Method for constructing multi-dimensional on-orbit imaging mode of space optical infrared camera

Abstract

The present application relates to a kind of space optical infrared camera multidimensional on-orbit imaging mode construction method, belong to space optical infrared camera on-orbit application technical field.The construction method of the present application, first obtains the calibration absolute responsivity and best response linear interval of space optical infrared camera;Then obtain global ground surface temperature, global ground object emissivity and global atmospheric profile database, simulate and calculate the equivalent spectral radiance of the entrance pupil of space optical infrared camera from multiple dimensions;Again, according to the equivalent spectral radiance database of entrance pupil and calibration absolute responsivity, construct the multidimensional on-orbit imaging mode of space optical infrared camera, so that it works in the best response linear interval, obtains its on-orbit imaging mode initial value;Finally, after space optical infrared camera enters orbit, according to its early on-orbit response characteristics, the multidimensional on-orbit imaging mode is optimized.The construction method, through suitable imaging mode, the imaging capability of space optical camera is brought out, the detection capability is maximized.

Description

TECHNICAL FIELD

[0001] The application relates to a method for constructing a multi-dimensional on-orbit imaging mode of a space optical infrared camera, in particular to a method for constructing a four-dimensional on-orbit imaging mode of a space optical infrared camera by using an absolute response function of the space optical infrared camera and a global ground surface temperature library, and belongs to the technical field of on-orbit application of the space optical infrared camera. BACKGROUND

[0002] The space optical infrared camera can realize earth imaging and air imaging, and is widely used in fields such as marine / land / air military target detection, national survey, agricultural quantitative remote sensing and the like. A large-aperture long-focus optical-mechanical system, high-performance (quantum efficiency, D*) infrared focal plane and high-precision assembly and adjustment integration technology can guarantee that the space infrared optical camera has the capability of high-performance imaging, and a suitable imaging mode setting is a key to exert the imaging capability of the space optical camera. In order to maximize the detection capability of the space optical camera, the on-orbit imaging mode table of the space optical infrared camera needs to be planned and designed.

[0003] The space optical infrared camera imaging link includes the following links: ground object spectrum radiation, atmospheric transmission, an optical system, a detector and an electronic system, data compression and storage, data transmission, data receiving and processing and the like. The ground object is a scene on the earth surface, and the ground object emits infrared radiation energy upward through self-radiation, and the infrared radiation energy reaches a satellite after atmospheric radiation transmission, and an image corresponding to the ground object is obtained through space optical infrared camera imaging. When the atmospheric absorption and scattering are ignored and only the target ground object itself infrared radiation is discussed, the image gray scale output by the infrared camera is a product result of the transmittance of the optical system and the filter and the response of the infrared focal plane detector and the infrared radiation energy of the ground object, that is, the radiation response equation of the space optical infrared camera is shown as formula (1).

[0004]

[0005] In the formula, DN is a digital output value of the image; L(T, sigma) is the infrared radiation brightness of the ground object at temperature T and emission rate sigma; tau atm is an atmospheric transmittance; D is a camera aperture; f is a camera focal length; tau opt is an optical system transmittance; tau fil is a filter transmittance; R det is an absolute responsivity of the infrared focal plane; beta e is a gain of the electronic system; t int is an integration time, and DN dark is a background radiation response of the space optical infrared camera.

[0006] It can be seen from (formula 1) that the radiation response of the space optical infrared camera mainly depends on factors such as the radiation characteristics of the ground object (the infrared radiation brightness of the ground object), the atmospheric transmission characteristics (atmospheric transmittance), and the space optical infrared camera transmission characteristics (absolute responsivity). In 2015, the Changchun Institute of Optics, Fine Mechanics and Physics of the Chinese Academy of Sciences proposed a method for establishing an on-orbit imaging mode of a space optical visible camera. First, the radiation brightness before the camera entrance pupil is calculated using an atmospheric radiation simulation software. Second, the radiation calibration data of the camera are analyzed, including the responsivity of each imaging mode, the radiation brightness range, the integral time relationship, etc. Third, the integral time relationship of the camera during swing imaging and flat flight imaging is analyzed to obtain the radiation brightness range of each imaging mode of the camera at each side swing angle. Finally, a two-dimensional imaging mode table under the combination of the solar elevation angle and the camera side swing angle is established according to the radiation brightness range of the imaging mode and the radiation brightness range of the scene at each solar elevation angle (Optical Precision Engineering, 2015, (07): 1852-1858), but this method is not suitable for space optical infrared cameras. SUMMARY

[0007] Therefore, in order to ensure that the space optical infrared camera adopts the most appropriate imaging mode during on-orbit imaging and achieve the best performance of the space optical infrared camera, the application provides a multi-dimensional on-orbit imaging mode construction method for a space optical infrared camera.

[0008] The technical scheme adopted by the application to achieve the above-mentioned purposes is as follows.

[0009] The multi-dimensional on-orbit imaging mode construction method for the space optical infrared camera comprises the following steps:

[0010] Firstly, the calibration absolute responsivity and the best response linear interval of the space optical infrared camera are obtained.

[0011] Secondly, a global ground surface temperature, a global ground object emissivity, and a global atmospheric profile database are obtained, the entrance pupil equivalent spectral radiance of the space optical infrared camera is simulated and calculated from multiple dimensions, and an entrance pupil equivalent spectral radiance database of the space optical infrared camera is established.

[0012] Thirdly, the multi-dimensional on-orbit imaging mode of the space optical infrared camera is constructed according to the entrance pupil equivalent spectral radiance database of the space optical infrared camera and the calibration absolute responsivity of the space optical infrared camera, the space optical infrared camera is caused to work in the best response linear interval, and the initial value of the multi-dimensional on-orbit imaging mode of the space optical infrared camera is obtained.

[0013] Fourthly, after the space optical infrared camera is launched into space, the multi-dimensional on-orbit imaging mode of the space optical infrared camera is optimized according to the response characteristics of the space optical infrared camera in the early stage of on-orbit operation.

[0014] Preferably, in the first step, a space optical infrared camera radiation calibration system is used to obtain a calibration absolute responsivity and an optimal response linear range of the space optical infrared camera through an infrared radiation calibration test;

[0015] The space optical infrared camera radiation calibration system consists of a vacuum low-temperature environment simulation device, an infrared black body, a low-temperature baffle, a satellite integrated simulator and an image data acquisition system. The vacuum low-temperature environment simulation device provides a vacuum low-temperature environment for the space optical infrared camera. The space optical infrared camera, the infrared black body and the low-temperature baffle are placed in the vacuum low-temperature environment simulation device. The infrared black body provides the space optical infrared camera with simulated on-orbit ground object radiation, and the low-temperature baffle provides the space optical infrared camera with background radiation. The satellite integrated simulator and the image data acquisition system are both connected to the space optical infrared camera. The satellite integrated simulator injects suitable imaging parameters into the space optical infrared camera, and the image data acquisition system collects and stores image data from the space optical infrared camera.

[0016] More preferably, the method of the infrared radiation calibration test is:

[0017] The infrared black body is set to the lowest temperature T1 of the dynamic range of the space optical infrared camera. After the infrared black body is stable, the low temperature baffle is cut out, and the space optical infrared camera saves the image of the infrared black body and the image of the low temperature baffle. Then the low temperature baffle is cut in, and the space optical infrared camera saves the image of the infrared black body and the image of the low temperature baffle.

[0018] The temperature of the infrared blackbody is set in 5K increments until it reaches the highest temperature T2 in the dynamic range. After the temperature stabilizes, the images of the infrared blackbody and the low-temperature baffle stored by the space optical infrared camera are collected respectively.

[0019] The response DN values ​​of the infrared blackbody and cryogenic baffle images at different temperatures were counted, and the radiation brightness of the infrared blackbody and cryogenic baffle was calculated as L using the Planck formula. The radiation calibration coefficients k and b were obtained by fitting using the least squares method.

[0020]

[0021] DN = k*L + b (Formula 3)

[0022] In Equations 2 and 3, T is the temperature of the infrared blackbody; ε is the emissivity of the infrared blackbody; λ1 and λ2 are the starting wavelength and ending wavelength of the space optical infrared camera, respectively; λ is the wavelength of the space optical infrared camera; c1 is the first radiation constant, c1 = 3.7148e16 (W·m 2); c2 is the second radiation constant, c2 = 1.4388e-2 (m K); R(λ) is the spectral response curve of the space optical infrared camera; L(T, ε) is the integral radiation brightness of the infrared blackbody with the temperature T and the emissivity ε in the response spectral range of the space optical infrared camera; DN is the response value of the space optical infrared camera, k is the absolute response slope of the space optical infrared camera; and b is the absolute response slope of the space optical infrared camera.

[0023] Preferably, in the second step, the dimensions are longitude, latitude, month and day-night.

[0024] More preferably, in the second step, the granularity of the longitude dimension is 5 degrees, and there are 72 intervals; the granularity of the latitude dimension is 5 degrees, and there are 36 intervals; the granularity of the month dimension is 1 month, and there are 12 intervals; and the day-night dimension is divided into two intervals according to the criterion of the positive and negative of the solar elevation angle.

[0025] Preferably, in the second step, the global surface temperature, the global surface emissivity and the global atmospheric profile database are substituted into the atmospheric radiation transmission software to calculate the equivalent spectral radiance at the entrance pupil of the space optical infrared camera.

[0026] Preferably, in the second step, the databases are all mean value databases.

[0027] Preferably, in the fourth step, the initial time is within one week after the space optical infrared camera is launched.

[0028] Preferably, in the fourth step, after the space optical infrared camera is launched, the response DN values of the typical ground objects of the space optical infrared camera in the initial stage in orbit and the corresponding multiple dimension information are counted;

[0029] The equivalent spectral radiance at the entrance pupil of the space optical infrared camera is calculated according to the multiple dimension information, and the response DN value of the typical ground object is calculated as a theoretical expected value according to the calibrated absolute responsivity;

[0030] The deviation of the statistical value and the theoretical expected value is compared, if the deviation is within a reasonable range, no imaging mode adjustment is needed, otherwise the imaging mode is updated according to the deviation and the calibrated absolute responsivity.

[0031] More preferably, the reasonable range is within 20%.

[0032] Compared with the prior art, the space optical infrared camera multi-dimensional imaging mode construction method has the following beneficial effects:

[0033] The space optical infrared camera multi-dimensional imaging mode construction method can bring out the imaging capability of the space optical infrared camera through a suitable imaging mode, and the detection capability of the space optical infrared camera is maximized. BRIEF DESCRIPTION OF DRAWINGS

[0034] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following briefly introduces the drawings required for use in the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0035] Figure 1 This is a flow chart of the method for constructing a multi-dimensional on-orbit imaging mode for a space optical infrared camera of the present invention;

[0036] Figure 2 This is a schematic structural diagram of the space optical infrared camera radiation calibration system of the present invention;

[0037] In the figure: 1. Vacuum low-temperature environment simulation device, 2. Space optical infrared camera, 3. Infrared blackbody, 4. Low-temperature baffle, 5. Satellite integrated simulator, 6. Image data acquisition system. DETAILED DESCRIPTION

[0038] The present invention will be further described in detail below with reference to the accompanying drawings.

[0039] like Figure 1 As shown in the figure, the method for constructing a multi-dimensional on-orbit imaging mode of a space optical infrared camera is as follows:

[0040] The first step is to use the space optical infrared camera radiation calibration system to obtain the calibration absolute response and the best response linear range of the space optical infrared camera 2 through infrared radiation calibration test. Figure 2 As shown, the space optical infrared camera radiation calibration system consists of a vacuum low-temperature environment simulation device 1, an infrared blackbody 3, a cryogenic baffle 4, a satellite integrated simulator 5, and an image data acquisition system 6. The vacuum low-temperature environment simulation device 1 provides a vacuum low-temperature environment (preferably 1E-3Pa, 100K) for the space optical infrared camera 2. The space optical infrared camera 2, the infrared blackbody 3, and the cryogenic baffle 4 are placed in the vacuum low-temperature environment simulation device 1. The infrared blackbody 3 provides the space optical infrared camera 2 with infrared blackbody radiation of any temperature within the dynamic range to simulate the radiation of on-orbit ground objects. The cryogenic baffle 4 provides the space optical infrared camera 2 with background radiation (preferably 100K). The satellite integrated simulator 5 is connected to the space optical infrared camera 2. The image data acquisition system 6 is connected to the space optical infrared camera 2. The satellite integrated simulator 5 injects appropriate imaging parameters into the space optical infrared camera 4. The image data acquisition system 6 collects and stores image data from the space optical infrared camera 4.

[0041] The infrared radiation calibration test method is as follows: the infrared black body 3 is set to the lowest temperature T1 of the dynamic range of the space optical infrared camera 2; after the infrared black body 3 is stabilized, the low temperature baffle 4 is cut out, and the space optical infrared camera 2 saves the image of the infrared black body 3 and the image of the low temperature baffle 4; then the low temperature baffle 4 is cut in, and the space optical infrared camera 2 saves the image of the infrared black body 3 and the image of the low temperature baffle 4; the temperature of the infrared black body 3 is set in 5K increments until it reaches the highest temperature T2 of the dynamic range; after the temperature is stabilized, the images of the infrared black body 3 and the images of the low temperature baffle 4 saved by the space optical infrared camera 2 are respectively collected;

[0042] The response DN values ​​of the images of the infrared blackbody 3 and the cryogenic baffle 4 at different temperatures were counted, and the radiation brightness L of the infrared blackbody 3 and the cryogenic baffle 4 was calculated using the Planck formula. The radiation calibration coefficients k and b were obtained by fitting using the least squares method.

[0043]

[0044] DN = k*L + b (Formula 3)

[0045] In Equations 2 and 3, T is the temperature of the infrared blackbody 3; ε is the emissivity of the infrared blackbody 3; λ1 and λ2 are the starting wavelength and ending wavelength of the space optical infrared camera 2, respectively; λ is the wavelength of the space optical infrared camera 2; c1 is the first radiation constant, c1 = 3.7148e16 (W·m 2 ); c2 is the second radiation constant, c2 = 1.4388e-2 (m·K); R(λ) is the spectral response curve of the space optical infrared camera 2; L(T,ε) is the integrated radiation brightness of the infrared blackbody 3 with temperature T and emissivity ε in the response spectrum of the space optical infrared camera 2; DN is the response value of the space optical infrared camera 2, k is the absolute response slope of the space optical infrared camera 2; b is the absolute response slope of the space optical infrared camera 2.

[0046] Second step, obtain global land surface temperature, global land surface emissivity and global atmospheric profile database, simulate the equivalent spectral radiance at the entrance pupil of the space optical infrared camera 2 from multiple dimensions, and establish the equivalent spectral radiance at the entrance pupil database of the space optical infrared camera 2; preferably, the four dimensions are longitude dimension, latitude dimension, month dimension and day-night dimension. According to the requirements, define the granularity of the four dimensions, for example, the longitude dimension granularity is 5 degrees, a total of 72 intervals; the latitude dimension granularity is 5 degrees, a total of 36 intervals; the month dimension granularity is 1 month, a total of 12 intervals; the day-night dimension is divided into two intervals according to the positive and negative of the solar elevation angle. Substitute the global land surface temperature, global land surface emissivity and global atmospheric profile database into the atmospheric radiation transfer software to calculate the equivalent spectral radiance at the entrance pupil of the space optical infrared camera 2, and establish the equivalent spectral radiance at the entrance pupil database of the space optical infrared camera 2. The first level lookup table of the equivalent spectral radiance at the entrance pupil database and the second level lookup table 1 of the equivalent spectral radiance at the entrance pupil are shown in Tables 1 and 2, respectively.

[0047] Table 1 First level lookup table of equivalent spectral radiance at entrance pupil database

[0048]

[0049]

[0050] Table 2 Second level lookup table 1 of equivalent spectral radiance at entrance pupil (month: mon = 1, solar elevation angle: sl≤0°)

[0051]

[0052] Third step, according to the equivalent spectral radiance at the entrance pupil database of the space optical infrared camera 2 and the calibration absolute responsivity of the space optical infrared camera 2, construct the multi-dimensional on-orbit imaging mode of the space optical infrared camera 2, make the space optical infrared camera 2 work in the best response linear interval, and get the initial value of the multi-dimensional on-orbit imaging mode of the space optical infrared camera 2; for example, taking four dimensions (longitude dimension, latitude dimension, month dimension and day-night dimension) as an example, the imaging parameter lookup table is divided into two levels, the first level lookup table of the imaging parameter and the second level lookup table 1 of the imaging parameter are shown in Tables 3 and 4, respectively. The granularity of the four dimensions is as follows: the longitude dimension granularity is 5 degrees, a total of 72 intervals; the latitude dimension granularity is 5 degrees, a total of 36 intervals; the month dimension granularity is 1 month, a total of 12 intervals; the day-night dimension is divided into two intervals according to the positive and negative of the solar elevation angle.

[0053] Table 3 First level lookup table of imaging parameter

[0054]

[0055] Table 4 Second level lookup table 1 of imaging parameter (month: mon = 1, solar elevation angle: sl≤0°)

[0056]

[0057] Fourthly, after the space optical infrared camera 2 is launched into orbit, the response DN values of typical ground objects and the information of corresponding longitude dimension, latitude dimension, month dimension and day-night dimension of the space optical infrared camera 2 in the early stage of the space optical infrared camera 2 in orbit (within the first week) are counted;

[0058] The entrance pupil equivalent spectral radiance of the space optical infrared camera 2 is calculated according to the information of the longitude dimension, the latitude dimension, the month dimension and the day-night dimension, and the response DN value of the typical ground object is calculated as a theoretical expected value according to the calibrated absolute responsivity;

[0059] The deviation of the statistical value and the theoretical expected value is compared, if the deviation is within 20%, no imaging mode adjustment is needed, otherwise the updated imaging mode is calculated according to the deviation and the calibrated absolute responsivity.

Claims

1. A method for constructing multi-dimensional on-orbit imaging modes for a space optical infrared camera, characterized in that, The method comprises the following steps: In the first step, the calibration absolute responsivity and the best response linear interval of the space optical infrared camera (2) are obtained; In the second step, a global land surface temperature, a global land surface emissivity and a global atmospheric profile database are obtained, the equivalent spectral radiance at the entrance pupil of the space optical infrared camera (2) is simulated and calculated in multiple dimensions, and a database of the equivalent spectral radiance at the entrance pupil of the space optical infrared camera (2) is established; In the second step, the dimensions include longitude, latitude, month and day and night; In the third step, the multi-dimensional on-orbit imaging mode of the space optical infrared camera (2) is constructed according to the database of the equivalent spectral radiance at the entrance pupil of the space optical infrared camera (2) and the calibration absolute responsivity of the space optical infrared camera (2), the space optical infrared camera (2) is caused to work in the best response linear interval, and the initial value of the multi-dimensional on-orbit imaging mode of the space optical infrared camera (2) is obtained; In the fourth step, after the space optical infrared camera (2) is launched into space, the multi-dimensional on-orbit imaging mode of the space optical infrared camera (2) is optimized according to the response characteristics of the space optical infrared camera (2) in the initial stage of the on-orbit operation; In the fourth step, after the space optical infrared camera (2) is launched into space, the response DN values of typical land surfaces in the initial stage of the on-orbit operation of the space optical infrared camera (2) and corresponding multi-dimensional information are counted; The equivalent spectral radiance at the entrance pupil of the space optical infrared camera (2) is calculated according to the multi-dimensional information, and the response DN value of the typical land surface is calculated as a theoretical expected value according to the calibration absolute responsivity; The deviation of the statistical value and the theoretical expected value is compared, if the deviation is within a reasonable range, the imaging mode adjustment is not needed, otherwise, the updated imaging mode is calculated according to the deviation and the calibration absolute responsivity.

2. The method of claim 1, wherein, In the first step, the calibration absolute responsivity and the best response linear interval of the space optical infrared camera (2) are obtained through infrared radiation calibration test by using a space optical infrared camera radiation calibration system; The space optical infrared camera radiation calibration system comprises a vacuum low-temperature environment simulation device (1), an infrared black body (3), a low-temperature baffle (4), a satellite comprehensive simulator (5) and an image data acquisition system (6), the vacuum low-temperature environment simulation device (1) provides a vacuum low-temperature environment for the space optical infrared camera (2), the space optical infrared camera (2), the infrared black body (3) and the low-temperature baffle (4) are arranged in the vacuum low-temperature environment simulation device (1), the infrared black body (3) provides simulated on-orbit land surface radiation for the space optical infrared camera (2), the low-temperature baffle (4) provides background radiation for the space optical infrared camera (2), the satellite comprehensive simulator (5) and the image data acquisition system (6) are connected with the space optical infrared camera (2), the satellite comprehensive simulator (5) injects suitable imaging parameters into the space optical infrared camera (4), and the image data acquisition system (6) acquires and stores image data of the space optical infrared camera (4).

3. The method of claim 2, wherein, The method of the infrared radiation calibration test is as follows: The infrared blackbody (3) is set as the lowest temperature T1 of the dynamic range of the space optical infrared camera (2), after the infrared blackbody (3) is stable, the low-temperature baffle (4) is cut out, the space optical infrared camera (2) saves the image of the infrared blackbody (3) and the image of the low-temperature baffle (4), and then the low-temperature baffle (4) is cut in, the space optical infrared camera (2) saves the image of the infrared blackbody (3) and the image of the low-temperature baffle (4); The temperature of the infrared blackbody (3) is set in sequence with a temperature interval of 5K until the highest temperature T2 of the dynamic range is reached, after the temperature is stable, the image of the infrared blackbody (3) and the image of the low-temperature baffle (4) saved by the space optical infrared camera (2) are collected respectively; The response DN values of the images of the infrared blackbody (3) and the low-temperature baffle (4) at different temperatures are counted, the radiation brightness of the infrared blackbody (3) and the low-temperature baffle (4) is calculated through the Planck formula , and the radiation calibration coefficients k and b are obtained through the least square method fitting. (Formula 2) (Formula 3) In formula 2 and formula 3, T is the temperature of the infrared blackbody (3); is the emissivity of the infrared blackbody (3); and are the start wavelength and the end wavelength, respectively, of the spatial optical infrared camera (2); λ is the wavelength of the space optical infrared camera (2); is the first radiation constant, ; is the second radiation constant, ; is the spectral response curve of the space optical infrared camera (2); is the integral radiance of the infrared blackbody (3) with temperature T and emissivity DN is the response value of the space optical infrared camera (2), k is the absolute response slope of the space optical infrared camera (2), and b is the absolute response slope of the space optical infrared camera (2).

4. The method of claim 1, wherein, In the second step, the granularity of the longitude dimension is 5 degrees, a total of 72 intervals; the granularity of the latitude dimension is 5 degrees, a total of 36 intervals; the granularity of the month dimension is 1 month, a total of 12 intervals; the day and night dimension is divided into two intervals with the positive and negative of the solar elevation angle as the criterion.

5. The method of claim 1, wherein, In the second step, the global surface temperature, global surface emissivity and global atmospheric profile database are substituted into the atmospheric radiation transmission software to calculate the equivalent spectral radiance of the entrance pupil of the space optical infrared camera (2).

6. The method of claim 1, wherein, In the second step, the databases are all mean value databases.

7. The method of claim 1, wherein, In the fourth step, the initial time is within one week of entering the orbit.

8. The method of claim 1, wherein, The reasonable range of the deviation is within 20%. The reasonable range of the deviation is within 20%.

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