A method and system for daytime celestial navigation with visible light

Abstract

The application discloses a visible light astronomical navigation day star measurement system and method, and belongs to the field of astronomical navigation. In view of the problems of large volume, high cost or insufficient star measurement capacity of the existing airborne star measurement scheme, the application adopts a star measurement assembly, a rotating table assembly and a shield assembly; the star measurement assembly is integrated with a sun measurement channel and a star measurement channel back to back, the star measurement channel adopts a near-infrared enhanced visible light detector, a periscopic lens and a long-wave pass filter film, works in a near-infrared wave band to suppress daytime stray light, and the sun measurement channel adopts a large field of view wide-angle lens and an attenuator to realize stable sun imaging; the star measurement assembly is installed on a single-shaft rotating table or fixedly connected to an airplane platform. The application can synchronously observe the sun and at least one bright star under strong background radiation in the daytime, meets multi-star navigation calculation, reduces the system volume and weight by more than 80%, reduces the cost by more than 50%, and is suitable for unmanned aerial vehicles and other light-weight airborne platforms.

Description

Technical Field

[0001] This invention relates to the field of astronomical navigation technology, specifically to a daytime star-measuring method and system for airborne autonomous navigation using visible light astronomical navigation. Background Technology

[0002] Celestial navigation is an autonomous navigation method that determines the position and attitude of a vehicle by observing celestial bodies such as stars and the sun. Because it does not rely on external signals and has strong resistance to electromagnetic interference, it holds an irreplaceable position in the aviation, aerospace, and maritime fields. Especially in complex electromagnetic warfare environments, celestial navigation is considered a crucial backup method to ensure the safe navigation of aircraft.

[0003] For aircraft platforms, a large number of missions are carried out during the day, so airborne astronomical navigation systems must have the ability to measure stars during the day. However, the strong background light of the sky during the day (especially sunlight scattered by the atmosphere) can severely overwhelm the weak signals of stars, making daytime star measurement a long-standing technical challenge in the field of astronomical navigation.

[0004] Currently, the existing technologies for achieving airborne daytime satellite tracking mainly employ the following two technical approaches: I. Shortwave Infrared Small Field-of-View Tracking Satellite Measurement Technology This technology utilizes the relatively low energy of atmospheric background radiation in the short-wave infrared band (e.g., 1.0μm–1.7μm). It employs a short-wave infrared detector combined with a long focal length, large-aperture optical system (large F# design) to achieve high-precision star measurement with an extremely small field of view (typically less than 1°). To cover multiple stars to meet navigation calculation requirements, the system must be equipped with a dual-axis precision tracking system, completing multi-star measurements through star-by-star scanning and tracking. While this approach effectively suppresses daytime background stray light, its inherent drawbacks include: the short-wave infrared detector is expensive, requires cooling, is noisy, and has a limited lifespan; simultaneously, the long focal length, large-aperture optical system, and dual-axis turntable result in a large system size and considerable weight, severely limiting its adaptability to compact, weight-constrained airborne platforms, and the overall system reliability and economy are not ideal.

[0005] II. Visible Light Wide Field-of-View Star Measurement Technology This technology utilizes visible light detectors, offering significant advantages such as low detector cost, no need for cooling, long lifespan, and high reliability. It has been successfully applied in low-background environments, such as outside the space atmosphere. However, when applied to aircraft platforms within the atmosphere, the atmospheric background radiation intensity in the visible light band during the day is much higher than in the shortwave infrared band. This results in a large amount of stray light entering the system over a wide field of view (typically above 10°), causing a sharp drop in the signal-to-noise ratio and severely limiting actual star-measuring capabilities. Typically, only a very small number of bright stars (such as those of magnitude three or higher) can be detected. Since astronomical navigation calculations require the simultaneous observation of at least two celestial targets, a simple wide-field-of-view visible light star-measuring technique cannot reliably meet navigation requirements under airborne daytime conditions. To improve visible light star-measuring capabilities, some solutions have been forced to reduce the field of view and increase the aperture, but these still rely on a dual-axis tracking system for multi-star search and measurement, similarly resulting in large system size and weight, high cost, and reduced reliability.

[0006] In summary, existing daytime star observation technologies face two contradictory bottlenecks: shortwave infrared small field-of-view schemes are feasible in performance but too costly to implement in engineering, while visible light large field-of-view schemes offer significant advantages in lightweight design but lack sufficient daytime star observation capabilities. How to overcome the limitations imposed by strong background stray light during the day on the number of stars that can be observed while maintaining the advantages of low cost, lightweight design, and high reliability of visible light detectors, and thus achieve reliable daytime multi-satellite observations on airborne platforms, remains a pressing technical challenge in the field of astronomical navigation. Summary of the Invention

[0007] This invention provides a novel visible light daytime star measurement system and method that integrates large field-of-view solar measurement and near-infrared enhanced star measurement, aiming to achieve daytime multi-satellite navigation measurement on airborne platforms with a lightweight and low-cost system architecture.

[0008] In a first aspect, the present invention provides a visible light astronomical navigation daytime star-measuring system, comprising: Protective shield assembly; A turntable assembly is disposed below or inside the protective cover assembly; The satellite measuring component is mounted on and supported by the turntable assembly, and is entirely located within the internal cavity of the protective cover assembly, which covers the outside of the satellite measuring component. The star-measuring component includes a solar measurement channel and a star-measuring channel, which are fixedly connected back-to-back. The solar measurement channel is used to capture and stably observe the sun during the day, and the star-measuring channel is used to capture and observe bright stars during the day. The optical axes of the star-measuring channel and the solar-measuring channel are both tilted upwards at an angle of 15° to 40° to the horizontal plane, pointing towards the zenith, and the two channels are arranged symmetrically back to back. The turntable assembly is fixedly connected to the star measuring assembly and is used to drive the star measuring assembly to rotate around the vertical axis in order to adjust the horizontal orientation of the field of view of the star measuring channel and the solar measuring channel. The star-measuring component, through the rotation of the turntable component, enables the star-measuring channel to search and detect multiple bright stars and the solar-measuring channel to simultaneously measure the sun, outputting observation vectors of at least two celestial bodies for astronomical navigation calculations.

[0009] In some instances, the solar measurement channel includes a wide-angle lens with a large field of view, an attenuator, and a solar measurement camera arranged sequentially along the optical path; the wide-angle lens has a field of view of 80° to 120°, and the attenuator is used to attenuate the solar energy entering the solar measurement camera by 4 to 5 orders of magnitude.

[0010] In some instances, the wide-angle lens has a field of view of 100° and an angle between its optical axis and the horizontal plane of 60° to 80°. When the solar altitude angle is greater than 20° and the angle between the sunlight and the optical axis is less than 50°, the sun enters the field of view of the wide-angle lens.

[0011] In some examples, the star-measuring channel includes a periscope optical lens and a star-measuring camera arranged sequentially along the optical path; the periscope optical lens includes a reflector and a transmission lens group, with a field of view of 10° to 20° and an F-number of 2.0 to 4.0; the surface of the transmission lens group of the periscope optical lens is coated with a long-pass filter, the passband wavelength of which is above 600nm and the cutoff wavelength is below 600nm; the star-measuring camera uses a near-infrared enhanced visible light detector, enabling the star-measuring channel to operate in the near-infrared band.

[0012] In some instances, the turntable assembly is located at the bottom of the protective cover assembly and includes a turntable structure, a torque motor, an angular displacement sensor, a slip ring, and a servo module; The turntable structure includes a fixed part and a rotating part. The fixed part is fixedly connected to the bottom of the protective cover assembly or the carrier platform. The rotating part is rotatably supported on the fixed part about a vertical axis. The upper end of the rotating part is fixedly connected to the satellite measuring assembly. The torque motor includes a stator and a rotor. The stator is fixedly mounted on the fixed part of the turntable structure, and the rotor is fixedly mounted on the rotating part of the turntable structure. The torque motor is used to directly drive the rotating part to rotate about a vertical axis relative to the fixed part. The angular displacement sensor includes a fixed end and a measuring end. The fixed end is installed on the fixed part of the turntable structure, and the measuring end is installed on the rotating part of the turntable structure. It is used to detect the angular position information of the rotating part in real time and feed it back to the servo module. The slip ring includes a fixed end and a rotating end. The fixed end is mounted on the fixed part of the turntable structure, and the rotating end is mounted on the rotating part of the turntable structure. The cable of the satellite measuring component is connected to an external power supply and a data processing unit via the slip ring, for transmitting power and image data when the satellite measuring component rotates continuously with the rotating part. The servo module is electrically connected to the torque motor, the angular displacement sensor and the slip ring respectively, and is used to receive the angular position information fed back by the angular displacement sensor and control the torque motor to drive the rotating part to rotate to the target angle.

[0013] In some instances, the protective housing assembly includes a housing shell and a stargazing window glass disposed on the housing shell. The inner wall of the housing shell is provided with a light-blocking ring and coated with a black paint layer. The light-blocking ring is arranged circumferentially along the inner wall of the housing shell and extends inwardly. The stargazing window glass is high-strength glass and coated with a filter film. The stargazing window glass is disposed on the field of view exit path of the star-measuring assembly.

[0014] In some instances, the protective cover assembly and the turntable assembly are provided with inflation / deflation components and sealing components. The inflation / deflation components are disposed on the protective cover housing and communicate with the internal cavity. The sealing components are disposed at the connection between the protective cover housing and the turntable assembly, as well as at each cable interface, to enable the system to adapt to rain, dust, and salt spray environments.

[0015] In some instances, the satellite measuring components are fixed to the aircraft platform, and the field of view coverage of the satellite measuring channel and the solar measuring channel is expanded by using the attitude maneuver of the aircraft; or 2 to 3 sets of the satellite measuring components are installed in different parts of the aircraft, and each satellite measuring component observes different sky areas at different elevation angles to achieve joint detection of multiple stars and the sun.

[0016] In some instances, the astrophotography camera and the solar astrophotography camera each include a visible light detector and a front panel. The astrophotography camera and the solar astrophotography camera share a processing board and a power interface board. The front panel and the processing board are electrically connected via connectors or flexible printed circuit boards.

[0017] Secondly, the present invention provides a visible light astronomical navigation daytime star measurement method based on any one of the above-mentioned visible light astronomical navigation daytime star measurement systems, comprising: S1: Activate the visible light astronomical navigation daytime star measurement system and complete the system self-test; S2: Obtain the current carrier time information, geographical location information, and attitude information, and calculate the theoretical orientation of the sun and navigation star; S3: Select a navigation star and correct its position error; S4: Control the turntable assembly to rotate around the vertical axis, so that the star measurement channel of the star measurement assembly points to the target bright star and the solar measurement channel points to the sun, so as to acquire star images and solar images respectively; S5: Denoise, perform optical correction and star point extraction processing on the acquired star images and solar images, and calculate the star observation vector and solar observation vector respectively; S6: After accumulating observations of at least two navigation satellites, including the Sun, output the observation vectors of each navigation satellite and calculate the inertial attitude information of the carrier.

[0018] In summary, compared with the prior art, the above-described technical solutions conceived by this invention can achieve the following beneficial effects: By independently integrating the solar measurement channel and the star measurement channel into the star measurement component, the Sun, which is only an interference source in traditional astronomical navigation, is transformed into a usable navigation star. This replaces the traditional requirement of detecting two stars with just the Sun and one bright star, fundamentally overcoming the bottleneck of insufficient visible light star detection in strong background stray light during the day. This eliminates the need for expensive, cooled, and short-lifespan short-wave infrared detectors, as well as long-focal-length, large-aperture optical systems and dual-axis precision tracking systems, to meet the multi-star navigation calculation requirements. Simultaneously, the two channels are positioned at 15°... With a tilt angle of ~40° arranged back-to-back symmetrically, and combined with a single-axis turntable rotating around the vertical axis, a field of view sweep can be achieved within a horizontal 180° annular range. Single-axis rotation replaces the azimuth and pitch two-dimensional motion of the traditional dual-axis turntable. While achieving multi-satellite synchronous measurement, it greatly simplifies the system structure, significantly reduces size and weight, lowers costs, extends working life, and improves reliability and airborne adaptability. Thus, it effectively solves the technical problems of large size and weight, high cost and short life of shortwave infrared schemes and insufficient daytime satellite measurement capability of visible light schemes in the background technology. Attached Figure Description

[0019] To more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0020] Figure 1 This is a schematic diagram of the visible light airborne astronomical navigation system provided in an embodiment of the present invention; Figure 2 This is a schematic diagram of the internal components of the visible light airborne astronomical navigation system provided in an embodiment of the present invention; Figure 3 This is a schematic diagram of the composition of the star-measuring component provided in an embodiment of the present invention; Figure 4This is a schematic diagram of the turntable assembly provided in an embodiment of the present invention; Figure 5 This is a schematic diagram of the protective cover assembly provided in an embodiment of the present invention; Figure 6 This is a flowchart of the visible light airborne astronomical navigation system provided in an embodiment of the present invention. Detailed Implementation

[0021] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0022] In the following description, specific embodiments of the invention will be illustrated with reference to steps and symbols performed by one or more computers, unless otherwise stated. Therefore, these steps and operations will be referred to several times as being performed by a computer, and computer execution as referred to herein includes operations by a computer processing unit representing electronic signals of data in a structured format. This operation transforms the data or maintains it at a location in the computer's memory system, which can be reconfigured or otherwise alter the operation of the computer in a manner well known to those skilled in the art. The data structure maintained by the data is the physical location of the memory, which has specific characteristics defined by the data format. However, the principles of the invention described above are not intended to be limiting, and those skilled in the art will understand that many of the following steps and operations can also be implemented in hardware.

[0023] The terms "module" or "unit" as used herein can be considered as software objects executing on the computing system. Different components, modules, engines, and services described herein can be considered as implementations on the computing system. The apparatus and methods described herein are preferably implemented in software, but can also be implemented in hardware, both of which are within the scope of this invention.

[0024] Those skilled in the art will understand that, unless specifically stated otherwise, the singular forms “a,” “an,” and “the” used herein may also include the plural forms. It should be further understood that the term “comprising” as used in this specification means the presence of features, integers, steps, operations, elements, and / or components, but does not exclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and / or groups thereof. It should be understood that when we say an element is “connected” or “coupled” to another element, it can be directly connected or coupled to the other element, or there may be intermediate elements. Furthermore, “connected” or “coupled” as used herein can include wireless connections or wireless coupling. The term “and / or” as used herein includes all or any units and all combinations of one or more associated listed items.

[0025] This invention proposes a new daytime star measurement technology for airborne autonomous navigation using visible light astronomical navigation. It simultaneously measures stars and the sun in the visible light band, enabling multi-star measurement. It has the advantages of small size, weight, and low cost of visible light astronomical navigation equipment. It is an innovative daytime star measurement solution and a feasible solution to the problem of visible light daytime star measurement on airborne platforms.

[0026] To address the issues of existing large-field-of-view star measurement technology airborne platforms being limited to measuring bright stars during the day, and small-field-of-view daytime star measurement technologies being bulky, heavy, poorly adaptable, expensive, and unreliable, this paper proposes adding a solar measurement channel to the existing large-field-of-view star measurement technology system. This allows for the simultaneous measurement of bright stars and the sun in the visible light band during the day, enabling multi-star detection and astronomical navigation calculations. This meets the requirements of visible light airborne astronomical navigation and solves the problem of lightweight and low-cost daytime star measurement for airborne platforms.

[0027] The Sun is an extremely bright star with a magnitude of approximately -27. During the day, a relatively large field of view of about 100° is sufficient to make it easier to enter the field of view and achieve long-term stable observation. At the altitude of the airborne platform, a large field of view star measurement technique of 10° to 20° can achieve the observation of bright stars of about magnitude 3. The visible light airborne astronomical navigation daytime star measurement system proposed in this invention is a new type of star sensor daytime star measurement technology that combines a solar measurement component with a large field of view of about 100° and a bright star measurement component with a large field of view of about 10° to achieve simultaneous measurement of multiple stars during the day.

[0028] The visible light airborne astronomical navigation system provided in this invention mainly consists of a stellar measurement component (including a solar measurement channel and a stellar measurement channel), a turntable component, a protective housing component, connectors, etc. Its prototype components are as follows: Figure 1 As shown in the diagram, the internal components are as follows: Figure 2 As shown.

[0029] The astrometry module mainly consists of a solar measurement channel and a astrometry channel. The components of the astrometry module are as follows: Figure 3 As shown, the solar measurement channel and the astrometry channel are arranged back-to-back, with their centers pointing upwards at a certain angle (e.g., 15° to 40°) to the horizontal plane. This facilitates the use of a turntable to expand the field of view of both channels in a 180° annular shape. This allows the astrometry channel to avoid the sun and quickly search for and detect multiple bright stars within the astrometry ring, while also allowing the sun to enter the solar measurement channel's field of view. Ultimately, this achieves simultaneous measurement of the sun and bright stars, enabling synchronous measurement of multiple stars. Furthermore, for areas where space is limited and a turntable cannot be installed, the astrometry components can be directly mounted on the aircraft, utilizing the aircraft's angular movement to expand the field of view of both the astrometry and solar measurement channels. For situations where aircraft angular movement is not possible, 2-3 sets of astrometry components can be installed at different locations on the aircraft. Each observation channel of the astrometry components has a different elevation angle, allowing observation of different sky regions and achieving synchronous measurement of multiple stars and the sun.

[0030] The satellite measurement channel consists of a periscope optical lens and a satellite measurement camera (including a visible light detector, front panel, processing board, and power interface board). The periscope optical lens has a field of view of approximately 10° to 20° and employs a transmissive integrated structure and a reflector to achieve optical path refraction, enabling a compact design and stray light suppression. While maintaining a large aperture to ensure satellite measurement capabilities, it also uses a suitable F-number (e.g., 2.0 to 4.0) and is coated with a near-infrared long-pass filter (e.g., passing above 600nm and cutting off below 600nm) to achieve good daytime background stray light suppression capabilities on the airborne platform. To achieve low cost, based on the spectral characteristics of the observed target and the main background stray light, the satellite measurement camera uses a near-infrared enhanced visible light detector, combined with a filter, to enable the system to operate in the near-infrared band, achieving a better signal-to-noise ratio for daytime satellite measurement. The system's detector and operating band can be optimized according to the specific flight mission; for example, the higher the operating altitude, the more biased towards the blue light band.

[0031] The solar measurement channel consists of a solar camera (including a visible light detector, a front panel, and a shared processing board and power interface board with the satellite camera), an attenuator, and a wide-angle lens with a large field of view. The wide-angle lens has a wide angle of approximately 100°, with an angle of approximately 70° between the optical axis and the horizontal direction. When the solar altitude angle is above 20° and the angle between the sunlight and the optical axis is less than 50°, it can ensure that the sun enters the field of view. The attenuator can reduce the intensity of sunlight by four to five orders of magnitude, making the solar image clear and visible without saturation.

[0032] The turntable assembly mainly consists of a turntable structure, torque motor, angular displacement sensor, slip ring, servo module, etc., as shown in the schematic diagram below. Figure 4 As shown. The star-measuring component is connected to the turntable assembly servo module via a cable to control the turntable's rotation angle, enabling rapid alignment with the sun and bright stars. To ensure high accuracy of the star-measuring channel, the turntable's axial wobble accuracy and angular measurement accuracy should be superior to the overall angular measurement accuracy.

[0033] The protective housing assembly consists of a housing shell, an observation window glass, etc., and is mainly used to protect the star-measuring components. To provide the star-measuring components with the best possible observation environment, a light-blocking ring can be installed on the inner wall of the housing to block stray light, and then painted black. A schematic diagram of its composition is shown below. Figure 5 As shown.

[0034] To adapt to various application environments such as rain, dust, and salt spray, inflation and deflation and sealing components can be designed on the protective cover assembly and turntable housing, and sealing measures can be taken at each connection point, so that astronomical navigation daytime star measurement technology can be applied on various platforms.

[0035] Existing airborne astronomical navigation daytime star measurement generally employs small field-of-view dual-axis tracking daytime star measurement technology, which suffers from problems such as large system size and weight, high cost, short lifespan, and insufficient reliability. Existing large field-of-view star sensor daytime star measurement technology faces challenges in daytime star measurement. The visible light airborne astronomical navigation daytime star measurement technology proposed in this invention uses the visible light band to simultaneously measure stars and the sun, achieving multi-star measurement. It uses a single-axis turntable rotation or aircraft maneuvering to achieve lateral channel avoidance of the sun and pointing to bright stars. It has the advantages of small size and weight and low cost of visible light astronomical navigation, and its adaptability is also greatly improved. It is a novel and pioneering airborne daytime star measurement solution and a feasible solution to the problem of lightweight and low-cost daytime star measurement on airborne platforms.

[0036] In another embodiment of the present invention, a visible light airborne astronomical navigation daytime star-measuring system is provided, aiming to solve the problems of difficulty in star measurement, large system size and weight, high cost, and low reliability caused by strong atmospheric background stray light during daytime astronomical navigation on airborne platforms in the prior art. The visible light airborne astronomical navigation daytime star-measuring system of this embodiment of the present invention achieves all-weather, low-cost, and lightweight airborne autonomous navigation by integrating wide-field-of-view solar detection and high-precision bright star detection functions. The preferred embodiments of the present invention will be further described in detail below with reference to the accompanying drawings. Figure 1 and Figure 2 As shown, this invention provides a visible light airborne astronomical navigation daytime star measurement device, which mainly consists of a star measurement component (including a solar measurement channel and a star measurement channel), a turntable component, a protective cover component, a connector, etc.

[0037] (1) Integration and functional configuration of the satellite measurement component like Figure 2 As shown, the star-measuring component of this embodiment includes a solar measurement channel and a star measurement channel. The star-measuring component adopts a "back-to-back" dual-channel integrated design to form a symmetrical layout. The optical axes of both channels point upwards towards the zenith at a certain tilt angle (e.g., 15°–40°) to achieve synchronous detection of the sun and bright stars, and facilitates field-of-view sweeping and rapid target alignment by rotating the turntable.

[0038] This design is highly innovative: by using a dual-channel coaxial arrangement, it effectively utilizes limited space to achieve simultaneous detection of the Sun and bright stars; by using turntable rotation or aircraft attitude maneuvering, it enables rapid searching of the star-measuring channel within a 180° annular range, avoiding areas of intense sunlight and improving detection efficiency; in the absence of a turntable or under limited installation space, multiple star-measuring components can be fixed to different parts of the aircraft, observing different sky areas at different elevation angles, achieving joint detection of multiple stars and the Sun, and enhancing system redundancy and adaptability.

[0039] Satellite measurement channel design: such as Figure 2 and Figure 3 As shown, the channel consists of a periscope optical lens and a star-measuring camera. The star-measuring channel employs a periscope optical system with a field of view of 10°–20°. The periscope optical lens comprises a reflector and a conventional transmission lens, achieving a compact structure and the ability to deflect stray light. The transmission lens uses a moderate design with an F-number of 2.0–4.0, effectively suppressing the strong atmospheric background radiation of the airborne platform during the day while ensuring high-sensitivity detection. The star-measuring camera includes a visible light detector, a front-end board, a processing board, and a power interface board. The detector uses a near-infrared enhanced visible light sensor, combined with a long-pass filter coated on the optical lens with a passband above 600nm and a cutoff below 600nm, enabling the entire star-measuring channel to operate in the near-infrared band. This significantly improves the signal-to-noise ratio of the airborne platform during daytime star measurement, making it particularly suitable for bright star detection in high background radiation environments. The innovation of this invention is that it combines a near-infrared enhanced detector with a large field-of-view periscope structure for the first time, achieving the triple advantages of "large field of view + high signal-to-noise ratio + suppression of stray light", breaking through the bottleneck of traditional large field-of-view star measurement systems that cannot effectively detect due to strong background stray light.

[0040] Solar channel design: such as Figure 2 and Figure 3 As shown, this channel consists of a wide-angle lens with a large field of view, an attenuator, and a solar camera. The wide-angle lens features a wide angle of approximately 100°, with an optical axis angle of about 70° to the horizontal plane. This design allows the astronomical navigation system to easily observe the sun under various installation conditions, ensuring that the sun can stably enter the field of view when the solar altitude angle is greater than 20° and the angle between the sunlight and the optical axis is less than 50°. To prevent solar overexposure, the attenuator is coated with a high-performance filter film. The attenuator is structurally integrated between the lens and the solar camera, reducing the solar energy entering the imaging detector by 4-5 orders of magnitude, achieving a clear and unsaturated solar image, which is beneficial for long-term stable solar observation. The solar camera includes a visible light detector and a front panel, and shares a processing board and power interface board with the astronomical camera. The front panel and the astronomical camera processing board are connected via connectors or flexible printed circuit boards.

[0041] The innovation lies in the use of a combination of "wide-angle and large field of view + super attenuation" to achieve stable and high dynamic range imaging of the sun, thus expanding the observation targets of traditional astronomical navigation.

[0042] (2) Turntable assembly The turntable assembly mainly consists of a turntable structure, torque motor, angular displacement sensor, slip ring, servo module, etc., as shown in the schematic diagram below. Figure 4 As shown. The star-measuring component is connected to the turntable assembly servo module via a cable to control the turntable's rotation angle, enabling rapid alignment with the sun and bright stars. To ensure high accuracy of the star-measuring channel, the turntable's axial wobble accuracy and angular measurement accuracy should be superior to the overall angular measurement accuracy.

[0043] The single-axis turntable enables dual-channel field-of-view sweeping and target alignment, replacing the traditional dual-axis tracking system, significantly reducing system size, weight and cost, and achieving the goal of "lightweight, low cost and high reliability".

[0044] (3) Protective shield assembly The protective housing assembly consists of a housing shell, an observation window glass, etc., and is mainly used to protect the star-measuring components. To provide the star-measuring components with the best possible observation environment, a light-blocking ring can be installed on the inner wall of the housing to block stray light, and then painted black. A schematic diagram of its composition is shown below. Figure 5 As shown.

[0045] The stargazing window is made of high-strength glass and coated with a filter film for a specific operating band to suppress stray light and improve the signal-to-noise ratio of star measurement during the day.

[0046] To adapt to various application environments such as rain, dust, and salt spray, inflation and deflation and sealing components can be designed on the protective cover assembly and turntable housing, and sealing measures can be taken at each connection point, so that astronomical navigation daytime star measurement technology can be applied on various platforms.

[0047] (4) Satellite measurement process like Figure 6 As shown, the visible light airborne astronomical navigation system automatically completes startup and self-test after power-on. Then, based on the time, geographic position, and geographic attitude provided by the airborne platform, it automatically selects navigation stars and corrects navigation star position errors. The system controls the turntable assembly to rotate so that the optical axis of the star measurement assembly points to the corresponding observation area for star image capture. When the star measurement group has cumulatively observed at least two navigation stars (including the Sun), it can output the observed navigation star vector and inertial frame attitude information.

[0048] The relevant working process is as follows: The visible light airborne astronomical navigation system's star-measuring component calculates the direction of the sun and stars based on the current time, the aircraft's position and attitude information, and selects navigation stars. It controls the turntable component to rotate so that the star-measuring channel points to bright stars and the solar-measuring channel points to the sun, and takes star charts of the corresponding observation areas. After a star or the sun enters the corresponding field of view, the optical lens completes the acquisition and projection of the optical image of the star or the sun. The visible light imaging detector converts the optical signal projected onto the visible light detector into an electronic image. The image processing board acquires, denoises, performs optical correction, extracts star points, and calculates star vectors for the electronic image. When the star sensor observes two or more navigation stars (including the sun), it outputs the observed navigation star vector and inertial frame attitude information to control the turntable to track and observe multiple stars, realizing multi-position star measurement.

[0049] The system of this invention can achieve stable detection of the sun and at least one bright star by an airborne platform during the day and in high background radiation environments. Compared with traditional astronomical navigation systems, the system size and weight can be reduced by more than 80%, the cost is reduced by about 50%, and the reliability is significantly improved. It is suitable for lightweight airborne platforms such as UAVs, unmanned surface vessels, and small aircraft, and has broad application value.

[0050] The above provides a detailed description of a visible light astronomical navigation daytime star measurement method and system provided by the embodiments of the present invention. Specific examples have been used to illustrate the principles and implementation methods of the present invention. The description of the above embodiments is only for the purpose of helping to understand the method and core ideas of the present invention. At the same time, for those skilled in the art, there will be changes in the specific implementation methods and application scope based on the ideas of the present invention. Therefore, the content of this specification should not be construed as a limitation of the present invention.

Claims

1. A visible light astronomical navigation daytime star-measuring system, characterized in that it includes: Protective shield assembly; A turntable assembly is disposed below or inside the protective cover assembly; The satellite measuring component is mounted on and supported by the turntable assembly, and is entirely located within the internal cavity of the protective cover assembly, which covers the outside of the satellite measuring component. The star-measuring component includes a solar measurement channel and a star-measuring channel, which are fixedly connected back-to-back. The solar measurement channel is used to capture and stably observe the sun during the day, and the star-measuring channel is used to capture and observe bright stars during the day. The optical axes of the star-measuring channel and the solar-measuring channel are both tilted upwards at an angle of 15° to 40° to the horizontal plane, pointing towards the zenith, and the two channels are arranged symmetrically back to back. The turntable assembly is fixedly connected to the star measuring assembly and is used to drive the star measuring assembly to rotate around the vertical axis in order to adjust the horizontal orientation of the field of view of the star measuring channel and the solar measuring channel. The star-measuring component, through the rotation of the turntable component, enables the star-measuring channel to search and detect multiple bright stars and the solar-measuring channel to simultaneously measure the sun, outputting observation vectors of at least two celestial bodies for astronomical navigation calculations.

2. The system according to claim 1, characterized in that the solar measurement channel includes a wide-angle lens with a large field of view, an attenuator, and a solar measurement camera arranged sequentially along the optical path; the field of view of the wide-angle lens is 80° to 120°, and the attenuator is used to attenuate the solar energy entering the solar measurement camera by 4 to 5 orders of magnitude.

3. The system according to claim 2, characterized in that the field of view of the wide-angle lens is 100°, the angle between its optical axis and the horizontal plane is 60° to 80°, and when the solar altitude angle is greater than 20° and the angle between the sunlight and the optical axis is less than 50°, the sun enters the field of view of the wide-angle lens.

4. The system according to claim 3, characterized in that the star-measuring channel includes a periscope optical lens and a star-measuring camera arranged sequentially along the optical path; the periscope optical lens includes a reflector and a transmission lens group, with a field of view of 10° to 20° and an F number of 2.0 to 4.0; the surface of the transmission lens group of the periscope optical lens is coated with a long-pass filter film, the passband wavelength of the long-pass filter film being above 600nm and the cutoff wavelength being below 600nm; the star-measuring camera adopts a near-infrared enhanced visible light detector, so that the star-measuring channel operates in the near-infrared band.

5. The system according to claim 4, characterized in that the turntable assembly is disposed at the bottom of the protective cover assembly, and includes a turntable structure, a torque motor, an angular displacement sensor, a slip ring, and a servo module; The turntable structure includes a fixed part and a rotating part. The fixed part is fixedly connected to the bottom of the protective cover assembly or the carrier platform. The rotating part is rotatably supported on the fixed part about a vertical axis. The upper end of the rotating part is fixedly connected to the satellite measuring assembly. The torque motor includes a stator and a rotor. The stator is fixedly mounted on the fixed part of the turntable structure, and the rotor is fixedly mounted on the rotating part of the turntable structure. The torque motor is used to directly drive the rotating part to rotate about a vertical axis relative to the fixed part. The angular displacement sensor includes a fixed end and a measuring end. The fixed end is installed on the fixed part of the turntable structure, and the measuring end is installed on the rotating part of the turntable structure. It is used to detect the angular position information of the rotating part in real time and feed it back to the servo module. The slip ring includes a fixed end and a rotating end. The fixed end is mounted on the fixed part of the turntable structure, and the rotating end is mounted on the rotating part of the turntable structure. The cable of the satellite measuring component is connected to an external power supply and a data processing unit via the slip ring, for transmitting power and image data when the satellite measuring component rotates continuously with the rotating part. The servo module is connected to the torque motor, the angular displacement sensor and the slip ring respectively, and is used to receive the angular position information fed back by the angular displacement sensor and control the torque motor to drive the rotating part to rotate to the target angle.

6. The system according to claim 5, characterized in that the protective housing assembly includes a protective housing shell and a star-viewing window glass disposed on the protective housing shell, the inner wall of the protective housing shell is provided with a light-blocking ring and coated with a black paint layer, the light-blocking ring is arranged circumferentially along the inner wall of the protective housing shell and extends inwardly; the star-viewing window glass is high-strength glass and coated with a filter film, and the star-viewing window glass is disposed on the field of view exit path of the star-measuring assembly.

7. The system according to claim 6, characterized in that the protective cover assembly and the turntable assembly are provided with an inflation / deflation component and a sealing component, the inflation / deflation component is disposed on the protective cover housing and communicates with the internal cavity, and the sealing component is disposed at the connection between the protective cover housing and the turntable assembly and at each cable interface, for making the system adaptable to the environment.

8. The system according to claim 7, characterized in that the star-measuring component is fixed to the aircraft platform, and the field of view coverage of the star-measuring channel and the solar-measuring channel is expanded by the attitude maneuver of the aircraft; or 2 to 3 sets of the star-measuring components are installed in different parts of the aircraft, and each star-measuring component observes different sky areas at different elevation angles, so as to realize the joint detection of multiple stars and the sun.

9. The system according to claim 8, characterized in that the astrophotography camera and the solar camera respectively include a visible light detector and a front panel, the astrophotography camera and the solar camera share a processing board and a power interface board, and the front panel and the processing board are electrically connected via connectors or flexible printed circuit boards.

10. A daytime star-measuring method for visible light astronomical navigation based on any one of claims 1 to 9, characterized in that, include: S1: Activate the visible light astronomical navigation daytime star measurement system and complete the system self-test; S2: Obtain the current carrier time information, geographical location information, and attitude information, and calculate the theoretical orientation of the sun and navigation star; S3: Select a navigation star and correct its position error; S4: Control the turntable assembly to rotate around the vertical axis, so that the star measurement channel of the star measurement assembly points to the target bright star and the solar measurement channel points to the sun, so as to acquire star images and solar images respectively; S5: Denoise, perform optical correction and star point extraction processing on the acquired star images and solar images, and calculate the star observation vector and solar observation vector respectively; S6: After accumulating observations of at least two navigation satellites, including the Sun, output the observation vectors of each navigation satellite and calculate the inertial attitude information of the carrier.

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