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] An artificial satellite according to one aspect of the present disclosure comprises a main body having an arrangement surface and an imaging device, the imaging device comprising a plurality of optical systems arranged in at least one row on the arrangement surface, an image sensor, and a light receiving unit that forms an image on the image sensor of light incident on each of the plurality of optical systems.

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 observe it and generate observation images 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-axial 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

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In order to accurately observe a wide area on the ground, there is a demand for a satellite with improved imaging performance, such as an increase in the observation width or an improvement in resolution.

[0005] The present disclosure aims to provide a satellite equipped with an imaging device with improved imaging performance, and an image generation system including such an execution satellite.

Means for Solving the Problems

[0006] A satellite according to an aspect of the present disclosure includes a main body having an arrangement surface, and an imaging device. The imaging device includes a plurality of optical systems arranged in at least one row on the arrangement surface, an imaging element, and a light receiving unit that forms an image of light incident on each of the plurality of optical systems on the imaging element.

[0007] An image generation system according to one aspect of the present disclosure comprises a main body having an arrangement surface, an imaging device for generating image information, and a communication unit, wherein the imaging device comprises an artificial satellite having a plurality of optical systems, an image sensor, and a light receiving unit for forming an image on the image sensor of light incident on each of the plurality of optical systems, and a ground station for receiving the image information transmitted from the artificial satellite. [Effects of the Invention]

[0008] We can provide artificial satellites with improved imaging capabilities. [Brief explanation of the drawing]

[0009] [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 multiple optical systems at an angle. [Figure 4] Block diagram showing an example of the functional configuration of an artificial satellite. [Figure 5] Schematic diagram illustrating the configuration of the imaging device. [Figure 6] Figure illustrating a second variant of the satellite of this disclosure. [Figure 7] A diagram illustrating a third variant of the satellite of this disclosure. [Modes for carrying out the invention]

[0010] 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.

[0011] (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, because countermeasures against cosmic rays, low temperatures, and vacuum are necessary to ensure smooth operation in outer space, imaging devices tended to become larger.

[0012] 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 artificial satellites, the amount of information obtained will decrease significantly, making it difficult to observe the Earth's surface with high accuracy.

[0013] To solve these problems, this disclosure provides an artificial satellite equipped with an imaging device comprising a lens array composed of multiple optical systems arranged in at least one row, an image sensor, and a composite optical system that images the light incident on each of the multiple optical systems onto the image sensor. With this configuration, even if each of the multiple imaging devices is small and has a relatively small actual aperture diameter, by imaging the light incident on the multiple optical systems onto a single image sensor, it is possible to obtain image information and transmission resolution that can be obtained from an imaging device with a larger aperture diameter.

[0014] <Image generation system 100> Figure 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 Figure 1, the image generation system 100 comprises an artificial satellite 200 and a ground station 300.

[0015] Satellite 200 is, for example, a low-Earth orbit satellite orbiting the Earth at an altitude of 100 km to 2000 km. However, the satellites described herein are not limited to low-Earth orbit satellites, but may also be satellites flying in medium Earth orbit or geostationary orbit.

[0016] The artificial satellite 200 is an observation satellite that has an imaging device and generates images by photographing the earth's surface using the imaging device, as will be described later.

[0017] Also, as will be described later, the artificial satellite 200 has a communication unit and communicates with the ground station 300 using radio waves. The artificial satellite 200 may communicate directly with the ground station 300, or depending on the positional relationship between the artificial satellite 200 and the ground station 300, it may communicate indirectly with the ground station 300 via a relay satellite in, for example, a geostationary orbit.

[0018] The ground station 300 is installed on the earth's surface and is equipment for communicating with the artificial satellite 200. The ground station 300 is communicably connected to, for example, a control device that controls the artificial satellite 200 and transmits control information to the artificial satellite 200. Also, the ground station 300 receives the image data generated by the artificial satellite 200 and transmits the image data to a predetermined facility that uses the image data.

[0019] With such a configuration, the image generation system 100 can observe the earth's surface.

[0020] <Artificial Satellite 200> Next, the artificial satellite 200 will be described. FIG. 2 is a schematic diagram showing an example of the appearance of the artificial satellite 200. FIG. 2A is a perspective view showing the appearance of the side of the artificial satellite 200 facing the earth's surface when flying in orbit, and FIG. 2B is a perspective view showing the side of the artificial satellite 200 facing away from the earth's surface when flying in orbit.

[0021] As shown in FIG. 2A, the artificial satellite 200 has a main body 201, a mounting surface 202, a back surface 203, an imaging device 205 having a plurality of optical systems 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.

[0022] 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. A plane-shaped arrangement surface 202 is provided on the first face 201T of the rectangular parallelepiped shape of the main body 201. The first face 201T is the face of the main body 201 that faces the Earth's surface when the artificial satellite 200 is flying in orbit.

[0023] In the following description, the direction parallel to one side of the rectangle constituting the arrangement surface 202 is referred to as the X direction, the direction parallel to one side of the rectangle constituting the arrangement surface 202 that is perpendicular to the X direction is referred to as the Y direction, and the direction perpendicular to both the X and Y directions is referred to as the Z direction.

[0024] 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.

[0025] A back surface 203 is provided on the second surface 201B of the main body 201, 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.

[0026] 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.

[0027] Multiple optical systems 204 are arranged on the arrangement surface 202. In the example shown in Figure 2A, multiple optical systems 204 are arranged 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, multiple optical systems 204 may be arranged in at least one row on the arrangement surface 202. That is, multiple optical systems 204 may be arranged in a row along only one direction, either the X or the Y direction.

[0028] In the example shown in Figure 2A, the multiple optical systems 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 optical systems 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 optical systems 204 arranged in a row be at least 5. For example, a large number of optical systems 204, about 50 each along the X and Y directions, may be arranged on the arrangement surface.

[0029] Each of the multiple optical systems 204 is composed of relatively small-diameter lenses, prisms, mirrors, and cases enclosing them. Specifically, the aperture diameter of the lenses in each optical system 204 is, for example, about 10 cm. It is desirable that the lenses in each of the multiple optical systems 204 have the same aperture diameter.

[0030] Furthermore, multiple optical systems 204 may be arranged on the arrangement surface 202 at an angle in the X or Y direction. Figure 3 is a schematic diagram showing multiple optical systems 204 at an angle. For simplicity, Figure 3 shows an example in which four optical systems 204 are arranged in both the X and Y directions.

[0031] In the example shown in Figure 3, of the four optical systems 204 arranged along the X direction, the optical systems 204E located at both ends are tilted in either the positive or negative direction in the X direction, respectively. In other words, the optical systems 204E at both ends are tilted outward with respect to the arrangement along the X direction. In such a case, the multiple optical systems 204 can receive light from a wide range of areas on the ground.

[0032] 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 205 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 205 so that they face the desired direction.

[0033] Figure 3 shows an example in which only the optical systems 204E located at both ends of four optical systems 204 arranged along the X direction are tilted, but the disclosure is not limited to this. For example, multiple optical systems 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 to the ends of the arrangement along the X direction.

[0034] Let's explain with a specific example. For instance, consider a case where 31 optical systems 204 are arranged in a row along the X and Y directions on the arrangement plane 202, and each optical system 204 is tilted so that it faces outward from the center of the arrangement as it approaches the edges. In this case, the tilt angle of each optical system 204 increases by 3.4 degrees as it moves from the center of the arrangement towards the edges.

[0035] In this case, the optical system 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 optical system 204 located from the end in the X direction is tilted at 47.6 degrees toward the positive direction of X. The third optical system 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 magnitude of the tilt angle of the optical system 204 gradually decreases as you move away from the end in the X direction and toward the opposite direction of X. The 16th optical system 204 from the end in the X direction is in the center of the array of optical systems 204 along the X direction, and its tilt angle is 0 degrees. The tilt angles of the optical systems 204 from the 17th onward increase by 3.4 degrees toward the negative direction of X. The 31st optical system 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.

[0036] In this way, by increasing the inclination angle as it approaches the edges, the range of the Earth surface that each optical system 204 receives light from can be shifted on the artificial satellite 200 flying in orbit. If the altitude of the artificial satellite 200 is approximately 400 km and the aperture diameter of the optical system 204 is 10 cm, one optical system 204 can receive light from an area of ​​24 km in length and width on the Earth's surface. Furthermore, by tilting the optical systems 204 at a suitable angle as in the example above, the range of the Earth surface that adjacent optical systems 204 can receive light from can be made adjacent to each other without overlapping. While maintaining the attitude of the artificial satellite 200, an area of ​​approximately 700 km can be photographed at once by 31 optical systems 204.

[0037] In this disclosure, the inclination of each optical system 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, an optical system 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 an optical system 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 optical systems 204 may be inclined toward the inside of the array as they approach the ends of the array. In such a case, each optical system 204 can receive light from the same specific point.

[0038] Furthermore, each optical system 204 may be tilted 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 optical systems 204 are arranged in a matrix in both the X and Y directions, each optical system 204 may be tilted 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.

[0039] The tilt angle of each of the multiple optical systems 204 may be determined and fixed, for example, during the manufacturing of the artificial 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.

[0040] The imaging device 205 generates image information based on the light incident on the multiple optical systems 204. Details of the imaging device 205 will be described later.

[0041] 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.

[0042] 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.

[0043] 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.

[0044] 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.

[0045] 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.

[0046] 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.

[0047] Figure 4 is a block diagram showing an example of the functional configuration of artificial satellite 200. In the example shown in Figure 4, artificial satellite 200 has the following functional configuration: main computer 221, communication unit 222, attitude control device 223, power supply unit 224, image processing unit 225, optical communication device 212, imaging device 205, and tilting device 226.

[0048] 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.

[0049] 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.

[0050] The attitude control device 223 performs position estimation and attitude control 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.

[0051] 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 205 on the arrangement plane 202 and the direction of orbital travel.

[0052] 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.

[0053] The image processing device 225 generates an image based on the light incident on the multiple optical systems 204. The image processing device 225 performs various image processing based on the image information obtained from the imaging device 205.

[0054] The tilting device 226 can arbitrarily change the tilt angle of the multiple optical systems 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 optical systems 204, but in reality, it is desirable to provide a tilting device 226 for each of the multiple optical systems 204.

[0055] <Configuration and operation of imaging device 205> The configuration and operation of the imaging device 205 will be described below. Figure 5 is a schematic diagram illustrating the configuration of the imaging device 205. As shown in Figure 5, the imaging device 205 has a plurality of optical systems 204, a light-receiving unit 214, and an image sensor 215.

[0056] The light-receiving unit 214 combines light incident from multiple optical systems 204 using methods such as the composite aperture method and directs it onto the image sensor 215. This causes the light incident from the multiple optical systems 204 to form an image on the image sensor 215. The light-receiving unit 214 is composed of, for example, at least one of a lens, mirror, half-mirror, or prism, and a support for these components, and is housed inside the main body 201. The light-receiving unit 214 uses the composite aperture method to form an image on the image sensor 215 from the light incident from the multiple optical systems 204.

[0057] The image sensor 215 is, for example, a CCD (Charge Coupled Devices) sensor or a CMOS (Complementary Metal Oxide Semiconductor) sensor. The image sensor 215 generates an electrical signal on a pixel-by-pixel basis based on the amount of light received by each pixel and outputs it as image information.

[0058] With this configuration, the optical system 204 has a resolution substantially equivalent to that of a large-aperture optical system. For example, if each optical system 204 has an aperture diameter of 10 cm, and 30 optical systems 204 are arranged on the arrangement surface 202 along the X and Y directions, for a total of 900 optical systems 204, then a resolution equivalent to that of an optical system with an aperture diameter of 3 m can be secured by simple calculation.

[0059] In this way, by arranging multiple relatively small-diameter optical systems 204, the mass can be significantly reduced compared to the case where a single large-diameter lens is installed. For example, it is empirically known that the mass of mirrors used in an optical system increases by approximately 2.6 times with respect to the aperture diameter. In this calculation, the total mass of optical systems 204 arranged in a sequence of 900 optical systems 204 with an aperture diameter of 10 cm is approximately 1 / 7.7 of the mass of one optical system with an aperture diameter of 3 m, demonstrating that the mass can be significantly reduced. Furthermore, for example, it is known that the time required for grinding and polishing lenses increases dramatically as the size of the lens increases. Therefore, by miniaturizing each individual lens, the optical system 204 of the satellite 200 of this disclosure can be manufactured in a significantly shorter time than that of a large optical system.

[0060] <Mechanism of action, effect> As described above, the artificial satellite 200 according to the embodiment of this disclosure has a structure in which a plurality of optical systems 204 are arranged in at least one row on the arrangement surface 202 of the main body 201. The imaging device 205 generates image information by forming an image on a single image sensor 215 using a light receiving unit 214 to capture the light incident on the plurality of optical systems 204. Therefore, even if the aperture diameter of each optical system 204 is relatively small, it is possible to secure a resolution substantially equivalent to that of a large-aperture optical system having an aperture diameter equal to the sum of the aperture diameters of the plurality of optical systems 204 arranged in the same direction. Thus, it is possible to achieve both a low mass and miniaturization of the artificial satellite 200 and high image quality.

[0061] <Variation> The embodiments of this disclosure described above are merely examples of how this disclosure may be implemented, and this disclosure is not limited to such embodiments.

[0062] (First variation) When the artificial satellite 200 is manufactured on the ground, vibrations during launch may cause slight misalignment of the configuration of the imaging device 205, particularly the alignment of each optical component in the light-receiving unit 214. For this reason, the light-receiving unit 214 may have a configuration that allows for fine adjustment of the position of each optical component after the artificial satellite 200 is placed into orbit.

[0063] (Second and third variations) In addition to the method described in the above embodiment (combining light incident from multiple optical systems 204 to form an image on the image sensor 215), the following methods can be considered as ways to improve the resolution of the optical system 204.

[0064] Figure 6 is a diagram illustrating a second modification of the satellite 200 of this disclosure. In the second modification shown in Figure 6, the optical system 204 has an extendable function. Before the satellite 200 is placed into orbit (from manufacturing to launch), the extendable function of the optical system 204 is in a retracted state, and after the satellite 200 is placed into orbit, the extendable function extends. Compared to when the optical system 204 is not extended, the focal length can be increased, and consequently, higher resolution can be ensured.

[0065] Figure 7 illustrates a third modified example of the artificial satellite 200 of this disclosure. In the third modified example shown in Figure 7, a recess 202D is provided on the arrangement surface 202 of the main body 201, and a plurality of optical systems 204 are arranged within the recess 202D. This allows for a longer focal length for each optical system 204 compared to the case where the recess 202D is not provided, thereby ensuring high resolution.

[0066] In addition, while the second and third modifications described above have been explained as methods for increasing the focal length of each optical system 204, a method may also be employed in which the focal length is substantially increased by, for example, providing a mirror within the optical system 204 and increasing the optical path length from the light incident on the optical system 204 to the image sensor 215. [Industrial applicability]

[0067] This disclosure is useful for small artificial satellites. [Explanation of symbols]

[0068] 100 Image Generation Systems 200 satellites 201 Main body 202 Placement plane 202D recess 203 Back 204 Optical system 205 Imaging device 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 214 Light receiving part 215 Image sensor 216 Extension function 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, Imaging device and Equipped with, The imaging device is Multiple optical systems arranged in at least one row on the aforementioned arrangement surface, Image sensor and A light-receiving unit that forms an image on the image sensor of light incident on each of the plurality of optical systems, An artificial satellite equipped with [a specific feature / equipment].

2. The optical system has an extension function that extends in the direction that increases the focal length. The artificial satellite according to claim 1.

3. The aforementioned placement surface has a recess, The plurality of optical systems are arranged inside the recess, The artificial satellite according to claim 1.

4. An artificial satellite comprising a main body having an arrangement surface, an imaging device that generates image information, and a communication unit, wherein the imaging device comprises a plurality of optical systems, an image sensor, and a light receiving unit that forms an image on the image sensor of light incident on each of the plurality of optical systems, A ground station that receives the image information transmitted from the artificial satellite, An image generation system equipped with the following features.

Images