CN115265524B - A near-space X-ray arcsecond star tracker - Google Patents

Abstract

The present invention provides a near-space X-ray arc-second star tracker, comprising an X-ray imager, a two-dimensional precision tracker and an information processing unit. The X-ray imager is used to achieve high-precision imaging of natural X-ray sources in space, and output the spatial position of the space X-ray source relative to the X-ray imager. The two-dimensional precision tracker expands the imaging range of the X-ray imager 1 to tens of degrees through two-dimensional large-range tracking of pitch and deflection, thereby solving the problem of difficulty in capturing strong X-ray sources on the celestial sphere due to the small field of view of the X-ray imager 1 and the sparse distribution of strong X-ray sources on the celestial sphere. The information processing unit combines the pitch and deflection angle information of the two-dimensional precision tracker with the star point positioning information of the X-ray imager to achieve continuous output of arc-second high-precision attitude information of the star tracker. The present invention utilizes the high penetration characteristics of hard X-rays to solve the problem of accurate attitude measurement under atmospheric thermal barrier conditions of near-space high-speed aircraft.

Description

A near-space X-ray arcsecond star tracker

Technical Field

The invention relates to a near-space X-ray arc-second star tracker, belonging to the technical field of space gamma-ray detection.

Background Art

Autonomous navigation and autonomous control of near-space high-speed aircraft have an urgent need for accurate measurement of aircraft attitude. The flight environment of near-space high-speed aircraft is extremely special. The aerodynamic heat generated by the friction between the high-speed movement of the aircraft and the atmosphere limits the application of traditional optical attitude sensors working in the visible light and infrared bands. Traditional sun sensors and star sensors cannot be used on near-space high-speed aircraft.

At present, the attitude measurement of high-speed aircraft in near-space mainly uses optical attitude sensors, which determine their own attitude by observing the sun or stars in the visible light or infrared band. However, there is still a thin atmosphere in near-space, and the friction between the hypersonic aircraft and the atmosphere when flying at high speed generates a lot of startup heat, accompanied by luminescence in the infrared and visible light bands, which seriously interferes with the work of traditional optical attitude sensors.

Summary of the invention

The technical problem solved by the present invention is: to overcome the above-mentioned deficiencies of the prior art, to propose a near-space X-ray arcsecond-level star tracker, to provide high-precision attitude measurement information for autonomous navigation and autonomous control of near-space high-speed aircraft, and to solve the problem of aerodynamic thermal interference of optical attitude sensors in near-space hypersonic aircraft.

The technical solution of the present invention is: a near-space X-ray arc-second star tracker, the star tracker comprises an X-ray imager, a two-dimensional precision tracker and an information processing unit; the X-ray imager is mounted on the two-dimensional precision tracker, and the two-dimensional precision tracker is mounted on the near-space aircraft;

An X-ray imager is used to detect natural X-ray sources in space, image the natural X-ray sources in space, obtain a target source image, perform star point extraction calculation based on the target source image to obtain a relative attitude of the X-ray imager relative to the celestial coordinate system, and send the relative attitude of the X-ray imager relative to the celestial coordinate system to an information processing unit;

A two-dimensional precision tracker is used to drive the X-ray imager to deflect in the two-dimensional directions of pitch and yaw, expanding the imaging range of the X-ray imager to dozens of degrees;

The information processing unit obtains the pitch and yaw two-dimensional deflection angle information of the two-dimensional precision tracker and the relative attitude of the X-ray imager to the celestial coordinate system, combines the relative position and attitude relationship between the two-dimensional precision tracker coordinate system and the near-space vehicle body coordinate system, and the relative position and attitude relationship between the X-ray imager body coordinate system and the two-dimensional precision tracker body coordinate system, and obtains the relative attitude of the near-space vehicle body coordinate system to the celestial coordinate system through a coordinate system conversion method, thereby realizing the attitude determination of the near-space vehicle.

Preferably, the X-ray imager comprises a hard X-ray Fourier space modulation imaging component and a hard X-ray semiconductor focal plane imaging component;

The hard X-ray Fourier spatial modulation imaging component uses a built-in dual collimator system to modulate incident photons, measures the Fourier components of the modulated optical signal, performs inverse Fourier transform on these Fourier components to obtain a target source image, and sends the target source image to the hard X-ray semiconductor focal plane imaging component;

The hard X-ray semiconductor focal plane imaging component calculates the relative attitude of the X-ray source star point with respect to the optical axis of the X-ray imager through star point extraction, and then obtains the relative attitude of the X-ray imager with respect to the celestial coordinate system.

Preferably, the dual collimator system comprises n rows×n columns of sub-collimators with different placement angles and pitches, n≥4, the placement angles of the sub-collimators in each row are the same and the pitches are different, the placement angles of the sub-collimators in each row are integer multiples of 180°/n, and the n pitches of the sub-collimators in each column are 2 ^(n-1) λ, where λ is the minimum pitch of the n sub-collimators in the same row.

Preferably, the resolution ν of the target source image is determined by the minimum pitch λ and the focal length L of the sub-collimator, and is calculated as follows: ν=λ/L.

Preferably, the comprehensive aperture D of the X-ray imager is determined by the sub-collimator size d and the focal length L, and the calculation formula is: D=d/L.

Preferably, the focal plane imaging component is a pixel-type X-ray semiconductor detector.

Preferably, the field of view of the X-ray imager is 1-2°.

Preferably, the sensor angular resolution of the X-ray imager is better than 10 arc seconds.

Preferably, the X-ray star point positioning accuracy of the X-ray imager is better than 5 arc seconds.

The beneficial effects of the present invention compared with the prior art are:

(1) The present invention proposes a near-space star tracker operating in the X-ray band. By utilizing the high penetration characteristics of hard X-rays, it can solve the problem of accurate attitude measurement of near-space high-speed aircraft under atmospheric thermal barrier conditions. The observation field of view can reach tens of degrees, and the star point positioning accuracy can reach the arc second level.

(2) The present invention adopts a small-field-of-view hard X-ray Fourier space modulation imaging method, modulates the incident photons through a dual collimator system, uses an X-ray semiconductor focal plane imaging detector to measure the specific Fourier components of the source distribution, performs inverse Fourier transform on these Fourier components to obtain an X-ray celestial source image, and further combines the pitch and deflection angle information of the two-dimensional precision tracker and the imaging information of the X-ray celestial source by the X-ray imager to achieve arcsecond-level high-precision attitude measurement based on X-ray star point positioning.

(3) The present invention adopts precision tracking technology to expand the imaging range of the X-ray imager through two-dimensional large-range tracking of pitch and deflection, taking into account the large field of view and high-precision measurement of the near-space star tracker, and solving the problem that the X-ray imager has a small field of view and is difficult to capture sparsely distributed strong X-ray sources on the celestial sphere;

(4) The focal plane imaging component in the X-ray imager of the present invention adopts a pixel-type X-ray semiconductor detector, which has high energy resolution and counting rate, and is small in size and low in power consumption.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG1 is a schematic diagram of the composition of a near-space X-ray arc-second-level high-precision star tracker according to an embodiment of the present invention;

FIG. 2 is a schematic diagram of a dual collimator system (4×4) in a Fourier space modulation imaging assembly according to an embodiment of the present invention.

DETAILED DESCRIPTION

The present invention is further described in detail below with reference to the accompanying drawings and specific embodiments:

The present invention provides a near-space X-ray arc-second-level high-precision star tracker. The star tracker is based on a small-field-of-view hard X-ray imaging detector. By imaging the natural X-ray source in the universe and combining it with a two-dimensional precision tracking device, the optical axis pointing of the output sensor in the celestial coordinate system is output, thereby performing arc-second-level high-precision attitude measurement of near-space high-speed aircraft based on the X-ray celestial source to determine the attitude information of the aircraft.

As shown in Fig. 1, the near-space X-ray arc-second-level high-precision star tracker consists of three parts: an X-ray imager 1, a two-dimensional precision tracker 2, and an information processing unit 3. The X-ray imager 1 is mounted on the two-dimensional precision tracker 2, and the two-dimensional precision tracker 2 is mounted on the near-space aircraft;

An X-ray imager 1 is used to detect natural X-ray sources in space, image the natural X-ray sources in space, obtain a target source image, perform star point extraction calculation based on the target source image to obtain a relative attitude of the X-ray imager 1 relative to the celestial coordinate system, and send the relative attitude of the X-ray imager 1 relative to the celestial coordinate system to an information processing unit 3;

A two-dimensional precision tracker 2 is used to drive the X-ray imager 1 to deflect along the two-dimensional directions of pitch and yaw, thereby expanding the imaging range of the X-ray imager 1 to tens of degrees;

The information processing unit 3 obtains the pitch and yaw two-dimensional deflection angle information of the two-dimensional precision tracker 2 and the relative attitude of the X-ray imager 1 relative to the celestial coordinate system, combines the relative position and attitude relationship between the coordinate system of the two-dimensional precision tracker 2 and the coordinate system of the near-space vehicle body, and the relative position and attitude relationship between the coordinate system of the X-ray imager 1 body and the coordinate system of the two-dimensional precision tracker 2 body, and obtains the relative attitude of the coordinate system of the near-space vehicle body relative to the celestial coordinate system through a coordinate system conversion method, thereby realizing the attitude determination of the near-space vehicle.

The X-ray imager 1 includes a hard X-ray Fourier spatial modulation imaging component 4 and a hard X-ray semiconductor focal plane imaging component 5. The Fourier modulation imaging component 4 uses a built-in dual collimator system to modulate incident photons, measures the Fourier components of the modulated light signal, performs inverse Fourier transform on these Fourier components to obtain a target source image, and sends the target source image to the hard X-ray semiconductor focal plane imaging component 5.

The hard X-ray semiconductor focal plane imaging component 5 calculates the relative posture of the X-ray source star point relative to the optical axis of the X-ray imager 1 through star point extraction, and then obtains the relative posture of the X-ray imager 1 relative to the celestial coordinate system.

The dual collimator system includes n rows×n columns of sub-collimators with different placement angles and different pitches, n≥4, the placement angles of the sub-collimators in each row are the same, and the pitches are different, the placement angles of the sub-collimators in each row are integer multiples of 180°/n, and the pitches of the sub-collimators in each column are 2 ^(n-1) λ, where λ is the minimum pitch of the n sub-collimators in the same row. As shown in FIG2 , in a specific embodiment of the present invention, n is 4, the placement angle of the sub-collimators in the first row is 90°, the placement angle of the sub-collimators in the second row is 45°, the placement angle of the sub-collimators in the third row is 180°, and the placement angle of the sub-collimators in the fourth row is 135°. The pitch of the sub-collimators in the first column is the smallest, the pitch of the sub-collimators in the second column is 2λ, the pitch of the sub-collimators in the third column is 4λ, and the pitch of the sub-collimators in the fourth column is 8λ.

The resolution ν of the target source image is determined by the minimum pitch λ and the focal length L of the sub-collimator, and is calculated as follows: ν=λ/L.

The comprehensive aperture D of the X-ray imager 1 is determined by the sub-collimator size d and the focal length L, and the calculation formula is: D=d/L.

The focal plane imaging component 5 adopts a pixel-type X-ray semiconductor detector represented by an X-ray CMOS, a cadmium telluride CdTe and a cadmium zinc telluride CdZnTe detector, which has high energy resolution and counting rate, and is small in size and low in power consumption.

By optimizing the design of the parameters of the X-ray imager 1, the present invention can design the field of view of the near-space X-ray arc second-level high-precision star tracker to be 1 to 2 degrees, the sensor angular resolution can be better than 10 arc seconds, and the X-ray star point positioning accuracy can be better than 5 arc seconds.

Since the X-ray imager has a small field of view and the strong X-ray sources on the celestial sphere are sparsely distributed, in order to make the sensor output attitude continuously, a two-dimensional precision tracker 2 is used to track and observe the strong radiation celestial X-ray sources. The two-dimensional precision tracker 2 can expand the imaging range of the X-ray imager to tens of degrees through two-dimensional large-range tracking in pitch and deflection, solving the problem of difficulty in capturing due to the small field of view of the X-ray imager 1 and the sparse distribution of strong X-ray sources on the celestial sphere.

The two-dimensional precision tracker 2 is essentially a two-dimensional turntable, which is used here to expand the observation range of the X-ray imager 1. Because the X-ray imager 1 can only image a few strong X-ray sources in space and the field of view is very small (1-2°), a two-dimensional tracking mechanism is required to capture and track the target X-ray source. The innovation lies in that the combined application enhances the practicality of the X-ray imager 1.

Since the relative position and attitude relationship between the coordinate system of the two-dimensional precision tracker 2 and the aircraft body is known, and the relative position and attitude relationship between the coordinate system of the X-ray imager 1 and the coordinate system of the two-dimensional precision tracker 2 is known, the information processing unit 3 can combine the pitch and deflection angle information of the two-dimensional precision tracker and the star point positioning information of the X-ray imager, and realize the continuous output of the arc-second-level high-precision attitude information of the star tracker by using the position of the natural X-ray source through coordinate system conversion.

Example:

The field of view of the near-space X-ray angular second-level high-precision star tracker X-ray imager 1 of the present invention is 2°. The dual collimator system of the Fourier space modulation imaging component 4 is composed of 16 sub-collimators with different pitches and placed at angles of 45°. The minimum pitch of the sub-collimator is 30μm, the focal length is 300mm, and the imaging resolution is 10″. The size of the sub-collimator is 10.5mm×10.5mm. The hard X-ray semiconductor focal plane imaging component 5 adopts a 16-piece X-ray CMOS detector array, each detector corresponds to a sub-collimator, the pixel size is 15μm, the pixel size should be 1/n of the minimum pitch of the collimator, the side length of the detector should be larger than the sub-collimator size, and the pixel resolution is 512×512.

The tracking range of the two-dimensional precision tracker 2 is 120°×80°, and the tracking range is determined according to the field of view requirements. The tracking accuracy is 10″. The tracking accuracy should not be lower than the imaging resolution.

The near-space X-ray arc-second-level high-precision star tracker has a measurement range of 120°×80°, an X-ray star point positioning accuracy better than 5″, and an attitude measurement accuracy better than 10″.

The contents not described in detail in the specification of the present invention belong to the common knowledge of those skilled in the art.

Claims (8)

1. An adjacent space X-ray angular second star tracker is characterized by comprising an X-ray imager (1), a two-dimensional precision tracker (2) and an information processing unit (3); the X-ray imager (1) is arranged on the two-dimensional precise tracker (2), and the two-dimensional precise tracker (2) is arranged on the near space vehicle;

The X-ray imager (1) is used for detecting a natural X-ray source in the space, imaging the natural X-ray source in the space to obtain a target source image, performing star point extraction operation according to the target source image to obtain the relative posture of the X-ray imager (1) relative to a celestial coordinate system, and sending the relative posture of the X-ray imager (1) relative to the celestial coordinate system to the information processing unit (3);

The two-dimensional precise tracker (2) is used for driving the X-ray imager (1) to deflect along the pitching and yawing two-dimensional directions, and expanding the imaging range of the X-ray imager (1) to tens of degrees;

The information processing unit (3) is used for acquiring pitching and yawing two-dimensional deflection angle information of the two-dimensional precise tracker (2), the relative posture of the X-ray imager (1) relative to the celestial coordinate system, combining the relative position posture relation between the two-dimensional precise tracker (2) coordinate system and the adjacent space aircraft body coordinate system and the relative position posture relation between the X-ray imager (1) body coordinate system and the two-dimensional precise tracker (2) body coordinate system, and acquiring the relative posture of the adjacent space aircraft body coordinate system relative to the celestial coordinate system through a coordinate system conversion method to realize the posture determination of the adjacent space aircraft;

The X-ray imager (1) comprises a hard X-ray Fourier space modulation imaging component (4) and a hard X-ray semiconductor focal plane imaging component (5);

A hard X-ray Fourier space modulation imaging component (4) which adopts a built-in double collimator system to modulate incident photons, measures Fourier components of modulated optical signals, performs inverse Fourier transform on the Fourier components to obtain a target source image, and sends the target source image to a hard X-ray semiconductor focal plane imaging component (5);

And the hard X-ray semiconductor focal plane imaging assembly (5) is used for calculating the relative posture of the star point of the X-ray source relative to the optical axis of the X-ray imager (1) through star point extraction, so as to obtain the relative posture of the X-ray imager (1) relative to the celestial coordinate system.

2. The near space X-ray angular second star tracker of claim 1, wherein the dual collimator system comprises n rows and n columns of sub-collimators with different arrangement angles and different pitches, wherein n is greater than or equal to 4, the arrangement angles of each row of sub-collimators are the same, the pitches are different, the arrangement angles of each row of sub-collimators are respectively integer multiples of 180 degrees/n, n pitches of each column of sub-collimators are respectively 2 ^(n-1) λ, and λ is the minimum pitch of n sub-collimators in the same row.

3. A near space X-ray angular second star tracker according to claim 1, characterized in that the resolution v of the target source image is determined by the minimum pitch λ and focal length L of the sub-collimator, and the calculation formula is: v=λ/L.

4. A near space X-ray angular second star tracker according to claim 1, characterized in that the synthetic aperture D of the X-ray imager (1) is determined by the sub-collimator size D and the focal length L, calculated as: d=d/L.

5. A near space X-ray angular second star tracker according to claim 1, characterized in that the focal plane imaging assembly (5) is a pixel type X-ray semiconductor detector.

6. A near space X-ray angular second star tracker according to claim 1, characterized in that the field of view of the X-ray imager (1) is 1-2 °.

7. A near space X-ray angular second star tracker according to claim 1, characterized in that the angular resolution of the sensor of the X-ray imager (1) is better than 10 angular seconds.

8. A near space X-ray star tracker of the order of a corner second according to claim 1, characterized in that the X-ray star point positioning accuracy of the X-ray imager (1) is better than 5 corner seconds.