Low-orbit remote sensing satellite minimum relative image motion imaging method for high-orbit target

Abstract

The application relates to a minimum relative image movement imaging method of a low-orbit remote sensing satellite on a high-orbit target, and solves the problem of poor imaging effect on the high-orbit target. The application is convenient for the low-orbit remote sensing satellite to perform long-exposure imaging on the high-orbit target under the condition that the low-orbit remote sensing satellite is in an inertial space stable attitude. The method is as follows: the low-orbit remote sensing satellite observes a high-orbit target to be observed at an angle alpha, the relative speed of the high-orbit target to be observed relative to the low-orbit remote sensing satellite is zero in the projection of the relative direction normal; the high-orbit target to be observed is located on the orbit plane of the low-orbit remote sensing satellite, and the normal is located on the orbit plane; the angle alpha satisfies:

Description

Technical Field

[0001] This invention relates to the field of aerospace technology, and more specifically to a method for imaging high-orbit targets with minimal relative image shift using a low-orbit remote sensing satellite. Background Technology

[0002] High-orbit spacecraft have wide applications in meteorology, communications, and other fields due to their advantages such as large field of view, wide coverage, stable latitude and longitude corresponding to their nadir points, and difficulty in being monitored. Correspondingly, research on high-orbit target surveillance has become one of the key directions in space target monitoring, including target cataloging, real-time orbit monitoring, functional analysis, and technical detail research.

[0003] For high-orbit targets, due to the numerous technical difficulties in close-range observation, the current observation methods mainly rely on long-range ground-based observation and space-based observation.

[0004] Ground-based monitoring involves observing high-orbit targets using fixed ground-based remote sensing equipment, such as ground-based telescopes. This method cannot eliminate interference from atmospheric and ground-based light, resulting in a low signal-to-noise ratio for target observation. In poor weather conditions, it may even be impossible to observe targets, and the field of view is limited due to the influence of ground objects.

[0005] In contrast, space-based observation, which utilizes on-orbit satellites for remote sensing of targets, is completely unaffected by the atmosphere and can achieve a wider observation range through omnidirectional satellite maneuvers and orbital motions. Existing space-based observation methods typically employ multi-directional spatially stabilized area array imaging and linear pushbroom imaging. Due to the relative motion between the target and the observing satellite, the target image shifts, making it difficult to simultaneously perform long exposures of the target and stars during imaging. This results in insufficient ability to identify faint targets, inadequate target orientation accuracy, and the need for frequent maneuvers during imaging missions, making it unsuitable for imaging high-orbit targets. Summary of the Invention

[0006] To address the aforementioned problems, this invention provides a method for imaging high-orbit targets using low-orbit remote sensing satellites with minimal relative image shift.

[0007] The technical solution adopted by this invention to solve the technical problem is as follows:

[0008] A method for imaging high-orbit targets with minimal relative image shift using low-orbit remote sensing satellites, the method is as follows:

[0009] The low-orbit remote sensing satellite observes the high-orbit satellite at an angle α. The projection of the relative velocity of the high-orbit satellite to the low-orbit remote sensing satellite onto the normal of the relative direction of the high-orbit satellite to the low-orbit remote sensing satellite is zero. The high-orbit satellite is located on the orbital plane of the low-orbit remote sensing satellite, and the normal is located on the orbital plane. The angle α satisfies formula (7).

[0010] (7)

[0011] Where R_A is the orbital radius of the low-Earth orbit remote sensing satellite, and R_B is the orbital radius of the high-Earth orbit satellite to be observed.

[0012] V_A represents the velocity of the low-orbit remote sensing satellite relative to the inertial frame, and V_B represents the velocity of the high-orbit satellite to be observed relative to the inertial frame.

[0013] The beneficial effects of this invention are:

[0014] This invention presents a method for low-Earth orbit (LEO) remote sensing satellites to image high-Earth orbit (HEO) targets with minimal relative image shift. Through a orbital design that is parallel to the target's orbital plane and aligned with the LEO satellite's trajectory, and a specific imaging azimuth angle, the target remains stable relative to inertial space within the imaging field of view for a short period. This allows the LEO satellite to perform long-exposure imaging of HEO targets without motion blur while maintaining a stable attitude in inertial space. Simultaneously, background stars can be extracted as orientation references, significantly improving the imaging and recognition capabilities and orbit determination accuracy of HEO targets. This, in turn, enhances the satellite's ability to identify, extract, and analyze the azimuth of distant targets. Furthermore, this method can maintain long-term stability, enabling continuous scanning and monitoring of a series of HEO targets within the same plane. The method is simple in principle, easy to implement, and applicable to practical engineering applications. Attached Figure Description

[0015] Figure 1 This is a schematic diagram of the imaging position for a low-orbit remote sensing satellite imaging method for high-orbit targets with minimal relative image shift according to the present invention.

[0016] Figure 2 This is a schematic diagram illustrating a practical application embodiment of the present invention;

[0017] Figure 3 for Figure 2 The corresponding curve showing the change in the relative angular velocity of the target satellite with respect to the observation satellite in the inertial frame. Detailed Implementation

[0018] The present invention will now be described in further detail with reference to the accompanying drawings and embodiments.

[0019] A method for imaging high-orbit targets using a low-orbit remote sensing satellite with minimal relative image shift is proposed. The method involves the low-orbit remote sensing satellite observing the high-orbit target satellite at an angle α. The projection of the normal of the high-orbit target satellite relative to the low-orbit remote sensing satellite in the relative direction between the high-orbit target satellite and the low-orbit remote sensing satellite is zero. In other words, the projection of V_B onto the normal direction of line segment AB equals the projection of V_A onto the normal direction of line segment AB, where line segment AB is the line connecting the high-orbit target satellite and the low-orbit remote sensing satellite.

[0020] The high-orbit satellite to be observed is located on the orbital plane of the low-orbit remote sensing satellite, and the normal direction is located on the orbital plane; the α angle satisfies formula (7).

[0021] (7)

[0022] Where R_A is the orbital radius of the low-orbit remote sensing satellite, R_B is the orbital radius of the high-orbit satellite to be observed, V_A is the velocity of the low-orbit remote sensing satellite relative to the inertial frame, and V_B is the velocity of the high-orbit satellite to be observed relative to the inertial frame.

[0023] Angle α represents the phase difference between the high-orbit observation satellite and the low-orbit remote sensing satellite. The orbital planes of the high-orbit observation satellite and the low-orbit remote sensing satellite are the same. Both the high-orbit observation satellite and the low-orbit remote sensing satellite have circular orbits.

[0024] Low-Earth orbit remote sensing satellites are used as observation satellites, while high-Earth orbit satellites to be observed are used as targets for the observation satellites. The design process and basic principles of the above imaging methods are described in detail below.

[0025] First, ensure that the orbital plane of the low-Earth orbit (LEO) remote sensing satellite is essentially aligned with the high-Earth orbit (HEO) satellite being observed. Simultaneously, adjust the velocities of both the HEO and LEO satellites, as well as the orientation of the HEO satellite relative to the LEO satellite, so that the projection of the relative velocity of the HEO satellite relative to the LEO satellite onto the normal direction of their relative orientation is zero. At this point, the target direction appears stationary relative to the inertial frame from the perspective of the observing satellite, allowing for stable imaging over a short period. Furthermore, for two circular orbit satellites on the same orbital plane, their orbital linear velocities are constant and always within the same plane. Therefore, it can be inferred that there exists an observation elevation angle for the LEO satellite. At this elevation angle, the HEO satellite's relative velocity onto the normal direction of its relative orientation is zero. By maintaining this elevation angle, the LEO satellite can continuously obtain long-exposure, low-image-shift images of the high-Earth target.

[0026] This invention patent achieves this method of minimum relative image shift imaging monitoring of high-orbit targets using a low-orbit array imaging remote sensing satellite through the following technical solution. Taking the imaging of geostationary orbit targets by a 500km, 0° inclination prograde orbit satellite as an example, the steps are as follows:

[0027] like Figure 1 As shown, the Earth's center is point O, the low-orbit remote sensing satellite is point A, the high-orbit satellite to be observed is point B, the two dashed circles represent the orbits of the two satellites, with orbital radii of R_A and R_B, and instantaneous velocities relative to the inertial frame of reference of V_A and V_B, respectively.

[0028] When the high-orbit observation satellite and the low-orbit remote sensing satellite in the same orbital plane move relative to each other to a certain phase difference α, the distance between the high-orbit observation satellite and the low-orbit remote sensing satellite is: Then by As can be seen from the fact that angle γ is the complementary angle of the intermediate angle:

[0029] (1)

[0030] Angle γ is the angle between the line containing V_B and the first line, which is a line on the track surface perpendicular to line segment AB.

[0031] Furthermore, by the Law of Cosines, we can obtain:

[0032] (2)

[0033] Furthermore, according to the Law of Sines:

[0034] (3)

[0035] At the same time, we can obtain the formula for the interior angles of a triangle:

[0036] (4)

[0037] Then angle β can be calculated:

[0038] (5)

[0039] Angle β is the angle between the line containing V_A and the first line.

[0040] Imaging requires that during the imaging of a high-orbit satellite by a low-orbit remote sensing satellite, the two satellites have no relative angular velocity, meaning that the projected angular velocity along the normal direction of the line connecting their positions AB is consistent.

[0041] (6)

[0042] Right now:

[0043] (7)

[0044] In the above formula (7), only α is an unknown. Both the low-orbit remote sensing satellite and the high-orbit star to be observed can obtain the velocity as long as the orbital radius is given, and then the specific angle α can be solved. The low-orbit remote sensing satellite can maintain this angle to observe the high-orbit star, thus achieving long-term stable exposure of the high-orbit target and background stars.

[0045] To address the need for building a low-Earth orbit space monitoring constellation to observe high-Earth orbit targets, a 500km high, 0-inclination circular orbit satellite was designed using the method described above to observe geostationary orbit targets. Calculations showed that the relative angular velocity was zero when the α angle was 57.8623°. Figure 2 As shown. Through simulation analysis of the relative motion of the target satellite with respect to the observed satellite in the inertial frame during this time period, the following results were obtained. Figure 3The results show that imaging at a specific angle can provide an opportunity to obtain an image of a target that is almost relatively stable in inertial space within a certain time. If the target angular velocity is set to 0.0001° / s as the threshold, the imaging window time exceeds 20 seconds. Afterward, due to the target's relative angle deviating from angle α, the target's relative angular velocity gradually increases. However, new targets enter the field of view in the same direction, and the observation satellite can continue to observe the geostationary orbit satellites without any attitude maneuvers, completing one scan of the geostationary orbit within one low-Earth orbit period.

[0046] This invention presents a method for low-Earth orbit (LEO) remote sensing satellites to image high-Earth orbit (HEO) targets with minimal relative image shift. Through a orbital design that is parallel to the target's orbital plane and aligned with the LEO satellite's trajectory, and a specific imaging azimuth angle, the target remains stable relative to inertial space within the imaging field of view for a short period. This allows the LEO satellite to perform long-exposure imaging of HEO targets without motion blur while maintaining a stable attitude in inertial space. Simultaneously, background stars can be extracted as orientation references, significantly improving the imaging and recognition capabilities and orbit determination accuracy of HEO targets. This, in turn, enhances the satellite's ability to identify, extract, and analyze the azimuth of distant targets. Furthermore, this method can maintain long-term stability, enabling continuous scanning and monitoring of a series of HEO targets within the same plane. The method is simple in principle, easy to implement, and applicable to practical engineering applications.

[0047] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for imaging high-orbit targets with minimal relative image shift using a low-orbit remote sensing satellite, characterized in that, The method is as follows: The low-orbit remote sensing satellite observes the high-orbit satellite at an angle α. The projection of the relative velocity of the high-orbit satellite to the low-orbit remote sensing satellite onto the normal of the relative direction of the high-orbit satellite to the low-orbit remote sensing satellite is zero. The high-orbit satellite is located on the orbital plane of the low-orbit remote sensing satellite, and the normal is located on the orbital plane. The angle α satisfies formula (7). （7） Where R_A is the orbital radius of the low-Earth orbit remote sensing satellite, and R_B is the orbital radius of the high-Earth orbit satellite to be observed. V_A represents the instantaneous velocity of the low-orbit remote sensing satellite relative to the inertial frame, and V_B represents the instantaneous velocity of the high-orbit satellite to be observed relative to the inertial frame; angle α represents the phase difference between the high-orbit satellite to be observed and the low-orbit remote sensing satellite.

2. The method for imaging high-orbit targets with minimal relative image shift using a low-orbit remote sensing satellite as described in claim 1, characterized in that, The process of obtaining the formula (7) is as follows: Let the Earth's center be point O, the low-orbit remote sensing satellite be point A, the high-orbit satellite to be observed be point B, the two dashed circles be the orbits of the two satellites, with orbital radii R_A and R_B respectively, and instantaneous velocities relative to the inertial frame V_A and V_B respectively. When the high-orbit observation satellite and the low-orbit remote sensing satellite in the same orbital plane move relative to each other to a certain phase difference α, the distance between the high-orbit observation satellite and the low-orbit remote sensing satellite is: Then by As can be seen from the fact that angle γ is the complementary angle of the intermediate angle: （1） Angle γ is the angle between the line containing V_B and the first line, which is a line on the track surface perpendicular to line segment AB. Furthermore, by the Law of Cosines, we can obtain: （2） Furthermore, according to the Law of Sines: （3） At the same time, we can obtain the formula for the interior angles of a triangle: （4） Then angle β can be calculated: （5） Angle β is the angle between the line containing V_A and the first line; The imaging requirement is that during the imaging of a high-orbit satellite by a low-orbit remote sensing satellite, the two satellites have no relative angular velocity, meaning that the projected velocities along the normal direction of the line connecting their positions AB are consistent. Therefore: （6） According to formulas (2), (3), (5), and (6), we have: （7）。

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