and tracking method shown in Fig. 24, the orientation of the electromagnetic wave acquiring unit can be controlled by the satellite, so that the orientation of the electromagnetic wave acquiring unit can be controlled even when real-time control cannot be performed from the ground due to communication delays, etc. Furthermore, according to the acquisition and tracking method shown in Fig. 24, the relative orbital motion of the target object and the attitude data of the satellite can be reflected in the control of the orientation of the electromagnetic wave acquiring unit, and in this respect, the orientation of the electromagnetic wave acquiring unit can be controlled with high precision.

[0234] FIG. 25 is a schematic block diagram illustrating the configuration of a computer according to at least one embodiment. In the configuration shown in FIG. 25, a computer 700 includes a CPU 710, a main memory device 720, an auxiliary memory device 730, an interface 740, and a non-volatile recording medium 750.

[0235] One or more of the above-described object direction calculation system 4, control system 5, direction calculation unit 613, control unit 614, direction calculation unit 623, control unit 624, and control unit 631, or a part thereof, may be implemented in the computer 700. In this case, the operation of each of the above-described units is stored in the form of a program in the auxiliary storage device 730. The CPU 710 reads the program from the auxiliary storage device 730, loads it into the main storage device 720, and executes the above-described processing in accordance with the program.

[0236] Furthermore, the CPU 710 allocates a storage area in the main memory device 720 for each unit to perform processing in accordance with the program. Communication between each unit and other devices is achieved by the interface 740 having a communication function and performing communication under the control of the CPU 710. Interaction between each unit and the user is achieved by the interface 740 having an input / output device, performing output such as displaying various images under the control of the CPU 710, and accepting user operations.

[0237] One or more of the above-described programs may be recorded on nonvolatile recording medium 750. In this case, interface 740 may read the programs from nonvolatile recording medium 750. CPU 710 may then directly execute the programs read by interface 740, or may temporarily store the programs in main storage device 720 or auxiliary storage device 730 and then execute them.

[0238] Note that a program for executing all or part of the processing performed by the object direction calculation system 4, the control system 5, the direction calculation unit 613, the control unit 614, the direction calculation unit 623, the control unit 624, and the control unit 631 may be recorded on a computer-readable recording medium, and the program recorded on this recording medium may be read into a computer system and executed to perform the processing of each unit. Note that the term "computer system" here includes hardware such as an OS and peripheral devices. Furthermore, "computer-readable recording media" refers to portable media such as flexible disks, optical magnetic disks, ROMs (Read Only Memory), and CD-ROMs (Compact Disc Read Only Memory), as well as storage devices such as hard disks built into computer systems. The program may be one that realizes part of the aforementioned functions, or may be one that can realize the aforementioned functions in combination with a program already stored in the computer system.

[0239] Although an embodiment of the present invention has been described above in detail with reference to the drawings, the specific configuration is not limited to this embodiment, and includes designs within the scope of the gist of the present invention.

[0240] A part or all of the above-described embodiments can be described as, but not limited to, the following supplementary notes.

[0241] (Appendix 1) an electromagnetic wave acquiring means mounted on the satellite and configured to acquire electromagnetic waves from a target; a driving means for rotating the electromagnetic wave acquiring means to change the orientation of the electromagnetic wave acquiring means; a direction calculation means for calculating a direction of the object from the electromagnetic waves acquired by the electromagnetic wave acquisition means; a control means for calculating a rotation angle of the drive means so as to minimize the magnitude of the deviation indicated by an evaluation function value of the magnitude of the deviation between the direction of the center of the field of view of the electromagnetic wave acquirer and the direction of the object as seen from the electromagnetic wave acquirer, based on a relative orbital motion model of the object with respect to the satellite, an attitude rate of the satellite, and a state transition model indicating a change in the direction of the object within the field of view of the electromagnetic wave acquirer caused by the drive means rotating the electromagnetic wave acquirer; and for operating the drive means at the calculated rotation angle; An acquisition and tracking system comprising:

[0242] (Appendix 2) a transmitting means that is installed so as to face the same direction as the electromagnetic wave acquiring means and transmits electromagnetic waves to the target object; 2. The acquisition and tracking system of claim 1, further comprising:

[0243] (Appendix 3) Both the target object and the artificial satellite are affected by the gravity of a celestial body other than the target object, the control means uses a relative orbital motion model that indicates that both the object and the artificial satellite are affected by the gravity of a celestial body other than the object in a three-dimensional orthogonal coordinate system having the center of mass of the artificial satellite as the origin, a first axis in the direction from the center of mass of the celestial body to the center of mass of the artificial satellite, a second axis in the direction of the satellite's movement, and a third axis in a direction perpendicular to these two directions; 10. The acquisition and tracking system of claim 1 or 2.

[0244] (Appendix 4) The satellite is subjected to the gravitational influence of the object, The control means uses a relative orbital motion model that indicates that the artificial satellite is affected by the gravity of the object in a three-dimensional orthogonal coordinate system having the center of mass of the artificial satellite as the origin, a first axis in the direction from the center of mass of the artificial satellite to the center of mass of the object at the time when the artificial satellite and the object are closest to each other, a second axis in the direction of the satellite's movement at that time, and a third axis in a direction perpendicular to these two directions. 10. The acquisition and tracking system of claim 1 or 2.

[0245] (Appendix 5) Both the object and the satellite undergo uniform linear motion due to inertia, The control means uses a relative orbital motion model that indicates that both the object and the artificial satellite are moving at a uniform velocity in a straight line due to inertia in a three-dimensional orthogonal coordinate system having the center of mass of the artificial satellite as the origin, a first axis in the direction from the center of mass of the artificial satellite to the center of mass of the object at the time when the artificial satellite comes closest to the object, a second axis in the direction of the satellite's movement at that time, and a third axis in a direction perpendicular to these two directions. 10. The acquisition and tracking system of claim 1 or 2.

[0246] (Appendix 6) the driving means rotates around the elevation axis, the second axis, and the third axis, and the azimuth axis, and is disposed so that the rotation around the elevation axis also rotates the azimuth axis; the electromagnetic wave acquiring means changes a direction of a center of a field of view of the electromagnetic wave acquiring means in accordance with the rotation of the driving means around the elevation axis and the rotation of the driving means around the azimuth axis, the control means uses a state transition model that indicates a change in the deviation between the direction of the object as seen from the electromagnetic wave acquiring means and the direction of the center of the field of view of the electromagnetic wave acquiring means, based on the rotation amount of the driving means, the attitude rate of the satellite, and the relative orbital motion of the object, for each of the azimuth direction and the elevation direction; 6. The acquisition and tracking system of any one of claims 3 to 5.

[0247] (Appendix 7) the control means uses an evaluation function value based on the sum of magnitudes of deviations between the direction of the center of the field of view of the electromagnetic wave acquiring means and the direction of the object as seen from the electromagnetic wave acquiring means, for each time step included in the time from the start to the end of control of the drive means based on the electromagnetic waves acquired by the electromagnetic wave acquiring means; 7. The acquisition and tracking system of any one of claims 1 to 6.

[0248] (Appendix 8) the control means uses an evaluation function in which a portion indicating the rotation amount of the drive means per time step is weighted based on the control responsiveness and control accuracy of the drive means. 8. The acquisition and tracking system of claim 7.

[0249] (Appendix 9) the control means uses an evaluation function in which a portion indicating the magnitude of deviation between the direction of the center of the field of view of the electromagnetic wave acquiring means and the direction of the object as seen from the electromagnetic wave acquiring means at the last time step among the time steps included in the time from the start to the end of control of the drive means based on the electromagnetic waves acquired by the electromagnetic wave acquiring means is weighted by a weight calculated by solving a Riccati algebraic equation. 10. An acquisition and tracking system according to claim 7 or 8.

[0250] (Appendix 10) an electromagnetic wave acquiring means for acquiring an electromagnetic wave from an object; a driving means for rotating the electromagnetic wave acquiring means to change the orientation of the electromagnetic wave acquiring means; a direction calculation means for calculating a direction of the object from the electromagnetic waves acquired by the electromagnetic wave acquisition means; a control means for calculating a rotation angle of the drive means so as to minimize the magnitude of the deviation indicated by an evaluation function value of the magnitude of the deviation between the direction of the center of the field of view of the electromagnetic wave acquirer and the direction of the object as seen from the electromagnetic wave acquirer, based on a relative orbital motion model of the object with respect to the satellite, an attitude rate of the satellite, and a state transition model indicating a change in the direction of the object within the field of view of the electromagnetic wave acquirer caused by the drive means rotating the electromagnetic wave acquirer; and for operating the drive means at the calculated rotation angle; An artificial satellite equipped with

[0251] (Appendix 11) a control means for calculating a rotation angle of the drive means based on a relative orbital motion model of the object with respect to the satellite, an attitude rate of the satellite, and a state transition model showing a change in the direction of the object within the field of view of the electromagnetic wave acquirer caused by a drive means rotating the electromagnetic wave acquirer that acquires electromagnetic waves from the object, so as to minimize the magnitude of the deviation indicated by an evaluation function value of the magnitude of the deviation between the direction of the center of the field of view of the electromagnetic wave acquirer and the direction of the object as seen from the electromagnetic wave acquirer, and for operating the drive means at the calculated rotation angle; A control device comprising:

[0252] (Appendix 12) The computer Acquire electromagnetic waves from the target object via electromagnetic wave acquisition means mounted on the satellite, Calculating the direction of the object from the electromagnetic waves; calculate a rotation angle of the drive means so that the magnitude of the deviation indicated by an evaluation function value of the magnitude of the deviation between the center direction of the field of view of the electromagnetic wave acquirer and the direction of the object as seen from the electromagnetic wave acquirer is minimized based on a relative orbital motion model of the object with respect to the satellite, an attitude rate of the satellite, and a state transition model showing a change in the direction of the object within the field of view of the electromagnetic wave acquirer caused by the drive means rotating the electromagnetic wave acquirer, and operate the drive means at the calculated rotation angle; An acquisition and tracking method comprising:

[0253] (Appendix 13) On the computer, Acquiring electromagnetic waves from a target object via electromagnetic wave acquisition means mounted on the satellite; calculating a direction of the object from the electromagnetic waves; calculating a rotation angle of the drive means so as to minimize the magnitude of the deviation indicated by an evaluation function value of the magnitude of the deviation between the direction of the center of the field of view of the electromagnetic wave acquirer and the direction of the object as seen from the electromagnetic wave acquirer, based on a relative orbital motion model of the object with respect to the satellite, an attitude rate of the satellite, and a state transition model indicating a change in the direction of the object within the field of view of the electromagnetic wave acquirer caused by the drive means rotating the electromagnetic wave acquirer; and operating the drive means at the calculated rotation angle; A program to execute. [Explanation of symbols]

[0254] 1, 13, 620 satellites 2, 12 Object 3 Camera 4 Object direction calculation system 5. Control System 6 motors 7 Satellite Bus System 8. Terrestrial System 9 State Transition Model 10 Evaluation Functions 11 Earth 15 Microwave transmitter 16 Microwave Receiver 610 Acquisition and Tracking System 611, 621 Electromagnetic wave acquisition section 612, 622 Drive unit 613, 623 Direction calculation unit 614, 624, 631 Control section 630 Control Device

Claims

1. an electromagnetic wave acquiring means mounted on the satellite and configured to acquire electromagnetic waves from a target; a driving means for rotating the electromagnetic wave acquiring means to change the orientation of the electromagnetic wave acquiring means; a direction calculation means for calculating a direction of the object from the electromagnetic waves acquired by the electromagnetic wave acquisition means; a control means for calculating a rotation angle of the drive means so as to minimize the magnitude of the deviation indicated by an evaluation function value of the magnitude of the deviation between the direction of the center of the field of view of the electromagnetic wave acquirer and the direction of the object as seen from the electromagnetic wave acquirer, based on a relative orbital motion model of the object with respect to the satellite, an attitude rate of the satellite, and a state transition model indicating a change in the direction of the object within the field of view of the electromagnetic wave acquirer caused by the drive means rotating the electromagnetic wave acquirer; and for operating the drive means at the calculated rotation angle; An acquisition and tracking system comprising:

2. Both the target object and the artificial satellite are affected by the gravity of a celestial body other than the target object, the control means uses a relative orbital motion model that indicates that both the object and the artificial satellite are affected by the gravity of a celestial body other than the object in a three-dimensional orthogonal coordinate system having the center of mass of the artificial satellite as the origin, a first axis in the direction from the center of mass of the celestial body to the center of mass of the artificial satellite, a second axis in the direction of the satellite's movement, and a third axis in a direction perpendicular to these two directions; 10. The acquisition and tracking system of claim 1.

3. The satellite is subjected to the gravitational influence of the object, The control means uses a relative orbital motion model that indicates that the artificial satellite is affected by the gravity of the object in a three-dimensional orthogonal coordinate system having the center of mass of the artificial satellite as the origin, a first axis in the direction from the center of mass of the artificial satellite to the center of mass of the object at the time when the artificial satellite and the object are closest to each other, a second axis in the direction of the satellite's movement at that time, and a third axis in a direction perpendicular to these two directions.

10. The acquisition and tracking system of claim 1.

4. the driving means rotates around the elevation axis, the second axis, and the third axis, and the azimuth axis, and is disposed so that the rotation around the elevation axis also rotates the azimuth axis; the electromagnetic wave acquiring means changes a direction of a center of a field of view of the electromagnetic wave acquiring means in accordance with the rotation of the driving means around the elevation axis and the rotation of the driving means around the azimuth axis, the control means uses a state transition model that indicates a change in the deviation between the direction of the object as seen from the electromagnetic wave acquiring means and the direction of the center of the field of view of the electromagnetic wave acquiring means, based on the rotation amount of the driving means, the attitude rate of the satellite, and the relative orbital motion of the object, for each of the azimuth direction and the elevation direction; 4. An acquisition and tracking system according to claim 2 or claim 3.

5. the control means uses an evaluation function value based on the sum of magnitudes of deviations between the direction of the center of the field of view of the electromagnetic wave acquiring means and the direction of the object as seen from the electromagnetic wave acquiring means, for each time step included in the time from the start to the end of control of the drive means based on the electromagnetic waves acquired by the electromagnetic wave acquiring means; An acquisition and tracking system according to any one of claims 1 to 4.

6. the control means uses an evaluation function in which a portion indicating the magnitude of deviation between the direction of the center of the field of view of the electromagnetic wave acquiring means and the direction of the object as seen from the electromagnetic wave acquiring means at the last time step among the time steps included in the time from the start to the end of control of the drive means based on the electromagnetic waves acquired by the electromagnetic wave acquiring means is weighted by a weight calculated by solving a Riccati algebraic equation.

5. The acquisition and tracking system of claim 4.

7. an electromagnetic wave acquiring means for acquiring an electromagnetic wave from an object; a driving means for rotating the electromagnetic wave acquiring means to change the orientation of the electromagnetic wave acquiring means; a direction calculation means for calculating a direction of the object from the electromagnetic waves acquired by the electromagnetic wave acquisition means; a control means for calculating a rotation angle of the drive means so as to minimize the magnitude of the deviation indicated by an evaluation function value of the magnitude of the deviation between the direction of the center of the field of view of the electromagnetic wave acquirer and the direction of the object as seen from the electromagnetic wave acquirer, based on a relative orbital motion model of the object with respect to the satellite, an attitude rate of the satellite, and a state transition model indicating a change in the direction of the object within the field of view of the electromagnetic wave acquirer caused by the drive means rotating the electromagnetic wave acquirer; and for operating the drive means at the calculated rotation angle; An artificial satellite equipped with

8. a control means for calculating a rotation angle of the drive means based on a relative orbital motion model of the object with respect to the satellite, an attitude rate of the satellite, and a state transition model showing a change in the direction of the object within the field of view of the electromagnetic wave acquirer caused by a drive means rotating the electromagnetic wave acquirer that acquires electromagnetic waves from the object, so as to minimize the magnitude of the deviation indicated by an evaluation function value of the magnitude of the deviation between the direction of the center of the field of view of the electromagnetic wave acquirer and the direction of the object as seen from the electromagnetic wave acquirer, and for operating the drive means at the calculated rotation angle; A control device comprising:

9. The computer Acquire electromagnetic waves from the target object via electromagnetic wave acquisition means mounted on the satellite, Calculating the direction of the object from the electromagnetic waves; calculate a rotation angle of the drive means so that the magnitude of the deviation indicated by an evaluation function value of the magnitude of the deviation between the center direction of the field of view of the electromagnetic wave acquirer and the direction of the object as seen from the electromagnetic wave acquirer is minimized based on a relative orbital motion model of the object with respect to the satellite, an attitude rate of the satellite, and a state transition model showing a change in the direction of the object within the field of view of the electromagnetic wave acquirer caused by the drive means rotating the electromagnetic wave acquirer, and operate the drive means at the calculated rotation angle; An acquisition and tracking method comprising:

10. On the computer, Acquiring electromagnetic waves from a target object via electromagnetic wave acquisition means mounted on the satellite; calculating a direction of the object from the electromagnetic waves; calculating a rotation angle of the drive means so as to minimize the magnitude of the deviation indicated by an evaluation function value of the magnitude of the deviation between the direction of the center of the field of view of the electromagnetic wave acquirer and the direction of the object as seen from the electromagnetic wave acquirer, based on a relative orbital motion model of the object with respect to the satellite, an attitude rate of the satellite, and a state transition model indicating a change in the direction of the object within the field of view of the electromagnetic wave acquirer caused by the drive means rotating the electromagnetic wave acquirer; and operating the drive means at the calculated rotation angle; A program to execute.

Images