CN112699533A - Observation simulation method of high infrared spectrometer of geostationary satellite - Google Patents
Observation simulation method of high infrared spectrometer of geostationary satellite Download PDFInfo
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Abstract
The invention discloses an observation simulation method of a geostationary satellite infrared high-speed spectrometer, which utilizes a radiation transmission mode RTTOV to obtain entrance pupil energy and bright temperature; obtaining an ideal interference pattern and an ideal spectrogram according to the Nyquist sampling theorem and the laser sampling frequency of the infrared high-speed spectrograph of the geostationary satellite, and calculating an ideal brightness temperature; adding an off-axis effect on the basis of the ideal spectrogram to obtain a spectrum containing the off-axis effect, and obtaining a corresponding brightness temperature through a Planck function; calculating to obtain an interferogram and a spectrogram which are actually measured and contain nonlinear influence due to the quadratic nonlinear relation between the input light intensity and the output light intensity, and calculating to obtain the corresponding brightness temperature; and respectively carrying out nonlinear correction and off-axis correction on the basis of the generated simulation data, and analyzing the error between the corrected brightness temperature and the ideal brightness temperature by comparison. The observation simulation method of the geostationary satellite infrared high-speed spectrometer provided by the invention has the advantages of clear physical process, simplicity and feasibility, and the reliability is demonstrated through error analysis.
Description
Technical Field
The invention relates to the technical field of infrared hyperspectral interferometers, in particular to an observation simulation method of a geostationary satellite infrared hyperspectral spectrometer.
Background
The high spectral resolution of the infrared hyperspectral interferometer has obvious advantages in monitoring of atmospheric temperature and humidity profiles, and the accuracy of numerical weather forecast is obviously improved. The infrared high-spectrum spectrometer with the static orbit can obtain frequent observation atmosphere, and is an important direction for the development of the infrared high-spectrum interferometer. FY-4A GIIRS is the first stationary orbit infrared hyperspectral interferometer in the world, FY-4B will also be launched in 2020, and GIIRS is still an important load carried by the GIIRS. After the satellite is on the day, due to the change of the environment of the satellite, the parameters of the instrument can change, radiation errors are caused, the inversion accuracy of atmospheric temperature and humidity profiles is reduced, and the accuracy of numerical weather forecast is further influenced. In order to better perform on-orbit monitoring on the instrument, the generated simulation data and the monitoring experience of the FY-4A GIIRS are combined, so that the possible on-orbit condition can be better predicted, and the radiation error analysis can be better performed. In order to better and more quickly analyze the radiation error change from the FY-4B instrument in-orbit state and trace the error source, the establishment of simulation data is an extremely important step.
Disclosure of Invention
The invention aims to provide an observation simulation method of a geostationary satellite infrared high-speed spectrometer, which is based on the real physical parameters of the geostationary satellite infrared high-speed spectrometer, utilizes a radiation transmission mode to simulate and obtain real entrance pupil energy, sequentially considers the off-axis effect and the nonlinear effect of the spectrometer, finally obtains interferogram data, sequentially performs nonlinear correction and off-axis correction, completely describes the physical process of the spectrometer by comparing the entrance pupil energy and the corrected radiation brightness, is accurate and clear in physical process, and is simple and feasible.
In order to achieve the purpose, the invention provides the following scheme:
an observation simulation method of a geostationary satellite infrared high-speed spectrometer comprises the following steps:
s1, obtaining simulated entrance pupil energy by using an RTTOV (real time optical over glass) fast radiation transmission mode according to the real pixel position information, and calculating to obtain a corresponding bright temperature BT _0 by using a Planck function;
s2, calculating an ideal interferogram I obtained by sampling entrance pupil energy through an instrument according to the Nyquist sampling theorem and the laser sampling frequency of the geostationary satellite infrared high-speed spectrometer, obtaining an ideal spectrum B after Fourier transform, and obtaining a corresponding ideal bright temperature BT _1 through a Planck function;
s3, adding a self-apodization matrix on the basis of the ideal spectrum B to obtain an interference pattern I _ lz with an off-axis effect, a spectrum B _ lz and a brightness temperature BT _ 2;
s4, calculating an interference pattern I _ lz _ nl, a spectrogram B _ lz _ nl and a brightness temperature BT _3 with nonlinear influence based on the quadratic nonlinear relation between the input light intensity and the output light intensity;
s5, selecting wavelet number segments to estimate nonlinear coefficients, and calculating an interferogram, a spectrogram and a brightness temperature BT _4 after nonlinear correction;
s6, performing off-axis correction on the interferogram, the spectrogram and the bright temperature BT _4 after the nonlinear influence correction based on an inverse matrix of the auto-apodization matrix to obtain an interferogram I _ cnl _ clz, a spectrogram B _ cnl _ clz and a bright temperature BT _5 which are subjected to the nonlinear correction and the off-axis correction; and comparing and analyzing the corrected bright temperature BT _5 with the ideal bright temperature BT _1, and representing the reliability of the simulation process through the bright temperature difference.
Optionally, in step S2, according to the nyquist sampling theorem and the laser sampling frequency of the geostationary satellite infrared high-speed spectrometer, an ideal interferogram I obtained by sampling the entrance pupil energy with an instrument is calculated, an ideal spectrum B is obtained after fourier transform, and a corresponding ideal bright temperature BT _1 is obtained through the planck function, which specifically includes:
the maximum optical path difference of the infrared high-speed spectrograph of the geostationary satellite is set to be L, sampling is controlled by a laser, a group of discrete sampling points are obtained, the Nyquist sampling principle is met, the laser sampling interval is delta x, and the number of sampling points is N on the premise of bilateral sampling:
the corresponding spectral sampling resolution Δ σ is:
due to the discretization sampling, the restored spectrum B [ n ] after the Fourier transform discretization is:
the discretized interferogram I [ k ] is:
where n is the nth point in the spectral domain and k is the kth sampling point in the interferogram.
Optionally, in step S3, the auto-apodization matrix is calculated according to the instrument parameters of the geostationary satellite infrared high-speed spectrometer, and specifically includes:
according to the real physical parameters of the infrared high-spectrum instrument of the geostationary satellite, the central coordinate (x) of each probe element is calculatedc，yc) Combining the length and width A and B of the probe element to obtain the distances from four angular points of the square probe element to the center of the focal plane, and recording as r according to the distancemin、rc1、rc2And rmax，rminIs the distance, r, from the center of the focal plane to the lower left corner of the probe elementmaxIs the distance, r, from the center of the focal plane to the upper right corner of the probe elementc1And rc2Is the distance from the center of the focal plane to the upper left corner point and the lower right corner point, and r is the distance from the center of the focal plane to the upper left corner point and the lower right corner point due to the different positions of the probe elements on the focal planec1And rc2The linear function represents the spectral response of the probe element, and is defined as the normalization of the opening angle corresponding to the arc intercepted by the probe element on the focal plane, and is expressed as follows:
wherein alpha is1Angle alpha between the arc of finger probe and y axis2The included angle between the arc intercepted by the finger probe element and the x axis; let rc1<rc2The linear function of the probe element is expressed as a piecewise function:
because the optical path difference is limited, the actual interferogram is expressed by multiplying a rectangular truncation function in an interferogram form relative to an infinite optical path, the actual interferogram is expressed by convolution with a sinc function in a spectrum, and the ILS and the sinc function form an auto-intercept matrix SA:
SA＝ILS*sinc (9)
optionally, in the step S3, on the basis of the ideal spectrum B, a self-apodization matrix is added to obtain a spectrogram B _ lz, an interferogram I _ lz and a brightness temperature BT _2 with an off-axis effect, which specifically includes:
spectrum B _ lz is:
B_lz＝SA*B (10)
the interferogram I _ lz is calculated based on equations (6) and (10) as:
optionally, in step S4, calculating an interferogram I _ lz _ nl, a spectrogram B _ lz _ nl and a brightness temperature BT _3 with nonlinear influence based on a quadratic nonlinear relationship between the input light intensity and the output light intensity, specifically including:
the interference pattern I _ lz _ nl comprises a direct current signal V and an alternating current signal I, and because the input light intensity and the output light intensity are in a quadratic nonlinear relation, the input signal is marked as an ideal signal and V is usediAnd IiIndicating that the output signal is the actual measurement signal, denoted by VmAnd ImExpressed as follows:
Vi+Ii＝Vm+Im+a2(Vm+Im)2 (12)
and obtaining an expression of actually measured light intensity for the above expression conversion form:
Vm+Im＝Vi+Ii-a2(Vm+Im)2 (13)
and removing the direct current components at the two sides of the above formula, simplifying the above formula into:
Im＝Im-2a2Ii·Vi-a2Ii 2 (14)
wherein, a2For the initial nonlinear coefficient, an interferogram I _ lz _ nl and a spectrogram B _ lz _ nl containing nonlinear influence can be obtained based on equation 14
I_lz_nl＝I_lz-2α2·I_lz·V-α2·I_lz2 (15)
Where I _ lz is the simulated interferogram containing the off-axis effect and V is the corresponding DC component.
Optionally, in step S5, selecting a wavelet coefficient segment to estimate a nonlinear coefficient, and calculating a nonlinear-corrected interferogram, a spectrogram and a brightness temperature BT _4, specifically including:
the dc term is removed and fourier transformed for equation (12), which is expressed as:
the ideal spectrum should be 0 out of band, then the spectrum outside the selected mid and long wave band should theoretically be 0, the small wave band is less disturbed, 50-300cm-1 is often selected as the estimated nonlinear coefficient:
then:
and (4) after the nonlinear coefficient is estimated, substituting the nonlinear coefficient into the formula (14) to obtain a nonlinear corrected interference pattern I _ cnl, and obtaining a spectrogram B _ cnl and a corresponding brightness temperature BT _4 through Fourier transformation.
Optionally, in step S6, the off-axis correction of the interferogram, the spectrogram, and the bright temperature BT _4 after the nonlinear influence correction based on the inverse matrix of the self-apodization matrix specifically includes:
from the formula (10), when off-axis correction is performed, the corrected interferogram I _ cnl _ clz and spectrogram B _ cnl _ clz can be obtained by multiplying the inverse matrix of the self-cutting matrix:
the corrected interferogram I _ cnl _ clz is calculated according to formula (21):
the spectrogram B _ cnl _ clz was calculated according to equation (22):
B_cnl_clz＝SA-1*B_cnl (22)
according to the specific embodiment provided by the invention, the invention discloses the following technical effects: the invention provides an observation simulation method of a geostationary satellite infrared high-speed spectrometer, which comprises the steps of firstly calculating entrance pupil radiance and brightness temperature by utilizing a radiation transmission mode RTTOV based on instrument index parameters; the method comprises the following steps that (1) interference occurs after a light source enters an interferometer, an ideal interference pattern and an ideal spectrogram are obtained through laser sampling discretization, and an ideal brightness temperature is calculated; adding an off-axis effect on the basis of an ideal spectrogram, wherein the off-axis effect is mainly generated by an extended light source, calculating to obtain a spectral response function of each probe element based on the position of the probe element on a focal plane to obtain a self-apodization matrix to obtain a spectrum containing the off-axis effect, and simultaneously obtaining the brightness temperature containing the off-axis effect by using a Planck function; calculating to obtain an interferogram and a spectrogram which are actually measured and contain nonlinear influence due to the quadratic nonlinear relation between the input light intensity and the output light intensity, and calculating to obtain the brightness temperature; on the basis of the generated simulation data, nonlinear correction and off-axis correction are respectively carried out, and the error between the corrected brightness temperature and the ideal brightness temperature is about 10-3K through comparison, so that the feasible reliability of the method is demonstrated.
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In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings needed to be used in the embodiments will be briefly described below, and it is obvious that the drawings in the following description are only some embodiments of the present invention, and it is obvious for those skilled in the art to obtain other drawings without inventive exercise.
FIG. 1 is a flow chart of an observation simulation method of a geostationary satellite infrared high-speed spectrometer according to an embodiment of the present invention;
FIG. 2 is the error between the entrance pupil bright temperature and the ideal bright temperature after instrument sampling;
FIG. 3 is a graph of the error between an ideal bright temperature and a bright temperature including an off-axis effect;
FIG. 4 is a graph of the effect of adding a non-linear effect on the brightness temperature error;
FIG. 5 is a photograph of a nonlinear stitch against a bright temperature error;
FIG. 6 is an illustration of the effect of off-axis stapling on bright temperature error;
fig. 7 is an error analysis of the corrected brightness temperature and the ideal brightness temperature.
Detailed Description
The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
The invention aims to provide an observation simulation method of a geostationary satellite infrared high-speed spectrometer, which is based on the real physical parameters of the geostationary satellite infrared high-speed spectrometer, utilizes a radiation transmission mode to simulate and obtain real entrance pupil energy, sequentially considers the off-axis effect and the nonlinear effect of the spectrometer, finally obtains interferogram data, sequentially performs nonlinear correction and off-axis correction, completely describes the physical process of the spectrometer by comparing the entrance pupil energy and the corrected radiation brightness, is accurate and clear in physical process, and is simple and feasible.
In order to make the aforementioned objects, features and advantages of the present invention comprehensible, embodiments accompanied with figures are described in further detail below.
As shown in fig. 1, the observation simulation method of the geostationary satellite infrared high-speed spectrometer provided by the invention comprises the following steps:
s1, obtaining simulated entrance pupil energy by using an RTTOV (real time optical over glass) fast radiation transmission mode according to the real pixel position information, and calculating to obtain a corresponding bright temperature BT _0 by using a Planck function;
s2, calculating an ideal interferogram I obtained by sampling entrance pupil energy through an instrument according to the Nyquist sampling theorem and the laser sampling frequency of the geostationary satellite infrared high-speed spectrometer, obtaining an ideal spectrum B after Fourier transform, and obtaining a corresponding ideal bright temperature BT _1 through a Planck function;
s3, adding a self-apodization matrix on the basis of the ideal spectrum B to obtain an interference pattern I _ lz with an off-axis effect, a spectrum B _ lz and a brightness temperature BT _ 2;
s4, calculating an interference pattern I _ lz _ nl, a spectrogram B _ lz _ nl and a brightness temperature BT _3 with nonlinear influence based on the quadratic nonlinear relation between the input light intensity and the output light intensity;
s5, selecting wavelet number segments to estimate nonlinear coefficients, and calculating an interferogram, a spectrogram and a brightness temperature BT _4 after nonlinear correction;
s6, performing off-axis correction on the interferogram, the spectrogram and the bright temperature BT _4 after the nonlinear influence correction based on an inverse matrix of the auto-apodization matrix to obtain an interferogram I _ cnl _ clz, a spectrogram B _ cnl _ clz and a bright temperature BT _5 which are subjected to the nonlinear correction and the off-axis correction; and comparing and analyzing the corrected bright temperature BT _5 with the ideal bright temperature BT _1, and representing the reliability of the simulation process through the bright temperature difference.
In step S2, according to the nyquist sampling theorem and the laser sampling frequency of the geostationary satellite infrared high-speed spectrometer, an ideal interferogram I obtained by sampling the entrance pupil energy with an instrument is calculated, an ideal spectrum B is obtained after fourier transform, and a corresponding ideal bright temperature BT _1 is obtained through the planck function, which specifically includes:
the maximum optical path difference of the infrared high-speed spectrograph of the geostationary satellite is set to be L, sampling is controlled by a laser, a group of discrete sampling points are obtained, the Nyquist sampling principle is met, the laser sampling interval is delta x, and the number of sampling points is N on the premise of bilateral sampling:
the corresponding spectral sampling resolution Δ σ is:
due to the discretization sampling, the restored spectrum B [ n ] after the Fourier transform discretization is:
the discretized interferogram I [ k ] is:
where n is the nth point in the spectral domain and k is the kth sampling point in the interferogram.
In the step S3, the auto-apodization matrix is calculated according to the instrument parameters of the geostationary satellite infrared hyperspectral spectrometer, and specifically includes:
according to the real physical parameters of the infrared high-spectrum instrument of the geostationary satellite, the central coordinate (x) of each probe element is calculatedc，yc) Combining the length and width A and B of the probe element to obtain four angular points of the square probe elementThe distance of the focal plane center is respectively recorded as r according to the distancemin、rc1、rc2And rmax，rminIs the distance, r, from the center of the focal plane to the lower left corner of the probe elementmaxIs the distance, r, from the center of the focal plane to the upper right corner of the probe elementc1And rc2Is the distance from the center of the focal plane to the upper left corner point and the lower right corner point, and r is the distance from the center of the focal plane to the upper left corner point and the lower right corner point due to the different positions of the probe elements on the focal planec1And rc2The linear function represents the spectral response of the probe element, and is defined as the normalization of the opening angle corresponding to the arc intercepted by the probe element on the focal plane, and is expressed as follows:
wherein alpha is1Angle alpha between the arc of finger probe and y axis2The included angle between the arc intercepted by the finger probe element and the x axis; let rc1<rc2The linear function of the probe element is expressed as a piecewise function:
because the optical path difference is limited, the actual interferogram is expressed by multiplying a rectangular truncation function in an interferogram form relative to an infinite optical path, the actual interferogram is expressed by convolution with a sinc function in a spectrum, and the ILS and the sinc function form an auto-intercept matrix SA:
SA＝ILS*sinc (9)
in the step S3, on the basis of the ideal spectrum B, a self-apodization matrix is added to obtain a spectrogram B _ lz, an interferogram I _ lz and a brightness temperature BT _2 with an off-axis effect, which specifically includes:
spectrum B _ lz is:
B_lz＝SA*B (10)
the interferogram I _ lz is calculated based on equations (6) and (10) as:
in step S4, calculating an interferogram I _ lz _ nl, a spectrogram B _ lz _ nl and a brightness temperature BT _3 having nonlinear effects based on a quadratic nonlinear relationship between the input light intensity and the output light intensity, specifically including:
the interference pattern I _ lz _ nl comprises a direct current signal V and an alternating current signal I, and because the input light intensity and the output light intensity are in a quadratic nonlinear relation, the input signal is marked as an ideal signal and V is usediAnd IiIndicating that the output signal is the actual measurement signal, denoted by VmAnd ImExpressed as follows:
Vi+Ii＝Vm+Im+a2(Vm+Im)2 (12)
and obtaining an expression of actually measured light intensity for the above expression conversion form:
Vm+Im＝Vi+Ii-a2(Vm+Im)2 (13)
and removing the direct current components at the two sides of the above formula, simplifying the above formula into:
Im＝Im-2a2Ii·Vi-a2Ii 2 (14)
wherein, a2For the initial nonlinear coefficient, an interferogram I _ lz _ nl and a spectrogram B _ lz _ nl containing nonlinear influence can be obtained based on equation 14
I_lz_nl＝I_lz-2α2·I_lz·V-α2·I_lz2 (15)
Where I _ lz is the simulated interferogram containing the off-axis effect and V is the corresponding DC component.
In the simulation calculation, three target ground objects are calculated, namely a ground target (es), a cold air target (ds) and an inner blackbody target (ict). In the simulation process of the off-axis effect, the calculation processes of three target ground objects are the same, and a spectrogram B and an interferogram I containing the off-axis effect are respectively calculated according to a formula (10) and a formula (11) and are respectively marked as Ids _ lz, Bds _ lz, Ies _ lz, Bes _ lz, Iict _ lz and Bict _ lz. As shown in the formula (15), in the process of adding the nonlinear effect, as shown in the formula (15), the required ground is required to be according to the target interferogram (I _ lz) and the nonlinear coefficient a2And a target direct current voltage V, wherein the three parameters need to be calculated respectively aiming at the three targets, particularly V, the direct current voltage of the cold air can be considered as a background value, the maximum value of the interference pattern is usually taken, and the direct current voltages of the ground target and the inner black body target need to be calculated according to the formula (17). As shown in equation (17), the dc voltage V _ es of the ground target needs to be solved by the difference sum calculation of the cold-air dc voltage V _ ds and the ground target spectrum Bes _ lz and the cold-air spectrum Bds _ lz.
In order to verify the reliability of the simulation process, the nonlinear correction is performed on the basis of the generated data containing the off-axis effect and the nonlinear effect, in step S5, a wavelet coefficient segment is selected to estimate a nonlinear coefficient, and an interferogram, a spectrogram and a brightness temperature BT _4 after the nonlinear correction are calculated, specifically including:
the dc term is removed and fourier transformed for equation (12), which is expressed as:
the ideal spectrum should be 0 out of band, then the spectrum outside the selected mid and long wave band should theoretically be 0, the small wave band is less disturbed, 50-300cm-1 is often selected as the estimated nonlinear coefficient:
then:
and (4) after the nonlinear coefficient is estimated, substituting the nonlinear coefficient into the formula (14) to obtain a nonlinear corrected interference pattern I _ cnl, and obtaining a spectrogram B _ cnl and a corresponding brightness temperature BT _4 through Fourier transformation.
In step S6, the off-axis correction of the interferogram, the spectrogram, and the bright temperature BT _4 after the nonlinear influence correction based on the inverse matrix of the auto-apodization matrix specifically includes:
from the formula (10), when off-axis correction is performed, the corrected interferogram I _ cnl _ clz and spectrogram B _ cnl _ clz can be obtained by multiplying the inverse matrix of the self-cutting matrix:
the corrected interferogram I _ cnl _ clz is calculated according to formula (21):
the spectrogram B _ cnl _ clz was calculated according to equation (22):
B_cnl_clz＝SA-1*B_cnl (22)
since the brightness temperature is a physical quantity for representing the radiation capacity of the object, the corrected brightness temperature BT _5 is compared with the ideal brightness temperature BT _1 for analysis, and the reliability of the simulation process is represented by the brightness temperature difference. The bright temperature in each step is subjected to error analysis and comparison step by step to obtain error data graphs in fig. 2-7, and it can be known that, as shown in fig. 7, the ideal bright temperature BT _1 obtained by the instrument and the corrected bright temperature BT _5 are subjected to comparative analysis, and the error is about 10-3K, which fully explains the rationality and correctness of the simulation process.
The observation simulation method of the geostationary satellite infrared high-speed spectrometer completely expounds the simulation process of the observation simulation data of the infrared high-speed spectrometer in steps 1-4, the whole physical process is clear and accurate, the instrument principle of an interferometer is easy to understand, and the generation process of the data of the infrared high-speed spectrometer is understood; the method is accurate and feasible and has high precision; and 5-6, completing nonlinear correction and off-axis correction of simulation data, comparing the error between the corrected brightness temperature and the ideal brightness temperature, and explaining the reliability of the method from the reverse angle, wherein the error is small.
The principles and embodiments of the present invention have been described herein using specific examples, which are provided only to help understand the method and the core concept of the present invention; meanwhile, for a person skilled in the art, according to the idea of the present invention, the specific embodiments and the application range may be changed. In view of the above, the present disclosure should not be construed as limiting the invention.
Claims (7)
1. An observation simulation method of a geostationary satellite infrared high-speed spectrometer is characterized by comprising the following steps:
s1, obtaining simulated entrance pupil energy by using an RTTOV (real time optical over glass) fast radiation transmission mode according to the real pixel position information, and calculating to obtain a corresponding bright temperature BT _0 by using a Planck function;
s2, calculating an ideal interferogram I obtained by sampling entrance pupil energy through an instrument according to the Nyquist sampling theorem and the laser sampling frequency of the geostationary satellite infrared high-speed spectrometer, obtaining an ideal spectrum B after Fourier transform, and obtaining a corresponding ideal bright temperature BT _1 through a Planck function;
s3, adding a self-apodization matrix on the basis of the ideal spectrum B to obtain an interference pattern I _ lz with an off-axis effect, a spectrum B _ lz and a brightness temperature BT _ 2;
s4, calculating an interference pattern I _ lz _ nl, a spectrogram B _ lz _ nl and a brightness temperature BT _3 with nonlinear influence based on the quadratic nonlinear relation between the input light intensity and the output light intensity;
s5, selecting wavelet number segments to estimate nonlinear coefficients, and calculating an interferogram, a spectrogram and a brightness temperature BT _4 after nonlinear correction;
s6, performing off-axis correction on the interferogram, the spectrogram and the bright temperature BT _4 after the nonlinear influence correction based on an inverse matrix of the auto-apodization matrix to obtain an interferogram I _ cnl _ clz, a spectrogram B _ cnl _ clz and a bright temperature BT _5 which are subjected to the nonlinear correction and the off-axis correction; and comparing and analyzing the corrected bright temperature BT _5 with the ideal bright temperature BT _1, and representing the reliability of the simulation process through the bright temperature difference.
2. The observation simulation method of the geostationary satellite infrared high-speed spectrometer according to claim 1, wherein in the step S2, according to the nyquist sampling theorem and the laser sampling frequency of the geostationary satellite infrared high-speed spectrometer, an ideal interferogram I obtained by sampling the entrance pupil energy through an instrument is calculated, an ideal spectrum B is obtained after fourier transform, and a corresponding ideal bright temperature BT _1 is obtained through a planckian function, which specifically comprises:
the maximum optical path difference of the infrared high-speed spectrograph of the geostationary satellite is set to be L, sampling is controlled by a laser, a group of discrete sampling points are obtained, the Nyquist sampling principle is met, the laser sampling interval is delta x, and the number of sampling points is N on the premise of bilateral sampling:
the corresponding spectral sampling resolution Δ σ is:
due to the discretization sampling, the restored spectrum B [ n ] after the Fourier transform discretization is:
the discretized interferogram I [ k ] is:
where n is the nth point in the spectral domain and k is the kth sampling point in the interferogram.
3. The observation simulation method of the geostationary satellite infrared hyperspectral imager as claimed in claim 2, wherein in the step S3, the self-apodization matrix is calculated according to the instrument parameters of the geostationary satellite infrared hyperspectral imager, specifically comprising:
according to the real physical parameters of the infrared high-spectrum instrument of the geostationary satellite, the central coordinate (x) of each probe element is calculatedc，yc) Combining the length and width A and B of the probe element to obtain the distances from four angular points of the square probe element to the center of the focal plane, and recording as r according to the distancemin、rc1、rc2And rmax，rminIs the distance, r, from the center of the focal plane to the lower left corner of the probe elementmaxIs the distance, r, from the center of the focal plane to the upper right corner of the probe elementc1And rc2Is the distance from the center of the focal plane to the upper left corner point and the lower right corner point, and r is the distance from the center of the focal plane to the upper left corner point and the lower right corner point due to the different positions of the probe elements on the focal planec1And rc2The linear function represents the spectral response of the probe element, and is defined as the normalization of the opening angle corresponding to the arc intercepted by the probe element on the focal plane, and is expressed as follows:
wherein alpha is1Angle alpha between the arc of finger probe and y axis2The included angle between the arc intercepted by the finger probe element and the x axis; let rc1<rc2The linear function of the probe element is expressed as a piecewise function:
because the optical path difference is limited, the actual interferogram is expressed by multiplying a rectangular truncation function in an interferogram form relative to an infinite optical path, the actual interferogram is expressed by convolution with a sinc function in a spectrum, and the ILS and the sinc function form an auto-intercept matrix SA:
SA＝ILS*sinc (9) 。
4. the observation simulation method for a geostationary satellite infrared hyperspectral spectrometer according to claim 3, wherein in the step S3, a self-apodization matrix is added on the basis of the ideal spectrum B to obtain a spectrogram B _ lz, an interferogram I _ lz and a brightness temperature BT _2 with an off-axis effect, which specifically comprises:
spectrum B _ lz is:
B_lz＝SA*B (10)
the interferogram I _ lz is calculated based on equations (6) and (10) as:
5. the observation simulation method for the geostationary satellite infrared hyperspectral spectrometer according to claim 4, wherein in the step S4, the interference pattern I _ lz _ nl and the spectrogram B _ lz _ nl and the bright temperature BT _3 which have nonlinear effects are calculated based on the quadratic nonlinear relationship between the input light intensity and the output light intensity, and specifically comprises:
the interference pattern I _ lz _ nl comprises a direct current signal V and an alternating current signal I, and because the input light intensity and the output light intensity are in a quadratic nonlinear relation, the input signal is marked as an ideal signal and V is usediAnd IiIndicating that the output signal is the actual measurement signal, denoted by VmAnd ImExpressed as follows:
Vi+Ii＝Vm+Im+a2(Vm+Im)2 (12)
and obtaining an expression of actually measured light intensity for the above expression conversion form:
Vm+Im＝Vi+Ii-a2(Vm+Im)2 (13)
and removing the direct current components at the two sides of the above formula, simplifying the above formula into:
Im＝Im-2a2Ii·Vi-a2Ii 2 (14)
wherein, a2For the initial nonlinear coefficient, an interferogram I _ lz _ nl and a spectrogram B _ lz _ nl containing nonlinear influence can be obtained based on equation 14
I_lz_nl＝I_lz-2α2·I_lz·V-α2·I_lz2 (15)
Where I _ lz is the simulated interferogram containing the off-axis effect and V is the corresponding DC component.
6. The observation simulation method of the geostationary satellite infrared hyperspectral spectrometer according to claim 5, wherein in the step S5, the wavelet coefficient segment is selected to estimate the nonlinear coefficient, and the interferogram, the spectrogram and the brightness temperature BT _4 after nonlinear correction are calculated, specifically comprising:
the dc term is removed and fourier transformed for equation (12), which is expressed as:
the ideal spectrum should be 0 out of band, then the spectrum outside the selected mid and long wave band should theoretically be 0, the small wave band is less disturbed, 50-300cm-1 is often selected as the estimated nonlinear coefficient:
then:
and (4) after the nonlinear coefficient is estimated, substituting the nonlinear coefficient into the formula (14) to obtain a nonlinear corrected interference pattern I _ cnl, and obtaining a spectrogram B _ cnl and a corresponding brightness temperature BT _4 through Fourier transformation.
7. The observation simulation method for a geostationary satellite infrared hyperspectral spectrometer according to claim 6, wherein in the step S6, the off-axis correction of the interferogram, the spectrogram and the brightness temperature BT _4 after the nonlinear influence correction based on the inverse matrix of the auto-apodization matrix specifically comprises:
from the formula (10), when off-axis correction is performed, the corrected interferogram I _ cnl _ clz and spectrogram B _ cnl _ clz can be obtained by multiplying the inverse matrix of the self-cutting matrix:
the corrected interferogram I _ cnl _ clz is calculated according to formula (21):
the spectrogram B _ cnl _ clz was calculated according to equation (22):
B_cnl_clz＝SA-1*B_cnl (22)。
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