Artificial satellites and image generation systems

Abstract

The present invention provides an artificial satellite equipped with an improved imaging device, and an image generation system including such an operational satellite. [Solution] The artificial satellite of this disclosure comprises a main body having an arrangement surface, and an imaging device array consisting of a plurality of imaging devices arranged in at least one row on the arrangement surface.

Description

Technical Field

[0001] The present disclosure relates to a satellite and an image generation system that photograph the earth's surface and generate images.

Background Art

[0002] Satellites that photograph the earth's surface to generate observation images for observing the earth's surface are known. For example, in a patent document, there is disclosed a technique for generating an image of a specific point on the earth by photographing the same point on the earth using four co-visual telescopes, respectively passing different images to a focal plane array, and the focal plane array capturing by combining these images.

Prior Art Documents

Patent Documents

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0008] An artificial satellite according to one aspect of the present disclosure comprises a main body having an arrangement surface, an imaging device array composed of a plurality of imaging devices arranged in at least one row on the arrangement surface, and an image processing device that generates an image based on a plurality of image information generated by the plurality of imaging devices and the arrangement of each imaging device in the imaging device array. [Effects of the Invention]

[0009] We can provide artificial satellites with improved imaging capabilities. [Brief explanation of the drawing]

[0010] [Figure 1] A diagram showing an example of the configuration of the image generation system according to the embodiment of this disclosure. [Figure 2] A schematic diagram showing an example of the appearance of an artificial satellite. [Figure 3] A schematic diagram showing how multiple imaging devices constituting an imaging device array are tilted. [Figure 4] Block diagram showing an example of the functional configuration of an artificial satellite. [Figure 5] A schematic diagram showing how each imaging device, arranged parallel to the AT direction, captures images of different points in a single shooting timing. [Figure 6] This diagram illustrates how a satellite takes multiple images at different timings while flying along the orbital direction (AT). [Figure 7] A schematic diagram showing how imaging devices, arranged parallel to the CT direction, capture images of different locations at the same time. [Figure 8]A schematic diagram showing how imaging devices arranged parallel to the CT direction capture the same target point at different timings. [Figure 9] A schematic diagram showing the relationship between the AT direction and CT direction, the arrangement direction of the imaging device, and the arrangement direction of the photodetector in the fourth example of operation. [Figure 10] A diagram illustrating the respective shooting ranges of multiple imaging devices in the fourth operational example. [Modes for carrying out the invention]

[0011] Each embodiment of this disclosure will be described in detail below with reference to the drawings. However, detailed explanations of already well-known matters and redundant explanations of substantially identical configurations may be omitted. In addition, common components in each embodiment will be denoted by the same reference numerals, and redundant explanations may be omitted.

[0012] (The process leading to the invention) Traditionally, artificial satellites have been designed specifically for the performance requirements they demand. For example, to accurately observe the Earth's surface and atmosphere, a large imaging device with a large-aperture optical system is desirable, and it was common practice to design the entire satellite to accommodate such a large imaging device. In particular, imaging devices tended to become larger because they needed to be protected from cosmic rays, low temperatures, and vacuum to operate without problems in space, as well as from vibrations and shocks during launch.

[0013] In recent years, there has been an increasing demand for miniaturization of artificial satellites to reduce costs and improve ease of operation. However, it is difficult to mount large imaging devices like those mentioned above on small artificial satellites. On the other hand, if imaging devices are also miniaturized to match the miniaturization of the artificial satellite, the amount of information obtained will decrease significantly, making it difficult to observe the Earth's surface with high accuracy. This trend is particularly pronounced in low Earth orbit satellites.

[0014] In order to solve these problems, the present disclosure arranges a plurality of small imaging devices side by side on the placement surface (ground-facing surface) of the artificial satellite body. As described above, conventionally, since each artificial satellite has been designed according to the imaging device to be mounted, it can be said that the idea of arranging a plurality of small imaging devices on an artificial satellite itself did not exist. The present disclosure has arrived at an unprecedented idea of arranging a plurality of imaging devices on an artificial satellite in recent years because the durability of small imaging devices has improved and small imaging devices that can be used even in space have been developed.

[0015] Further, the present disclosure generates an image with a relatively large amount of information based on the image information obtained from a plurality of imaging devices and the arrangement positions of the plurality of imaging devices on the ground-facing surface. In the present disclosure, by arranging a plurality of small imaging devices side by side on the ground-facing surface of the artificial satellite, even if the amount of image information that each imaging device can acquire is less than that of a conventional large imaging device, an image with a relatively large amount of information can be generated based on the image information obtained from the plurality of imaging devices and the positions where the plurality of imaging devices are arranged.

[0016] <Image generation system 100> FIG. 1 is a diagram showing an example of the configuration of an image generation system 100 according to an embodiment of the present disclosure. As shown in FIG. 1, the image generation system 100 includes an artificial satellite 200 and a ground station 300.

[0017] The artificial satellite 200 is, for example, a low-earth orbit satellite that orbits the earth at an altitude of 100 km to 2000 km. Note that the artificial satellite of the present disclosure is not limited to a low-earth orbit satellite, and may be a satellite flying in a medium-earth orbit or a geostationary orbit.

[0018] As will be described later, the artificial satellite 200 has an imaging device and is an observation satellite that uses the imaging device to photograph the ground and generate an image.

[0019] Furthermore, as will be described later, satellite 200 is equipped with a communication unit and optical communication equipment, and communicates with ground station 300 using radio waves and light. Satellite 200 may communicate directly with ground station 300, or, depending on the relative positions of satellite 200 and ground station 300, it may communicate indirectly with ground station 300 via a relay satellite, for example, in geostationary orbit.

[0020] Ground station 300 is installed on the Earth's surface and is equipment that communicates with satellite 200. Ground station 300 is, for example, communicatively connected to a control device that controls satellite 200 and transmits control information to satellite 200. Ground station 300 also receives image data generated by satellite 200 and transmits said image data to a predetermined facility that will use it.

[0021] With this configuration, the image generation system 100 can observe the Earth's surface.

[0022] <Satellite 200> Next, we will describe satellite 200. Figure 2 is a schematic diagram showing an example of the appearance of satellite 200. Figure 2A is a perspective view showing the side of satellite 200 facing the Earth's surface when it is in orbit, and Figure 2B is a perspective view showing the side of satellite 200 facing away from the Earth's surface when it is in orbit.

[0023] As shown in Figure 2A, the artificial satellite 200 includes a main body 201, a mounting surface 202, a back surface 203, an imaging device array 205 composed of multiple imaging devices 204, a star tracker 206, a thruster 207, an X-band antenna 208, an S-band antenna 209, a solar panel 210, an S-band antenna 211, an optical communication device 212, and a positioning antenna 213.

[0024] The main body 201 is the main body on which the components of the artificial satellite 200 are mounted. In the example shown in Figures 2A and 2B, the main body 201 has a roughly rectangular parallelepiped shape. The main body 201 has a mounting surface 202 on its first surface 201T of its rectangular parallelepiped shape. The first surface 201T is the surface of the main body 201 that faces the Earth's surface when the artificial satellite 200 is flying in orbit.

[0025] In the example shown in Figure 2A, the placement surface 202 is formed as a flat surface, but the disclosure is not limited to this. For example, the placement surface 202 may be a curved surface.

[0026] In the following description, the direction parallel to one side of the rectangle constituting the planar arrangement surface 202 of the main body 201 is defined as the X direction, the direction parallel to one side of the rectangle perpendicular to the X direction is defined as the Y direction, and the direction perpendicular to both the X and Y directions is defined as the Z direction. The positive direction in the X direction is an example of the first direction of this disclosure. The positive direction in the Y direction is an example of the second direction of this disclosure.

[0027] The main body 201 is formed with a thinner thickness in the Z direction compared to its width in the X and Y directions. This allows the satellite 200 to be thin and compact. The width of the main body 201 in the X and Y directions is preferably between 1m and 5m, and more preferably 3m. The width of the main body 201 in the X direction and the width in the Y direction do not have to be the same, and may be different within the above range. The thickness of the main body 201 in the Z direction is preferably between 30cm and 1m, and more preferably 50cm.

[0028] The main body 201 has a back surface 203 on the second surface 201B, which is opposite the first surface 201T. The second surface 201B is the surface of the main body 201 that faces away from the Earth's surface when the satellite 200 is flying in orbit. In addition, the surfaces of the main body 201 other than the first surface 201T and the second surface 201B (hereinafter referred to as the side surfaces 201S of the main body 201) function as heat dissipation surfaces.

[0029] Each surface of the main body 201 is arranged with the various components of the satellite 200. Figures 2A and 2B show examples of the arrangement of each component when the satellite 200 is flying in the positive direction in the X direction. In Figures 2A and 2B, the positions of each component are examples and can be changed depending on the intended use of the satellite 200.

[0030] Multiple imaging devices 204 are arranged on the arrangement surface 202 to form an imaging device array 205. In the example shown in Figure 2A, the imaging device array 205 is formed by arranging multiple imaging devices 204 in a matrix in both the X and Y directions. However, this disclosure is not limited to the example shown in Figure 2A. For example, the imaging device array 205 may be formed by arranging multiple imaging devices 204 in at least one row on the arrangement surface 202. That is, multiple imaging devices 204 may be arranged in a row along only one of the directions, either the X or the Y.

[0031] In the example shown in Figure 2A, the multiple imaging devices 204 are arranged in a matrix on the arrangement surface 202, 18 each along the X and Y directions, excluding the corners. In this disclosure, the number of imaging devices 204 arranged on the arrangement surface 202 is not limited to the example shown in Figure 2A. It is desirable that the number of multiple imaging devices 204 arranged in a row be at least 5. For example, a large number of imaging devices 204, about 50 each along the X and Y directions, may be arranged on the arrangement surface.

[0032] Each of the multiple imaging devices 204 is a relatively small imaging device. Specifically, the aperture diameter of each imaging device 204 is, for example, about 10 cm. Alternatively, the aperture diameter of each imaging device 204 may be appropriately set within the range of 10 cm to 60 cm. It is desirable that each of the multiple imaging devices 204 has the same aperture diameter.

[0033] Furthermore, multiple imaging devices 204 may be arranged on the arrangement surface 202 in a state of inclination in the X direction or the Y direction. Figure 3 is a schematic diagram showing how multiple imaging devices 204 constituting the imaging device array 205 are inclined. For simplicity, Figure 3 shows an example in which the imaging device array 205 is configured with four imaging devices 204 arranged in both the X direction and the Y direction.

[0034] In the example shown in Figure 3, of the four imaging devices 204 arranged along the X direction, the imaging devices 204E located at both ends are tilted in either the positive or negative direction in the X direction, respectively. In other words, the imaging devices 204E at both ends are tilted outward relative to the arrangement along the X direction. In such a case, the imaging device array 205 can generate images over a wide area.

[0035] In the example shown in Figure 3, the placement surface 202 is a flat surface, but the placement surface 202 may also be a curved surface in which the central part of the placement surface 202 is more bulging than the peripheral part. Having such a curved surface on the placement surface 202 makes it easier to fix the multiple imaging devices 204 to the placement surface 202 so that they each face outwards. In this disclosure, if the placement surface 202 is a curved surface, the shape of the curved surface is not limited to the example described above. The surface shape of the placement surface 202 may be any shape that makes it easy to fix the multiple imaging devices 204 so that they face the desired direction.

[0036] Figure 3 shows an example in which only the imaging devices 204E located at both ends of four imaging devices 204 arranged along the X direction are tilted, but the disclosure is not limited to this. For example, multiple imaging devices 204 arranged along the X direction may be fixed to the arrangement surface 202 such that the absolute value of the tilt angle increases or decreases from the center of the arrangement along the X direction towards the ends.

[0037] Let's explain with a specific example. For instance, consider an imaging array 205 composed of 31 imaging devices 204 arranged in a row along both the X and Y directions, where each of these imaging devices 204 is tilted so that it faces outward from the center of the array as it approaches the edges. In this case, the tilt angle of each imaging device 204 increases by 3.4 degrees as it moves from the center of the array towards the edges.

[0038] In this case, the imaging device 204 located at the outermost end (hereinafter referred to as "end") in the X direction is tilted at 51 degrees toward the positive direction of X. The second imaging device 204 located from the end in the X direction is tilted at 47.6 degrees toward the positive direction of X. The third imaging device 204 located from the end in the X direction is tilted at 44.2 degrees toward the positive direction of X. In this way, the tilt angle of the imaging device 204 gradually decreases as you move away from the end in the X direction and toward the opposite direction of X. The 16th imaging device 204X from the end in the X direction is in the center of the arrangement of imaging devices 204 along the X direction, and its tilt angle is 0 degrees. The tilt angles of the imaging devices 204 from the 17th onward increase by 3.4 degrees toward the negative direction of X. The 31st imaging device 204 from one end in the X direction, i.e., the one at the far end, will be tilted 51 degrees toward the negative direction in the X direction.

[0039] In this way, by increasing the inclination angle as it approaches the edge, when multiple imaging devices 204 photograph the Earth's surface from an orbiting satellite 200, their respective imaging ranges can be staggered. If the satellite 200 is at an altitude of approximately 400 km and the aperture diameter of the imaging device 204 is 10 cm, one imaging device 204 can photograph a range of 24 km. Furthermore, by tilting the imaging devices 204 at a suitable angle as in the example described above, the imaging ranges of adjacent imaging devices 204 can be made adjacent to each other without overlapping. In this case, while maintaining the attitude of the satellite 200, a range of approximately 700 km can be photographed at once by 31 imaging devices 204.

[0040] In this disclosure, the inclination of each imaging device 204 is not limited to the inclination toward the outside of the array as shown in Figure 3. Contrary to the example shown in Figure 3, imaging devices 204 located in the positive direction in the X direction between the center and the ends of the array may be inclined toward the negative direction in the X direction, and imaging devices 204 located in the negative direction in the X direction may be inclined toward the positive direction in the X direction. In other words, multiple imaging devices 204 may be inclined toward the inside of the array as they approach the ends of the array. In such a case, each imaging device 204 of the imaging device array 205 can generate an image that includes a specific same point.

[0041] Furthermore, each imaging device 204 may tilt in the positive or negative direction in the Y direction instead of in the positive or negative direction in the X direction. Also, if multiple imaging devices 204 are arranged in a matrix in both the X and Y directions, each imaging device 204 may tilt in the positive or negative direction in both the X and Y directions, and in both the positive or negative direction in the Y direction.

[0042] The tilt angle of each of the multiple imaging devices 204 may be determined and fixed, for example, during the manufacturing of the satellite 200, but it may also be configured so that the tilt angle can be arbitrarily changed by a tilting device 226, for example, as described later.

[0043] Returning to the explanation of Figure 2, the star tracker 206 measures the position of a star and detects the attitude of the satellite 200 as it flies in orbit. In the example shown in Figure 2A, the star tracker 206 is located on the side 201S of the main body 201 of the satellite 200 as it flies in orbit, on the side that does not face the Earth or the Sun.

[0044] The thrusters 207 are propulsion devices used for attitude control of the satellite 200. In the example shown in Figure 2A, the thrusters 207 are located on the rear side 201S of the main body 201 of the satellite 200 as it flies in orbit.

[0045] The X-band antenna 208 and the S-band antenna 209 are antennas for communication with ground equipment (for example, the ground station 300 shown in Figure 1). The X-band antenna 208 and the S-band antenna 209 can communicate with each other at different frequencies. The X-band antenna 208 and the S-band antenna 209 are each located on the first surface 201T of the main body 201.

[0046] The solar panel 210 generates power for the operation of the satellite 200 using sunlight. The solar panel 210 is located on the back surface 203.

[0047] The S-band antenna 211 and optical communication device 212 communicate with other satellites (e.g., relay satellites) orbiting in higher orbits (e.g., geostationary orbit). This allows communication via relay satellites even during times when communication with the ground station 300 using the X-band antenna 208 or S-band antenna 209 is not possible.

[0048] The positioning antenna 213 communicates with other positioning satellites, for example. Based on the positioning information obtained by the positioning antenna 213 and the information obtained by the star tracker 206, the satellite 200 can accurately estimate its own position and attitude.

[0049] Figure 4 is a block diagram showing an example of the functional configuration of the artificial satellite 200. In the example shown in Figure 4, the artificial satellite 200 has the following functional configuration: a main computer 221, a communications unit 222, an attitude control device 223, a power supply unit 224, an image processing device 225, an optical communications device 212, and an imaging device array 205 including multiple imaging devices 204.

[0050] The main computer 221 controls the entire satellite 200. The main computer 221 is a computer that includes, for example, a processing unit (processor) and memory. Based on the power supplied from the power supply unit 224, the main computer 221 performs calculations to control various parts of the satellite 200.

[0051] The communications unit 222 uses the X-band antenna 208, the S-band antenna 209, and the S-band antenna 211 (see Figure 2) to communicate with other satellites and ground stations 300 (see Figure 1). The communications unit 222 outputs various information acquired through communication to the main computer 221 and transmits various information acquired from the main computer 221.

[0052] The attitude control device 223 controls the attitude of the satellite 200 based on various information acquired by the communication unit 222 and positioning information obtained from the star tracker 206 or positioning antenna 213. The attitude control device 223 can perform attitude control by, for example, controlling the thrust pressure of the thrusters 207 or rotating the reaction wheels built into the main body 201. The attitude control device 223 may also perform orbital control of the satellite 200 in addition to attitude control. Orbital control of the satellite 200 may also be performed by an orbital control device provided separately from the attitude control device 223.

[0053] The attitude control device 223 can control the attitude of the satellite 200 as it flies in orbit. Specifically, the attitude control device 223 usually controls the attitude of the satellite 200 so that the X direction is parallel to the direction of orbital travel. The attitude control device 223 may also control the attitude of the satellite 200 so that the Y direction is parallel to the direction of orbital travel, if necessary. By controlling the attitude of the satellite 200, the attitude control device 223 determines the relationship between the arrangement direction of the multiple imaging devices 204 on the arrangement plane 202 and the direction of orbital travel.

[0054] The power supply unit 224 supplies power to each part of the artificial satellite 200 as needed. The power supply unit 224 includes, for example, a battery that stores the power generated by the solar panels 210, and a power supply control unit that controls the power supply to each component.

[0055] The image processing device 225 generates an image based on image information acquired from an imaging device array 205 which includes multiple imaging devices 204, and the arrangement of the multiple imaging devices 204 in the imaging device array 205.

[0056] The tilting device 226 can arbitrarily change the tilt angle of the multiple imaging devices 204. The tilting device 226 is, for example, a gimbal mechanism. In the example shown in Figure 4, the tilting device 226 is shown independently of the multiple imaging devices 204, but in practice, it is desirable to provide a tilting device 226 for each of the multiple imaging devices 204.

[0057] As described above, the artificial satellite 200 according to the embodiment of the present disclosure has a structure in which a plurality of imaging devices 204 are arranged in at least one row on the arrangement surface 202 of the main body 201. With this structure, the artificial satellite 200 according to the embodiment of the present disclosure can secure a large amount of information in total, even if the amount of image information that each imaging device 204 can generate is relatively small, by using a plurality of imaging devices 204.

[0058] Furthermore, in the artificial satellite 200 according to the embodiment of this disclosure, the image processing device 225 generates an image based on image information acquired from an imaging device array 205 including a plurality of imaging devices 204, and the arrangement of the plurality of imaging devices 204 in the imaging device array 205. As a result, even if the amount of image information that each individual imaging device 204 can generate is relatively small, by using the multiple image information from multiple imaging devices 204, an image with a relatively large amount of information can be generated. In addition, by considering the arrangement of the plurality of imaging devices 204 in the imaging device array 205 when generating the image, it is possible to achieve higher accuracy, higher resolution, and wider coverage of the generated image.

[0059] <Example of operation of satellite 200> The following describes in detail an example of operation when the artificial satellite 200 having the above configuration generates image information from multiple imaging devices 204, and the image processing device 225 performs image processing based on the image information.

[0060] (Example of operation 1: Video generation process for the target location) In the first operational example, the multiple imaging devices 204 included in the imaging device array 205 are arranged in at least one line along the X direction. In the first operational example, the attitude control device 223 controls the attitude of the satellite 200 so that the direction of travel of the satellite 200 in orbit (orbital direction of travel) is the positive direction of the X direction. In other words, in the first operational example, the satellite 200 flies so that the direction in which the multiple imaging devices 204 are arranged and the orbital direction of travel are parallel to each other. In the first operational example, each of the multiple imaging devices 204 included in the imaging device array 205 is tilted to face outwards from the arrangement in the X direction.

[0061] The direction of travel of the artificial satellite 200 in orbit (orbital travel direction) is sometimes called the Along Track (AT) direction. The first example of operation is a process in which, when the attitude of the artificial satellite 200 is controlled so that multiple imaging devices 204 are arranged parallel to the AT direction, the image processing device 225 generates a moving image of a target point by taking pictures of an area including a specific target point on the Earth's surface at different timings.

[0062] Each of the multiple imaging devices 204, which are arranged parallel to the AT direction, can be configured to suitably set the aperture diameter of the imaging device 204, the altitude of the satellite 200, and the tilt angle of each imaging device 204, as shown in Figure 5, so that while the satellite 200 maintains the same attitude in orbit, each of the multiple imaging devices 204 can photograph different points on the Earth's surface in the AT direction. In this specification, the range that each imaging device 204 can photograph is referred to as the imaging range.

[0063] Figure 5 is a schematic diagram showing how each of the imaging devices 204, arranged parallel to the AT direction, photographs a different point in a single imaging timing. In Figure 5, each triangle connecting the satellite 200 and the Earth's surface schematically represents the imaging range of each imaging device 204. For example, if the aperture diameter of the imaging device 204 is 10 cm, the altitude of the satellite 200 is 400 km, and 31 imaging devices 204 are arranged along the X direction (parallel to the AT direction), with the inclination increasing by 3.4 degrees from the center of the arrangement towards the edges, then the range of the Earth's surface that one imaging device 204 can photograph is approximately 24 km parallel to the AT direction. Therefore, with 31 imaging devices 204, the range of the Earth's surface that the satellite 200 can photograph in a single imaging timing is approximately 700 km in width parallel to the AT direction.

[0064] When the satellite 200 is flying in this attitude, the image processing device 225 can generate a moving image of a target point on the Earth's surface by the following processing. The target point is, for example, a point on the Earth's surface predetermined by the user of the image generation system 100, and is the point that is the target of the image generation processing by the satellite 200. Consider the case where the satellite 200, which can generate a wide-area image along the AT direction in a single shooting timing, takes multiple images at different shooting timings while flying along the AT direction in orbit.

[0065] Figure 6 shows how the satellite 200 takes multiple images at different timings while flying along the AT direction in orbit. For simplicity, Figure 6 shows an example in which the satellite 200 has three imaging devices 204 arranged along the AT direction. Each of these imaging devices 204 is tilted toward the AT direction or the opposite direction.

[0066] As the artificial satellite 200 moves along the AT direction, at time T1, the target point can be photographed by the imaging device 204 positioned in front of the orbital direction (AT direction) in the arrangement of imaging devices 204. In this specification, photographing the target point means photographing the area of ​​the Earth's surface that includes the target point.

[0067] At time T2, the satellite 200 can photograph the target location using the imaging device 204 positioned in the center of the array relative to the AT direction. At time T3, the satellite 200 can also photograph the target location using the imaging device 204 positioned at the rear of the array relative to the AT direction. In this way, by controlling the attitude of the satellite 200 so that multiple imaging devices 204 tilted outward are arranged parallel to the AT direction, the same target location can be photographed at different timings and by different imaging devices 204.

[0068] Thus, in this first operational example, the image processing device 225 can collect image information generated by different imaging devices 204, each capturing the target location at a different timing while the satellite 200 passes over the target location once, for a number of images equal to the number of imaging devices 204 arranged in the array. The image processing device 225 can generate a moving image of the area including the target location by arranging the multiple images with different capture timings in order based on the capture timings.

[0069] Here, the image processing device 225 corrects each image piece of information based on the position of the imaging device 204 that generated each image piece of information within the imaging device array 205 and the longitude of its tilt, and then generates a moving image based on the corrected image information. For example, by applying a tilt-accommodating correction to the image information generated by an imaging device 204 with a large tilt angle, differences in viewpoint between the image information generated by other imaging devices 204 become less likely, and higher quality moving images can be generated.

[0070] In this specification, the information indicating the position of the imaging device 204 that generated each image information within the imaging device array 205, and the longitude inclination of that device, is referred to as the "position of imaging device 204".

[0071] Figure 6 shows, for simplicity, an example in which a video is generated based on three image data points generated at three different time points. However, in practice, it is more desirable that the satellite 200 of this disclosure be configured to generate a video with more information based on more image data generated at more acquisition timings by more imaging devices 204. Specifically, it is desirable that the number of imaging devices 204 arrays in the X or Y direction included in the imaging device array 205 be five or more.

[0072] Furthermore, the first example of operation described above explained the process of generating moving images using image information from multiple imaging devices 204 arranged in a row parallel to the AT direction (along the X direction). Similar processing can also be applied when multiple imaging devices 204 are arranged in a matrix along the X and Y directions, as illustrated in Figures 2A and 3. In this case, the image processing device 225 can generate a wide-area image in a direction perpendicular to the Earth's surface relative to the AT direction, based on the image information generated by the multiple imaging devices 204 arranged along the Y direction.

[0073] (Second example of operation: Wide-area image generation processing in the CT direction) In the second operational example, when the multiple imaging devices 204 are arranged in at least one line along the X direction, the attitude control device 223 controls the attitude of the satellite 200 so that the orbital direction (AT) is perpendicular to the X direction, or in other words, the AT direction is parallel to the Y direction. That is, in the second operational example, the satellite 200 flies such that the arrangement direction of the multiple imaging devices 204 is perpendicular to the AT direction.

[0074] The direction perpendicular to the orbital direction (AT direction) on a plane parallel to the Earth's surface is sometimes called the cross-track (CT) direction. The second operational example is when the attitude of the satellite 200 is controlled so that multiple imaging devices 204 are aligned along the CT direction. In this second operational example, the image processing device 225 can generate a wide-area image of the Earth's surface along the CT direction in a single imaging timing.

[0075] In the second example of operation, as in the first example of operation, each of the multiple imaging devices 204 included in the imaging device array 205 is tilted to face outward in the X direction.

[0076] In the second operational example, the image processing device 225 generates an image based on multiple image information generated by multiple imaging devices 204 arranged perpendicular to the AT direction, or in other words, parallel to the CT direction. Therefore, in the second operational example, an image can be generated with a wide observation width (scan width) in the CT direction.

[0077] Figure 7 is a schematic diagram showing how each of the imaging devices 204, arranged parallel to the CT direction, captures images of different locations at the same time. In Figure 7, the satellite 200 is flying towards the foreground of the figure. In this way, while the satellite 200 maintains the same attitude, each of the multiple imaging devices 204 can capture images of different locations on the Earth's surface in the CT direction at the same time. As a result, the image processing device 225 can generate an image that covers a wide area of ​​the Earth's surface in the CT direction in a single capture timing.

[0078] Furthermore, in the second example of operation, when the image processing device 225 generates a wide-area image based on the image information generated by multiple imaging devices 204, it is more desirable to perform a process to correct the image information generated by each imaging device 204 based on the arrangement position of the imaging devices 204 before generating the image.

[0079] In the second example of operation, the image processing device 225 may arbitrarily change the tilt angle of each imaging device 204 by controlling the tilt device 226. By increasing the tilt angle of the imaging devices 204 with the tilt device 226, the image processing device 225 can generate an image of a wider area in a single imaging timing. However, since the range that one imaging device 204 can capture is predetermined by the aperture diameter and the altitude of the artificial satellite 200, if the tilt angle of some imaging devices 204 is increased in the CT direction or the opposite direction, a gap will be created between the capture range of other imaging devices 204. In this case, it is desirable for the tilt device 226 to suitably adjust the tilt angle of each imaging device 204 so that there is as little gap as possible between the capture ranges of adjacent imaging devices 204.

[0080] (Third example of operation: Stereoscopic image generation process of the target location) The third example of operation is similar to the second example of operation, in which the attitude of the satellite 200 is controlled so that the arrangement direction of the multiple imaging devices 204 is parallel to the CT direction. In the third example of operation, when the satellite 200 passes over the target point at different positions at different times, a stereoscopic image including the target point is generated using multiple image information obtained from these different positions.

[0081] Artificial satellites orbiting in low Earth orbit complete one orbit in about an hour and a half. During this time, due to the Earth's rotation, they pass over different points in the sky from the perspective of a specific target location. In the third example of operation, image information obtained at the time of the first pass over the target location and image information obtained at the time of the second pass are used. Since these images are different but depict the same target location, a stereoscopic image can be generated based on them.

[0082] Figure 8 is a schematic diagram showing how any of the imaging devices 204, which are arranged parallel to the CT direction, take images of the same target point at different timings. In the example shown in Figure 8, at times T4, T5, and T6, the satellite 200 passes through different positions in the sky near the target point.

[0083] In the example shown in Figure 8, at time T4, satellite 200 passes overhead to the left in the CT direction from the target point. At this time, satellite 200 can photograph the target point using the imaging device 204 located on the right side in the alignment direction (in this case, the CT direction). At time T5, satellite 200 passes almost directly overhead from the target point. At this time, satellite 200 can photograph the target point using the imaging device 204 located in the center of the alignment direction. At time T6, satellite 200 passes overhead to the right in the CT direction from the target point. At this time, satellite 200 can photograph the target point using the imaging device 204 located on the left side in the alignment direction.

[0084] In this way, by controlling the attitude of the satellite 200 so that multiple imaging devices 204 tilted outward in the alignment direction are parallel to the CT direction, the same target point can be imaged by different imaging devices 204 at different imaging timings.

[0085] Thus, in this third operational example, the image processing device 225 can collect a large amount of image information generated by different imaging devices 204 capturing images of the target location at different timings while the satellite 200 passes over the target location multiple times at different positions in the sky. As a result, the image processing device 225 can generate a stereoscopic image of the area including the target location based on a large amount of image information obtained by capturing the same target location from different viewpoints. In the example shown in Figure 8, a moving image is generated based on three images of information generated at three different time points, but in reality, the satellite 200 of this disclosure generates a more accurate stereoscopic image based on more image information generated from more viewpoints by more imaging devices 204.

[0086] Furthermore, in the third example of operation, when the image processing device 225 generates a stereoscopic image based on the image information generated by the multiple imaging devices 204, it is more desirable for the image processing device 225 to perform a process to correct the image information generated by each imaging device 204 based on the arrangement position of the imaging devices 204 before generating the image.

[0087] (Fourth example of operation: Image processing using TDI technology) The fourth example of operation describes image processing using TDI (Time Delay Integration) technology. TDI technology is a technique that uses a line sensor having multiple photodetectors arranged in a line, and improves sensitivity by transferring and accumulating electric charge between the photodetectors in accordance with the movement of the object being photographed.

[0088] In the fourth operational example, each of the multiple imaging devices 204 is assumed to have a line sensor 204S containing multiple photodetectors 204R. In the fourth operational example, the multiple imaging devices 204 are arranged in at least one line along the X direction, and each imaging device 204 has multiple photodetectors 204R arranged along the X direction. In the fourth operational example, the attitude control device 223 controls the attitude of the satellite 200 so that the AT direction is parallel to the X direction (arrangement direction). In other words, in the fourth operational example, the satellite 200 flies such that the direction in which the multiple imaging devices 204 are arranged, the direction in which the multiple photodetectors 204R included in the line sensor 204S of each imaging device 204 are arranged, and the orbital direction (AT direction) are parallel to each other.

[0089] Figure 9 is a schematic diagram showing the relationship between the AT direction and CT direction, the arrangement direction of the imaging device 204, and the arrangement direction of the photodetector 204R in the fourth example of operation. Figure 9A illustrates the line sensor 204S and photodetector 204R in one imaging device 204, and Figure 9B illustrates the relationship between the arrangement direction of the imaging device 204 and the arrangement direction of the photodetector 204R on the arrangement surface 202. Although Figure 9B shows an example in which multiple imaging devices 204 are arranged in only one row along the X direction, the disclosure is not limited to this, and they may also be arranged in the Y direction.

[0090] Furthermore, in the fourth operational example, the multiple imaging devices 204 arranged along the X direction are tilted in either the positive or negative direction in the X direction so that each of them photographs the same area of ​​the Earth's surface. Figure 10 is a diagram illustrating the respective imaging ranges of the multiple imaging devices 204 in the fourth operational example.

[0091] To achieve the imaging range shown in Figure 10, the multiple imaging devices 204 need to be tilted inward in the X-direction. Specifically, if the tilt angle of the imaging device 204 located in the center of the array is 0, then the imaging device 204 adjacent to it in the positive direction of the X-direction will tilt in the negative direction of the X-direction by, for example, 0.5 arcsec, and as it approaches the end of the array in the positive direction of the X-direction, its tilt angle increases by 0.5 arcsec in the negative direction. The imaging device 204 adjacent to the imaging device 204 located in the center of the array in the negative direction of the X-direction will tilt in the positive direction of the X-direction by, for example, 0.5 arcsec, and as it approaches the end of the array in the negative direction of the X-direction, its tilt angle increases by 0.5 arcsec in the positive direction. For example, if the imaging array 205 is composed of 31 imaging devices 204, the tilt angle of the imaging device 204 located at the positive end in the X direction will be tilted by 7.5 arcsec in the negative direction in the X direction, and the tilt angle of the imaging device 204 located at the negative end in the X direction will be tilted by 7.5 arcsec in the positive direction in the X direction.

[0092] In the fourth operational example, assuming that the satellite 200 is flying in this state, the image processing device 225 causes each imaging device 204 to take an image at the same timing. In this case, the image processing device 225 transfers and accumulates charge between the photodetectors 204R of the line sensors 204S of each imaging device 204 for an exposure time corresponding to the flight speed of the satellite 200, thereby effectively extending the exposure time of the target point. This prevents situations where, when photographing a target point on the Earth's surface, the exposure time is insufficient due to the high-speed flight of the satellite 200, resulting in the generation of images with insufficient information, and also enables the generation of images with sufficient information even with short exposure times. Furthermore, since multiple imaging devices 204 take images at the same timing, it is possible to prevent situations where the shooting timing is shifted between imaging devices when accumulating charge during TDI processing. This prevents degradation of the MTF (Modulation Transfer Function) and enables the generation of higher sensitivity and higher image quality images.

[0093] Furthermore, the image processing device 225 may transfer and accumulate charge between each imaging device 204. In this case, by transferring and accumulating charge between corresponding photodetectors 204R among the multiple photodetectors 204R that constitute the line sensor 204S of each imaging device 204, it is possible to generate images with higher sensitivity and higher image quality.

[0094] In the fourth example of operation described above, the explanation assumed that each image sensor 204 has a line sensor 204S in which multiple light-receiving elements 204R are arranged in a line. However, the method can also be applied to cases where each image sensor 204 has an area sensor in which multiple light-receiving elements are arranged in a matrix.

[0095] If the imaging device 204 has an area sensor, charge can be transferred and accumulated between photodetectors at the same coordinates in the area sensor matrix between multiple imaging devices 204 arranged along the X direction. This makes it possible to generate images with higher sensitivity and higher image quality even when the imaging device 204 has an area sensor.

[0096] (Fifth example of operation: Each imaging device detects light of different wavelengths) In the fifth operational example, multiple imaging devices 204 constituting the imaging device array 205 are each capable of detecting light in different wavelength ranges. In the fifth operational example, for example, each of the multiple imaging devices 204 is capable of detecting one of the following: visible light, infrared light, ultraviolet light, X-rays, or gamma rays.

[0097] The imaging device 204, which detects infrared radiation (wavelengths of approximately 830 nm to 1 mm), can obtain data on plant growth, wildfires, missile and rocket launches, and more.

[0098] The imaging device 204, which detects ultraviolet light (wavelengths of approximately 10 nm to 360 nm), can obtain data useful for observing the Earth's atmosphere or ozone layer, and for understanding global warming.

[0099] According to the imaging device 204, which detects X-rays (wavelengths of approximately 0.1 nm to 10 nm), observing the upper atmosphere can provide data useful for understanding global warming.

[0100] Gamma rays (wavelength approximately 10 -12 m or more 10 -14 According to the imaging device 204 that detects (less than m), data useful for monitoring nuclear power plant accidents, conflict zones, etc., can be obtained.

[0101] According to the fifth example of operation, similar to the fourth example of operation, by tilting each imaging device 204 so that multiple imaging devices 204 include the same target point in their imaging range, image information of various wavelength ranges relating to the same target point can be acquired.

[0102] The image processing device 225 generates images for each wavelength range based on image information for each wavelength range acquired from multiple imaging devices 204. Alternatively, the image processing device 225 may generate images using image information from multiple wavelength ranges.

[0103] (Sixth example of operation: Super-resolution processing) In the sixth operational example, the imaging device array 205 is constructed by arranging multiple imaging devices 204 in a matrix along the X and Y directions, respectively. In the sixth operational example, the multiple imaging devices 204 are tilted so that they face outwards from the array in both the X and Y directions. This allows the imaging device array 205 to acquire image information of a wide area including the target location in a single imaging timing. Furthermore, by taking images at multiple timings while the satellite 200 is flying above the target location, a large number of images of a wide area including the target location can be generated, each with a slightly shifted range.

[0104] In the sixth example of operation, the image processing device 225 generates a high-resolution image including the target point by performing super-resolution processing using images of a wide area including the target point, each with slightly different ranges.

[0105] Super-resolution processing is a process that generates a high-resolution image by using multiple low-resolution images in which at least a portion of the captured area overlaps with each other, and estimating the pixel values ​​of pixels corresponding to the overlapping area. Several types of super-resolution processing are known, including nearest neighbor interpolation, bilinear interpolation, and reconstruction-type super-resolution processing, and the image processing device 225 can perform super-resolution processing using an appropriate known method.

[0106] According to the sixth embodiment, even if the resolution of the image that can be generated based on the image information obtained from each imaging device 204 is low, it is useful because a higher resolution image can be generated based on multiple images.

[0107] (Seventh example of operation: Optical synthesis of multiple images) In the seventh embodiment, the imaging timing of each of the multiple imaging devices 204 constituting the imaging device array 205 is monitored by an ultra-high-precision clock, such as an optical lattice clock, thereby using the entire imaging device array 205 as a single optical system to acquire high-precision images.

[0108] Generally, even if multiple imaging devices 204 are instructed to take images at the same timing, slight timing differences occur due to the response characteristics of each imaging device 204, making it impossible to simply combine the images from each imaging device 204. In this seventh operational example, a highly accurate clock is used to record the phase of the output signal of each imaging device 204, and the phases of each imaging device 204 are adjusted to prevent the effects of phase differences.

[0109] The optical lattice clock is an ultra-high-precision clock that, for example, only deviates by about one second in 30 billion years. This allows for high-precision detection of even minute timing discrepancies between imaging devices 204.

[0110] The image processing device 225 detects the phase difference in acquisition timing between different imaging devices 204 and corrects the phase. This makes it possible to suppress the impact on the image caused by the phase difference between the imaging devices 204.

[0111] <Variation> The configuration of satellite 200 and the examples of operation described above are merely illustrative of how this disclosure may be implemented, and this disclosure is not limited to these configurations or examples of operation.

[0112] In the above description, the satellite 200 has an image processing device 225, and the image processing device 225 generates an image based on image information obtained from multiple imaging devices 204, but the disclosure is not limited to this. For example, the satellite 200 does not have to have an image processing device 225. In this case, for example, a ground station 300 (see Figure 1) has an image processing function, or the ground station 300 is communicably connected to an image processing device installed on the ground, and the satellite 200 transmits image information obtained from multiple imaging devices 204 to the ground station 300, thereby generating an image based on the image information on the ground. In this case, each process described as being performed by the image processing device 225 in the above example of operation may be appropriately performed by the image processing function of the ground station 300 or by an image processing device installed on the ground.

[0113] In the above description, the shape of the main body 201 of the satellite 200 is assumed to be approximately a rectangular parallelepiped, but this disclosure is not limited to this. In this disclosure, the main body of the satellite may have shapes such as cylindrical, prism, frustoconical, truncated pyramidal, elliptical cylinder, or frustoconical pyramidal. However, in this disclosure, in order to make the satellite thin and compact, it is desirable that the main body be formed to be thin in the thickness direction, regardless of its shape. [Industrial applicability]

[0114] This disclosure is useful for small artificial satellites. [Explanation of Symbols]

[0115] 100 Image Generation Systems 200 satellites 201 Main body 202 Placement plane 203 Back 204 Imaging device 204R photodetector 204S Line Sensor 204X imaging device 205 Imaging device array 206 Star Tracker 207 Thruster 208 X-band antenna 209 S-band antenna 210 solar panels 211 S-band antenna 212 Optical communication device 213 Positioning antenna 221 Main computer 222 Communications Department 223 Attitude control system 224 Power Supply 225 Image Processing Device 226 Tilt device 300 Ground stations

Claims

1. A main body having a mounting surface, An imaging device array comprising a plurality of imaging devices arranged in at least one row on the aforementioned arrangement surface, An artificial satellite equipped with [a specific feature / equipment].

2. The artificial satellite is further provided with an attitude control device that controls its attitude while flying in orbit. In the imaging device array, the plurality of imaging devices are arranged in a line along at least one direction. The attitude control device controls the attitude such that the first direction is parallel to or perpendicular to the orbital direction of the artificial satellite. The artificial satellite according to claim 1.

3. In the aforementioned imaging device array, the plurality of imaging devices are arranged in a matrix along the arrangement surface. The artificial satellite according to claim 2.

4. The aforementioned arrangement surface is a plane that faces the Earth's surface when the artificial satellite is flying in the aforementioned orbit. The plurality of imaging devices are arranged in a matrix along the first direction and a second direction perpendicular to the first direction in the plane, The artificial satellite according to claim 3.

5. In the imaging device array, at least one of the plurality of imaging devices arranged along the first direction is fixed to the arrangement surface in a state inclined toward the positive or negative direction in the first direction. The artificial satellite according to claim 4.

6. In the imaging device array, the plurality of imaging devices are fixed to the arrangement surface such that the inclination angle increases or decreases from the center to the ends of the arrangement along the first direction. The artificial satellite according to claim 5.

7. The artificial satellite, which flies in the orbit with a first direction parallel to the orbital direction of travel, further comprises an image processing device that generates a moving image relating to the target point based on a plurality of image information obtained by a plurality of imaging devices at different timings from each other, which capture an area including the target point on the Earth's surface. The artificial satellite according to claim 6.

8. The system further includes a tilting device that changes the tilt angle of each of the aforementioned multiple imaging devices. The artificial satellite according to claim 5.

9. The artificial satellite, which flies in the orbit with a first direction perpendicular to the orbital direction of travel, further comprises an image processing device that generates a stereoscopic image relating to the target point based on a plurality of still images taken by a plurality of imaging devices at different timings, covering an area including the target point on the Earth's surface. The artificial satellite according to claim 8.

10. The attitude control device is capable of changing the attitude of the satellite between an attitude in which the first direction is parallel to the orbital direction and an attitude in which the first direction is perpendicular to the orbital direction. The artificial satellite according to claim 2.

11. The imaging device has a plurality of light-receiving elements arranged parallel to the first direction, The artificial satellite further comprises an image processing device that, when the satellite is flying in an attitude in which the first direction is parallel to the orbital direction, transfers the charge generated by the plurality of photodetectors, each of the plurality of imaging devices, along the first direction and generates a TDI image based on the accumulated charge. The artificial satellite according to claim 2.

12. The image processing device generates the TDI image based on the accumulated charge, which is obtained by transferring and accumulating the charge generated by the multiple photodetectors, each of the multiple imaging devices that has captured the same point on the Earth's surface. The artificial satellite according to claim 11.

13. The artificial satellite flying in the aforementioned orbit further comprises an image processing device that generates a super-resolution image of a target point on the Earth's surface based on a plurality of still images taken by the plurality of imaging devices at different timings. The artificial satellite according to claim 3.

14. The plurality of imaging devices have a timing function that measures the phase difference of the output signals that constitute the image information. The image processing device generates the image based on the phase difference of the output signal. The artificial satellite according to claim 1.

15. In the aforementioned imaging device array, the number of imaging devices arranged in a row is five or more. The artificial satellite according to claim 1.

16. An artificial satellite comprising a main body having an arrangement surface, an imaging device array composed of a plurality of imaging devices arranged in at least one row on the arrangement surface, and a communication unit, A ground station that receives the image information transmitted from the artificial satellite, An image generation system equipped with the following features.

17. A main body having a mounting surface, An imaging device array comprising a plurality of imaging devices arranged in at least one row on the aforementioned arrangement surface, An image processing device that generates an image based on multiple image information generated by the multiple imaging devices and the arrangement of each imaging device in the imaging device array, An artificial satellite equipped with [a specific feature / equipment].

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