Flight body, orientation control system and observation method

Abstract

To fix a variation direction of an electric field vector of horizontally polarized waves emitted to an observation object at a right angle with respect to a specific plane.SOLUTION: The orientation direction of an antenna 201 is adjusted so that an azimuth direction Az of the antenna 201 coincides with a normal direction of a specific plane, and a bore site direction Boa of the antenna 201 is oriented in a direction deviated according to a deviation angle from a direction oriented to an observation object 102. The specific plane is a plane obtained by rotating a plane formed by a relative direction of the antenna 201 to the observation object 102 and the normal direction of a ground surface at the position of the observation object 102, according to a surface rotation angle around the normal direction of the ground surface at the position of the observation object 102. The surface rotation angle is set as the angle around the normal direction of the ground surface. The deviation angle is an angle in an elevation direction of the antenna 201.SELECTED DRAWING: Figure 11

Description

Technical Field

[0001] The present disclosure relates to beam direction control for observing an object to be observed.

Background Art

[0002] Conventionally, observations using spacecraft have been carried out. Non-Patent Document 1 discloses controlling the rotation of a beam so that the beam is directed at an object to be observed.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Patent Document 2

Patent Document 3

Non-Patent Documents

[0004]

Non-Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] In Non-Patent Document 1, the beam direction (vector) is aligned with the direction of the object to be observed, but the rotation around the beam direction is not defined. Therefore, the direction of variation of the electric field vector of the electromagnetic wave irradiated on the object to be observed cannot be controlled in the intended direction, and the object to be observed cannot be observed under the desired electric field vector incident conditions.

[0006] The present disclosure aims to enable the direction of variation of the electric field vector of the horizontally polarized wave irradiated on the observation target to be fixed at a right angle to the normal direction of the plane in which the observation target is located.

Means for Solving the Problems

[0007] The flying object of the present disclosure is an antenna for irradiating a beam and receiving the beam reflected by the observation target located on the ground surface, an antenna control device for adjusting the pointing direction of the antenna so that the azimuth direction of the antenna coincides with the normal direction of a specific plane and the boresight direction of the antenna points in a direction deviated according to the deviation angle from the direction pointing to the observation target, a beam control device for irradiating a beam from the pointing direction of the antenna to a direction deviated according to the deviation angle by electronic scanning, a receiving device for receiving the beam reflected by the observation target using the antenna, and is a flying object including wherein the specific plane is a plane formed by the relative direction of the antenna with respect to the observation target and the normal direction of the ground surface at the position of the observation target, and is a plane rotated according to the surface rotation angle around the normal direction of the ground surface at the position of the observation target, the surface rotation angle is set as an angle around the normal direction of the ground surface, and the deviation angle is an angle in the elevation direction of the antenna.

Advantages of the Invention

[0008] According to the present disclosure, it becomes possible to fix the direction of variation of the electric field vector of the horizontally polarized wave irradiated on the observation target at a right angle to the normal direction of the plane in which the observation target is located.

Brief Description of the Drawings

[0009]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Figure 9

Figure 10

Figure 11

MODE FOR CARRYING OUT THE INVENTION

[0010] In the embodiments and the drawings, the same elements or corresponding elements are denoted by the same reference numerals. The description of the elements denoted by the same reference numerals as the described elements will be omitted or simplified as appropriate. The arrows in the figures mainly indicate the flow of signals, data or processes.

[0011] Embodiment 1. The satellite observation system 100 will be described with reference to FIGS. 1 to 9.

[0012] ***Description of the configuration*** Based on FIG. 1, the configuration of the satellite observation system 100 as an observation system will be described. The satellite observation system 100 includes an observation satellite 200 as a flying object and a ground station 110. The satellite observation system 100 is an example of an observation system that performs observations using a flying object. The flying object is an artificial satellite or an aircraft, etc. Observation satellite 200 is an artificial satellite that observes the observation target 102. Observation is performed by irradiating a beam and receiving the beam reflected by the observation target 102 located on the ground surface. An artificial satellite is also called a spacecraft. Antenna 201 is also called an aerial. The pointing target 101 is the point pointed from the antenna 201. Specifically, the observation target 102 becomes the pointing target 101. The observation target 102 is what is to be observed. The specific observation target 102 is fixed to the ground surface. The ground station 110 communicates with the observation satellite 200.

[0013] The dashed arrow passing through the observation satellite 200 represents the orbit along which the observation satellite 200 flies. The orbit is also called a path.

[0014] The dashed-dotted arrow from the observation satellite 200 to the pointing target 101 represents the beam pointing direction Beam. The beam pointing direction Beam is the pointing direction of the beam irradiated from the antenna 201. The beam is an electromagnetic wave.

[0015] The satellite position Psat is the position of the observation satellite 200. The satellite position Psat corresponds to the position of the antenna 201. The three arrows attached to the observation satellite 200 indicate the boresight direction Boa, the azimuth direction Az, and the elevation direction El. The boresight direction Boa is the boresight direction of the antenna 201. The azimuth direction Az corresponds to the horizontal polarization excitation direction of the antenna 201. The elevation direction El is the elevation direction of the antenna 201 and is perpendicular to the boresight direction Boa and the azimuth direction Az.

[0016] The target position Pg is the position of the observation target 102. The upward arrow attached to the observation target 102 represents the normal direction N. The normal direction N is the normal direction of the target plane at the position of the observation target 102. The target plane is a plane based on the position of the observation target 102. Specifically, the target plane is the ground surface. When the observation target 102 is a building, the normal direction N corresponds to the floor direction of the building.

[0017] Based on FIG. 2, the configuration of the observation satellite 200 will be described. The observation satellite 200 includes an antenna 201S, an antenna 201R, a position sensor 202, and an attitude sensor 203. The antenna 201S is a transmitting antenna 201. The antenna 201R is a receiving antenna 201. The position sensor 202 is a sensor for positioning the observation satellite 200. A specific example of the position sensor 202 is GPS. GPS is an abbreviation for Global Positioning System. The attitude sensor 203 is a sensor for measuring the attitude of the observation satellite 200. A specific example of the attitude sensor 203 is a star tracker.

[0018] The observation satellite 200 includes devices (computers) such as a communication device 211 and a target recording device 212. The observation satellite 200 includes a pointing control system 220. The pointing control system 220 includes devices such as a pointing control device 221, an antenna control device 222, and a beam control device 223. The observation satellite 200 includes devices such as a receiving device 231 and an observation result recording device 232. The device includes a processing circuit. The processing circuit may be dedicated hardware or a processor that executes a program stored in a memory. When the processing circuit is dedicated hardware, the processing circuit is, for example, a single circuit, a composite circuit, a programmed processor, a parallel programmed processor, an ASIC, an FPGA, or a combination thereof. ASIC is an abbreviation for Application Specific Integrated Circuit. FPGA is the abbreviation of Field Programmable Gate Array

[0019] The terrestrial station 110 is equipped with a communication device 111.

[0020] ***Explanation of the operation*** The procedure of the operation of the observation satellite 200 corresponds to the observation method.

[0021] Based on Figure 3, the features of the observation method will be described. The solid line arrow from the observation target 102 to the antenna 201 represents the relative direction of the antenna 201 with respect to the observation target 102. The plane of crosshatching is the plane in which the electric field vector of the horizontal polarization of the beam exists. The dashed line arrow attached to the observation target 102 in the plane of crosshatching represents the direction in which the electric field vector of the horizontal polarization of the beam incident on the observation target 102 fluctuates. The dotted line arrow attached to the observation target 102 on the ground surface represents the elevation direction El projected onto the ground surface.

[0022] The device of the observation satellite 200 operates as follows. The antenna control device 222 adjusts the pointing direction of the antenna 201 so that the azimuth direction Az of the antenna 201 coincides with the normal direction of a specific plane, and the boresight direction Boa of the antenna 201 points to the target 101. Note that the antenna control device 222 adjusts the pointing direction of the antenna 201 in accordance with the progress of the observation satellite 200. The specific plane is the plane formed by the relative direction of the antenna 201 with respect to the observation target 102 and the normal direction N of the ground surface at the position of the observation target 102. The beam control device 223 irradiates a beam in the pointing direction of the antenna 201S. However, since the antenna 201S is pointing to the observation target 102, the beam control device 223 does not need to adjust the beam pointing direction from the pointing direction of the antenna 201S by electronic scanning. The receiving device 231 receives the beam reflected by the observation target 102 using the antenna 201R.

[0023] Based on FIG. 4, the procedure in the observation method will be described. In step S110, the observation satellite 200 receives one or more pieces of target information. The target information indicates a target position Pg, a normal direction N, and observation conditions. The observation conditions specify an observation orbit and a satellite observation point, etc. The observation orbit is the orbit on which the observation is carried out. The satellite observation point is the position where the observation is carried out. The observation satellite 200 observes the observation target 102 from the satellite observation point of the observation orbit.

[0024] The target information is received as follows. The operator inputs the target information into the control device of the ground station 110. The communication device 111 transmits the target information input into the control device. The communication device 211 receives the target information. The target recording device 212 includes a storage device such as a memory and records the received target information. A target list is stored in the target recording device 212. The target list indicates one or more pieces of target information.

[0025] In step S120, based on the target information, the pointing control device 221 calculates the pointing direction (Boa, Az, El) of the antenna 201 and the beam pointing direction Beam.

[0026] The pointing direction of the antenna 201 and the beam pointing direction Beam are calculated by the following procedure. The position sensor 202 positions the observation satellite 200 at each time. The attitude sensor 203 measures the attitude of the observation satellite 200 at each time. The pointing control device 221 selects from the target list the target information indicating the observation conditions that match the satellite position Psat. Based on the satellite position Psat, the target position Pg, and the normal direction N, the pointing control device 221 calculates the pointing direction of the antenna 201 and the beam pointing direction Beam. The target position Pg and the normal direction N are indicated in the selected target information.

[0027] Details of the calculation of the pointing direction (Boa, Az, El) of the antenna 201 and the beam pointing direction Beam will be described later.

[0028] In step S130, the antenna control device 222 points the antenna 201 in the pointing direction.

[0029] The antenna 201 is pointed in the pointing direction as follows. The pointing control device 221 outputs an antenna pointing command. The antenna pointing command indicates the pointing direction of the antenna 201. The output antenna pointing command is input to the antenna control device 222. The antenna control device 222 points the antenna 201 in the pointing direction indicated by the antenna pointing command. At this time, the antenna control device 222 points the antenna 201 in the pointing direction indicated by the antenna pointing command by adjusting the attitude of the observation satellite 200 or the attitude of the antenna 201. However, the antenna control device 222 may point the antenna 201 in the pointing direction of the antenna 201 by adjusting the attitude of the observation satellite 200 and the attitude of the antenna 201. Also, the antenna control device 222 may point the antenna 201 in the pointing direction indicated by the antenna pointing command by adjusting only the attitude of the observation satellite 200. Also, the antenna control device 222 may point the antenna 201 in the pointing direction indicated by the antenna pointing command by adjusting only the attitude of the antenna 201. The attitude of the observation satellite 200 is adjusted by controlling the attitude control device provided in the observation satellite 200. Examples of the attitude control device are a reaction wheel, a control moment gyro, and a thruster. Also, the antenna 201 may be provided with a drive mechanism. The attitude of the antenna 201 is adjusted by controlling the drive mechanism provided in the antenna 201. An example of the drive mechanism is a gimbal. The antenna control device 222 performs feedback control or feedforward control to adjust each of the attitude of the observation satellite 200 and the attitude of the antenna 201.

[0030] In step S140, the beam control device 223 irradiates a beam from the antenna 201 in the beam pointing direction Beam.

[0031] The beam is irradiated as follows. The pointing control device 221 outputs a beam pointing command. The beam pointing command indicates the beam pointing direction Beam. The output beam pointing command is input to the beam control device 223. The beam control device 223 uses the antenna 201S to irradiate a beam in the beam pointing direction Beam indicated by the beam pointing command.

[0032] In step S150, the observation satellite 200 obtains an observation result for the observation target 102. The observation result is data obtained by observing the observation target 102.

[0033] The observation result is obtained as follows. The beam (transmission wave) irradiated from the antenna 201S is reflected by the observation target 102. The beam (reflected wave) reflected by the observation target 102 is incident on the antenna 201R. The receiving device 231 receives the beam from the antenna 201R and processes the received beam. Thereby, the observation result is obtained. The observation result recording device 232 includes a storage device such as a memory and records the observation result.

[0034] The details of the calculation of the pointing direction in step S120 will be described. The pointing control device 221 calculates the following formula. Thereby, the pointing direction (Boa, Az, El) of the antenna 201 and the beam pointing direction Beam are calculated.

[0035]

Equation

[0036] The arrow attached above each symbol means a vector.

[0037] The boresight direction Boa corresponds to the relative direction of the satellite position Psat with respect to the target position Pg. The boresight direction Boa is calculated by calculating Equation (1-1). The azimuth direction Az corresponds to the normal direction of the plane (specific plane) formed by the boresight direction Boa and the normal direction N. When the observation target 102 is located on the right side of the satellite nadir track as viewed from the observation satellite 200, the azimuth direction Az is calculated by calculating Equation (1-2R). When the observation target 102 is located on the left side of the satellite nadir track as viewed from the observation satellite 200, the azimuth direction Az is calculated by calculating Equation (1-2L). The satellite nadir track is the track of the point directly below the observation satellite 200. That is, the satellite nadir track corresponds to the orbit of the observation satellite 200 projected onto the earth's surface. The elevation direction El corresponds to the cross product of the boresight direction Boa and the azimuth direction Az. The elevation direction El is calculated by calculating Equation (1-3). The beam pointing direction Beam is equal to the boresight direction Boa as shown in Equation (1-4).

[0038] Each direction may be represented in vector form or in angular form indicating the angle from the reference direction.

[0039] ***Supplement to Embodiment 1*** Embodiment 1 relates to beam pointing control for keeping the fluctuation direction of the electric field vector of the beam irradiated on the observation target 102 constant in observation using SAR (Synthetic Aperture Radar). The antenna control device 222 makes the azimuth direction of the antenna 201 coincide with the normal vector of the specific plane by controlling the two degrees of freedom of rotation of the antenna 201. The two degrees of freedom of rotation are rotations around any two axes. The specific plane is a plane formed by the relative position vector from the observation target 102 to the antenna 201 and the normal vector of the earth's surface of the observation target 102. The antenna control device 222 controls the remaining one degree of rotational freedom of the antenna 201 to direct the bore sight direction of the antenna 201 toward the observation target 102. The one degree of rotational freedom is rotation about the axis in the azimuth direction of the antenna 201. Through these series of controls, the beam is directed at the observation target 102. Further, the angle formed by the direction of variation of the electric field vector of the horizontally polarized wave irradiated on the observation target 102 and the ground surface normal vector of the observation target 102 is fixed at a right angle.

[0040] ***Effect of Embodiment 1*** Fig. 5 illustrates beam pointing control in observation by a conventional spacecraft. A spacecraft is equipped with an antenna. The "intersection point" means the intersection of the bore sight direction of the antenna and the ground surface. The two solid arrows attached to the intersection point represent the direction in which the elevation direction of the antenna is projected onto the ground surface and the direction in which the azimuth direction of the antenna is projected onto the ground surface. Conventionally, the beam was directed at the observation target by controlling the rotation of the beam. The rotation control of the beam was realized by electronic scanning or mechanical drive. However, while the beam direction (vector) is adjusted to the direction of the observation target, the rotation around the beam direction is not defined. And controlling the direction of variation of the electric field vector of the electromagnetic wave irradiated on the observation target to the intended direction has not been implemented. Therefore, there has been a problem that the observation target cannot be observed under the desired electric field vector incident conditions.

[0041] According to Embodiment 1, it becomes possible to fix the direction of variation of the electric field vector of the horizontally polarized wave irradiated on the observation target at a right angle to the ground surface normal direction of the observation target.

[0042] ***Description of Examples*** The target position Pg may be set from the ground station 110 to the observation satellite 200, or may be set based on the conditions of the pointing target 101 on the observation satellite 200. The satellite position Psat may be measured at the observation satellite 200, or may be calculated at the ground station 110 and set for the observation satellite 200. For example, at the ground station 110, the distance from each of a plurality of radars to the observation satellite 200 is measured, and the satellite position Psat is calculated by triangulation. The normal direction N may be set from the ground station 110 to the observation satellite 200, or may be calculated at the observation satellite 200 based on the target position Pg.

[0043] Examples for the observation target 102 will be described below.

[0044] A first embodiment will be described with reference to FIG. 6. The observation target 102 is a point locus located on the ground surface in a direction matching the traveling direction of the observation satellite 200. The traveling direction of the observation target 102 corresponds to the direction in which the traveling direction of the observation satellite 200 is projected onto the ground surface. The observation target 102 travels in accordance with the travel of the observation satellite 200. The antenna control device 222 adjusts the pointing direction of the antenna 201 in accordance with the travel of the observation target 102 and the travel of the observation satellite 200.

[0045] A second embodiment will be described with reference to FIG. 7. The observation target 102 is a point locus located on the ground surface in a direction not matching the traveling direction of the observation satellite 200. The observation target 102 travels through the observation area regardless of the travel of the observation satellite 200. The antenna control device 222 adjusts the pointing direction of the antenna 201 in accordance with the travel of the observation target 102 and the travel of the observation satellite 200.

[0046] A third embodiment will be described with reference to FIG. 8. The observation target 102 may be a representative point on the path of the point locus located on the ground surface in a direction matching the traveling direction of the observation satellite 200. The position of the observation target 102 at any time during the observation period is the representative point. The antenna control device 222 calculates the pointing direction when the representative point is the observation target 102 at the satellite observation point. The pointing direction is maintained during the observation period. The relationship between the pointing direction of the antenna 201 and the spatial coordinate system is fixed. By maintaining the relationship between the pointing direction of the antenna 201 and the spatial coordinate system during the observation period, the following effects can be obtained. At all times during the observation period, the angle formed by the fluctuation direction of the electric field vector of the horizontally polarized wave irradiated on the ground surface and the normal vector of the ground surface at the radio wave irradiation point is approximately fixed at a right angle. The radio wave irradiation point is the intersection of the beam direction and the ground surface. The spatial coordinate system may be an orbital coordinate system or an inertial coordinate system.

[0047] Based on FIG. 9, a fourth embodiment will be described. The observation target 102 is a point underground. The radio wave irradiation point is the intersection of the beam direction and the ground surface. The target position Pg is the position of the observation target 102. The normal direction N is the normal direction of the ground surface at the latitude and longitude of the target position Pg. The normal direction of the target plane is the same as the normal direction N.

[0048] Embodiment 2. Regarding the form in which the beam is irradiated deviating from the pointing direction of the antenna 201, the main differences from Embodiment 1 will be described based on FIG. 10.

[0049] ***Description of the configuration*** The configuration of the satellite observation system 100 is the same as the configuration in Embodiment 1. However, the pointing target 101 does not have to be the observation target 102.

[0050] ***Description of the operation*** Based on FIG. 10, the characteristics of the observation method will be described. The antenna control device 222 adjusts the pointing direction of the antenna 201 so that the azimuth direction Az of the antenna 201 coincides with the normal direction of the specific plane, and the boresight direction Boa of the antenna 201 points in a direction deviated according to the deviation angle θ from the direction pointing to the observation target 102. The specific plane is a plane formed by the relative direction of the antenna 201 with respect to the observation target 102 and the normal direction of the ground surface at the position of the observation target 102. The beam control device 223 irradiates a beam in a direction deflected according to the deflection angle θ from the pointing direction of the antenna 201S by electronic scanning. The deflection angle θ is an angle in the elevation direction El of the antenna 201. The antenna 201 points to the pointing target 101 farther than the observation target 102, and the beam points to the observation target 102 closer than the pointing target 101. Or, the antenna 201 points to the pointing target 101 closer than the observation target 102, and the beam points to the observation target 102 farther than the pointing target 101.

[0051] The procedure in the observation method is the same as the procedure in Embodiment 1 (see FIG. 4). However, the target information received in step S110 further indicates the deflection angle θ. Also, the calculation formula for the pointing direction in step S120 is as follows.

[0052]

Equation

[0053] rotation{X,Y,Z} means an operation of rotating the unit vector X by Z degrees clockwise around the unit vector Y.

[0054] The azimuth direction Az corresponds to the cross product of the relative direction of the satellite position Psat with respect to the target position Pg and the normal direction N. When the observation target 102 is located on the right side of the satellite nadir point track as viewed from the observation satellite 200, the azimuth direction Az is calculated by calculating Equation (2-1R). When the observation target 102 is located on the left side of the satellite nadir point track as viewed from the observation satellite 200, the azimuth direction Az is calculated by calculating Equation (2-1L). The elevation direction El corresponds to the direction obtained by rotating the relative direction of the satellite position Psat with respect to the target position Pg around the axis of the azimuth direction Az by an angle θ. The elevation direction El is calculated by calculating Equation (2-2). The boresight direction Boa corresponds to the cross product of the azimuth direction Az and the elevation direction El. The boresight direction Boa is calculated by calculating Equation (2-3). The beam pointing direction Beam corresponds to the relative direction of the target position Pg with respect to the satellite position Psat. The beam pointing direction Beam is calculated by calculating Equation (2-4).

[0055] ***Supplement to Embodiment 2*** The antenna control device 222 makes the azimuth direction of the antenna 201 coincide with the normal vector of a specific plane by controlling the two degrees of freedom of rotation of the antenna 201. The specific plane is a plane formed by the relative position vector from the observation target 102 to the antenna 201 and the ground surface normal vector of the observation target 102. The antenna control device 222 controls the remaining one degree of freedom of rotation of the antenna 201 to direct the boresight direction of the antenna 201 to the target 101 deviated from the observation target 102 (the position deviated in the elevation direction El projected onto the ground surface) according to the deviation angle θ. The beam control device 223 directs the beam to the observation target 102 by electronic scanning. By these series of controls, the beam is directed to the observation target 102. Furthermore, the angle formed by the fluctuation direction of the electric field vector of the horizontally polarized wave irradiated on the observation target 102 and the ground surface normal vector of the observation target 102 is fixed at a right angle. Furthermore, by setting the deviation angle θ, it becomes possible to reduce the rotation rate around the boresight axis of the antenna 201.

[0056] When the deviation angle θ is zero, Embodiment 2 is equivalent to Embodiment 1.

[0057] ***Effects of Embodiment 2*** According to Embodiment 2, even if the rotation rate of the platform antenna around the bore-sight axis is not greatly improved, it is possible to fix the fluctuation direction of the electric field vector of the horizontally polarized wave irradiated on the observation target at a right angle to the normal direction of the ground surface of the observation target.

[0058] ***Description of Embodiment*** The deviation angle θ may be set from the ground station 110 to the observation satellite 200, or may be set on the observation satellite 200.

[0059] The deviation angle θ is set as an angle around the axis of the azimuth direction Az. Due to the deviation angle θ, the pointing point will deviate from the observation target in the elevation direction El. This is an embodiment considering that the adjustment range by electronic scanning is usually large in the elevation direction El.

[0060] The embodiment of Embodiment 1 may be applied to Embodiment 2.

[0061] Embodiment 3. Regarding the form in which the beam is irradiated while deviating from the pointing direction of the antenna 201, the main differences from Embodiment 1 will be described with reference to FIG. 11.

[0062] ***Description of Configuration*** The configuration of the satellite observation system 100 is the same as the configuration in Embodiment 1. However, the pointing target 101 does not have to be the observation target 102.

[0063] ***Description of Operation*** Based on FIG. 11, the features of the observation method will be described. The two-dot chain line attached to the observation satellite 200 represents the direction of the cross product of the normal direction N of the observation target 102 and the relative direction of the antenna 201 with respect to the observation target 102. The dotted arrow attached to the pointing target 101 on the ground surface represents the elevation direction El and the azimuth direction Az projected onto the ground surface.

[0064] The antenna control device 222 adjusts the pointing direction of the antenna 201 so that the azimuth direction Az of the antenna 201 coincides with the normal direction of a specific plane, and so that the boresight direction Boa of the antenna 201 points in a direction deviated according to the deviation angle θ from the direction pointing to the observation target 102. The specific plane is a plane formed by the relative direction of the antenna 201 with respect to the observation target 102 and the normal direction of the ground surface at the position of the observation target 102, and is a plane rotated by the plane rotation angle φ around the normal direction of the ground surface at the position of the observation target 102. The beam control device 223 irradiates a beam in the direction of the observation target 102 by electronic scanning.

[0065] The procedure in the observation method is the same as the procedure in Embodiment 1 (see FIG. 4). However, the target information received in step S110 further indicates the plane rotation angle φ and the deviation angle θ. Also, the calculation formula for the pointing direction in step S120 is as follows.

[0066]

Equation

[0067] rotation{X,Y,Z} means an operation of rotating the unit vector X by Z degrees in the right-hand direction around the unit vector Y.

[0068] The azimuth direction Az corresponds to a direction obtained by rotating the cross product of the relative direction of the satellite position Psat with respect to the target position Pg and the normal direction N around the axis of the normal direction N by the plane rotation angle φ. When the observation target 102 is located on the right side of the satellite nadir track as viewed from the observation satellite 200, the azimuth direction Az is calculated by calculating Equation (3-1R). When the observation target 102 is located on the left side of the satellite nadir track as viewed from the observation satellite 200, the azimuth direction Az is calculated by calculating Equation (3-1L). The boresight direction Boa corresponds to the direction obtained by rotating the relative direction of the target position Pg with respect to the satellite position Psat around the axis of the normal direction N according to the plane rotation angle φ and then rotating it around the axis of the azimuth direction Az according to the deviation angle θ. The boresight direction Boa is calculated by calculating equations (3-2) and (3-3). The elevation direction El corresponds to the cross product of the boresight direction Boa and the azimuth direction Az. The elevation direction El is calculated by calculating equation (3-4). The beam pointing direction Beam corresponds to the relative direction of the target position Pg with respect to the satellite position Psat. The beam pointing direction Beam is calculated by calculating equation (3-5).

[0069] ***Supplement to Embodiment 3*** The antenna control device 222 makes the azimuth direction of the antenna 201 coincide with the normal vector of a specific plane by controlling the two degrees of freedom of rotation of the antenna 201. The specific plane is a plane formed by the relative position vector from the observation target 102 to the antenna 201 and the ground surface normal vector of the observation target 102, and is a plane rotated according to the plane rotation angle φ around the normal direction of the ground surface at the position of the observation target 102. The antenna control device 222 directs the boresight direction of the antenna 201 in a direction according to the deviation angle θ by controlling the remaining one degree of freedom of rotation of the antenna 201. The beam control device 223 directs the beam to the observation target 102 by electronic scanning. Through this series of controls, the beam is directed at the observation target 102. Furthermore, the angle formed by the fluctuation direction of the electric field vector of the horizontally polarized wave irradiated on the observation target 102 and the ground surface normal vector of the observation target 102 is fixed at a right angle. Furthermore, by setting the deviation angle θ, it becomes possible to reduce the rotation rate around the boresight axis of the antenna 201.

[0070] When the plane rotation angle φ is zero and the deviation angle θ is zero, Embodiment 3 is equivalent to Embodiment 1. When the surface rotation angle φ is zero, Embodiment 3 is equivalent to Embodiment 2.

[0071] ***Effects of Embodiment 3*** According to Embodiment 3, even without significantly improving the rotation rate of the platform antenna around the bore-sight axis, it is possible to fix the fluctuation direction of the electric field vector of the horizontally polarized wave irradiated on the observation target perpendicular to the normal direction of the ground surface of the observation target.

[0072] ***Description of Examples*** The surface rotation angle φ and the deviation angle θ may be set from the ground station 110 to the observation satellite 200, or may be set on the observation satellite 200.

[0073] The surface rotation angle φ is set as the angle around the normal direction of the ground surface of the observation target. Due to the surface rotation angle φ, the pointing point will deviate from the observation target in the azimuth direction Az. The deviation angle θ is set as the angle around the azimuth direction Az axis. Due to the deviation angle θ, the pointing point will deviate from the observation target in the elevation direction El.

[0074] The examples of Embodiment 1 may be applied to Embodiment 3.

[0075] ***Supplementary Notes on Embodiments*** Each embodiment is an example of a preferred form and is not intended to limit the technical scope of the present disclosure. Each embodiment may be partially implemented or may be implemented in combination with other forms. The procedures described using flowcharts and the like may be appropriately changed.

[0076] "Device" may be read as "section", "process", "circuit" or "circuitry".

[0077] The various aspects of the present disclosure are described below as appendices. (Appendix 1) An antenna for irradiating a beam and receiving the beam reflected by an observation target located on the ground surface, An antenna control device that adjusts the pointing direction of the antenna so that the azimuth direction of the antenna coincides with the normal direction of a specific plane, A beam control device that irradiates a beam in the pointing direction of the antenna, A receiving device that receives the beam reflected by the observation target using the antenna, A flying object comprising: The specific plane is a plane formed by the relative direction of the antenna with respect to the observation target and the normal direction of the target plane at the position of the observation target, The target plane is the plane in which the observation target is located Flying object.

[0078] (Appendix 2) The antenna control device adjusts the pointing direction of the antenna so that the azimuth direction of the antenna coincides with the normal direction of the specific plane and the boresight direction of the antenna points to the observation target. The flying object according to Appendix 1.

[0079] (Appendix 3) The target plane is the ground surface, The observation target is fixed to the ground surface, The antenna control device adjusts the pointing direction of the antenna in accordance with the progress of the flying object. The flying object according to Appendix 1 or Appendix 2.

[0080] (Appendix 4) The target plane is the ground surface, The observation target is moving on the ground surface in a direction that coincides with the moving direction of the flying object, The antenna control device adjusts the pointing direction of the antenna in accordance with the progress of the observation target and the progress of the flying object. The flying object according to Appendix 1 or Appendix 2.

[0081] (Appendix 5) The target plane is the ground surface, The object to be observed travels on the ground surface in a direction that does not match the traveling direction of the flying object. The antenna control device adjusts the pointing direction of the antenna in accordance with the travel of the object to be observed and the travel of the flying object. The flying object according to appended claim 1 or appended claim 2.

[0082] (Appended claim 6) The target plane is the ground surface. The object to be observed is a representative point on the travel path that travels on the ground surface in a direction that matches the traveling direction of the flying object. The antenna control device adjusts the pointing direction of the antenna in accordance with the travel of the flying object. The flying object according to appended claim 1 or appended claim 2.

[0083] (Appended claim 7) The object to be observed is a point underground. The normal direction of the target plane is the same as the normal direction of the ground surface at the latitude and longitude of the object to be observed. The flying object according to appended claim 1 or appended claim 2.

[0084] (Appended claim 8) A pointing control system mounted on the flying object according to any one of appended claims 1 to 7, the antenna control device, the beam control device, and a pointing control system comprising the same.

[0085] (Appended claim 9) Adjust the pointing direction of the antenna so that the azimuth direction of the antenna coincides with the normal direction of the specific plane, irradiate a beam in the pointing direction of the antenna, receive the beam reflected by the object to be observed using the antenna, which is an observation method, The specific plane is a plane formed by the relative direction of the antenna with respect to the object to be observed and the normal direction of the target plane at the position of the object to be observed, The target plane is the plane in which the object to be observed is located. Observation method.

[0086] (Appendix 10) An antenna for irradiating a beam and receiving the beam reflected by an observation target located on the ground surface, An antenna control device for adjusting the pointing direction of the antenna such that the azimuth direction of the antenna coincides with the normal direction of a specific plane, and the boresight direction of the antenna points in a direction deviated according to a deviation angle from the direction pointing to the observation target; A beam control device for irradiating a beam from the pointing direction of the antenna to a direction deviated according to the deviation angle by electronic scanning; A receiving device for receiving the beam reflected by the observation target using the antenna, A flying object comprising: The specific plane is a plane formed by the relative direction of the antenna with respect to the observation target and the normal direction of the ground surface at the position of the observation target; The deviation angle is an angle in the elevation direction of the antenna Flying object.

[0087] (Appendix 11) The antenna points to a pointing target farther than the observation target, The beam points to the observation target closer than the pointing target The flying object according to Appendix 10.

[0088] (Appendix 12) The antenna points to a pointing target closer than the observation target, The beam points to the observation target farther than the pointing target The flying object according to Appendix 10.

[0089] (Appendix 13) A pointing control system mounted on the flying object according to any one of Appendices 10 to 12, The antenna control device, The beam control device, A pointing control system comprising:

[0090] (Appendix 14) Adjust the direction of the antenna so that the azimuth direction of the antenna coincides with the normal direction of a specific plane, and so that the boresight direction of the antenna points in a direction deviated according to the deviation angle from the direction pointing to the observation target. Irradiate a beam from the direction of the antenna in the direction deviated according to the deviation angle by electronic scanning. Receive the beam reflected by the observation target using the antenna. This is an observation method. The specific plane is a plane formed by the relative direction of the antenna with respect to the observation target and the normal direction of the ground surface at the position of the observation target. Observation method.

[0091] (Appendix 15) An antenna for irradiating a beam and receiving the beam reflected by an observation target located on the ground surface, An antenna control device that adjusts the direction of the antenna so that the azimuth direction of the antenna coincides with the normal direction of a specific plane, and so that the boresight direction of the antenna points in a direction deviated according to the deviation angle from the direction pointing to the observation target. A beam control device that irradiates a beam from the direction of the antenna in the direction deviated according to the deviation angle by electronic scanning. A receiving device that receives the beam reflected by the observation target using the antenna. This is an aircraft equipped with the above components. The specific plane is a plane formed by the relative direction of the antenna with respect to the observation target and the normal direction of the ground surface at the position of the observation target, and is a plane rotated according to the surface rotation angle around the normal direction of the ground surface at the position of the observation target. The surface rotation angle is set as an angle around the normal direction of the ground surface. The deviation angle is an angle in the elevation direction of the antenna. Aircraft.

[0092] (Appendix 16) The antenna points to a target point farther away from the object to be observed, and the beam points to the object to be observed closer to the target point. The flying object according to Appendix 15.

[0093] (Appendix 17) The antenna points to a target point closer to the object to be observed, and the beam points to the object to be observed farther from the target point. The flying object according to Appendix 15.

[0094] (Appendix 18) A direction control system mounted on the flying object according to any one of Appendices 15 to 17, the antenna control device, and the beam control device, comprising a direction control system.

[0095] (Appendix 19) Adjust the direction of the antenna so that the azimuth direction of the antenna coincides with the normal direction of a specific plane, and the bore site direction of the antenna points in a direction deviated according to the deviation angle from the direction pointing to the object to be observed, Irradiate the beam from the pointing direction of the antenna to a direction deviated according to the deviation angle by electronic scanning, Receive the beam reflected by the object to be observed using the antenna, which is an observation method, wherein the specific plane is a plane formed by the relative direction of the antenna with respect to the object to be observed and the normal direction of the ground surface at the position of the object to be observed, and is a plane rotated according to the plane rotation angle around the normal direction of the ground surface at the position of the object to be observed, and the plane rotation angle is set as an angle around the normal direction of the ground surface. Observation method.

Explanation of symbols

[0096] 100 Satellite Observation System, 101 Target to be Pointed, 102 Object to be Observed, 110 Ground Station, 111 Communication Device, 200 Observation Satellite, 201 Antenna, 202 Position Sensor, 203 Attitude Sensor, 211 Communication Device, 212 Target Recording Device, 220 Pointing Control System, 221 Pointing Control Device, 222 Antenna Control Device, 223 Beam Control Device, 231 Receiver, 232 Observation Result Recording Device, Az Azimuth Direction, Beam Beam Pointing Direction, Boa Boresight Direction, El Elevation Direction, N Normal Direction, Pg Target Position, Psat Satellite Position, θ Deviation Angle, φ Plane Rotation Angle.

Claims

1. an antenna for emitting a beam and receiving the beam reflected by an observation target located on the Earth's surface; an antenna control device that adjusts the direction of the antenna so that the azimuth direction of the antenna coincides with the normal direction of a specific plane and the boresight direction of the antenna points in a direction deviated from the direction of pointing at the observation target according to a deviation angle; a beam control device that irradiates a beam in a direction deviated from the pointing direction of the antenna in accordance with the deviation angle by electronic scanning; a receiving device that receives a beam reflected by the target using the antenna; A flying object comprising: the specific plane is a plane formed by a relative direction of the antenna with respect to the observation target and a normal direction of the ground surface at the position of the observation target, and rotated around the normal direction of the ground surface at the position of the observation target according to a plane rotation angle, the surface rotation angle is set as an angle around a normal direction of the ground surface; The deflection angle is the angle in the elevation direction of the antenna. Flying object.

2. The antenna is configured to point to a target that is farther than the observation target, The beam is directed to the observation target that is closer than the target. The flying object according to claim 1.

3. The antenna is configured to point to a target closer than the observation target, The beam is directed to the target object that is farther away than the target object. The flying object according to claim 1.

4. A pointing control system mounted on the flying object according to any one of claims 1 to 3, The antenna control device; The beam control device; A directional control system comprising:

5. adjusting the direction of the antenna so that the azimuth direction of the antenna coincides with the normal direction of the specific plane and the boresight direction of the antenna points in a direction deviated from the direction of pointing at the observation target according to a deviation angle; irradiating a beam in a direction deviated from the pointing direction of the antenna according to the deflection angle by electronic scanning; Using the antenna, receive the beam reflected from the target. It is an observation method, the specific plane is a plane formed by a relative direction of the antenna with respect to the observation target and a normal direction of the ground surface at the position of the observation target, and rotated around the normal direction of the ground surface at the position of the observation target according to a plane rotation angle; The surface rotation angle is set as an angle around the normal direction of the ground surface. Observation method.

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