A thermal infrared calibration method for low-frequency cold sky observations

Abstract

The present application relates to the field of infrared remote sensing cameras, and to a thermal infrared calibration method for low-frequency cold sky observations, the method comprising: obtaining satellite black body and cold sky data; calculating the rate of change of the radiation calibration coefficient according to the response value of the black body at different temperature points and the cold sky data; and calculating the first background response value or the second background response value according to the preset threshold of the radiation calibration coefficient. The present application can improve the radiation calibration accuracy of infrared remote sensing cameras that cannot frequently observe cold sky.

Description

Technical Field

[0001] The present invention relates to the field of infrared imaging, and in particular to the field of infrared remote sensing cameras. Background Art

[0002] The current radiometric calibration method is to update the linear coefficient of radiometric calibration with high frequency calibration. Radiometric calibration is to obtain data from various standard radiation sources, calculate the background response value, and solve the quantitative relationship between the spectral radiation brightness value at the entrance pupil of the imaging spectrometer and the digital quantization value output by the imaging spectrometer based on the background response value, so as to optimize the satellite earth observation image data. For example, the satellites Landsat 8 and GOES-R ABI are equipped with cold sky scene selection mirrors, which control the infrared remote sensing camera to observe black bodies and cold sky through the deflection of the scanning mechanism to complete the data acquisition of the radiation source. Since such satellites are equipped with cold sky scene selection mirrors, they can observe cold sky and black bodies frequently, and the changes in background response between two cold sky observations can be ignored, thereby realizing the update of the linear coefficient of radiometric calibration at high frequency.

[0003] However, for some satellites, due to their own structure, miniaturization and launch requirements, such satellites are not equipped with cold sky scene observation selection mirrors. Cold sky observation requires the satellite to swing sideways, and the frequency of cold sky observation is limited. Due to the fluctuation of the instrument temperature field, the instrument's own thermal radiation also fluctuates, resulting in errors in the target signal, affecting the quantitative accuracy of remote sensing data. Summary of the invention

[0004] The embodiments of the present application provide a thermal infrared calibration method for low-frequency cold sky observations, thereby solving the problems in the prior art of satellites that are not equipped with cold sky scene observation selection mirrors, limited cold sky observation frequency, and target signal errors caused by fluctuations in the instrument temperature field, thereby achieving the effect of improving the accuracy of remote sensing data.

[0005] The present application embodiment provides a thermal infrared calibration method for low-frequency cold sky observation, the method comprising:

[0006] Step 1, according to the number of days the satellite is in orbit and different temperature points of the black body, the response values ​​of the black body at different temperature points, the cold air response values ​​corresponding to the black body at different temperature points, and the black body response values ​​before the satellite observes the earth in each orbit, wherein the response values ​​of the black body at different temperature points include the response values ​​of the black body at a specified temperature, the black body response values ​​before the satellite observes the earth in each orbit include the response values ​​of the black body at a specified temperature before the satellite observes the earth in each orbit, and the specified temperature is set according to the situation of the satellite infrared detector;

[0007] Step 2, calculating the radiation calibration coefficient according to the response value of the black body at different temperature points and the cold air response value corresponding to the black body at different temperature points;

[0008] Step 3, calculating the rate of change of the radiation calibration coefficient according to the radiation calibration coefficient, if the rate of change of the radiation calibration coefficient is less than a threshold, executing step 4, otherwise executing step 5, the threshold is set according to the situation of the satellite infrared detector;

[0009] Step 4, calculating the first background response value according to the blackbody response value before each orbit of the satellite observes the earth, the last obtained response value of the blackbody at the specified temperature, and the last obtained cold air response value corresponding to the blackbody corresponding temperature point, and executing step 7;

[0010] Step 5: fitting the response function of the radiation calibration coefficient as the number of days the satellite is in orbit using the least squares method according to the radiation calibration coefficient;

[0011] Step 6, calculating a second background response value according to the response value of the black body at a specified temperature before each orbit of the earth observation and the response function of the radiation calibration coefficient changing with the number of days the satellite is in orbit;

[0012] Step 7: Using the first background response value or the second background response value to remove background response.

[0013] Furthermore, in the thermal infrared calibration method for low-frequency cold sky observation, the calculation of the radiation calibration coefficient further includes:

[0014] Calculate the theoretical value of the blackbody spectrum radiance, the calculation expression is:

[0015]

[0016] Where T is the black body surface temperature;

[0017] λ is a constant, which represents the wavelength of radiation used by a black body at temperature T;

[0018] ε is a constant representing the surface emissivity of the black body;

[0019] c1 and c2 are constants representing the first and second radiation constants respectively;

[0020] The theoretical value of the blackbody average spectral radiance is calculated according to the blackbody spectral radiance, and the corresponding expression is:

[0021]

[0022] Where T is the black body surface temperature;

[0023] λ1 and λ2 are constants, representing the starting wavelength and ending wavelength of the infrared channel of the imaging spectrometer;

[0024] R(λ) is the spectral response function;

[0025] The average spectral radiation brightness of the black body is fitted with the response value of the black body at different temperature points by using the least square method, and the radiation calibration coefficient is calculated.

[0026] Further, in the thermal infrared calibration method for low-frequency cold sky observation, the calculation expression of the first background response value is:

[0027] DN bg1 =DN Temp-BB-1 -DN Temp-BB-2 +DN bg last ;

[0028] Among them, DN bg1 represents the first background response value;

[0029] DN bg last Indicates the cold air response value corresponding to the blackbody corresponding temperature point finally obtained;

[0030] DN Temp-BB-1 represents the blackbody response value obtained last before the satellite observes the earth in each orbit;

[0031] DN Temp-BB-2 It represents the last obtained response value of the blackbody at the specified temperature.

[0032] Further, in the thermal infrared calibration method for low-frequency cold sky observation, the second background response value is calculated as:

[0033]

[0034] Among them, DN bg2 represents the second background response value;

[0035] DN Temp-BB-1 represents the blackbody response value obtained last before the satellite observes the earth in each orbit;

[0036] k(t) is the response function of the radiation calibration coefficient as the number of days the satellite is in orbit;

[0037] L is the theoretical value of the blackbody spectral radiance;

[0038] b is the intercept of the radiation calibration coefficient.

[0039] Furthermore, in the thermal infrared calibration method for low-frequency cold sky observation, the threshold is set to 1%.

[0040] Furthermore, in the thermal infrared calibration method for low-frequency cold sky observations, the different temperature points of the black body are set to 250K to 300K.

[0041] Furthermore, in the thermal infrared calibration method for low-frequency cold sky observations, the specified temperature is not higher than 250K.

[0042] The embodiment of the present application also provides a thermal infrared calibration system for low-frequency cold sky observation, including a memory and a processor;

[0043] The memory is used to store computer programs;

[0044] The processor is used to implement the thermal infrared calibration method for low-frequency cold sky observation when executing the computer program.

[0045] An embodiment of the present application further provides a computer-readable storage medium having a computer program stored thereon. When the computer program is executed by a processor, the thermal infrared calibration method for low-frequency cold sky observation is implemented.

[0046] The present application also provides a thermal infrared calibration device for low-frequency cold sky observation, including:

[0047] An acquisition module is used to acquire, according to the number of days the satellite is in orbit and different temperature points of the blackbody, the response values ​​of the blackbody at different temperature points, the cold air response values ​​corresponding to the blackbody at different temperature points, and the blackbody response values ​​before the satellite observes the earth in each orbit, wherein the response values ​​of the blackbody at different temperature points include the response values ​​of the blackbody at a specified temperature, the blackbody response values ​​before the satellite observes the earth in each orbit include the response values ​​of the blackbody at a specified temperature before the satellite observes the earth in each orbit, and the specified temperature is set according to the situation of the satellite infrared detector;

[0048] A first calculation module is used to calculate the radiation calibration coefficient based on the response value of the black body at different temperature points and the cold air response value corresponding to the black body at different temperature points;

[0049] A judgment module, which calculates the change rate of the radiation calibration coefficient according to the radiation calibration coefficient, and executes the second calculation module if the change rate of the radiation calibration coefficient is less than a threshold value, otherwise executes the fitting module, and the threshold value is set according to the situation of the satellite infrared detector;

[0050] A second calculation module calculates a first background response value and executes an application module according to the blackbody response value before the satellite observes the earth in each orbit, the last obtained response value of the blackbody at a specified temperature, and the last obtained cold air response value corresponding to the blackbody at a corresponding temperature point;

[0051] A fitting module, used to fit the response function of the radiation calibration coefficient changing with the number of days the satellite is in orbit by using the least square method according to the radiation calibration coefficient;

[0052] A third calculation module is used to calculate a second background response value according to the response value of the black body at a specified temperature before each orbit of the earth observation and the response function of the radiation calibration coefficient changing with the number of days the satellite is in orbit;

[0053] An application module is used for using the first background response value or the second background response value to remove background response.

[0054] One or more technical solutions provided in the embodiments of the present application have at least the following technical effects or advantages:

[0055] By adopting low-frequency cold sky observations to obtain instrument background basic data and high-frequency observations of black bodies combined with instrument temperature measurements to solve the changes in response values, we overcome the defects of reducing the number of cold sky observation scene selection mirrors on the satellite, the inability to observe cold sky at a high frequency, and the problem of target signal errors caused by fluctuations in the instrument temperature field, thereby improving the accuracy of satellite observation data. BRIEF DESCRIPTION OF THE DRAWINGS

[0056] The above invention content and the following specific embodiments of the present invention will be better understood when read in conjunction with the accompanying drawings. It should be noted that the accompanying drawings are only examples of the claimed invention. In the accompanying drawings, the same reference numerals represent the same or similar elements.

[0057] Figure 1 A method flow chart according to an embodiment of the present invention is shown;

[0058] Figure 2 A flow chart of a data collection process according to an embodiment of the present invention is shown;

[0059] Figure 3 A flowchart of a specific implementation process according to an embodiment of the present invention is shown. DETAILED DESCRIPTION

[0060] The detailed features and advantages of the present invention are described in detail in the specific implementation mode below, and the content is sufficient to enable any technical personnel in this field to understand the technical content of the present invention and implement it accordingly. According to the description, claims, and drawings disclosed in this specification, those skilled in the art can easily understand the relevant purposes and advantages of the present invention.

[0061] In order to solve the problems in the background technology, the present invention proposes a thermal infrared calibration method for low-frequency cold sky observation. Figure 1 , which shows a flow chart of a method 100 according to an embodiment of the present invention.

[0062] The method 100 includes: step 1, obtaining the response values ​​of the black body at different temperature points, the cold air response values ​​corresponding to the black body at different temperature points, and the black body response values ​​before the satellite observes the earth in each orbit according to the number of days the satellite is in orbit and the different temperature points of the black body, wherein the response values ​​of the black body at different temperature points include the response values ​​of the black body at a specified temperature, the black body response values ​​before the satellite observes the earth in each orbit include the response values ​​of the black body at a specified temperature before the satellite observes the earth in each orbit, and the specified temperature is set according to the situation of the satellite infrared detector.

[0063] The satellite observes the earth in a predetermined orbit, and collects data on the response value of the black body at a specified temperature before observing the earth in each orbit. In this embodiment, the specified temperature is preferably set to 250K, and the specified temperature is calculated based on the power consumption of the device.

[0064] The method 100 further includes: step 2, calculating the radiation calibration coefficient according to the response value of the black body at different temperature points and the cold air response value corresponding to the black body at different temperature points.

[0065] The step 2 of calculating the radiation calibration coefficient may include:

[0066] Calculate the theoretical value of the blackbody spectrum radiance, the calculation expression is:

[0067]

[0068] Where T is the black body surface temperature;

[0069] λ is a constant, which represents the wavelength of radiation used by a black body at temperature T;

[0070] ε is a constant representing the surface emissivity of the black body;

[0071] c1 and c2 are constants representing the first and second radiation constants respectively;

[0072] The theoretical value of the blackbody average spectral radiance is calculated based on the blackbody spectral radiance, and the corresponding expression is:

[0073]

[0074] Where T is the black body surface temperature;

[0075] λ1 and λ2 are constants, representing the starting wavelength and ending wavelength of the infrared channel of the imaging spectrometer;

[0076] R(λ) is the spectral response function;

[0077] It is worth noting that the constants and response functions in the above formulas can be obtained from the technical manual or the corresponding instruction manual of the spectrometer.

[0078] The average spectral radiation brightness of the black body and the response value of the black body at different temperature points are fitted using the least square method to solve the radiation calibration coefficient.

[0079] The method 100 also includes: step 3, calculating the rate of change of the radiation calibration coefficient according to the radiation calibration coefficient, if the rate of change of the radiation calibration coefficient is less than a threshold, executing step 4, otherwise executing step 5, the threshold is set according to the situation of the satellite infrared detector.

[0080] Among them, the threshold of the satellite infrared detector can be set according to the frequency of the satellite infrared detector observing the cold sky and the required observation accuracy.

[0081] The step 3, calculating the rate of change of the radiation calibration coefficient, specifically includes:

[0082] The radiation calibration coefficients obtained from multiple blackbody and cold sky calibration observations are counted. If the change rate of the radiation calibration coefficient k is less than 1%, the first background response value is directly calculated. If the change rate of the radiation calibration coefficient K is greater than 1%, it is necessary to calculate the response function of the radiation calibration coefficient changing with the number of days the satellite is in orbit.

[0083] The method 100 also includes: step 4, calculating the first background response value according to the blackbody response value before the satellite observes the earth in each orbit, the last obtained response value of the blackbody at the specified temperature, and the last obtained cold air response value corresponding to the blackbody corresponding temperature point, and executing step 7.

[0084] The step 4, calculating the first background response value, specifically includes:

[0085] DN bg1 =DN Temp-BB-1 -DN Temp-BB-2 +DN bg last ;

[0086] Among them, DN bg1 represents the first background response value;

[0087] DN bg last Indicates the cold air response value corresponding to the blackbody corresponding temperature point finally obtained;

[0088] DN Temp-BB-1 represents the blackbody response value obtained last before the satellite observes the earth in each orbit;

[0089] DN Temp-BB-2 It represents the last obtained response value of the blackbody at the specified temperature.

[0090] The calculated first background response value is used to analyze ground observation data.

[0091] The method 100 further includes: step 5, fitting the response function of the radiation calibration coefficient as the radiation calibration coefficient changes with the number of days the satellite is in orbit using the least square method according to the radiation calibration coefficient.

[0092] In one embodiment, the response function of the radiation calibration coefficient fitted by the least squares method with the change of the number of days the satellite is in orbit is:

[0093] k(t)=ln(kk*t)+bb;

[0094] In another embodiment, the response function of the radiation calibration coefficient fitted by the least squares method with the change of the number of days the satellite is in orbit is:

[0095] k(t)=e (-kk*t) +bb;

[0096] The method 100 also includes step 6, calculating a second background response value according to the response value of the black body at a specified temperature before each orbit of earth observation and the response function of the radiation calibration coefficient changing with the number of days the satellite is in orbit.

[0097] The step 6, calculating the second background response value specifically includes:

[0098]

[0099] Among them, DN bg2 represents the second background response value;

[0100] DN Temp-BB-1 represents the blackbody response value obtained last before the satellite observes the earth in each orbit;

[0101] k(t) is the response function of the radiation calibration coefficient as the number of days the satellite is in orbit;

[0102] L is the theoretical value of the blackbody spectral radiance;

[0103] b is the intercept in the radiation calibration coefficient.

[0104] The method 100 further includes, step 7, using the first background response value or the second background response value to remove background response.

[0105] The first background response value or the second background response value obtained is used to remove the background response. The step 7 further comprises:

[0106] The entrance pupil radiance is calculated using the background response value:

[0107] L=(DN earth -DN bg )×k(t)+b;

[0108] Where L is the entrance pupil radiance;

[0109] DN earth is the response value when the satellite observes the earth;

[0110] DN bg is the calculated first or second response value;

[0111] k(t) is the response function of the radiation calibration coefficient as the number of days the satellite is in orbit;

[0112] b is the intercept of the radiation calibration coefficient.

[0113] The entrance pupil equivalent brightness temperature can be obtained based on the calculated entrance pupil radiance, and the entrance pupil equivalent brightness temperature is used to remove background response and optimize satellite earth observation data.

[0114] like Figure 2 FIG. 1 is an example of a specific implementation process of step 1 of the method 100 of the present invention;

[0115] In the first step, the ground sends a command to heat up the black body, and the satellite controls the black body to heat up to 250K;

[0116] In the second step, the black body reaches the temperature point and stabilizes. The ground sends a command to control the satellite platform to swing sideways to image the cold sky and obtain the cold sky response value at the current temperature point.

[0117] In the third step, the satellite keeps its orientation to the cold sky. The ground sends a command, and the satellite controls the scanning mirror to rotate 90° at the zero point under the satellite to point to the black body, and collects the black body response value at the temperature point of 250K.

[0118] Step 4: Repeat steps 2 to 3 for 6 times, and finally complete the collection of blackbody response values ​​at six temperature points of 250K, 260K, 270K, 280K, 290K and 300K and cold air response values ​​at the corresponding temperatures;

[0119] In the fifth step, the calibration is completed, and the satellite transmits the collected blackbody response values ​​and cold sky response values ​​to the ground. A thermal infrared calibration method for low-frequency cold sky observation proposed in the present invention is used to process the calibration data to solve the background response value, which is used to remove the background response of the observation data.

[0120] Among them, the blackbody temperature change observation and cold sky observation are carried out every two weeks; the blackbody response value before each orbit observation is carried out in each orbit.

[0121] Figure 3 An embodiment of a specific operation process of a thermal infrared calibration method for low-frequency cold sky observation provided by the present invention;

[0122] The first step is to obtain the blackbody response value of variable temperature, the response value of cold sky observation, and the blackbody response value before each orbit observation;

[0123] The second step is to solve the radiation calibration coefficients k and b, and calculate the rate of change of the radiation calibration coefficient. Since the rate of change of the radiation calibration coefficient k in this embodiment exceeds the threshold, the relationship between the change of the black body response and time is fitted;

[0124] In the third step, the blackbody response values ​​at six temperature points of 250K, 260K, 270K, 280K, 290K and 300K are fitted to the function of the radiation calibration coefficient with the number of days on orbit. The function fitted by the least squares method in this embodiment is:

[0125] k(t)=e (-kk*t) +bb;

[0126] The fourth step is to fit the response function of the radiation calibration coefficient to the number of days the satellite is in orbit;

[0127] The radiation calibration coefficients at different temperature points are used to fit the response function of the radiation calibration coefficients as the number of days the satellite is in orbit using the least squares method;

[0128] The fifth step is to solve the background response value, entrance pupil radiation brightness and entrance pupil brightness temperature;

[0129] In the sixth step, the solved background response, entrance pupil radiation brightness and entrance pupil brightness temperature T response values ​​are used to remove the background response and optimize the satellite observation data.

[0130] In a preferred embodiment of the present application, a thermal infrared calibration system for low-frequency cold sky observation is also provided, comprising a memory and a processor;

[0131] The memory is used to store computer programs;

[0132] The processor is used to implement the thermal infrared calibration method for low-frequency cold sky observation when executing the computer program.

[0133] In addition, the present application also provides a computer-readable storage medium, on which a computer program is stored. When the computer program is executed by a processor, the thermal infrared calibration method for low-frequency cold sky observations is implemented.

[0134] The present application also provides a thermal infrared calibration device for low-frequency cold sky observation, including:

[0135] An acquisition module is used to acquire, according to the number of days the satellite is in orbit and different temperature points of the blackbody, the response values ​​of the blackbody at different temperature points, the cold air response values ​​corresponding to the blackbody at different temperature points, and the blackbody response values ​​before the satellite observes the earth in each orbit, wherein the response values ​​of the blackbody at different temperature points include the response values ​​of the blackbody at a specified temperature, the blackbody response values ​​before the satellite observes the earth in each orbit include the response values ​​of the blackbody at a specified temperature before the satellite observes the earth in each orbit, and the specified temperature is set according to the situation of the satellite infrared detector;

[0136] A first calculation module is used to calculate the radiation calibration coefficient based on the response value of the black body at different temperature points and the cold air response value corresponding to the black body at different temperature points;

[0137] A judgment module, which calculates the change rate of the radiation calibration coefficient according to the radiation calibration coefficient, and executes the second calculation module if the change rate of the radiation calibration coefficient is less than a threshold value, otherwise executes the fitting module, and the threshold value is set according to the situation of the satellite infrared detector;

[0138] A second calculation module calculates a first background response value and executes an application module according to the blackbody response value before the satellite observes the earth in each orbit, the last obtained response value of the blackbody at a specified temperature, and the last obtained cold air response value corresponding to the blackbody at a corresponding temperature point;

[0139] A fitting module, used to fit the response function of the radiation calibration coefficient changing with the number of days the satellite is in orbit by using the least square method according to the radiation calibration coefficient;

[0140] A third calculation module is used to calculate a second background response value according to the response value of the black body at a specified temperature before each orbit of the earth observation and the response function of the radiation calibration coefficient changing with the number of days the satellite is in orbit;

[0141] An application module is used for using the first background response value or the second background response value to remove background response.

[0142] By adopting low-frequency cold sky observations to obtain instrument background basic data and high-frequency observations of black bodies combined with instrument temperature measurements to solve the changes in response values, we overcome the defects of reducing the number of cold sky observation scene selection mirrors on the satellite, the inability to observe cold sky at a high frequency, and the problem of target signal errors caused by fluctuations in the instrument temperature field, thereby improving the accuracy of satellite observation data.

[0143] As shown in this application and claims, unless the context clearly indicates an exception, the words "a", "an", "an" and / or "the" do not refer to the singular and may also include the plural. Generally speaking, the terms "include" and "comprise" only indicate the inclusion of the steps and elements that have been clearly identified, and these steps and elements do not constitute an exclusive list. The method or device may also include other steps or elements.

[0144] Those skilled in the art will appreciate that information, signals, and data may be represented using any of a variety of different technologies and techniques. For example, data, instructions, commands, information, signals, bits, symbols, and chips cited throughout the above description may be represented by voltage, current, electromagnetic waves, magnetic fields or magnetic particles, optical fields or optical particles, or any combination thereof.

[0145] Those skilled in the art will further appreciate that the various illustrative logic blocks, modules, circuits, and algorithm steps described in conjunction with the embodiments disclosed herein may be implemented as electronic hardware, computer software, or a combination of the two. To clearly illustrate this interchangeability of hardware and software, various illustrative components, blocks, modules, circuits, and steps are generally described above in terms of their functionality. Whether such functionality is implemented as hardware or software depends on the specific application and the design constraints imposed on the overall system. The technician may implement the described functionality in different ways for each specific application, but such implementation decisions should not be interpreted as resulting in a departure from the scope of the present invention.

[0146] The various illustrative logic modules and circuits described in conjunction with the embodiments disclosed herein may be implemented or executed with a general purpose processor, a digital signal processor (DSP), an application specific integrated circuit (ASIC), a field programmable gate array (FPGA) or other programmable logic device, discrete gate or transistor logic, discrete hardware components, or any combination thereof designed to perform the functions described herein. A general purpose processor may be a microprocessor, but in the alternative, the processor may be any conventional processor, controller, microcontroller, or state machine. The processor may also be implemented as a combination of computing devices, such as a combination of a DSP and a microprocessor, a plurality of microprocessors, one or more microprocessors in cooperation with a DSP core, or any other such configuration.

[0147] The steps of the method or algorithm described in conjunction with the embodiments disclosed herein may be embodied directly in hardware, in a software module executed by a processor, or in a combination of the two. The software module may reside in a RAM memory, a flash memory, a ROM memory, an EPROM memory, an EEPROM memory, a register, a hard disk, a removable disk, a CD-ROM, or any other form of storage medium known in the art. An exemplary storage medium is coupled to a processor so that the processor can read and write information from / to the storage medium. In an alternative, a storage medium may be integrated into a processor. The processor and the storage medium may reside in an ASIC. The ASIC may reside in a user terminal. In an alternative, the processor and the storage medium may reside in a user terminal as discrete components.

[0148] In one or more exemplary embodiments, the functions described may be implemented in hardware, software, firmware, or any combination thereof. If implemented as a computer program product in software, each function may be stored on or transmitted by a computer-readable medium as one or more instructions or codes. Computer-readable media include both computer storage media and communication media, including any medium that facilitates the transfer of a computer program from one place to another. Storage media may be any available medium that can be accessed by a computer. As an example and not limitation, such a computer-readable medium may include RAM, ROM, EEPROM, CD-ROM or other optical disk storage, disk storage or other magnetic storage device, or any other medium that can be used to carry or store the desired program code in the form of an instruction or data structure and can be accessed by a computer. Any connection is also properly referred to as a computer-readable medium. For example, if the software is transmitted from a website, a server, or other remote source using a coaxial cable, a fiber optic cable, a twisted pair, a digital subscriber line (DSL), or wireless technologies such as infrared, radio, and microwaves, the coaxial cable, fiber optic cable, twisted pair, DSL, or wireless technologies such as infrared, radio, and microwaves are included in the definition of the medium. Disk and disc as used herein include compact disc (CD), laser disc, optical disc, digital versatile disc (DVD), floppy disk and Blu-ray disc, wherein disk often reproduces data magnetically, while disc reproduces data optically with lasers. Combinations of the above should also be included within the scope of computer-readable media.

[0149] The above embodiments are provided for persons familiar with the art to implement or use the present invention. Personnel familiar with the art can make various modifications or changes to the above embodiments without departing from the inventive concept of the present invention. Therefore, the protection scope of the present invention is not limited to the above embodiments, but should be the maximum scope of the innovative features mentioned in the claims.

Claims

1. A thermal infrared calibration method for low-frequency cold sky observations, characterized in that: The method comprises: Step 1, according to the number of days the satellite is in orbit and different temperature points of the black body, the response values ​​of the black body at different temperature points, the cold air response values ​​corresponding to the black body at different temperature points, and the black body response values ​​before the satellite observes the earth in each orbit, wherein the response values ​​of the black body at different temperature points include the response values ​​of the black body at a specified temperature, the black body response values ​​before the satellite observes the earth in each orbit include the response values ​​of the black body at a specified temperature before the satellite observes the earth in each orbit, and the specified temperature is set according to the situation of the satellite infrared detector; Step 2, calculating the radiation calibration coefficient according to the response value of the black body at different temperature points and the cold air response value corresponding to the black body at different temperature points; Step 3, calculating the rate of change of the radiation calibration coefficient according to the radiation calibration coefficient, if the rate of change of the radiation calibration coefficient is less than a threshold, executing step 4, otherwise executing step 5, the threshold is set according to the situation of the satellite infrared detector; Step 4, calculating the first background response value according to the blackbody response value before each orbit of the satellite observes the earth, the last obtained response value of the blackbody at the specified temperature, and the last obtained cold air response value corresponding to the blackbody corresponding temperature point, and executing step 7; Step 5: fitting the response function of the radiation calibration coefficient as the number of days the satellite is in orbit using the least squares method according to the radiation calibration coefficient; Step 6, calculating a second background response value according to the response value of the black body at a specified temperature before each orbit of the earth observation and the response function of the radiation calibration coefficient changing with the number of days the satellite is in orbit; Step 7: Using the first background response value or the second background response value to remove background response; Wherein, the radiation calibration coefficient calculation further includes: Calculate the theoretical value of the blackbody spectrum radiance, the calculation expression is: Where T is the black body surface temperature; λ is a constant, which represents the wavelength of radiation used by a black body at temperature T; ε is a constant representing the surface emissivity of the black body; c1 and c2 are constants representing the first and second radiation constants respectively; The theoretical value of the blackbody average spectral radiance is calculated according to the blackbody spectral radiance, and the corresponding expression is: Where T is the black body surface temperature; λ1 and λ2 are constants, representing the starting wavelength and ending wavelength of the infrared channel of the imaging spectrometer; R(λ) is the spectral response function; The average spectral radiation brightness of the black body is fitted with the response value of the black body at different temperature points by using the least square method to solve the radiation calibration coefficient; The calculation expression of the first background response value is: DN bg1 =DN Temp-BB-1 -DN Temp-BB-2 +DN bglast ; Among them, DN bg1 represents the first background response value; DN bglast Indicates the cold air response value corresponding to the blackbody corresponding temperature point finally obtained; DN Temp-BB-1 represents the blackbody response value obtained last before the satellite observes the earth in each orbit; DN Temp-BB-2 represents the response value of the black body at the specified temperature obtained last; The second background response value is calculated as follows: Wherein, DNbg2 represents the second background response value; DN Temp-BB-1 represents the blackbody response value obtained last before the satellite observes the earth in each orbit; k(t) is the response function of the radiation calibration coefficient as the number of days the satellite is in orbit; L is the theoretical value of the blackbody spectral radiance; b is the intercept of the radiation calibration coefficient.

2. The thermal infrared calibration method for low-frequency cold sky observation according to claim 1 is characterized in that: The threshold is set to 1%.

3. The thermal infrared calibration method for low-frequency cold sky observation according to claim 1 is characterized in that: The different temperature points of the black body are set to be 250K to 300K.

4. The thermal infrared calibration method for low-frequency cold sky observation according to claim 1 is characterized in that: The specified temperature is not higher than 250K.

5. A thermal infrared calibration system for low-frequency cold sky observations, characterized in that: including memory and processor; The memory is used to store computer programs; The processor is used to implement the thermal infrared calibration method for low-frequency cold sky observation as described in any one of claims 1 to 4 when executing the computer program.

6. A computer-readable storage medium, characterized in that: The storage medium stores a computer program, and when the computer program is executed by the processor, the thermal infrared calibration method for low-frequency cold sky observation according to any one of claims 1 to 4 is implemented.

7. A thermal infrared calibration device for low-frequency cold sky observation, characterized in that: include: An acquisition module is used to acquire, according to the number of days the satellite is in orbit and different temperature points of the blackbody, the response values ​​of the blackbody at different temperature points, the cold air response values ​​corresponding to the blackbody at different temperature points, and the blackbody response values ​​before the satellite observes the earth in each orbit, wherein the response values ​​of the blackbody at different temperature points include the response values ​​of the blackbody at a specified temperature, the blackbody response values ​​before the satellite observes the earth in each orbit include the response values ​​of the blackbody at a specified temperature before the satellite observes the earth in each orbit, and the specified temperature is set according to the situation of the satellite infrared detector; A first calculation module is used to calculate the radiation calibration coefficient based on the response value of the black body at different temperature points and the cold air response value corresponding to the black body at different temperature points; A judgment module, which calculates the change rate of the radiation calibration coefficient according to the radiation calibration coefficient, and executes the second calculation module if the change rate of the radiation calibration coefficient is less than a threshold value, otherwise executes the fitting module, and the threshold value is set according to the situation of the satellite infrared detector; A second calculation module calculates a first background response value and executes an application module according to the blackbody response value before the satellite observes the earth in each orbit, the last obtained response value of the blackbody at a specified temperature, and the last obtained cold air response value corresponding to the blackbody at a corresponding temperature point; A fitting module, used to fit the response function of the radiation calibration coefficient changing with the number of days the satellite is in orbit by using the least square method according to the radiation calibration coefficient; A third calculation module is used to calculate a second background response value according to the response value of the black body at a specified temperature before each orbit of the earth observation and the response function of the radiation calibration coefficient changing with the number of days the satellite is in orbit; an application module, configured to use the first background response value or the second background response value to remove background response; Wherein, the radiation calibration coefficient calculation further includes: Calculate the theoretical value of the blackbody spectrum radiance, the calculation expression is: Where T is the black body surface temperature; λ is a constant, which represents the wavelength of radiation used by a black body at temperature T; ε is a constant representing the surface emissivity of the black body; c1 and c2 are constants representing the first and second radiation constants respectively; The theoretical value of the blackbody average spectral radiance is calculated according to the blackbody spectral radiance, and the corresponding expression is: Where T is the black body surface temperature; λ1 and λ2 are constants, representing the starting wavelength and ending wavelength of the infrared channel of the imaging spectrometer; R(λ) is the spectral response function; The average spectral radiation brightness of the black body is fitted with the response value of the black body at different temperature points by using the least square method to solve the radiation calibration coefficient; The calculation expression of the first background response value is: DN bg1 =DN Temp-BB-1 -DN Temp-BB-2 +DN bglast ; Among them, DN bg1 represents the first background response value; DN bglast Indicates the cold air response value corresponding to the blackbody corresponding temperature point finally obtained; DN Temp-BB-1 represents the blackbody response value obtained last before the satellite observes the earth in each orbit; DN Temp-BB-2 represents the response value of the black body at the specified temperature obtained last; The second background response value is calculated as follows: Wherein, DNbg2 represents the second background response value; DN Temp-BB-1 represents the blackbody response value obtained last before the satellite observes the earth in each orbit; k(t) is the response function of the radiation calibration coefficient as the number of days the satellite is in orbit; L is the theoretical value of the blackbody spectral radiance; b is the intercept of the radiation calibration coefficient.

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