A super large field of view star sensor

Abstract

The present application relates to a kind of super large field of view star sensor, belong to the optical imaging sensor field for space vehicle.Using by small aperture sub-field optical element array and relay optical element constitute optical system, the starlight in super large field of view range is introduced into single detector imaging, generates the original star map containing sub-field array star image point, carries out sub-field and inter-sub-field calibration correction to original star map, obtains the observation star point information queue in the coordinate system of super large field of view range, carries out the attitude determination of three-axis precision consistent.The present application greatly improves the field of view of star sensor.

Description

Technical Field

[0001] This invention belongs to the field of optical imaging sensors for spacecraft, and relates to an ultra-large field-of-view star sensor. Background Technology

[0002] Spacecraft star sensors measure inertial attitude based on imaging and detection of stars. The field of view is one of their key internal parameters, determining the range of the sky a single star sensor can simultaneously detect. A larger field of view allows for the simultaneous detection of more stars, making it easier to improve core star sensor performance indicators such as measurement accuracy (average across multiple stars), dynamic range, and acquisition probability. However, a large field of view is susceptible to interference from strong spaceborne sources like the sun, and its design conflicts with the aperture parameters. Therefore, current star sensors typically have fields of view between 2° and 40°. Small field-of-view, large-aperture star sensors are suitable for high-precision, low-dynamic-range applications with less stringent size and weight constraints, while large field-of-view, small-aperture star sensors are suitable for low-precision, high-dynamic-range applications with stricter size and weight constraints. However, these star sensors are all susceptible to interference from strong cluttered light sources such as the sun. A single star sensor cannot work effectively in any orbital attitude, and in principle, a single star sensor cannot solve the problem of poor accuracy in horizontal attitude measurement. Therefore, spacecraft often use a multi-star sensor configuration to meet reliable attitude determination requirements, which raises the application threshold of star sensors. Summary of the Invention

[0003] The technical problem solved by this invention is to overcome the shortcomings of the prior art and provide a design idea for an ultra-large field-of-view star sensor based on sub-field fusion and gating, which is immune to the influence of sunlight and has consistent three-axis attitude measurement accuracy, thereby greatly improving the effective detection field of view of the optical imaging sensor.

[0004] The technical solution of the present invention is: an ultra-large field-of-view star sensor, comprising an optical system, a light shield, a detector, a processing unit, and a support structure; the optical system comprises a sub-field-of-view optical element array and a relay optical element; the sub-field-of-view optical element array and the relay optical element introduce starlight within the field of view into the detector through two-stage convergence;

[0005] The detector generates an original star map containing star image points of the sub-field array based on the introduced stellar light;

[0006] The processing unit performs calibration and correction on the original star map within and between sub-fields of view to obtain a queue of observed star points in coordinate system one within the ultra-large field of view, and achieves attitude determination with consistent three-axis accuracy based on the queue of observed star points.

[0007] Preferably, each sub-field of view in the sub-field of view optical element array is equipped with an independent sunshade and a gating mechanism. According to the control of the processing unit, when the sun is outside the sub-field of view suppression angle, stray light is suppressed by the sunshade, and when the sun is inside the sub-field of view suppression angle, the corresponding aperture is closed by the gating mechanism to achieve solar immunity.

[0008] Preferably, the processing unit determines the position of each sub-field optical axis in the central sub-field coordinate system through calibration; and, in conjunction with the position of the sun in the central sub-field coordinate system, determines whether the sun is inside or outside the sub-field suppression angle.

[0009] Preferably, the position of the sun in the central subfield of view coordinate system is obtained by input or by the processing unit based on the attitude quaternion obtained in the attitude determination.

[0010] Preferably, the sub-field-of-view optical element array is evenly distributed in front of the relay optical element, and the sub-field-of-view optical element array is imaged on the same sphere. Then, the spherical image is relayed to the planar image plane of the detector by the relay optical element.

[0011] Preferably, the optical axis of the unique central sub-field-of-view optical element coincides with the optical axis of the relay optical element, and the other sub-field-of-view optical elements are distributed in circles around the unique central sub-field-of-view optical element. The optical axes of the field-of-view optical elements in the same circle are at the same angle as the optical axis of the central sub-field-of-view optical element, and the optical axes of adjacent sub-field-of-view optical elements are at the same angle.

[0012] Preferably, the original star map contains stellar imaging spots within a very large field of view, with each star within the very large field of view corresponding to a unique image spot in the star map.

[0013] Preferably, the processing unit calibrates at least 6 sub-fields of view within an equilateral triangle each time. Through the spatial relationship transfer between the overlapping sub-fields of view between two calibrations, a unified transformation relationship between the three-dimensional vector of the object space point light source and the two-dimensional coordinates of the image plane image spot is constructed for the entire field of view, so that a queue of observed star point information in a unified coordinate system is obtained after the star points are extracted.

[0014] Preferably, the unified coordinate system uses the central sub-field optical axis as the Z-axis, the detector row direction as the X-axis, and the detector column direction as the Y-axis. After extracting the two-dimensional coordinates of star points and image spots on the image plane, the observation star point information queue under the unified coordinate system is obtained through transformation relationships. The three-dimensional vectors of stars in different sub-fields are all expressed under the unified coordinate system.

[0015] Preferably, inertial attitude information with consistent three-axis accuracy is obtained by reducing the three-dimensional vectors of stars in different sub-fields of view in the star point information queue under a unified coordinate system.

[0016] The beneficial effects of this invention compared to the prior art are as follows:

[0017] (1) This invention employs sub-field-of-view fusion technology, using a small-aperture sub-field-of-view optical element array and relay optical elements to image stellar rays within an ultra-large field of view onto a single detector. During star image processing, calibration and correction are performed within and between sub-fields of view to obtain a queue of observed star points with a unified coordinate system within the ultra-large field of view, thereby achieving ultra-large field-of-view star detection. Compared with existing technologies, this invention enables the star sensor's field of view to reach an ultra-large 180° range, and the overall optical parameter design is no longer limited by traditional relative aperture constraints.

[0018] (2) The star sensor of this invention is designed with an independent sunshade and gating mechanism for each sub-field of view. Based on the real-time calculated solar azimuth, it intelligently selects a few sub-apertures that are affected by the sun, and completes stellar imaging detection and attitude measurement through the remaining large number of sub-apertures that are not affected by the sun, thereby achieving solar immunity for the attitude determination function of the ultra-large field-of-view star sensor. Compared with the prior art, this invention makes the attitude measurement of a single star sensor solar immune, greatly improving the on-orbit utilization rate of the star sensor.

[0019] (3) This invention significantly increases the number of stars and interstellar angular distances involved in attitude calculation by imaging and detecting stars over a very large area. This effectively offsets the accuracy loss caused by the instantaneous increase in the field of view, thereby achieving high-precision attitude measurement for star sensors with a very large field of view. In addition, high-dynamic star tracking and high-probability attitude acquisition based on the image itself can be performed within the very large observation field of view. Compared with the prior art, this invention provides a completely new approach to achieving high-precision, high-dynamic, and high-acquisition-probability indicators for star sensors.

[0020] (4) This invention determines attitude based on the observation star point information queue of coordinate system one within a super-large field of view. The star sensor can obtain a high consistency of angle resolution in the three-axis motion direction around the measurement coordinate system, thereby achieving consistent three-axis attitude measurement accuracy of a single star sensor. Compared with the prior art, this invention overcomes the fundamental disadvantage of poor horizontal axis attitude measurement accuracy of a single star sensor. Attached Figure Description

[0021] Figure 1 This is a structural diagram of the present invention;

[0022] Figure 2 This is a diagram illustrating the sub-field-of-view element configuration of the present invention;

[0023] Figure 3 This is the sub-field-to-field calibration strategy of the present invention;

[0024] Figure 4 This is a schematic diagram showing the positions of the three-circle field-of-view optical elements in an embodiment of the present invention. Detailed Implementation

[0025] The present invention will now be described in detail with reference to the accompanying drawings.

[0026] This invention has been applied to a space star sensor project, such as... Figure 1 , 2 As shown in Figures 3 and 4, the ultra-large field-of-view star sensor of this invention is applicable to a field of view of 150° or even higher. It adopts an optical system composed of sub-field-of-view optical element arrays and relay optical elements. Each sub-field of view is 30°, and a total of 19 sub-fields of view are combined to form a 150° field of view. The starlight within the ultra-large field of view is introduced into a single detector for imaging. The detector generates an original star map containing star image points of the sub-field-of-view array, realizing attitude determination with consistent three-axis accuracy for ultra-large field-of-view star detection.

[0027] The star sensor includes an optical system, a sunshade, a detector, a processing unit, and a support structure. Each sub-field of view is designed with an independent sunshade and a gating mechanism. When the sun is outside the suppression angle of the sub-field of view, stray light is suppressed by the sunshade. When the sun is inside the suppression angle of the sub-field of view, the corresponding gating mechanism is turned off, thus achieving solar immunity.

[0028] In the optical system, the optical axis of the sole central sub-field-of-view optical element coincides with the optical axis of the relay optical element. The other sub-field-of-view optical elements are distributed in three concentric rings around the sole central sub-field-of-view optical element. The optical axes of the six sub-field-of-view optical elements in the first ring each form a 30° angle with the optical axis of the central sub-field-of-view optical element. Figure 4 In the middle B1 to B6, the optical axes of the six sub-field-of-view optical elements in the second ring are all at angles with the optical axis of the central sub-field-of-view optical element. 30°, such as Figure 4 In the middle C1 to C6, the optical axes of the six sub-field-of-view optical elements in the third ring are all at an angle of 2 times 30° to the optical axis of the central sub-field-of-view optical element. Figure 4 In the middle D1 to D6, the optical axis angle between adjacent sub-field optical elements is 30°, and all sub-field optical elements are evenly distributed in front of the relay optical element.

[0029] The star sensor processing unit performs calibration and correction on the original star map both within and between sub-fields of view. Each calibration calibrates six sub-fields of view within an equilateral triangle. Through the spatial relationship transfer between overlapping sub-fields of view in two calibrations, a unified transformation relationship between the three-dimensional vector of the object-space point source and the two-dimensional coordinates of the image spot is constructed across the entire field of view. This allows for the acquisition of a unified coordinate system for the observed star point information queue. The three-dimensional vectors of stars within different sub-fields of view in the unified coordinate system are then optimized for star map matching and attitude determination calculations, resulting in inertial attitude information with consistent three-axis accuracy.

[0030] Since the field of view of this invention reaches 150° during project implementation, under dynamic conditions, the spatial pointing calculation is performed and output based on the accurate coordinates of the star point imaging position obtained by this invention. The dynamic measurement accuracy can be basically consistent with that of the static one, avoiding the influence of star point imaging trailing and realizing the improvement of the dynamic measurement accuracy of the spatial pointing measurement sensor.

[0031] This invention employs sub-field fusion technology, which uses a small-aperture sub-field optical element array and relay optical elements to image star rays within an ultra-large field of view onto a single detector. During star image processing, calibration and correction are performed within and between sub-fields of view to obtain a queue of observed star point information with a unified coordinate system within the ultra-large field of view, thereby achieving ultra-large field of view star detection.

[0032] The star sensor of this invention is designed with an independent sunshade and gating mechanism for each sub-field of view. Based on the real-time calculated solar azimuth, it intelligently selects a few sub-apertures that are affected by the sun, and completes star imaging detection and attitude measurement through the remaining large number of sub-apertures that are not affected by the sun, thereby realizing the attitude determination function of the ultra-large field-of-view star sensor is immune to the sun.

[0033] This invention significantly increases the number of stars and interstellar angular distances involved in attitude calculation by imaging and detecting stars over a very large area. This effectively offsets the accuracy loss caused by the instantaneous increase in the field of view, thereby enabling high-precision attitude measurement of star sensors with a very large field of view. In addition, it enables high-dynamic star point tracking and high-probability attitude capture based on the pattern itself within the very large observation field of view.

[0034] This invention determines attitude based on a queue of observed star points within a coordinate system of an ultra-large field of view. The star sensor can obtain a high degree of consistent angular resolution by moving around the three axes of the measurement coordinate system, thereby achieving consistent three-axis accuracy of attitude measurement for a single star sensor.

[0035] The contents not described in detail in this specification are common knowledge to those skilled in the art.

Claims

1. A large field-of-view star sensor, comprising an optical system, a light shield, a detector, a processing unit, and a support structure; characterized in that, The optical system includes a sub-field-of-view optical element array and a relay optical element; the sub-field-of-view optical element array and the relay optical element combine in two stages to introduce starlight from the field of view into the detector; The detector generates an original star map containing star image points of the sub-field array based on the introduced stellar light; The processing unit performs calibration and correction on the original star map within and between sub-fields of view to obtain a queue of observed star points in coordinate system one within the ultra-large field of view, and achieves attitude determination with consistent three-axis accuracy based on the queue of observed star points. In the optical system, the optical axis of the unique central sub-field-of-view optical element coincides with the optical axis of the relay optical element. The other sub-field-of-view optical elements are distributed in three concentric rings around the unique central sub-field-of-view optical element. The optical axes of the first ring of six sub-field-of-view optical elements are all at an angle of 30° to the optical axis of the central sub-field-of-view optical element. The optical axes of the second ring of six sub-field-of-view optical elements are all at an angle of 30° to the optical axis of the central sub-field-of-view optical element. The optical axes of the six sub-field optical elements in the third ring are all at an angle of 2 times 30° to the optical axis of the central sub-field optical element. The optical axes of adjacent sub-field optical elements are all at an angle of 30°. All sub-field optical elements are evenly distributed in front of the relay optical element. Each subfield of view in the subfield optical element array is equipped with an independent sunshade and gating mechanism. According to the control of the processing unit, when the sun is outside the subfield suppression angle, stray light is suppressed by the sunshade. When the sun is inside the subfield suppression angle, the corresponding aperture is closed by the gating mechanism to achieve solar immunity. Each time, the processing unit calibrates at least 6 sub-fields of view within an equilateral triangle. Through the spatial relationship transfer between the overlapping sub-fields of view between two calibrations, it constructs a unified transformation relationship between the three-dimensional vector of the object space point light source and the two-dimensional coordinates of the image plane image spot across the entire field of view, so that after the star points are extracted, a queue of observed star point information in a unified coordinate system is obtained.

2. The star sensor according to claim 1, characterized in that: The processing unit determines the position of each sub-field optical axis in the central sub-field coordinate system through calibration; and, in conjunction with the position of the sun in the central sub-field coordinate system, determines whether the sun is inside or outside the sub-field suppression angle.

3. The star sensor according to claim 2, characterized in that: The position of the sun in the central subfield of view coordinate system is obtained by input or by the processing unit based on the attitude quaternion obtained in attitude determination.

4. The star sensor according to claim 1, characterized in that: The original star map contains stellar imaging spots within a very large field of view, with each star within the very large field of view corresponding to a unique image spot in the star map.

5. The star sensor according to claim 1, characterized in that: The unified coordinate system uses the central sub-field optical axis as the Z-axis, the detector row direction as the X-axis, and the detector column direction as the Y-axis. After extracting the two-dimensional coordinates of star points and image spots on the image plane, the observation star point information queue under the unified coordinate system is obtained through transformation relationships. The three-dimensional vectors of stars in different sub-fields are all expressed under the unified coordinate system.

6. The star sensor according to claim 1, characterized in that: By using the three-dimensional vectors of stars in different sub-fields of view in the star point information queue under a unified coordinate system, star map matching and attitude determination calculations are performed to obtain inertial attitude information with consistent three-axis accuracy.

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