CN118730125A - Astronomical navigation method based on space target optical angle measurement under altitude limiting condition - Google Patents
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Abstract
The invention discloses an astronomical navigation method based on space target optical angle measurement under the condition of altitude limitation, which utilizes an optical imaging system to observe a satellite and a fixed star simultaneously, carries out attitude calculation through fixed star observation information, and utilizes the constraint condition of altitude to complete positioning calculation by combining with the direction vector information of the satellite. The method obviously reduces the dependence on multiple observations or multi-satellite observations through single optical observation and direction measurement of one satellite, simplifies the measurement steps, improves the efficiency and the data availability, reduces the requirement on equipment precision, and is beneficial to reducing the cost. The invention is suitable for shipborne application conditions, and can provide a reliable, economical and efficient navigation and positioning solution for a dynamic platform in a complex electromagnetic environment.
Description
Technical Field
The invention relates to an astronomical navigation method in the field of navigation positioning, in particular to an astronomical navigation method based on space target optical angle measurement under the condition of altitude limitation.
Background
The high-precision navigation positioning information is the basis for the platforms such as a spacecraft, an airplane, a missile and a ship to execute various tasks. Satellite navigation is currently the most efficient means of achieving high-precision navigation, however, under complex electromagnetic environments, satellite navigation systems have the potential to be disturbed or deceptively synthesized. How to provide completely autonomous and high-precision positioning information for a motion carrier under the satellite rejection condition is a key technical problem to be solved in the navigation field.
Astronomical navigation is successfully applied to various platforms such as airplanes, ships, missiles and the like by observing the direction information of celestial bodies such as stars, sun and the like and combining horizontal reference information to finish positioning calculation, so that errors are not scattered along with time theoretically, and the astronomical navigation becomes a navigation bottom-keeping means under the satellite refusing condition. However, in the conventional astronomical navigation, a fixed star is used as a navigation beacon, the horizontal attitude reference information provided by an inertial navigation system is used for converting the direction vector of the fixed star into altitude angle information to perform positioning calculation, and the horizontal attitude error is introduced into a positioning result due to initial inertial navigation error, inertial device error and shafting error, and the error is difficult to suppress when no other external information is used for assistance.
In order to overcome the dependence of astronomical Navigation on inertial Navigation horizontal attitude information, the prior art provides an angle-only Navigation (angle Navigation) method, and positioning solution is realized by carrying out optical observation on more than 3 satellites, so that the positioning precision of astronomical Navigation can be remarkably improved. Because the method needs to observe a plurality of satellites simultaneously or observe the same satellite for a plurality of times, however, the method is easy to be interfered by cloud and fog when being observed on a ship platform, and the visibility of the satellites is poor, the availability and the instantaneity of navigation information are low, and the application of the method in a low-altitude area is limited.
How to reduce the requirement on astronomical target observation, simplify the measurement steps, improve the usability of data and further improve the positioning accuracy is a technical problem focused by the technicians in the field.
Disclosure of Invention
Aiming at the defects of the prior art, the space target determined by the orbits of satellites, space stations, space fragments or rocket debris is used as a navigation beacon, an astronomical navigation method based on space target optical angle measurement under the condition of limited altitude is provided, and the navigation positioning precision and the data availability are improved.
In order to solve the technical problems, the invention adopts the following technical scheme: an astronomical navigation method based on space target optical angle measurement under the condition of altitude limitation comprises the following steps:
S1, calculating space target coordinates, and screening space targets meeting an observation pitch angle threshold;
S2, predicting space target stars and the like screened in the step S1, selecting navigation space targets according to the stars and the like, and if the navigation space targets meeting the conditions exist, entering the step S3; otherwise, returning to the step S1;
s3, adjusting the optical axis of the optical imaging system to point to a navigation space target, and triggering a camera to expose and image;
s4, respectively extracting all stars in the navigation space target and the field of view from the photographed star map, and calculating the gesture of the optical imaging system by utilizing the star point image coordinate information of the stars;
s5, recalculating the current coordinates of the navigation space target according to the triggering moment of the camera, and completing positioning calculation by utilizing the space target coordinates and the camera gesture to obtain the local position coordinates.
The navigation calculation can be realized by only one-time space target measurement, so that the requirement on the observation condition is low, the measurement steps can be effectively simplified, and the measurement efficiency and the data availability can be improved.
In step S2, the calculation formula of m cs_k of the space target star is:
Where α represents the geometrical reflectivity of the space object, R SAT represents the radius of the space object, d SS represents the distance between the sun and the space object, d PS represents the distance between the observation point and the space object, ρ ⊙ is the solar phase angle, and h SAT is the space object height.
The specific implementation process for selecting the navigation space target according to the star comprises the following steps: all space targets of which the space target star and the like are lower than the detection threshold on duty for the week and the like are screened out to serve as candidate navigation space targets, and the space target with the lowest star and the like in the candidate navigation space targets is selected to serve as the navigation space target.
In step S2, before predicting the space target star, the method further includes: judging whether the space target is blocked by the ground shadow, if not, predicting the space target star and the like, and if so, returning to the step S1; wherein when the space target direction vector and the sun direction vector meetWhen the space target is considered to be not shielded by the ground shadow, R is the average radius of the earth,Represents the jth spatial target in the set of spatial targets that meet the observed pitch angle threshold,A unit vector indicating the incident direction of sunlight on the earth.
In step S4, if the navigation space object cannot be successfully extracted, the process returns to step S3.
In step S5, the coordinates of the observation point in the geodetic fixed coordinate system eThe method is adopted for calculation:
wherein, L is the spatial target position vectorIs provided for the length of (a),R is the average earth radius, R N is the earth equatorial radius,As a direction vector of the direction of the line of sight of the spatial target in the geographic coordinate system,F is the focal length of the camera, (u 0,v0) is the physical coordinates of the principal point of the camera, (u s,vs) is the centroid coordinates of the spatial target on the image, and θ is the spatial target position vectorAnd the direction of the line of sightThe included angle between the two parts is that,H is the altitude of the observation support,Is the pose of the optical imaging system.
As an inventive concept, the present invention also provides an astronomical navigation system based on a space target optical goniometry under an altitude limiting condition, including a memory, a processor and a computer program stored on the memory; the processor executes the computer program to implement the steps of the method described above.
As an inventive concept, the present invention also provides an astronomical navigation system based on a space target optical goniometry under an altitude limiting condition, comprising:
an optical imaging system for imaging the space object and the sidereal;
The double-shaft turntable comprises a base, an azimuth rotating mechanism and a pitching rotating mechanism; the pitching rotating mechanism is arranged on the azimuth rotating mechanism, and the azimuth rotating mechanism is arranged on the base; the optical imaging system is arranged on the pitching rotation mechanism;
The inertial measurement unit is used for providing attitude information of the base;
The time system equipment is used for providing UTC time information required by navigation calculation and time synchronization second pulses for data acquisition of each measurement control equipment;
The data processing unit is communicated with the optical imaging system, the double-shaft turntable, the inertia measurement unit and the time system equipment, and astronomical navigation calculation is realized by adopting the steps of the method;
the double-shaft turntable, the inertia measurement unit, the time system equipment and the data processing unit are all arranged on the measurement carrier.
In the invention, the visual angle of the optical imaging system is in the range of 5-30 degrees.
In the invention, the perpendicularity error between the azimuth rotation axis and the pitching rotation axis of the double-shaft turntable is smaller than 0.1 degrees, and when both the pitching rotation axis and the azimuth rotation axis of the double-shaft turntable are in zero positions, the parallelism between the optical axis of the optical imaging system and the azimuth rotation axis of the double-shaft turntable is better than 1 degree.
Compared with the prior art, the invention has the following beneficial effects: the invention provides an astronomical navigation scheme which does not depend on high-precision horizontal reference information, and can realize positioning only by astronomical observation through an optical imaging system; the double-shaft turntable and the inertia measurement unit which are needed by the invention are only used for providing rough measurement and control of the optical axis direction of the optical imaging system, have lower requirements on the precision of equipment, and are beneficial to reducing the hardware cost of the equipment; the navigation calculation can be realized by only one-time space target measurement, so that the requirement on the observation condition is low, the measurement steps can be effectively simplified, and the measurement efficiency and the data availability can be improved.
Drawings
FIG. 1 is a schematic diagram of an astronomical navigation device based on spatial target optical goniometry in an embodiment of the present invention;
FIG. 2 is a coordinate definition of an astronomical navigation device and method based on spatial target optical goniometry in accordance with an embodiment of the present invention;
FIG. 3 is an algorithm flow chart of an astronomical navigation method based on spatial target optical goniometry in an embodiment of the present invention;
fig. 4 is a schematic diagram of an astronomical navigation positioning calculation method based on space target optical angle measurement according to an embodiment of the present invention.
Detailed Description
For the purpose of making the objects, technical solutions and advantages of the embodiments of the present invention more clear, the technical solutions of the embodiments of the present invention will be clearly and completely described below by taking satellites in space targets as navigation beacons, and by referring to the drawings in the embodiments of the present invention, it is obvious that the described embodiments are some embodiments, but not all embodiments of the present invention. All other embodiments, which can be made by those skilled in the art based on the embodiments of the invention without making any inventive effort, are intended to be within the scope of the invention.
Example 1
An embodiment 1 of the present invention provides an astronomical navigation device, as shown in fig. 1, which includes an optical imaging system 1, a biaxial turntable 2, an inertial measurement unit 3, a data processing computer 4, and a time system apparatus 5.
As shown in fig. 2, the optical imaging system includes a camera 101 and an optical lens 102 for imaging satellites and stars. Typical optical imaging systems may employ either visible band optical imaging systems or near infrared enhanced optical imaging systems, which should have an appropriate field angle, typically in the range of 5 to 30. The optical imaging system selected in the embodiment of the invention is a visible light wave band optical imaging system, the field angle of the optical imaging system is 14 degrees, a camera can be a scientific grade or industrial camera, and a preferable scheme is a scientific grade camera. The selected camera may employ a CMOS image sensor or a CCD image sensor.
The biaxial turntable includes a turntable base 201, an azimuth rotation mechanism 202, and a pitch rotation mechanism 203, wherein the pitch rotation mechanism is mounted on the azimuth rotation mechanism, and the azimuth rotation axis and the pitch rotation axis should be mounted approximately perpendicularly. The biaxial turntable can be a general shelf product, and in this embodiment, the error in perpendicularity between the recommended azimuth axis of rotation and the pitch axis of rotation should be less than 0.1 °.
The optical imaging system is fixedly connected and installed on the pitching rotating mechanism, when the two rotating mechanisms of the double-shaft turntable are in zero positions, the optical axis of the optical imaging system is approximately parallel to the azimuth rotating shaft of the double-shaft turntable, and the double-shaft turntable is used for controlling the optical axis of the optical imaging system to point to the direction of the target satellite during astronomical observation. In the present embodiment, it is preferable to make the optical imaging system such that the angular deviation of the optical axis from the azimuth rotation axis of the biaxial turntable is not more than 1 ° when both the pitch axis and the azimuth axis of the biaxial turntable are at zero positions.
The inertial measurement unit is used for providing attitude information of the turntable base. The inertial measurement unit can adopt a laser gyro inertial measurement unit, a fiber optic gyro inertial measurement unit or an MEMS inertial measurement unit, and the fiber optic gyro inertial measurement unit can be optimized for considering the cost and the measurement precision. In another embodiment it is also possible that the inertial measurement unit is not required to be configured, but that the attitude and coarse position information of the measurement carrier is provided by means of a navigation device configured on the measurement carrier.
The time system device is used for providing UTC time information required by navigation calculation and time synchronization second pulses for data acquisition of each measurement control device. The time system equipment can be selected from a B code terminal, an atomic clock or other time system equipment. In another embodiment, the time system device is not required to be configured, and the universal time system device configured on the measurement carrier is used for providing time information and second pulse information for the astronomical navigation device.
The data processing computer is used for data acquisition of the optical imaging system, motion control of the double-shaft turntable, data acquisition of the inertial measurement unit and astronomical navigation calculation. The data processing computer can adopt a general purpose computer, an embedded computer or other data processing equipment, requires the data processing computer to have stronger computing power, and is required to be configured with a corresponding communication interface according to a data interface of the optical imaging system and a data interface of the inertial measurement unit for realizing camera image acquisition and inertial navigation data acquisition.
The biaxial turntable and the inertial measurement unit are fixedly arranged on the measurement carrier 6. The time system device and the data processing computer are preferably mounted on the measurement carrier using shock absorbers. The measuring carrier can be a carrier such as a ship, a vehicle, an airplane and the like, and in the embodiment, the ship is used as the measuring carrier.
FIG. 2 defines the coordinate system of the biaxial turret base as b-system O b-XbYbZb, the coordinate system of the optical imaging system as s-system O s-XsYsZs, the coordinate system of the turret table top as t-system O t-XtYtZt, the geocentric earth fixed coordinate system (ECEF) as e-system O e-XeYeZe, the local horizontal coordinate system n-system O n-XnYnZn (northeast-related coordinate system is adopted), and the inertial measurement unit coordinate system is rigidly connected with the turret base.
Referring now to the drawings, in which the method of the present invention is further described in terms of one embodiment, FIG. 3 is a general flow chart of a measurement method of the present invention, and the steps are implemented as follows:
Step 1: and calculating the current time coordinates of all satellites in the satellite library according to the orbit parameters and time information of the satellites in the navigation satellite library, and screening out the satellites which are positioned above the horizontal plane of the position where the observation carrier is positioned and the pitch angle of which is larger than the threshold value of the observation pitch angle according to the space coordinates of the satellites and the rough position information of the measurement carrier.
1.1 Calculating the coordinates of all satellites in the satellite base at the current time t k according to the orbit parameters and time information of the satellites in the navigation satellite baseWherein the navigation satellite base is a navigation satellite orbit parameter stored in the data processing computer in advance. One preferred satellite orbit parameter may be in the Two-row orbit number (Two-LINE ELEMENT, TLE) format disclosed by the north american air defense command (NORAD), and the navigation satellite library may be downloaded from the Space-Track website in the united states. The satellite real-time position can be calculated by adopting a simplified universal perturbation model (SIMPLIFIED GENERAL Perturbations, SGP 4), and the specific implementation mode of the algorithm is disclosed in the paper REVISITING SPACETRACK Report #3 published in 2006 by David A.Vallado.
1.2 According to the space coordinates of the satellitesAnd measuring the rough longitude of the carrierLatitude of latitudeAnd height information(With errors) screening out satellites which are located above the horizontal plane of the position where the measuring carrier is located and the pitch angle is higher than the threshold value of the observed pitch angle. The specific calculation method comprises the following steps:
first, the line of sight direction of the satellite relative to the observer is calculated K=1, 2, …, N is the total number of satellites in the navigation satellite constellation and further calculates the unit vector of the line of sight direction: For measuring the coordinates of the rough position of the carrier in the e-system (i.e. the position coordinates with errors) it is possible to use Conversion calculation is performed by a method of WGS-84 coordinate system specification,The longitude, latitude and elevation of the observation point are rough respectively.
Thereby calculating the n-system vector of the local horizontal coordinate systemWherein the method comprises the steps ofThe local calculation method comprises the following steps:
The satellite altitude angle is larger than the critical value gamma min, so that the requirement of observation sight can be met:
Wherein the subscript z represents a vector Projection on the n-axis Z n.
Satellites meeting the above requirements for observation and implementation are noted as
Step 2: forecasting satellites and the like of the satellites screened in the step 1, arranging satellites and the like in a sequence from low to high, screening satellites with a threshold value of Yu Xing and the like of the same height as candidate navigation satellites for observation, and returning to the step 1 if satellites meeting the threshold value requirement of the same height are not available:
2.1 firstly judging whether the satellite screened in the step 1 is in a ground shadow area, wherein the judging method comprises the following steps:
The unit vector of the incident direction of sunlight on the earth is expressed as Can be calculated by the method published in Andreas, paper Solar position algorithm for solar radiation application published in A.2003. When the satellite direction vector and the sun direction vector satisfy the following relationship, the satellite is considered not to be blocked by the ground shadow. Otherwise, the image is blocked by the ground shadow.
Where R is the average radius of the earth.
2.2 For satellites not blocked by ground shadows, the satellites and the like are calculated by the following method
Wherein the second term is related to the physical properties of the satellite itself, α represents the geometrical reflectivity of the satellite, and R SAT represents the radius of the satellite; in the third term, d SS denotes the distance between the sun and the satellite, d PS denotes the distance between the observation point and the satellite, ρ ⊙ is the solar phase angle (angle between the sun and the satellite's line of sight), and h SAT is the satellite height. Typically for Starlink satellites, α may be 0.2 and R SAT may be approximately 1m.
The satellite or the like of the satellite brightness blocked by the ground shadow is set to a value of m cs_k =20.0 or more.
2.3 Screening all satellites of which the satellite positions are lower than a detection threshold on duty for the week and the like, serving as candidate navigation satellites, arranging the candidate navigation satellites according to the sequence from low to high of the satellite positions, and selecting the satellite with the lowest satellite position as a target navigation satellite.
Whether the satellite satisfies m cs_k＜mTH,mTH as a detection threshold on duty for the week or not is determined. And selecting satellites meeting the threshold condition as navigation target satellites, wherein the sitting marks of the navigation target satellites are as followsThe star is denoted as m ns.mTH and is generally selected based on the probe star of the optical imaging system, in combination with the observation conditions, and typically the threshold on duty for the week is selected as 6 star.
2.4 If the navigation target star meeting the condition is not available, returning to the step 1.
Step 3: and (3) calculating the direction vector of the satellite under the coordinate system of the turntable base according to the coordinates of the target navigation satellite, the attitude information and the rough position information of the measurement carrier selected in the step (2), controlling the azimuth rotating mechanism and the pitching rotating mechanism of the biaxial turntable, triggering the camera to shoot and image the target satellite and the star in the field of view after the optical axis of the optical imaging system points to the target satellite, and recording the triggering moment of the camera.
3.1 According to the target navigation satellite coordinates selected in step 2Measuring attitude information of a carrierAnd coarse location informationThe direction vector of the satellite under the coordinate system of the turntable base is calculated by the following specific calculation method:
Wherein x b,yb,zb is Components in three directions.
3.2 Controlling an azimuth rotating mechanism and a pitching rotating mechanism of the double-shaft turntable to enable an optical axis of the optical imaging system to point to a target satellite, wherein the rotation angle calculating method of the azimuth rotating mechanism and the pitching rotating mechanism of the double-shaft turntable is as follows:
And 3.3, after the azimuth rotating mechanism and the pitching rotating mechanism of the double-shaft turntable rotate to target angles, the camera is controlled by the data processing computer to trigger exposure, and the navigation target star is imaged. The trigger can be performed once or a plurality of times of continuous triggers. And acquiring an image shot by the triggering camera each time, and recording the exposure triggering time as t trig.
Step 4: and respectively extracting all stars in the target satellite and the field of view from the photographed star map, and calculating the gesture of the optical imaging system by utilizing the extracted star point image coordinate information. If the target satellite cannot be successfully extracted, returning to the step 3, and tracking the next satellite with higher satellite number, such as a satellite; if the target satellite is successfully extracted, the step 5 is entered.
4.1 Firstly, carrying out data processing on the photographed star map, and solving to obtain an attitude matrix of the optical imaging systemThe data processing process can be realized by adopting a general data processing method in star sensor technology, and the specific data processing method can refer to the monograph 'APS CMOS star sensor system principle and realization method' published by the national defense industry press in 2017. 4.2 recalculating the coordinates of the navigation target star in the earth coordinate system at the moment T=t trig+texpo/2 according to the trigger moment T trig of the cameraT expo is the exposure time of the camera. The calculation method is the same as described in step 1.1.
4.3 Pose matrix Using optical imaging SystemAnd coordinates of the navigation target star in the earth coordinate systemEstimating the coordinates of the navigation satellite in the image coordinate system, and recording the estimated coordinates of the navigation satellite in the image coordinate system asThe specific estimation method is as follows:
firstly, calculating a direction vector of a sight direction of a navigation satellite at the triggering moment of a camera in a coordinate system of an optical imaging system:
Then estimating coordinates of the navigation satellite under an image coordinate system by adopting a camera imaging model:
Wherein (u 0,v0) is the physical coordinates of the main point of the camera, and f is the focal length of the camera, and these parameters can be provided by the optical imaging system manufacturer or calibrated in advance.
4.4 Coordinates of the estimated navigation satellite in the image coordinate SystemFor the center, a small extraction window is selected, and the position deviation (delta u s,δvs) of the center of mass coordinates of the navigation satellite in the small window relative to the center of the extraction window is extracted by adopting the method described in patent application No. CN202310656893.4 (star point extraction algorithm suitable for stray light interference). And finally calculating the barycenter coordinates (u s,vs) of the satellite in the whole image:
if the target satellite can not be successfully extracted, returning to the step 1; if the target satellite is successfully extracted, the step 5 is entered.
Step 5: and positioning calculation is completed by utilizing the satellite coordinates and the camera gestures, and the local position coordinates are obtained. The calculation principle is shown in fig. 4. The specific calculation method is as follows:
Firstly, calculating the distance from the level surface corresponding to the observation point to the earth center according to the rough latitude information of the observation carrier, wherein the calculation method comprises the following steps:
where R is the average earth radius and R N is the earth equatorial radius.
And then acquiring altitude information H of the observation carrier. For sea level observers, H≡0. For other land or aircraft carriers, altitude may be measured by an absolute barometric altimeter. The observer is located at a distance R e +H from the earth's center.
Calculating direction vector of satellite sight direction under geographic coordinate system
Where f is the camera focal length, (u 0,v0) is the physical coordinates of the camera principal point and (u s,vs) is the centroid coordinates of the satellite on the image.
Satellite position vectorAnd the direction of the line of sightIt is known that the angle θ between the two vectors is thus determined:
Wherein l is Is a length of (c).
D PS of the satellite and the observation point is solved by the following method:
in the geodetic coordinate system e system, the coordinate expression of the geodetic coordinate system of the observation point is as follows:
Step 6: judging whether a command for ending the measurement is received, ending the navigation if the command is received, and otherwise, jumping to the step 1.
Example 2
Embodiment 2 of the present invention provides a terminal device corresponding to embodiment 1 above, where the terminal device may be a processing device for a client, for example, an embedded computing device, a notebook computer, a mobile phone, a desktop computer, or the like, to perform the method of the embodiment above.
The terminal device of the present embodiment includes a memory, a processor, and a computer program stored on the memory; the processor executes the computer program on the memory to implement the steps of the method of embodiment 1 described above.
In some implementations, the memory may be a high-speed random access memory (RAM: random Access Memory), and may also include non-volatile memory (non-volatile memory), such as at least one disk memory.
In other implementations, the processor may be a Central Processing Unit (CPU), a Digital Signal Processor (DSP), or other general-purpose processor, which is not limited herein.
Example 3
Embodiment 3 of the present invention provides a computer-readable storage medium corresponding to embodiment 1 described above, on which a computer program/instructions is stored. The steps of the method of embodiment 1 described above are implemented when the computer program/instructions are executed by a processor.
The computer readable storage medium may be a tangible device that retains and stores instructions for use by an instruction execution device. The computer readable storage medium may be, for example, but not limited to, an electronic storage device, a magnetic storage device, an optical storage device, an electromagnetic storage device, a semiconductor storage device, or any combination of the preceding.
It will be appreciated by those skilled in the art that embodiments of the present application may be provided as a method, system, or computer program product. Accordingly, the present application may take the form of an entirely hardware embodiment, an entirely software embodiment or an embodiment combining software and hardware aspects. Furthermore, the present application may take the form of a computer program product embodied on one or more computer-usable storage media (including, but not limited to, disk storage, CD-ROM, optical storage, and the like) having computer-usable program code embodied therein. The scheme in the embodiment of the application can be realized by adopting various computer languages, such as an object-oriented programming language C++ and an transliteration script language JavaScript.
The present application is described with reference to flowchart illustrations and/or block diagrams of methods, apparatus (systems) and computer program products according to embodiments of the application. It will be understood that each flow and/or block of the flowchart illustrations and/or block diagrams, and combinations of flows and/or blocks in the flowchart illustrations and/or block diagrams, can be implemented by computer program instructions. These computer program instructions may be provided to a processor of a general purpose computer, special purpose computer, embedded processor, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, create means for implementing the functions specified in the flowchart flow or flows and/or block diagram block or blocks.
These computer program instructions may also be loaded onto a computer or other programmable data processing apparatus to cause a series of operational steps to be performed on the computer or other programmable apparatus to produce a computer implemented process such that the instructions which execute on the computer or other programmable apparatus provide steps for implementing the functions specified in the flowchart flow or flows and/or block diagram block or blocks.
While preferred embodiments of the present application have been described, additional variations and modifications in those embodiments may occur to those skilled in the art once they learn of the basic inventive concepts. It is therefore intended that the following claims be interpreted as including the preferred embodiments and all such alterations and modifications as fall within the scope of the application.
It will be apparent to those skilled in the art that various modifications and variations can be made to the present application without departing from the spirit or scope of the application. Thus, it is intended that the present application also include such modifications and alterations insofar as they come within the scope of the appended claims or the equivalents thereof.
Claims (10)
1. An astronomical navigation method based on space target optical angle measurement under the condition of altitude limitation is characterized by comprising the following steps:
S1, calculating space target coordinates, and screening space targets meeting an observation pitch angle threshold;
S2, predicting space target stars and the like screened in the step S1, selecting navigation space targets according to the stars and the like, and if the navigation space targets meeting the conditions exist, entering the step S3; otherwise, returning to the step S1;
s3, adjusting the optical axis of the optical imaging system to point to a navigation space target, and triggering a camera to expose and image;
s4, respectively extracting all stars in the navigation space target and the field of view from the photographed star map, and calculating the gesture of the optical imaging system by utilizing the star point image coordinate information of the stars;
s5, recalculating the current coordinates of the navigation space target according to the triggering moment of the camera, and completing positioning calculation by utilizing the space target coordinates and the camera gesture to obtain the local position coordinates.
2. The astronomical navigation method based on optical angle measurement of space target under the condition of altitude limitation according to claim 1, wherein in step S2, the calculation formula of m cs_k of the space target star is:
Where a denotes the geometrical reflectivity of the spatial target, R SAT denotes the radius of the spatial target, d SS denotes the distance between the sun and the spatial target, d PS denotes the distance between the observation point and the spatial target,
Ρ ⊙ is the solar phase angle and h SAT is the spatial target height.
3. Astronomical navigation method based on optical goniometry of spatial targets under altitude limitation conditions according to claim 1 or 2, characterized in that the specific implementation process of selecting navigation spatial targets according to stars comprises:
all space targets of which the space target star and the like are lower than the detection threshold on duty for the week and the like are screened out to serve as candidate navigation space targets, and the space target with the lowest star and the like in the candidate navigation space targets is selected to serve as the navigation space target.
4. The astronomical navigation method based on optical goniometry of spatial targets under altitude limiting conditions according to claim 1, characterized in that in step S2, before predicting the spatial target star, etc., it further comprises: judging whether the space target is blocked by the ground shadow, if not, predicting the space target star and the like, and if so, returning to the step S1; wherein when the space target direction vector and the sun direction vector meetWhen the space target is considered to be not shielded by the ground shadow, R is the average radius of the earth,Represents the jth spatial target in the set of spatial targets that meet the observed pitch angle threshold,A unit vector indicating the incident direction of sunlight on the earth.
5. The astronomical navigation method based on optical angle measurement of space object under the condition of altitude limitation according to claim 1, wherein in step S4, if the navigation space object cannot be successfully extracted, the procedure returns to step S3.
6. The astronomical navigation method based on the optical goniometry of the spatial target under the condition of altitude limitation according to claim 1, wherein in step S5, the coordinates of the observation point under the geodetic fixed coordinate system e-systemThe method is adopted for calculation:
wherein, L is the spatial target position vectorIs provided for the length of (a),R is the average earth radius, R N is the earth equatorial radius,
As a direction vector of the direction of the line of sight of the spatial target in the geographic coordinate system,
F is the focal length of the camera, (u 0,v0) is the physical coordinates of the principal point of the camera, (u s,vs) is the centroid coordinates of the spatial target on the image, and θ is the spatial target position vectorAnd the direction of the line of sightThe included angle between the two parts is that,H is the altitude of the observation support,Is the pose of the optical imaging system.
7. An astronomical navigation system based on space target optical angle measurement under the condition of limiting elevation comprises a memory, a processor and a computer program stored on the memory; characterized in that the processor executes the computer program to carry out the steps of the method according to one of claims 1 to 6.
8. An astronomical navigation system based on optical goniometry of a spatial target under altitude limiting conditions, comprising:
an optical imaging system for imaging the space object and the sidereal;
The double-shaft turntable comprises a base, an azimuth rotating mechanism and a pitching rotating mechanism; the pitching rotating mechanism is arranged on the azimuth rotating mechanism, and the azimuth rotating mechanism is arranged on the base; the optical imaging system is arranged on the pitching rotation mechanism;
The inertial measurement unit is used for providing attitude information of the base;
The time system equipment is used for providing UTC time information required by navigation calculation and time synchronization second pulses for data acquisition of each measurement control equipment;
A data processing unit which communicates with the optical imaging system, the biaxial turntable, the inertial measurement unit and the time system equipment and realizes astronomical navigation solution by adopting the steps of the method of one of claims 1 to 6; the double-shaft turntable, the inertia measurement unit, the time system equipment and the data processing unit are all arranged on the measurement carrier.
9. The system of claim 8, wherein the optical imaging system has a field angle in the range of 5 ° to 30 °.
10. The system of claim 8, wherein the azimuth axis of rotation of the dual-axis turntable has a perpendicularity error of less than 0.1 ° from the elevation axis of rotation, and wherein the optical axis of the optical imaging system has an angular deviation of no more than 1 ° from the azimuth axis of rotation of the dual-axis turntable when both the elevation axis and the azimuth axis of rotation of the dual-axis turntable are at zero positions.
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