Satellite-borne near-infrared two-dimensional temperature field imager and gravity wave three-dimensional structure detection method

Abstract

The invention discloses a satellite-borne near-infrared two-dimensional temperature field imager and a gravity wave three-dimensional structure detection method, and the imager uses near-infrared radiation of OH (3-1) spectral band airglow as a light source, and obtains horizontal two-dimensional space distribution of radiation intensity of two spectral lines P1 (2) and P1 (4) in an imaging mode. Compared with an existing limb observation spaceborne instrument which can only provide vertical profile information, the horizontal two-dimensional distribution information can be provided by the method and the device disclosed by the invention, and the space distribution of the horizontal two-dimensional temperature field on the height layer can be inversed through the radiation intensity ratio of the horizontal two-dimensional temperature field on the height layer; the method has important value for fine structure research of airglow radiation, atmospheric temperature and density and gravity wave disturbance.

Description

Technical Field

[0001] The present invention relates to the technical field of satellite remote sensing detection of middle and upper atmospheres, and in particular to a satellite-borne near-infrared two-dimensional temperature field imager and a gravity wave three-dimensional structure detection method. Background Art

[0002] In recent years, research on the middle and upper atmosphere (the layer of atmosphere 50 to 300 km above the Earth) has become a hot topic in the fields of atmosphere and space. Gravity waves, as a key dynamic phenomenon in the middle and upper atmosphere, have a profound impact on energy transport, atmospheric composition distribution, and the evolution of thermodynamic structure through their propagation process. They have important scientific and application value for studying atmospheric coupling mechanisms and space environment monitoring and assurance.

[0003] Satellite remote sensing of atmospheric parameters (such as airglow radiation and temperature) in the middle and upper atmosphere (such as airglow radiation and temperature) can obtain global, high-temporal and spatial resolution observational data over a wide area and has been widely used in scientific research and operational applications. However, due to the extremely low concentration of tracer gases in the middle and upper atmosphere and the very weak passive light source signals, current satellite remote sensing technology can only use limb observations to achieve effective detection. This method increases the signal accumulation strength by increasing the length of the atmospheric radiation or absorption path. Spaceborne instruments such as the TIMED satellite's SABER, the AURA satellite's MLS, and the Odin satellite's OSIRIS all employ similar limb hyperspectral detection techniques. While these techniques can effectively obtain the vertical distribution of atmospheric parameters through an "onion peeling" inversion method, they cannot obtain horizontal two-dimensional information about atmospheric parameters at a specific altitude. Because gravity wave perturbations in the atmosphere have a three-dimensional spatial structure, the vertical profiles obtained by current satellite remote sensing limb observations can only obtain two-dimensional information about gravity wave parameters in the vertical direction. These vertical profiles, coupled with long integration paths, significantly limit research on gravity wave propagation information and small-scale perturbation characteristics. Summary of the Invention

[0004] Purpose of the invention: The purpose of the present invention is to provide a satellite-borne near-infrared two-dimensional temperature field imager and a method for detecting the three-dimensional structure of gravity waves, which can obtain the horizontal two-dimensional spatial distribution of the radiation intensity of two spectral lines by imaging, and invert the spatial distribution of the two-dimensional temperature field at the altitude layer through their ratio; at the same time, a method for detecting the three-dimensional structure of gravity waves is provided, which uses two satellite-borne near-infrared two-dimensional temperature field imagers to form a front and rear dual-field collaborative observation, forming a binocular stereo vision imaging detection mode, and using a geometric reconstruction algorithm to invert and calculate the change in the center of mass height of the airglow layer caused by gravity wave disturbances, thereby obtaining the three-dimensional structure of gravity waves, so as to solve the problems existing in the background technology.

[0005] Technical solution: The satellite-borne near-infrared two-dimensional temperature field imager described in the present invention comprises: a front light shield, the inner wall of which is provided with a plurality of light shielding ring groups, the plurality of light shielding ring groups are connected to the front zero-distortion wide-angle lens through a platform connecting fixed frame, the front zero-distortion wide-angle lens is arranged at the end of the front light shield, for converging the incident light; a double-glued field mirror is provided at 0.5 times the focal length behind the front zero-distortion wide-angle lens for gathering the divergent light beam; a beam splitter chamber is provided at a certain distance between the double-glued field mirrors, the beam splitter in the beam splitter chamber is placed at 45 degrees to the optical axis, and the surface is coated with a semi-reflective and semi-transparent film for dividing the light beam into a transmitted parallel channel and a reflected vertical channel; the parallel channels are sequentially provided at a certain distance: a first double-glued collimating lens, a first electric filter wheel and its first narrow The invention relates to an imager comprising a filter, a first imaging lens, a first high-refractive-index thermal compensation lens, a first InGaAs sensor chip and a first scientific-grade camera, wherein the first narrow-band filter is used to obtain the airglow radiation image of the OH(3-1) spectral band P1(2) spectral line; a second double-glued collimating lens, a second electric filter wheel and a second narrow-band filter, a second imaging lens, a second high-refractive-index thermal compensation lens, a second InGaAs sensor chip and a second scientific-grade camera are sequentially arranged at a certain interval in the vertical channel, wherein the second narrow-band filter is used to obtain the airglow radiation image of the OH(3-1) spectral band P1(4) spectral line; all optical elements in the imager are fixed in a light-shielding lens barrel group, and all components are combined into a solid whole through the light-shielding lens barrel group.

[0006] Furthermore, except for the different central wavelengths and bandwidths of the first narrowband filter and the second narrowband filter, all optical elements and spacing distances of the parallel channel and the perpendicular channel are the same; the first high-refractive-index thermal compensation lens and the second high-refractive-index thermal compensation lens have negative thermal expansion coefficients, which are used to offset the defocusing of the optical lens caused by temperature fluctuations; the first InGaAs sensor chip and the second InGaAs sensor chip are respectively located on the focal planes of the first imaging lens and the second imaging lens.

[0007] Furthermore, the imager uses airglow radiation as a light source, and utilizes the characteristic relationship that the ratio of the intensity of the airglow radiation vibration and rotational energy level spectral lines changes regularly with temperature, and inverts the temperature by effectively detecting the intensity of the spectral lines.

[0008] Furthermore, the radiation intensity ratio R of the P1(2) spectral line to the P1(4) spectral line is related to the rotation temperature T r The relationship is used to invert the two-dimensional temperature field, and the formula is as follows: .

[0009] Furthermore, the bandwidth of the first narrowband filter and the second narrowband filter is 1-3 nm; the first electric filter wheel and the second electric filter wheel also include filters for acquiring atmospheric background infrared radiation images.

[0010] Furthermore, the thicknesses of the first high refractive index thermal compensation lens and the second high refractive index thermal compensation lens are determined by precise calculations to offset the defocusing of the positive thermal expansion coefficient optical lens caused by temperature fluctuations.

[0011] The present invention provides a method for detecting three-dimensional structures of gravity waves, based on a satellite-borne near-infrared two-dimensional temperature field imager for front and rear dual-field collaborative observation, comprising: (1) Obtain airglow image data and perform preprocessing by using a satellite-borne near-infrared two-dimensional temperature field imager to form a front-back dual-field collaborative observation; (2) The three-dimensional geometric reconstruction of the OH airglow layer centroid height includes: calculating the matching point epipolar lines, calculating the airglow radiance similarity using the normalized cross-correlation matching algorithm, and calculating the airglow layer centroid height using triangular inversion; (3) Visualize the results of three-dimensional inversion.

[0012] Furthermore, step (1) obtains the airglow image data as follows: the first satellite-borne near-infrared two-dimensional temperature field imager and the second satellite-borne near-infrared two-dimensional temperature field imager are symmetrically fixed on the instrument connecting rod, and are installed on the satellite platform through the payload fixing platform. The first observation field of view and the second observation field of view both observe downward toward the earth, and the field of view angle is 80°~100°, with an overlap of 5~10° in the middle for joint calibration; the two imagers maintain time synchronization for shooting, and after the first detection, the satellite flies a certain distance and performs a second detection, so that the projection area of ​​the second observation field of view of the first detection forms an overlap area of ​​at least 50% with the projection area of ​​the first observation field of view of the second detection.

[0013] Furthermore, the preprocessing is as follows: dark noise removal is performed to eliminate background signals caused by equipment noise or environmental factors, and discrete bright spots are removed to remove isolated bright spots or artifacts in the image; distorted images are removed by screening out images that do not meet the standards to ensure that only high-quality data is used for processing; flat field coefficient correction is performed to correct the uneven brightness caused by optical system unevenness; the tilt of the annular stripes is corrected; pincushion distortion is corrected by adjusting the radial distortion parameters using the inverse mapping algorithm to restore the true structure of the image; the background spectrum is removed to remove the interference of the background signal.

[0014] Furthermore, the normalized cross-correlation matching algorithm is used to calculate the airglow radiance similarity formula as follows: ; in I 1 and I 2 are the strengths of matching points P1 and P2, and the dimension (2 p +1,2 p+1) is defined around points P1 and P2, and For the local window (2 p +1) 2 The mean of the pixel values, ( x , y ) is the pixel position on the reference image, (d x , d y ) is the displacement of the matching point. k 、 l The increment of pixel coordinates is in the range of - p arrive p , used to traverse all pixels in the window around the matching point; after using the sliding window to calculate the NCC value within the range, find the peak position of the NCC value; the image block corresponding to the peak position is the area most similar to the reference image block, thereby locking the matching point.

[0015] Beneficial effects: Compared with the existing technology, the present invention has the following significant advantages: (1) The present invention proposes a satellite-borne near-infrared two-dimensional temperature field imager, which uses the near-infrared radiation of the OH (3-1) band airglow as a light source, and obtains the horizontal two-dimensional spatial distribution of the radiation intensity of the two spectral lines P1 (2) and P1 (4) in an imaging manner, and inverts the spatial distribution of the horizontal two-dimensional temperature field at the altitude layer through the ratio of their radiation intensity. Compared with the existing limb observation satellite-borne instruments that can only provide vertical profile information, the present invention can provide horizontal two-dimensional distribution information, which is of great value for the study of the fine structure of airglow radiation, atmospheric temperature and density, and gravity wave disturbances. (2) The present invention provides a method for detecting the three-dimensional structure of gravity waves. With the help of two satellite-borne near-infrared two-dimensional temperature field imagers, a binocular stereoscopic imaging detection mode is constructed. With the help of a geometric reconstruction algorithm, the change in the height of the center of mass of the airglow layer caused by the gravity wave disturbance can be inverted and calculated, thereby obtaining the three-dimensional structure of gravity waves. Compared with two-dimensional vertical profile detection or two-dimensional horizontal distribution detection, the detection of three-dimensional structure provides a new idea for gravity wave research. (3) The satellite-borne near-infrared two-dimensional temperature field imager proposed in the present invention adopts a split-beam optical path design, in which the parallel channel and the vertical channel are completely synchronized in terms of temporal and spatial distribution. Compared with traditional time series shooting, the error caused by the temporal and spatial displacement of the satellite on orbit is greatly reduced. (4) The satellite-borne near-infrared two-dimensional temperature field imager proposed in the present invention uses the airglow radiation of the OH (3-1) spectral band as the light source. The spectral lines of this spectral band are mainly distributed in the range of 1500-1560nm. Compared with the near-infrared OH (8-3) and (6-2) spectral bands (760-1000nm band) used by traditional satellite-borne instruments, its radiation intensity is about 50 times higher, which greatly reduces the exposure time of each detection and greatly improves the image displacement problem of remote sensing observation of the earth caused by the rapid flight of the satellite. (5) The satellite-borne near-infrared two-dimensional temperature field imager of the present invention proposes adding a high-refractive-index thermal compensation lens with a negative thermal expansion coefficient between the imaging lens and the InGaAs sensor chip. The thickness of the compensation lens can be determined by calculation to offset the defocusing of the optical lens with a positive thermal expansion coefficient caused by temperature fluctuations, thereby ensuring the final clear imaging of the instrument to a certain extent. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 This is a schematic diagram of the main optical structure of the satellite-borne near-infrared two-dimensional temperature field imager of the present invention; Figure 2 This is the distribution diagram of the OH (3-1) band airglow characteristic spectral line used in the present invention; Figure 3 The ratio R of the radiation intensity of the P1(2) and P1(4) lines in the OH(3-1) band used in the present invention and the rotation temperature T r Quantitative relationship curve diagram; Figure 4 This is a flow chart of the satellite-borne near-infrared two-dimensional temperature field imager of the present invention for realizing two-dimensional temperature field detection; Figure 5 This is a schematic diagram of the detection mode of a single satellite-borne near-infrared two-dimensional temperature field imager of the present invention; Figure 6 It is a schematic diagram of the main structure of the dual-field-of-view satellite-borne near-infrared two-dimensional temperature field imager of the present invention; Figure 7 This is a schematic diagram of a binocular stereo vision imaging detection mode constructed by the dual-field-of-view satellite-borne near-infrared two-dimensional temperature field imager of the present invention; Figure 8 This is a flow chart of the present invention for performing gravity wave stereo structure inversion based on overlapping areas of different fields of view; Figure 9 is a schematic diagram of a dual-field epipolar geometry model of the present invention; Figure 10 is a schematic diagram of normalized cross-correlation matching based on overlapping areas of the present invention; Figure 11 is a schematic diagram of an example of gravity wave three-dimensional structure inversion according to the present invention; In the figure: 1. Front light shield, 2. Light shielding ring assembly, 3. Platform connecting bracket, 4. Front zero-distortion wide-angle lens, 5. Light shielding lens barrel assembly, 6. Double-cemented field mirror, 7. Beam splitter chamber, 8. Beam splitter, 9. First double-cemented collimating lens, 10. First narrow-band filter, 11. First motorized filter wheel, 12. First imaging lens, 13. First high-refractive-index thermal compensation lens, 14. First InGaAs sensor chip, 15. First scientific-grade camera, 16. Second double-cemented collimating lens, 17. Second narrow-band filter, 18. Second motorized filter wheel, 19. Second imaging lens, 20. Second high-refractive-index thermal compensation lens, 21. Second InGaAs sensor chip, 22. Second scientific-grade camera, 23. Payload fixing platform, 24. Instrument connecting rod, 25. First satellite-borne near-infrared two-dimensional temperature field imager, 26. Second satellite-borne near-infrared two-dimensional temperature field imager, 27. First observation field of view, 28. Second observation field of view. DETAILED DESCRIPTION

[0017] The technical solution of the present invention will be further described below with reference to the accompanying drawings.

[0018] like Figure 1As shown, an embodiment of the present invention provides a satellite-borne near-infrared two-dimensional temperature field imager, with a front light shield 1 provided at the front end, and the inner wall of which is equipped with 7 to 10 light shielding ring groups 2 with decreasing inner diameters from front to back, forming a funnel-shaped conical light collection angle, which is the field of view angle for ground observation, and the light outside this field of view angle will be blocked by the light shielding ring group 2 and reflected to the outside world. A front zero-distortion wide-angle lens 4 is provided close to the end of the front light shield 1, and the two are fastened together using a platform connecting bracket 3. At the same time, the platform connecting bracket 3 is also responsible for fastening the entire instrument to the satellite platform. A double-cemented field mirror 6 is provided at 0.5 times the focal length behind the front zero-distortion wide-angle lens 4 to gather the divergent light beam. Then, a beam splitter 8, secured within the beam splitter prism chamber 7, is positioned at intervals. Beam splitter 8 is positioned at a 45° angle to the optical axis and coated with a semi-reflective, semi-transparent film with a transmittance ratio of 1:1. This splits the light beam from its front into two paths, dividing the optical system behind it into two parts. The light beam transmitted by beam splitter 8 propagates along the original optical path, with subsequent optical components forming a parallel channel. The light beam reflected by beam splitter 8 deflects and propagates at a 90° angle to the original optical path, with subsequent optical components forming a perpendicular channel. Within the parallel channel, a first double-cemented collimating lens 9, a first motorized filter wheel 11 equipped with a first narrowband filter 10, a first imaging lens 12, a first high-refractive-index thermal compensation lens 13, and a first scientific-grade camera 15 equipped with a first InGaAs sensor chip 14 are positioned at intervals. The first InGaAs sensor chip 14 is located at the focal plane of the first imaging lens 12. In the vertical channel, a second doublet collimating lens 16, a second motorized filter wheel 18 equipped with a second narrowband filter 17, a second imaging lens 19, a second high-refractive-index thermal compensation lens 20, and a second scientific-grade camera 22 equipped with a second InGaAs sensor chip 21 are sequentially spaced apart. The second InGaAs sensor chip 21 is located in the focal plane of the second imaging lens 19. Aside from the different optical parameters of the first narrowband filter 10 and the second narrowband filter 17, all other optical components and spacings in the parallel and vertical channels are identical. Furthermore, all optical components in the spaceborne near-infrared two-dimensional temperature field imager are secured within a light-shielding lens assembly 5, which secures the entire system together into a robust whole.

[0019] like Figure 1As shown, the imaging optical path principle of the satellite-borne near-infrared two-dimensional temperature field imager of the present invention is as follows: since the instrument is generally located in a polar satellite orbit 400~900km above the earth's surface, and the light source it detects comes from the airglow layer radiation about 85~92km above the earth's surface, when the light radiated at different positions on the distant airglow layer will be incident on the front light shield 1 from different directions as nearly parallel light, it will first pass through the joint action of the front zero-distortion wide-angle lens 4 and the double-glued field lens 6, and converge to the rear focal length of the double-glued field lens 6 to form an image. The position of this imaging surface needs to be exactly at one times the focal length of the first double-glued collimating lens 9 and the second double-glued collimating lens 16. Therefore, in the parallel channel, after being transmitted by beam splitter 8 and then converged by first doublet collimating lens 9, the light is transformed into a parallel beam and enters first narrowband filter 10, where it is filtered into the desired infrared light. It is then converged by first imaging lens 12 and imaged onto first InGaAs sensor chip 14 located at the focal plane of first imaging lens 12, forming an airglow infrared radiation image. Similarly, in the vertical channel, the reflected light forms an airglow infrared radiation image on second InGaAs sensor chip 21 in the same manner.

[0020] During in-orbit operation, the temperature environment within the satellite platform occasionally fluctuates significantly. These temperature fluctuations cause changes in the refractive index of the optical lenses, which can cause the final convergence point of light to defocus and deviate from the focal plane, resulting in unclear imaging. Because the thermal expansion coefficients of the optical lenses in the instrument are all positive, a first high-refractive-index thermal compensation lens 13 and a second high-refractive-index thermal compensation lens 20, both with negative thermal expansion coefficients, are placed between the first imaging lens 12 and the first InGaAs sensor chip 14, and between the second imaging lens 19 and the second InGaAs sensor chip 21, respectively. The thickness of these two compensation lenses, determined through precise calculations, precisely offsets the defocusing caused by temperature fluctuations, ensuring clear imaging.

[0021] The basic principle of the spaceborne near-infrared two-dimensional temperature field imager of the present invention for detecting temperature is to use airglow radiation (O2 molecules, OH molecules, etc.) as the light source, and to utilize the characteristic relationship that the ratio of the intensity of the airglow radiation vibration and rotational energy level spectral lines changes regularly with temperature, and to invert the temperature by effectively detecting the intensity of these spectral lines. Figure 2As shown, specifically, this instrument uses the airglow radiation of the OH (3-1) spectral band. The spectral lines of this spectral band are mainly distributed in the range of 1500~1560nm. Compared with the near-infrared OH (8-3) and (6-2) spectral bands (760~1000nm), its radiation intensity is about 50 times higher. Among them, two characteristic spectral lines P1(2): 1523.7 nm and P1(4): 1542.8 nm are selected as target light sources. The spectral lines are widely spaced and the radiation intensity ratio change rate is high, which is suitable for temperature inversion. In addition, the line-free area near 1521.4 nm needs to be selected as the atmospheric background radiation detection spectrum. Figure 3 As shown, by using the comprehensive analysis of the existing Boltzmann distribution, Einstein transition probability and spectral parameters, the ratio of the radiation intensity of the P1(2) and P1(4) spectral lines can be calculated. R and rotation temperature T r The quantitative relationship is: (1); This formula and curve provide a theoretical basis for detecting the inversion temperature of the OH (3-1) band spectral line radiation intensity ratio.

[0022] like Figure 1 and Figure 2 As shown, the center wavelength of the first narrowband filter 10 is set to 1523.7 nm and the bandwidth is 1~3 nm, so that the airglow infrared radiation image of the P1(2) spectrum line can be obtained in the parallel channel. Similarly, the center wavelength of the second narrowband filter 17 is set to 1542.8 nm and the bandwidth is 1~3 nm, so that the airglow infrared radiation image of the P1(4) spectrum line can be obtained in the vertical channel. However, since the atmosphere itself has background infrared radiation, which appears in the form of a continuous spectrum, the image detected by the first narrowband filter 10 and the second narrowband filter 17 is the result of the combined effect of the airglow spectrum radiation and the atmospheric background infrared radiation in the spectrum band. Therefore, it is also necessary to set a filter for detecting the atmospheric background infrared radiation in each of the first electric filter wheel 11 and the second electric filter wheel 18, and set its center wavelength to 1537.0 nm and the bandwidth to 1~3 nm. After each acquisition of the airglow infrared radiation image of the P1(2) spectrum line, switch the filter and obtain the atmospheric background infrared radiation image again.

[0023] The specific processing procedures are as follows Figure 4As shown, taking the parallel channel as an example, the infrared radiation image of the P1(2) spectral band is first detected using a filter with a central wavelength of 1523.7 nm, and then the first electric filter wheel 11 is quickly switched to a filter with a central wavelength of 1537.0 nm to detect the atmospheric background infrared radiation image under the same exposure parameters. The two images are then subtracted, and the remaining value becomes the airglow P1(2) spectral line radiation image. It can be considered that the current image is entirely contributed by the airglow P1(2) spectral line radiation. Similarly, the vertical channel can obtain the airglow P1(4) spectral line radiation image. At this time, by dividing the airglow P1(2) spectral line radiation image by the airglow P1(4) spectral line radiation image for each corresponding pixel, the radiation intensity ratio of the P1(2) spectral line to the P1(4) spectral line radiation image can be obtained. R The horizontal two-dimensional distribution image of , and then using the relationship given by (1), the temperature T of each pixel in the image can be calculated r , forming T r The horizontal two-dimensional distribution image is also the two-dimensional temperature field. It should be noted that due to the use of the beam splitter 8, the parallel channel and the vertical channel are completely synchronized in terms of temporal and spatial distribution. Compared with traditional time series photography, the error caused by the temporal and spatial displacement of the satellite in orbit is greatly reduced.

[0024] When a satellite carries a single satellite-borne near-infrared two-dimensional temperature field imager of the present invention, its detection mode is as follows: Figure 5 As shown in the figure, the OH airglow layer radiation is relatively stable, and its height is generally located at 85~90km above the earth, with a thickness of 3~5km. When gravity wave activity occurs at this altitude, it will cause periodic changes in the state of parameters such as the atmospheric temperature, density, wind speed, and composition of the airglow layer. The photochemical reaction that causes the airglow radiation is extremely sensitive to the changes in the parameter state of this layer of atmosphere. Therefore, the intensity of the airglow radiation will also show periodic changes. When the airglow radiation enters the field of view of the satellite-borne near-infrared two-dimensional temperature field imager, it will be detected by the image. Figure 1 The optical path principle shown in the will form an airglow spectrum radiation image, and through Figure 4 The two-dimensional temperature field is obtained using the process method in [1]. However, because the entire system belongs to the traditional passive remote sensing imaging system, the received radiation intensity is the accumulation of the radiation values ​​of the entire airglow layer, and the inverted temperature is the average temperature of the airglow layer. Therefore, it lacks high-level detection and resolution capabilities. When gravity wave activity causes periodic airglow disturbances, it can only obtain information such as the gravity wave period, wavelength, and propagation direction.

[0025] In fact, gravity wave activity can cause significant disturbances in the atmospheric parameters and the center-of-mass height of the airglow layer in three-dimensional space. Therefore, this paper proposes using two satellite-borne near-infrared two-dimensional temperature field imagers to form a dual field of view. Utilizing the principle of binocular stereo imaging by observing the same area twice in orbit, the changes in the center-of-mass height of the airglow layer caused by gravity waves can be inverted, thereby obtaining the three-dimensional structure of gravity waves. The details are as follows: like Figure 6 As shown, an instrument connecting rod 24 is fixed to the center of the top payload mounting platform 23. A first satellite-borne near-infrared two-dimensional temperature field imager 25 and a second satellite-borne near-infrared two-dimensional temperature field imager 26 are symmetrically fixed to the instrument connecting rod 24. The first observation field 27 and the second observation field 28 both observe the Earth downward, typically (80°-100°) x (80°-100°), one in front of the other, with a 5-10° overlap in the middle for joint calibration. The two cameras maintain temporal synchronization.

[0026] like Figure 7 As shown, due to the certain inclination angles between the first observation field 27 (i.e., observation field a) and the second observation field 28 (i.e., observation field b), their projections on the airglow layer form two symmetrical trapezoids. After the satellite completes its first detection, it flies a certain distance and conducts a second detection. This causes the projection area of ​​observation field b during the first detection to overlap with the projection area of ​​observation field a during the second detection, with the overlap accounting for at least 50% of the individual projection areas. At this time, due to the different Earth observation angles of observation field b during the first detection and observation field a during the second detection, binocular stereo imaging is formed within the overlapping area of ​​the two observations. Furthermore, due to the extremely high satellite flight speed, the interval between the two images is generally less than 30 seconds, while the minimum period of gravity waves is generally around 10-15 minutes. Therefore, it can be assumed that the gravity wave structure remains essentially unchanged between the two images, allowing for stereoscopic structure inversion.

[0027] like Figure 8 and Figure 9 As shown in the figure, the basic principle of stereo structure inversion is to obtain the depth information of the object in the image by calculating the parallax of each pixel point based on the different perspectives of the camera. In the application, the matching points of the same object in the two images are first found through the stereo matching algorithm (normalized cross-correlation algorithm). Then, by calculating the parallax of these matching points and combining the internal and external parameters of the camera, the precise position of each point in the three-dimensional space can be restored. Finally, by performing three-dimensional reconstruction on these points, the three-dimensional distribution of gravity waves in the observation area is obtained, including the height, wave speed and propagation direction of the waves. Specifically, the process of the binocular vision inversion algorithm based on overlapping areas of different fields of view is as follows: Step 1: Preprocess the airglow image data to eliminate optical inhomogeneities caused by the equipment and ensure that the image accurately reflects the atmospheric signal. To achieve this goal, image preprocessing typically includes the following key steps: S1 performs dark noise removal to eliminate background signals caused by equipment noise or environmental factors, which helps ensure that the image mainly reflects the target signal; it also removes discrete bright spots to remove isolated bright spots or artifacts in the image; and it removes distorted images by screening out images that do not meet the standards, ensuring that only high-quality data is used for processing.

[0028] S2 flat field coefficient correction corrects the uneven brightness caused by the unevenness of the optical system; corrects the tilt of the annular stripes; corrects the pincushion distortion, and restores the true structure of the image by using a specific geometric transformation model.

[0029] S3 removes the background spectrum to remove the interference of background signals.

[0030] Step 2, the three-dimensional geometric reconstruction of the OH airglow layer centroid height, includes the following steps: (21) In stereo vision systems, epipolar line calculation is the core of the matching process. Epipolar line geometry can be used to limit the search space when calculating matching points, thereby improving matching efficiency and accuracy. The epipolar plane is a plane consisting of a 3D point, the optical center of two cameras, and the projected image points of the 3D point in the two cameras.

[0031] like Figure 9 As shown, planes IM1 and IM2 are the image planes of the camera lens optical centers C1 and C2, respectively. To calculate the 3D position of point P, points P1 and P2 in the two images IM1 and IM2 correspond to the projection of the same physical point P. The key is to establish a correspondence between these pairs of points. Then, using the equations of the lines C1P1 and C2P2, the coordinates of the intersection point P can be obtained. Line C1C2 is called the baseline. Point P2 lies on line D2, called the epipolar line P3P4, which is the intersection of the epipolar plane and the image plane. The so-called epipolar constraint states that the five points P, C1, C2, P1, and P2 define a plane called the epipolar plane.

[0032] The epipolar line is calculated using the fundamental matrix, which maps the point P1 in C1 to the epipolar line D2 in C2. The formula is: (2); in Fis the fundamental matrix, P1 is the projection point in IM1, and D2 is the epipolar line in IM2. The fundamental matrix can be calculated using the camera's intrinsic and extrinsic parameters. Specifically, the geometric relationship between the two cameras can be derived using the camera's calibration parameters, parallax, and baseline distance. Considering that the airglow layer is approximately 7 kilometers thick (85-92 km), we can restrict the search range for matching points to this altitude range. Since the atmospheric signal is relatively thin, this restriction effectively reduces the search space and computational complexity.

[0033] (22) Figure 10 As shown in Figure 2, normalized cross-correlation matching of airglow radiance is performed. This method finds matching points by comparing corresponding pixels in the two images. The goal of normalized cross-correlation is to measure the similarity between two image regions. Specifically, it calculates the relative relationship between the pixel values ​​of two regions, rather than simply the difference in their absolute values.

[0034] (3); in I 1 and I 2 are the strengths of matching points P1 and P2, and the dimension (2 p +1,2 p +1) is defined around points P1 and P2, and For the local window (2 p +1) 2 The mean of the pixel values, ( x , y ) is the pixel position on the reference image, (d x , d y ) is the displacement of the matching point. k 、 l The increment of pixel coordinates is in the range of - p arrive p , used to traverse all pixels within a window around the matching point. After calculating the NCC value within the sliding window, the peak position of the NCC value is found. The image block corresponding to the peak position is the area most similar to the reference image block, thus locking the matching point.

[0035] The choice of window size directly impacts matching accuracy and computational efficiency. Larger windows help reduce the impact of noise, but increase computational complexity. Smaller windows improve matching accuracy, but may be affected by noise. Smaller windows can lead to false matches in noisy environments, so filtering or interpolation techniques are needed to improve matching accuracy. Sub-pixel interpolation techniques can further improve the accuracy of matching points. For example, bilinear interpolation or cubic interpolation can be used to estimate the sub-pixel positions of matching points.

[0036] (23) Perform triangulation inversion of the airglow centroid height. Before calculating the height, the parallax of the airglow radiant point needs to be determined. The matching points found in the previous matching step are calculated, and their position differences in the two images are calculated to obtain the parallax information. The accuracy of the parallax positioning directly affects the accuracy of the final airglow centroid height calculation. Parallax is the horizontal offset between corresponding points in two images. A disparity map is generated by calculating the parallax of each pair of matching points in the image. The larger the parallax, the closer the object is to the camera, and conversely, the smaller the parallax, the farther the object is. Using the internal and external parameters of the camera (such as focal length, baseline length, etc.) and the parallax of the matching points, triangulation is performed to restore the three-dimensional coordinates. Triangulation uses the camera's projection model to map two-dimensional image points to three-dimensional space. During the reconstruction process, error sources such as camera calibration error and matching error may be encountered. To reduce the impact of errors, optimization algorithms are used to further improve the reconstruction accuracy.

[0037] Based on the baseline length of two cameras B , camera focal length f , and the parallax of corresponding points in the images taken by the two cameras d , the height of the OH gasglow layer can be calculated Z : (4); This is the core basis for constructing a three-dimensional map of the centroid height of the airglow layer.

[0038] In order to quantify the intensity of gravity waves at the height of the OH airglow layer, the kinetic energy density of gravity waves is calculated: (5); in, W is the kinetic energy density of gravity waves, ρ is the air density at an altitude of 87 km, a is the amplitude of the gravity wave, π is pi, T is the period of the gravity wave. a The vertical fluctuation amplitude is extracted from the three-dimensional surface map. The calculated results are compared with those of other observation methods to verify the effectiveness of the stereo imaging method.

[0039] Step 3: After the 3D reconstruction is completed, the results need to be displayed through visualization technology: like Figure 11As shown in the figure, by comparing the spatial coverage of the projection area of ​​the observation field b of the first observation result and the projection area of ​​the observation field a of the second observation result, the overlapping area of ​​the two observations can be clearly identified. This overlapping area is the core range of subsequent analysis. With the help of the stereo matching technology detailed above, the observation data in this area are processed, the feature points at corresponding positions in different fields of view are identified, and matching calculations are performed in combination with spatial geometric relationships to complete the three-dimensional reconstruction. Finally, the three-dimensional distribution results of the centroid height of the airglow layer and the atmospheric temperature can be obtained. Figure 11 It can be seen intuitively in the three-dimensional distribution of the centroid height of the airglow layer reconstructed in the 2017 dataset that the centroid height distribution is concentrated in the 85-95km height range, and with the propagation of gravity waves, the height shows regular periodic fluctuations, which clearly reflects the dynamic changes of the airglow layer under the action of gravity waves. Figure 11 From the reconstructed three-dimensional distribution map of the atmospheric temperature in the airglow layer, it can be seen that the atmospheric temperature distribution is roughly in the range of 180~210K, and shows a trend of gradually decreasing with increasing altitude. The temperature difference from low to high reaches about 30K, forming a significant vertical temperature gradient.

Claims

1. A spaceborne near-infrared two-dimensional temperature field imager, characterized in that: include: A front light shield (1) is provided with a plurality of light shielding ring groups (2) on its inner wall, and the plurality of light shielding ring groups (2) are connected to a front zero-distortion wide-angle lens (4) through a platform connection fixing frame (3), and the front zero-distortion wide-angle lens (4) is arranged at the end of the front light shield (1) for converging incident light; a double-glued field lens (6) is provided at 0.5 times the focal length behind the front zero-distortion wide-angle lens (4) for gathering divergent light beams; a beam splitter chamber (7) is provided at a certain distance from the double-glued field lens (6), and a beam splitter (8) in the beam splitter chamber (7) is placed at 45 degrees to the optical axis and coated with a semi-reflective and semi-transparent film on the surface for dividing the light beam into a transmitted parallel channel and a reflected vertical channel; and the parallel channels are sequentially provided at a certain distance: a first double-glued collimating lens (9), a first electric filter wheel (11) and its first narrow-band filter (10), a first imaging lens (12), a first high-definition optical filter (13), a first high-definition optical filter (14), a first high-definition optical filter (15), a first high-definition optical filter (16), a first high-definition optical filter (17), a first high-definition optical filter (18), a first high-definition optical filter (19), a first high-definition optical filter (11), a first high-definition optical filter (11), a first high-definition optical filter (12), a first high-definition optical filter (13), a first high-definition optical filter (14), a first high-definition optical filter (15), a first high-definition optical filter (16), a first high-definition optical filter (17), a first high-definition optical filter (18), a first high-definition optical filter (19), a first high-def A refractive index thermal compensation lens (13), a first InGaAs sensor chip (14) and a first scientific-grade camera (15), wherein the first narrowband filter (10) is used to obtain an airglow radiation image of the OH (3-1) spectral band P1 (2) spectral line; a second double-glued collimating lens (16), a second electric filter wheel (18) and its second narrowband filter (17), a second imaging lens (19), a second high-refractive index thermal compensation lens (20), a second InGaAs sensor chip (21) and a second scientific-grade camera (22) are sequentially arranged at a certain distance in the vertical channel, wherein the second narrowband filter (17) is used to obtain an airglow radiation image of the OH (3-1) spectral band P1 (4) spectral line; all optical components in the imager are fixed in a light-shielding lens barrel group (5), and all components are combined into a solid whole through the light-shielding lens barrel group (5).

2. The satellite-borne near-infrared two-dimensional temperature field imager according to claim 1, characterized in that: Except for the central wavelengths and bandwidths of the first narrowband filter (10) and the second narrowband filter (17), all optical elements and spacing distances of the parallel channel and the perpendicular channel are the same; wherein the first high-refractive index thermal compensation lens (13) and the second high-refractive index thermal compensation lens (20) have negative thermal expansion coefficients and are used to offset the defocusing of the optical lens caused by temperature fluctuations; the first InGaAs sensor chip (14) and the second InGaAs sensor chip (21) are respectively located on the focal planes of the first imaging lens (12) and the second imaging lens (19).

3. The satellite-borne near-infrared two-dimensional temperature field imager according to claim 1, characterized in that: The imager uses airglow radiation as a light source, and utilizes the characteristic relationship that the ratio of the intensity of the airglow radiation vibration and rotational energy level spectral lines changes regularly with temperature, and inverts the temperature by effectively detecting the intensity of the spectral lines.

4. The satellite-borne near-infrared two-dimensional temperature field imager according to claim 1, characterized in that: The radiation intensity ratio R of the P1(2) spectral line to the P1(4) spectral line and the rotation temperature T r The relationship is used to invert the two-dimensional temperature field, and the formula is as follows: 。 5. The satellite-borne near-infrared two-dimensional temperature field imager according to claim 1, characterized in that: The bandwidth of the first narrowband filter (10) and the second narrowband filter (17) is 1-3 nm; the first electric filter wheel (11) and the second electric filter wheel (18) further include filters for acquiring an atmospheric background infrared radiation image.

6. The satellite-borne near-infrared two-dimensional temperature field imager according to claim 1, characterized in that: The thicknesses of the first high-refractive-index thermal compensation lens (13) and the second high-refractive-index thermal compensation lens (20) are determined by precise calculation and are used to offset the defocusing of the positive thermal expansion coefficient optical lens caused by temperature fluctuations.

7. A method for detecting three-dimensional structure of gravity waves, characterized in that: Based on the satellite-borne near-infrared two-dimensional temperature field imager, the front and rear dual-field collaborative observation is composed of: (1) Obtain airglow image data and perform preprocessing by using a satellite-borne near-infrared two-dimensional temperature field imager to form a front-back dual-field collaborative observation; (2) The three-dimensional geometric reconstruction of the OH airglow layer centroid height includes: calculating the matching point epipolar lines, calculating the airglow radiance similarity using the normalized cross-correlation matching algorithm, and calculating the airglow layer centroid height using triangular inversion; (3) Visualize the results of three-dimensional inversion.

8. The method for detecting three-dimensional structure of gravity waves according to claim 7, characterized in that: The step (1) of obtaining the airglow image data is as follows: the first satellite-borne near-infrared two-dimensional temperature field imager and the second satellite-borne near-infrared two-dimensional temperature field imager are symmetrically fixed on the instrument connecting rod, and are installed on the satellite platform through the payload fixing platform. The first observation field of view and the second observation field of view both observe the ground downward, and the field of view angle is 80°~100°, with an overlap of 5~10° in the middle for joint calibration; the two imagers are synchronized in time shooting, and after the first detection, the satellite flies a certain distance and performs a second detection, so that the projection area of ​​the second observation field of view of the first detection and the projection area of ​​the first observation field of view of the second detection form an overlap area of ​​at least 50%.

9. The method for detecting three-dimensional structure of gravity waves according to claim 7, characterized in that: The preprocessing in step (1) is as follows: dark noise removal is performed to eliminate background signals caused by equipment noise or environmental factors, and discrete bright spots are removed to remove isolated bright spots or artifacts in the image; distorted images are removed, and images that do not meet the standards are screened to ensure that only high-quality data are used for processing; Flat field coefficient correction, correcting the uneven brightness caused by the unevenness of the optical system; Corrected the tilt of the ring stripes; Correct pincushion distortion by adjusting radial distortion parameters using the inverse mapping algorithm to restore the true structure of the image; remove the background spectrum to eliminate the interference of background signals.

10. The method for detecting three-dimensional structure of gravity waves according to claim 7, characterized in that: Step (2) The formula for calculating the airglow radiance similarity using the normalized cross-correlation matching algorithm is as follows: ； Among them, I 1 and I 2 are the strengths of matching points P1 and P2, and the dimension (2 p +1,2 p +1) is defined around points P1 and P2, and For the local window (2 p +1) 2 The mean of the pixel values, ( x , y ) is the pixel position on the reference image, (d x , d y ) is the displacement of the matching point; k 、 l The increment of pixel coordinates is in the range of - p arrive p , used to traverse all pixels in the window around the matching point; after using the sliding window to calculate the NCC value within the range, find the peak position of the NCC value; the image block corresponding to the peak position is the area most similar to the reference image block, thereby locking the matching point.

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