A method for autonomous antenna pointing control using a small camera

Abstract

This invention discloses a method for autonomous antenna pointing control using a small camera, belonging to the field of space exploration technology. The method, based on the requirements for autonomous antenna pointing control, designs the camera's angular resolution, calculates the angle subtended by the Earth in the camera's view when observing the Earth from the spacecraft, and determines the camera's field of view; accordingly, it designs the camera's mounting on the antenna. Based on the Earth's position in the camera's field of view, it calculates the location of the center of mass; and based on the requirements for autonomous antenna pointing control, it controls the antenna to point towards the Earth's center. This invention establishes a method for autonomous antenna pointing control using a small camera, which can provide real-time guidance information for spacecraft antennas pointing towards the Earth in orbit, complete closed-loop control of spacecraft antenna pointing towards the Earth, and eliminate errors in pointing mechanisms, etc.

Description

Technical Field

[0001] This invention belongs to the field of space exploration technology, and in particular relates to a method for autonomous antenna pointing control using a small camera. Background Technology

[0002] Antenna peak gain is related to antenna aperture size; the larger the aperture, the higher the peak gain. In deep space exploration, large-aperture antennas are typically used to transmit more scientific data. Antenna beamwidth is also related to peak gain; the higher the peak gain, the narrower the beamwidth. To ensure effective data transmission, the antenna is usually required to be precisely pointed at the ground receiving station, ensuring it operates within a high-gain beam angle range.

[0003] Deep space exploration, especially exploration of solar polar orbits outside the ecliptic plane, involves a complex spatial distribution of the Sun, Earth, and spacecraft. In order to have more time to transmit data, data transmission antennas need to be equipped with antenna drive mechanisms with 2 or 3 degrees of freedom, so that they can still be pointed at Earth during scientific observations.

[0004] When high-gain antennas are mounted on satellites, there are inherent assembly errors. When operating in orbit, the complex antenna drive mechanism will produce pointing errors due to mechanism deformation and temperature changes. Even if the antenna drive mechanism itself is equipped with devices such as measuring code disks, there are still uneliminable errors that affect pointing accuracy.

[0005] We need a method to eliminate pointing errors and enable autonomous pointing. Summary of the Invention

[0006] The technical problem solved by this invention is to overcome the shortcomings of existing technologies, such as the low pointing accuracy of antennas for deep space exploration, especially solar polar orbit exploration spacecraft outside the ecliptic plane. This invention proposes a method that uses a small camera to image the Earth and uses the image data to determine the Earth's position for autonomous antenna pointing control, thereby meeting the requirement of high-precision antenna pointing to the Earth.

[0007] The technical solution of this invention is:

[0008] A method for autonomous antenna pointing control using a small camera includes the following steps:

[0009] (1) Design the camera angular resolution based on the requirements for autonomous antenna pointing control;

[0010] (2) Calculate the angle of the Earth in the camera when observing the Earth from the spacecraft, and design the camera field of view accordingly to ensure that the camera field of view can cover the Earth;

[0011] (3) Design the camera based on the camera angular resolution in step (1) and the camera field of view in step (2);

[0012] (4) The camera is fixedly mounted on the edge of the antenna. When running on the track, the camera moves with the antenna.

[0013] (5) Based on the orbital information, the spacecraft control antenna initially points to the Earth, and the camera images the Earth;

[0014] (6) Calculate the position of the centroid of the Earth image based on the position of the Earth in the camera's field of view and the camera parameters;

[0015] (7) The spacecraft controls the antenna to point to the center of the Earth based on the position of the center of mass calculated in step (6).

[0016] Preferably, in step (1), the camera angular resolution Where D is the effective aperture of the camera, and λ is the wavelength.

[0017] Preferably, in step (2), when the distance between the Earth and the spacecraft is S, the angular size of the Earth in the camera is... The unit is arcminutes (D). E This is the diameter of the Earth.

[0018] Preferably, in step (2), the camera's field of view is greater than the angle of the Earth in the camera.

[0019] Preferably, in step (6), when the distance between the Earth and the spacecraft is greater than 50 million km, the Earth is distributed as a point source in the camera image, and the point source is the centroid of the image.

[0020] Preferably, in step (6), when the spacecraft is located on the side of the line connecting the sun and the earth, the spacecraft takes a picture of the earth. The image is a part of the earth's circular outline. Based on the arc information, the spacecraft autonomously fits and recovers the image information to obtain the fitted center position, which is the image centroid position.

[0021] Preferably, in step (7), the spacecraft autonomously controls the antenna mechanism to adjust its pointing according to the difference between the centroid position and the camera optical axis, gradually reducing the difference between the image centroid position and the antenna central axis, accurately pointing to the Earth, and completing the tracking.

[0022] Preferably, the camera and antenna have the same orientation.

[0023] Compared with the prior art, the present invention has the following advantages:

[0024] (1) The small camera design determined by this invention can provide guidance information for spacecraft antennas to point to the Earth in real time on orbit, solving the problem of low pointing accuracy of spacecraft antennas in deep space exploration, especially solar polar orbit exploration in non-ecliptic plane, and meeting the requirement of high-precision pointing of antennas to the Earth.

[0025] (2) The design determined by the present invention can complete the closed-loop control of the spacecraft antenna pointing to the earth, eliminate the error of the pointing mechanism, etc., and reduce the processing requirements of the pointing mechanism, etc. Attached Figure Description

[0026] Various other advantages and benefits will become apparent to those skilled in the art upon reading the following detailed description of preferred embodiments. The accompanying drawings are for illustrative purposes only and are not intended to limit the invention. Furthermore, the same reference numerals denote the same parts throughout the drawings. In the drawings:

[0027] Figure 1 A schematic diagram showing the small camera of the present invention fixedly mounted on the edge of the antenna body;

[0028] Figure 2 The center of the image is restored by fitting the Earth's contour arc information according to the present invention; Detailed Implementation

[0029] Exemplary embodiments of the present disclosure will now be described in more detail with reference to the accompanying drawings. While exemplary embodiments of the present disclosure are shown in the drawings, it should be understood that the present disclosure may be implemented in various forms and should not be limited to the embodiments set forth herein. Rather, these embodiments are provided to enable a more thorough understanding of the present disclosure and to fully convey the scope of the disclosure to those skilled in the art. It should be noted that, unless otherwise specified, the embodiments and features described herein can be combined with each other. The present invention will now be described in detail with reference to the accompanying drawings and embodiments.

[0030] This invention provides a method for autonomous antenna pointing control using a small camera. The angular resolution of the small camera is no less than half the required accuracy of the autonomous antenna pointing control. Currently, the autonomous pointing control accuracy of deep-space antennas typically does not exceed 1′. The small cameras actually used have an aperture of approximately 5–10 mm and a weight typically not exceeding 200g. The camera parameter design and the autonomous antenna pointing control method include the following steps:

[0031] (1) Based on the requirements for autonomous pointing control of the antenna, design the camera angular resolution.

[0032] Where D is the effective aperture of the camera, and λ is the wavelength.

[0033] The antenna's autonomous pointing control requires an angular resolution of no less than 1′. Using a visible light camera with a wavelength λ designed at 600nm, and a camera aperture of 5mm, the camera's angular resolution can reach 0.5′.

[0034] (2) Calculate the angle of the Earth in the camera when observing the Earth from the spacecraft, and design the camera field of view.

[0035] When the distance between Earth and the spacecraft is S, the angle subtended by Earth relative to the spacecraft. The unit is arcminutes (D). E The diameter of the Earth is 12,742 km.

[0036] Antenna autonomous pointing control requires a ground distance of 10. 6 At a distance of km, the camera's field of view can cover the Earth. At this time, when observing Earth from the spacecraft, the corresponding subtended angle β = 43°. ′ Considering error factors, the camera's field of view should be designed to be no less than 60′.

[0037] (3) Complete the camera design according to steps (1) and (2).

[0038] (4) According to step (3), the camera is fixedly installed on the edge of the antenna. When running on the track, the camera moves with the antenna and has the same direction.

[0039] (5) According to step (4), based on the orbital information, the spacecraft control antenna initially points to the Earth. The Earth enters the effective field of view of the camera, and the camera images the Earth to observe its position in the camera's field of view.

[0040] (6) Calculate the location of the center of mass. When the distance between the Earth and the spacecraft is greater than 50 million km, the Earth appears as a point source in the camera image, which is approximately the location of the center of mass. When the distance is smaller, the Earth appears as a surface source in the camera image.

[0041] Due to the geometric relationship between the Sun, Earth, and spacecraft, the image captured by the camera is not a perfect circle, but rather a portion of the Earth's circular outline. Based on the arc information, the spacecraft autonomously fits and reconstructs the image information, obtaining the fitted center position, which approximates the image's centroid.

[0042] (7) Control the antenna to point to the center of the Earth.

[0043] The difference between the image centroid position and the camera optical axis (or antenna central axis) is Δα. The spacecraft autonomously controls the antenna mechanism to adjust its pointing direction, accurately pointing towards the Earth to complete the tracking.

[0044] In step (2), the camera is fixedly mounted on the edge of the antenna without affecting the antenna's performance.

[0045] This invention provides a method for autonomous antenna pointing control using a small camera, which can provide guidance information for spacecraft antennas to point towards Earth in real time on orbit, complete closed-loop control of spacecraft antennas pointing towards Earth, and eliminate errors in pointing mechanisms, etc.

[0046] Example:

[0047] Autonomous pointing control of the antenna requires an angular resolution of no less than 1′. Spacecraft-Earth distance: 10. 6 At a distance of km, the camera can guide the antenna to point towards the Earth, requiring that the camera's field of view can cover the Earth at this time.

[0048] A visible light camera is used, with a wavelength λ designed at 600nm, a camera aperture of 5mm, and an angular resolution of 0.5′.

[0049] Distance between the instrument and the ground 10 6 At km, when observing Earth from a spacecraft, the corresponding subtended angle β = 43° ′ Considering error factors, the camera's field of view is designed to be 60′.

[0050] The small camera is fixedly mounted on the edge of the antenna, with the same orientation, such as Figure 1 As shown. When operating in orbit, image information is transmitted to the spacecraft's onboard control system.

[0051] Based on information such as orbit, the spacecraft's control antenna is pointed roughly towards Earth.

[0052] When a spacecraft is positioned to the side of the line connecting the Sun and Earth, an image taken from the spacecraft shows a portion of the Earth's circular outline. Based on the curve information, the spacecraft autonomously reconstructs the image information, obtaining the fitted center position, which approximates the image's centroid. Figure 2 As shown.

[0053] Based on the difference between the image centroid position and the camera's optical axis, the spacecraft autonomously controls the antenna mechanism to adjust its pointing, gradually reducing the difference between the image centroid position and the antenna's central axis, accurately pointing towards the Earth and completing the tracking.

[0054] This invention identifies a method for autonomous antenna pointing control using a small camera, requiring minimal resources and capable of providing real-time guidance information for spacecraft antennas pointing towards Earth in orbit. The design defined in this invention enables closed-loop control of spacecraft antennas pointing towards Earth, eliminating errors in pointing mechanisms and reducing the processing requirements for these mechanisms.

[0055] Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make possible changes and modifications to the technical solutions of the present invention by utilizing the methods and techniques disclosed above without departing from the spirit and scope of the present invention. Therefore, any simple modifications, equivalent changes and alterations made to the above embodiments based on the technical essence of the present invention without departing from the content of the technical solutions of the present invention shall fall within the protection scope of the technical solutions of the present invention.

Claims

1. A method for autonomous antenna pointing control using a small camera, characterized in that, Includes the following steps: (1) Design the camera angular resolution based on the requirements for autonomous antenna pointing control; (2) Calculate the angle of the Earth in the camera when observing the Earth from the spacecraft, and design the camera field of view accordingly to ensure that the camera field of view can cover the Earth; (3) Design the camera based on the camera angular resolution in step (1) and the camera field of view in step (2); (4) The camera is fixedly mounted on the edge of the antenna. When running on the track, the camera moves with the antenna. (5) Based on the orbital information, the spacecraft control antenna initially points to the Earth, and the camera images the Earth; (6) Calculate the position of the centroid of the Earth image based on the position of the Earth in the camera's field of view and the camera parameters; (7) The spacecraft controls the antenna to point to the center of the Earth based on the position of the center of mass calculated in step (6).

2. The method for autonomous antenna pointing control using a small camera according to claim 1, characterized in that, In step (1), the camera angular resolution Where D is the effective aperture of the camera, and λ is the wavelength.

3. The method for autonomous antenna pointing control using a small camera according to claim 1, characterized in that, In step (2), when the distance between the Earth and the spacecraft is S, the angular size of the Earth in the camera is... The unit is arcminutes (D). E This is the diameter of the Earth.

4. The method for autonomous antenna pointing control using a small camera according to claim 1, characterized in that, In step (2), the camera's field of view is greater than the angle of the Earth in the camera.

5. The method for autonomous antenna pointing control using a small camera according to claim 1, characterized in that, In step (6), when the distance between the Earth and the spacecraft is greater than 50 million km, the Earth appears as a point source in the camera image, and this point source is the location of the image centroid.

6. The method for autonomous antenna pointing control using a small camera according to claim 1, characterized in that, In step (6), when the spacecraft is located on the side of the line connecting the sun and the earth, it takes a picture of the earth from the spacecraft. The image is a part of the earth's circular outline. Based on the arc information, the spacecraft automatically fits and recovers the image information to obtain the center position of the fitted circle, which is the centroid position of the image.

7. The method for autonomous antenna pointing control using a small camera according to claim 1, characterized in that, In step (7), based on the difference between the centroid position and the camera optical axis, the spacecraft autonomously controls the antenna mechanism to adjust its pointing, gradually reducing the difference between the image centroid position and the antenna central axis, accurately pointing to the Earth, and completing the tracking.

8. The method for autonomous antenna pointing control using a small camera according to claim 1, characterized in that, The camera and antenna are pointing in the same direction.

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