Cassegrain type optical apparatus mounted on cube-satellite and operating method for cube-satellite using the same

Abstract

The present invention provides an optical device comprising a primary reflector positioned toward the direction in which light is incident and having a hole in its center, and a secondary reflector positioned coaxially with the primary reflector so as to face the primary reflector in front of the primary reflector in the direction in which light is incident, and having a size smaller than the primary reflector and larger than the hole, and a method of operating a satellite using the same, wherein the optical device and the method of operating a microsatellite applicable thereto can reduce the influence of the space environment and secure reliable observation performance.

Description

Technology Field

[0001] The present invention relates to a Cassegrain-type optical device for mounting on a microsatellite and a method for operating a microsatellite using the same. More specifically, the invention relates to a Cassegrain-type optical device for mounting on a microsatellite and a method for operating a microsatellite using the same, which can reduce the influence of the space environment and secure reliable observation performance. Background Technology

[0003] Recently, the development of microsatellites has been proceeding in earnest. In other words, microsatellites capable of low-budget operation are being actively developed based on the fierce space development competition among nations and advancements in electronic components and sensors.

[0004] Meanwhile, microsatellites refer to satellites weighing 100 kg or less. Further subdivisions of microsatellites can be made into microsatellites, cubesatellites (also called nanosatellites), picosatellites, and femtosatellites. In this case, the weight of the satellite decreases as one moves from microsatellites to femtosatellites. Among them, cubesatellites can have dimensions of 10 cm × 10 cm × 10 cm, a cube shape, and a maximum weight of 2 kg.

[0005] CubeSats must be equipped with various electronic components for mission execution. In this regard, it is necessary to miniaturize the electronic components installed in the CubeSats to meet the required size, shape, and weight requirements.

[0006] The technology forming the background of the present invention is disclosed in the following patent documents. Prior art literature

[0007] (Patent Document 0001) KR 10-2022-0071645 A(Patent Document 0002) KR 10-1651792 B1 The problem to be solved

[0008] The present invention provides a Cassegrain-type optical device for mounting on a microsatellite, which can prevent the influence of the space environment and secure reliable observation performance, and a method for operating a microsatellite using the same. means of solving the problem

[0009] An optical device according to an embodiment of the present invention comprises: a main reflector positioned toward the direction in which light is incident and having a hole in its center; and a sub-reflector positioned coaxially with the main reflector so as to face the main reflector in front of the main reflector in the direction in which the light is incident, and having a size smaller than that of the main reflector and larger than that of the hole.

[0010] The main reflector may have a front surface formed as a concave reflective surface, and the auxiliary reflector may have a rear surface formed as a convex reflective surface.

[0011] The above concave reflective surface and the above convex reflective surface may be aspherical.

[0012] The shape of the above-mentioned concave reflective surface is defined by a first conic constant and an aspheric coefficient, and the shape of the above-mentioned convex reflective surface can be defined by a second conic constant and an aspheric coefficient that are different in magnitude from the first conic constant.

[0013] The above-mentioned concave reflective surface may have a parabolic shape as an aspherical surface, and the above-mentioned convex reflective surface may have a hyperbolic shape as an aspherical surface.

[0014] The above concave reflective surface and the above convex reflective surface may have a hyperbolic shape of the aspherical surface.

[0015] The diameter of the main mirror and the diameter of the sub-mirror can satisfy the following mathematical formula.

[0016] [Mathematical Formula]

[0017]

[0018] Here, is the effective focal length, d+b is the system's back focal length, The diameter of the primary mirror, can represent the diameter of the sub-reflector.

[0019] The diameter of the above auxiliary mirror may be less than 50% of the diameter of the above main mirror.

[0020] The above hole may have a diameter large enough to allow the optical axis of the reflected light reflected from the above sub-reflector to pass through.

[0021] It may include a light sensor positioned behind the main reflector in the direction in which the light is incident and facing the sub-reflector through the hole.

[0022] The above-mentioned main reflector, the above-mentioned sub-reflector, and the above-mentioned optical sensor can be mounted on a satellite.

[0023] The above satellite may include a microsatellite.

[0024] A method for operating a satellite according to an embodiment of the present invention comprises: a process of launching a satellite equipped with a primary mirror and a secondary mirror into space; a process of performing a mission for a surveillance area using the primary mirror and the secondary mirror; and a process of reducing monochromatic aberration of light reflected in the order of the primary mirror and the secondary mirror while performing the mission.

[0025] The process of reducing the monochromatic aberration of the light may include: a process of directing incident light traveling from the monitoring area to the satellite from the outside of the sub-reflector so that the incident light does not pass through the sub-reflector; a process of directing the incident light onto an aspherical concave reflective surface of the main reflector; a process of directing a first reflected light reflected from the concave reflective surface onto an aspherical convex reflective surface of the sub-reflector; and a process of passing a second reflected light reflected from the convex reflective surface through a hole in the center of the main reflector to be directed to the light sensor of the satellite.

[0026] The above concave reflective surface and the above convex reflective surface may have different conic constants. Effects of the invention

[0027] According to an embodiment of the present invention, by coaxially arranging a sub-reflector that is smaller in size than the main reflector but larger in size than the hole in the center of the main reflector in front of the main reflector so that it faces the main reflector, even if the size of the reflector is reduced, a sufficient distance can be secured for light to travel from the point of incidence to the focal point within the optical device, and monochromatic aberration of light can be reduced.

[0028] In addition, according to an embodiment of the present invention, the correction plate can be removed, thereby reducing the size of the reflector, and thus reducing the impact of the optical device on the space environment, and thus minimizing thermal deformation of the primary mirror and secondary mirror due to rapid temperature changes. Brief explanation of the drawing

[0029] FIG. 1 is a schematic diagram of a Cassegrain-type optical device for mounting on a microsatellite according to an embodiment of the present invention and a microsatellite mounted thereon. FIG. 2 is a conceptual diagram illustrating the structure of the main mirror and the auxiliary mirror of a Cassegrain-type optical device for mounting on a micro-satellite according to an embodiment of the present invention. FIG. 3 is a flowchart for explaining a method of operating a microsatellite applied to a Cassegrain-type optical device for microsatellite mounting according to an embodiment of the present invention. Specific details for implementing the invention

[0030] Hereinafter, embodiments of the present invention will be described in detail with reference to the attached drawings. However, the present invention is not limited to the embodiments disclosed below and may be implemented in various different forms. The embodiments of the present invention are provided merely to ensure that the disclosure of the present invention is complete and to fully inform those skilled in the art of the scope of the invention. To illustrate the embodiments of the present invention, the drawings may be exaggerated, and like reference numerals in the drawings refer to like elements.

[0031] The present invention relates to a Cassegrain-type optical device for mounting on a microsatellite and a method for operating a microsatellite using the same. Hereinafter, embodiments of the present invention will be described in detail by exemplifying cases where the Cassegrain-type optical device for mounting on a microsatellite and the method for operating a microsatellite using the same are applied to a CubeSat. Of course, the optical device and the method for operating a satellite according to the embodiments of the present invention can be applied to satellites of various sizes. Meanwhile, for convenience of explanation, the Cassegrain-type optical device for mounting on a microsatellite will be referred to as the "optical device" and the method for operating a microsatellite using the Cassegrain-type optical device for mounting on a microsatellite will be referred to as the "method for operating a satellite."

[0032] Hereinafter, an optical device according to an embodiment of the present invention will be described in detail.

[0033] FIG. 1 is a schematic diagram of an optical device according to an embodiment of the present invention and a microsatellite equipped with the same.

[0034] Referring to FIG. 1, an optical device (10) according to an embodiment of the present invention comprises: a main mirror (100) positioned toward the direction in which light is incident and having a hole (h) in the center; and a sub-mirror (200) positioned coaxially with the main mirror (100) so as to face the main mirror (100) in front of the main mirror (100) in the direction in which light is incident, and having a size smaller than the main mirror (100) and larger than the hole (h).

[0035] Here, the optical device (10) according to an embodiment of the present invention may not include a correction plate (also called a correction lens). Here, the correction plate may refer to a correction plate used in a Maksutov-Cassegrain type optical device.

[0036] Additionally, the optical device (10) according to an embodiment of the present invention may include a light sensor (300) positioned behind the main reflector (100) in the direction in which light is incident and facing the sub-reflector (200) through a hole (h).

[0037] In the following description, light emitted from the forward monitoring area of ​​the micro-satellite (1) and incident on the main reflector (100) is named incident light (IL), light reflected from the main reflector (100) and proceeding to the sub-reflector (200) is named first reflected light (rm1), and light reflected from the sub-reflector (200) and proceeding to the light sensor (300) is named second reflected light (rm2).

[0038] The main reflector (100) serves to reflect incident light (IL) emitted from a monitoring area and incident on a microsatellite (1) equipped with an optical device (10) to the sub-reflector (200). That is, the main reflector (100) acts as an incident pupil. The main reflector (100) can be mounted on the microsatellite (1).

[0039] The main reflector (100) may have a front surface formed as a concave reflective surface (rm1). The concave reflective surface (rm1) may be an aspherical surface. Additionally, the shape of the aspherical surface of the concave reflective surface (rm1) may be defined by a first conic constant and a predetermined aspherical coefficient. For example, the first conic constant may be -1, and thus the aspherical surface of the concave reflective surface (rm1) may have a parabolic shape. Additionally, for example, the first conic constant may be a constant of a predetermined size smaller than -1, and thus the aspherical surface of the concave reflective surface (rm1) may have a hyperbolic shape. Furthermore, the aspherical shape of the concave reflective surface (rm1) may be defined in various ways by using the first conic constant and the aspherical coefficient together. The aspherical coefficient may vary within a range that satisfies the ability to create a predetermined concave shape of the concave reflective surface (rm1), and is not specifically limited in the embodiments.

[0040] Meanwhile, a hole (h) may be formed in the center of the main mirror (100). The hole (h) may have a diameter large enough to allow the optical axis of the second reflected light (RL2), which is reflected light from the sub-mirror (200), to pass through. Additionally, the number of main mirrors (100) may be one. That is, from the perspective of the optical device (10), the main mirror (100) may be referred to as a single main mirror (100).

[0041] Incident light (IL) emitted from the forward monitoring area of ​​the microsatellite (1) and proceeding to the optical device (10) of the microsatellite (1) can be reflected by the concave reflective surface (rm1) of the main reflector (100) and can proceed toward the sub-reflector (200). At this time, the light reflected by the concave reflective surface (rm1) and proceeding toward the sub-reflector (200) is named the first reflected light (RL1).

[0042] The sub-reflector (200) reflects the first reflected light (RL1) and directs it toward the light sensor (300), and serves to form a focus on the light sensor (300). That is, the sub-reflector (200) directs the light collected by the main reflector (100) in the opposite direction to increase the focal length. At this time, the light reflected from the sub-reflector (200) and directed toward the light sensor (300) is named the second reflected light (RL2). The sub-reflector (200) can be mounted on a micro-satellite (1).

[0043] Additionally, the sub-reflector (200) may be positioned in front of the main reflector (100). Specifically, it may be coaxially positioned in front of the main reflector (100) so as to face the main reflector (100) in the front-rear direction. Also, the number of sub-reflectors (200) may be one. That is, the sub-reflector (200) may be mounted on the optical device (10) and may be matched one-to-one with a single main reflector (100).

[0044] The rear surface of the sub-reflector (200) may be formed as a convex reflective surface (rm2). The convex reflective surface (rm2) may be an aspherical surface. The shape of the aspherical surface of the convex reflective surface (rm2) may be defined by a second conic constant and a predetermined aspherical coefficient. At this time, the second conic constant may have a different magnitude from the first conic constant. For example, the second conic constant may be a constant of a predetermined magnitude that is less than -1 and different from the first conic constant, and thus the shape of the aspherical surface of the convex reflective surface (rm2) may be different from the shape of the aspherical surface of the concave reflective surface (rm1) and may have a hyperbolic shape. Additionally, the shape of the aspherical surface of the convex reflective surface (rm2) may be defined by using the second conic constant and a predetermined aspherical coefficient together. At this time, the aspherical coefficient may vary within a range that satisfies the condition that the shape of the aspherical surface of the convex reflective surface (rm2) is different from the shape of the aspherical surface of the concave reflective surface and can be defined as convex, and is not specifically limited thereto. In this way, by making the shape of the aspherical surface of the convex reflective surface (rm2) of the sub-reflector (200) different from the shape of the aspherical surface of the concave reflective surface (rm1) of the main reflector (100), monochromatic aberration of light at the focal plane of the light sensor (300) can be reduced or eliminated. Meanwhile, the diameter of the sub-reflector (200) may be less than 50% of the diameter of the main reflector (100).

[0045] The first reflected light (RL1), which is reflected from the concave reflective surface (rm1) of the main reflector (100) and proceeds to the convex reflective surface (rm2) of the sub-reflector (200), can be reflected from the convex reflective surface (rm2) of the sub-reflector (200). The second reflected light (RL2), which is reflected from the convex reflective surface (rm2) of the sub-reflector (200), can proceed toward the light sensor (300), pass through the hole (h) of the main reflector (100) and be incident on the light sensor (300), and can form a focus on the focal plane of the light sensor (300).

[0046] The light sensor (300) can be mounted on the microsatellite (1) and connected to the control unit (20) of the microsatellite (1), and can receive the second reflected light (RL2) to acquire an image of the surveillance area. The acquired image can be output to the control unit (20). At this time, the image of the surveillance area may include a visible light image and a near-infrared image. Of course, the types of images of the surveillance area may vary. Meanwhile, the control unit (20) of the microsatellite (1) plays a role in controlling the overall operation of the microsatellite (1). For example, the control unit (20) can control the attitude of the microsatellite (1) for observing the Earth's surface and the operation of the reflection device (20).

[0047] According to an embodiment of the present invention, light reflected from the main mirror (100) is reflected to the sub-mirror (200) and then passed through the hole (h) of the main mirror (100) to be incident on the light sensor (300), so that the distance the light travels can be sufficiently secured within the optical device (10). Accordingly, even if the size of the main mirror (100) and the sub-mirror (200) are reduced, the resolution and spatial resolution of the optical device (10) can be improved, and furthermore, as the size is reduced, thermal deformation of the main mirror (100) and the sub-mirror (200) due to extreme temperature changes in space can be minimized. In addition, by making both the concave reflective surface (rm1) of the main mirror (100) and the convex reflective surface (rm2) of the sub-mirror (200) as spherical, the thermal deformation of the main mirror (100) and the sub-mirror (200) due to extreme temperature changes in space can be further minimized. In addition, by making the first conic constant of the aspherical surface of the concave reflective surface (rm1) of the main mirror (100) and the second conic constant of the aspherical surface of the convex reflective surface (rm2) of the sub-mirror (200) different, monochromatic aberration of light incident on the light sensor (300) can be reduced or eliminated, and thus the Earth observation performance can be improved.

[0048] FIG. 2 is a conceptual diagram illustrating the structure of the main mirror and the auxiliary mirror of a Cassegrain-type optical device for mounting on a micro-satellite according to an embodiment of the present invention.

[0049] Referring to FIG. 2, the structure of the main mirror (100) and the sub-mirror (200) is described exemplarily.

[0050] In Fig. 2 The focal length of the main mirror (100), + is the back focal length of the optical device, It can also be expressed as. Also, can mean the effective focal length. D1 can mean the size of the main mirror (100), and D2 can mean the size of the sub-mirror (200). At this time, the size may also be referred to as the aperture.

[0051] Referring to FIG. 2, the relationship between the effective focal length of the optical device (20) according to an embodiment of the present invention, the focal length of the main mirror (100), and the focal length of the sub-mirror (200) is given by the following equation 1.

[0052] [Relationship 1]

[0053]

[0054] Here, represents the sub-reflector magnification and can be expressed as the ratio of the focal length extended by the sub-reflector to the focal length determined by the curvature of the primary mirror. Here, represents the focal length of the sub-reflector.

[0055] In addition, the rear focal length can be expressed by the following relationship 2.

[0056] [Relationship 2]

[0057]

[0058] In addition, the effective focal length of the optical device (10) according to an embodiment of the present invention, the focal length of the main mirror (100), and the focal length of the sub-mirror (200) can be expressed by the following relationship equations 3 to 5.

[0059] [Relationship 3]

[0060]

[0061] [Relationship 4]

[0062]

[0063] [Relationship 5]

[0064]

[0065] When the specifications of the aperture are determined according to the specifications required for a micro-satellite, the distance between the main mirror (100) and the sub-mirror (200) and the focal length of the sub-mirror (200) can be obtained through the magnification of the sub-mirror (200), the distance between the sub-mirror (200) and the light sensor (300), and the focal length of the main mirror (100), as shown in the following equations 6 to 7.

[0066] [Relationship 6]

[0067]

[0068] [Relationship 7]

[0069]

[0070] In addition, from the aforementioned relationships, a mathematical formula for the minimum diameter of the sub-reflector (200) to ensure no light loss in the axial direction, for example, the front-rear direction, can be obtained as follows, and the diameter (D1) of the main reflector (100) and the diameter (D2) of the sub-reflector (200) can satisfy the following mathematical formula.

[0071] [Mathematical Formula]

[0072]

[0073] Here, is the effective focal length, d+b is the back focal length of the system, The diameter of the primary mirror, can represent the diameter of the sub-reflector.

[0075] FIG. 3 is a flowchart for explaining a method of operating a satellite according to an embodiment of the present invention.

[0076] Referring to FIGS. 1 and 3, a method of operating a satellite according to an embodiment of the present invention includes the process of launching a satellite equipped with a main mirror (100) and a sub-mirror (200) into space (S100), the process of performing a mission for a surveillance area using the main mirror (100) and the sub-mirror (200) (S200), and the process of reducing monochromatic aberration of light reflected in the order of the main mirror (100) and the sub-mirror (200) while performing the mission (S300).

[0077] First, a process (S100) of launching a satellite equipped with a primary reflector (100) and a secondary reflector (200) into space is performed. For example, a microsatellite (1) equipped with an optical device (10) according to an embodiment of the present invention is prepared. The prepared microsatellite (1) is loaded onto a launch vehicle, launched from the ground into space, and at an appropriate time, the microsatellite (1) is separated from the launch vehicle to settle the microsatellite (1) into a predetermined orbit.

[0078] Next, a process (S200) is performed to carry out a task for a surveillance area using the main mirror (100) and the sub-mirror (200). By operating the optical device (10), light emitted from the surveillance area of ​​the Earth is collected by the optical device (10), and an image of the surveillance area can be generated using the collected light.

[0079] Additionally, a process (S300) is performed to reduce monochromatic aberration of light reflected in the order of the main mirror (100) and the sub-mirror (200) during the mission. To this end, incident light (IL) traveling from the monitoring area to the micro-satellite can be directed outside the sub-mirror (200) so that the incident light (IL) does not pass through the sub-mirror (200). That is, the path of the incident light (IL) can be formed outside the circumference of the sub-mirror (200) so that the path of the incident light (IL) and the sub-mirror (200) do not overlap. Additionally, the incident light (IL) can be directed onto the aspherical concave reflective surface (rm1) of the main mirror (100). Accordingly, the first reflected light (RL1) can be reflected from the concave reflective surface (rm1). Additionally, the first reflected light reflected from the concave reflective surface (rm1) can be incident on the convex reflective surface (rm2) of the sub-reflector (200) which has an aspherical shape. Accordingly, the second reflected light (RL2) can be reflected from the convex reflective surface (rm2). Furthermore, the second reflected light (RL2) reflected from the convex reflective surface (rm2) can be passed through the hole (h) in the center of the main reflector (100) and incident on the light sensor (300) of the micro-satellite (1). At this time, the difference in conic constants between the concave reflective surface and the convex reflective surface can be utilized to reduce or eliminate monochromatic aberration of light.

[0081] The above embodiments of the present invention are for the purpose of illustrating the present invention and are not intended to limit the present invention. It should be noted that the configurations and methods disclosed in the above embodiments of the present invention may be combined or intersected in various forms and modified, and that such modified examples may also be considered within the scope of the present invention. That is, the present invention will be implemented in various different forms within the scope of the claims and equivalent technical concepts, and those skilled in the art to which the present invention pertains will understand that various embodiments are possible within the scope of the technical concept of the present invention. Explanation of the symbols

[0082] 100: Primary mirror 200: Subreflector

Claims

Claim 1 A main mirror positioned toward the direction in which light is incident and having a hole in the center; a secondary mirror positioned coaxially with the main mirror so as to face the main mirror in front of the main mirror in the direction in which the light is incident, and having a size smaller than the main mirror and larger than the hole; and a light sensor having a focal plane positioned at the rear of the main mirror in the direction in which the light is incident, directly facing the auxiliary mirror through the hole, and positioned at a location where a focal point is formed by the auxiliary mirror; wherein, so as to allow the light reflected from the auxiliary mirror and passing through the hole to be directly incident on the light sensor, a correction lens is not included between the light sensor, the main mirror, and the auxiliary mirror, wherein the front surface of the main mirror is formed as a concave reflective surface, and the rear surface of the auxiliary mirror is formed as a convex reflective surface, wherein the shape of the concave reflective surface is defined by a first conic constant and an aspheric coefficient, and the shape of the convex reflective surface is defined by a second conic constant and an aspheric coefficient that is different in magnitude from the first conic constant, and wherein the shape of the aspheric surface of the concave reflective surface and the convex reflective surface is a hyperbolic surface, and the diameter of the main mirror and the diameter of the auxiliary mirror are as follows An optical device that satisfies the mathematical formula and is mounted on a microsatellite.[Mathematical Formula] Here, is the effective focal length, d+b is the system's back focal length, The diameter of the primary mirror, represents the diameter of the sub-reflector. Claim 2 delete Claim 3 delete Claim 4 delete Claim 5 A main mirror positioned toward the direction in which light is incident and having a hole in the center; a secondary mirror positioned coaxially with the main mirror so as to face the main mirror in front of the main mirror in the direction in which the light is incident, and having a size smaller than the main mirror and larger than the hole; and a light sensor having a focal plane positioned at the rear of the main mirror in the direction in which the light is incident, directly facing the auxiliary mirror through the hole, and positioned at a location where a focal point is formed by the auxiliary mirror; wherein, so as to allow the light reflected from the auxiliary mirror and passing through the hole to be directly incident on the light sensor, a correction lens is not included between the light sensor, the main mirror, and the auxiliary mirror, wherein the front surface of the main mirror is formed as a concave reflective surface, and the rear surface of the auxiliary mirror is formed as a convex reflective surface, wherein the shape of the concave reflective surface is defined by a first conic constant and an aspheric coefficient, and the shape of the convex reflective surface is defined by a second conic constant and an aspheric coefficient that is different in magnitude from the first conic constant, wherein the shape of the concave reflective surface is a paraboloid, and the shape of the convex reflective surface is a hyperboloid, and the diameter of the main mirror and The diameter of the above-mentioned sub-reflector satisfies the following mathematical formula, and the optical device mounted on a microsatellite.[Mathematical Formula] Here, is the effective focal length, d+b is the system's back focal length, The diameter of the primary mirror, represents the diameter of the sub-reflector. Claim 6 delete Claim 7 delete Claim 8 An optical device according to claim 1 or claim 5, wherein the diameter of the sub-reflector is less than 50% of the diameter of the main reflector. Claim 9 An optical device according to claim 1 or claim 5, wherein the hole has a diameter of a size through which the optical axis of reflected light reflected from the sub-reflector can pass. Claim 10 delete Claim 11 delete Claim 12 delete Claim 13 A process of launching into space a microsatellite equipped with an optical device described in claim 1 or claim 5 having a primary reflector and a secondary reflector; a process of performing a mission for a surveillance area using the primary reflector and the secondary reflector; and a process of reducing monochromatic aberration of light reflected in the order of the primary reflector and the secondary reflector while performing the mission; wherein the process of reducing monochromatic aberration of light comprises: a process of directing incident light traveling from the surveillance area to the satellite from the outside of the secondary reflector so that the incident light does not pass through the secondary reflector; a process of directing the incident light onto an aspherical concave reflective surface of the primary reflector; and a process of directing a first reflected light reflected from the concave reflective surface onto an aspherical convex reflective surface of the secondary reflector. A method for operating a satellite that reduces monochromatic aberration of light without a correction lens, comprising: a process of passing a second reflected light reflected from the convex reflective surface through a hole in the center of the main reflector to be incident on the light sensor of the satellite; wherein the process of incidenting on the light sensor involves directly incidenting the second reflected light on the light sensor without using a correction lens between the convex reflective surface and the light sensor, wherein the concave reflective surface and the convex reflective surface have different conic constants and the aspherical shape is a hyperbolic surface, or, wherein the concave reflective surface has a parabolic shape and the convex reflective surface has a hyperbolic shape and the conic constants are different. Claim 14 delete Claim 15 delete

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