Satellite-borne interferometric infrared hyperspectral detector data quantization bit code adjustment method

Abstract

The application provides a kind of satellite-borne interferometric infrared hyperspectral detector data quantization bit code adjustment method, it is related to satellite-borne infrared hyperspectral detection technical field, this method is through extracting envelope line on interferogram, traverses global observation data, iteratively compares envelope line before and after, retains the maximum extreme point of same position and the new extreme point of different position, forms global maximum interferogram envelope line, sets up analog-digital converter bit trimming mask based on global maximum interferogram envelope line.The bit trimming mask can adapt to the maximum signal fluctuation when the instrument observes real earth scene by increasing bit code in the oscillation signal interval formed by atmospheric spectrum corresponding to the sampling sequence of interferogram optical path difference, and adjusting high bit code in the wing area near the central peak.The application overcomes the unreasonable situation that bit code threshold is too large or too small based on blackbody interferogram signal envelope before satellite launch, and realizes the optimization of data transmission rate.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of spaceborne infrared hyperspectral detection technology, and particularly relates to a data quantization code adjustment method for a spaceborne interferometric infrared hyperspectral detector. BACKGROUND

[0002] The information directly measured by the spaceborne interferometric infrared hyperspectral detector is an interferogram signal. The interferogram is an alternating oscillation signal generated by the modulation of the radiation incident on the instrument by the internal interferometer of the instrument. The spectral information of the incident radiation can be calculated only by performing Fourier transform on the interferogram signal. If the incident radiation is monochromatic light of a single frequency, the interferogram is a sine or cosine signal with a frequency of light frequency. For blackbody radiation or earth atmospheric radiation, which is broadband radiation containing a variety of complex frequencies, the interferogram is an even-symmetric time sequence signal with a central oscillation waveform having a maximum amplitude and wings having a rapidly decaying amplitude. When the signal is digitally quantized and sampled by an analog-to-digital converter (ADC), the central peak signal occupies a relatively large ADC range, and the wing signal occupies a relatively small ADC range. Therefore, when the wing signal is digitally encoded, the high bits of the wing signal are filled with invalid all-zero code values. Due to the limited data transmission and storage resources on the satellite, in order to losslessly compress the original data rate, a segmented variable code quantization technology is generally adopted according to the characteristics of the interferogram signal. That is, the central signal of the interferogram is encoded with full range, and the wing signal is encoded with variable range according to the signal threshold in different intervals, so as to eliminate the invalid high-bit zero code values.

[0003] The existing segmented variable code quantization method is mainly based on the bit trimming mask (ADC Bit-trimming Mask) set by the envelope of the blackbody interferogram signal and the optical filter bandwidth during the instrument observation laboratory experiment in a high-temperature vacuum environment before satellite launch. Since the central peak signal of the interferogram is actually the energy integration of the radiation incident on the instrument, the higher the blackbody temperature and the stronger the radiation energy, the stronger the central peak signal, and the more the corresponding encoding bits. When the encoded blackbody radiation is higher than the limit of the earth radiation, the encoding bits of the central peak signal are sufficient to adapt to any earth scene. However, unlike the characteristic that the wing signals of the blackbody interferogram monotonically decrease away from the central peak, the interferogram signals obtained by observing the earth contain rich and varied atmospheric spectral information, so the wing signals exhibit different signal characteristics at different positions in the interferogram. The wing signals are no longer monotonically decreasing. For example, for 8-15 μm long-wave infrared radiation, the corresponding interferogram will form a strong oscillation signal at the wings of the interferogram with an optical path difference of 0.66 cm due to the CO2 absorption spectral line near 15 μm. When the bit code threshold is set too low, the interferogram at this position will cause bit code overflow, resulting in errors in the calculation of the CO2 absorption band spectrum after Fourier transform. SUMMARY

[0004] In view of this, in order to ensure that the infrared hyperspectral detector does not experience bit code overflow and thus cause interferogram measurement distortion when observing any Earth scene, and at the same time avoids bit redundancy in the encoded interferogram, the purpose of this invention is to propose a bit code adjustment method for data quantization of a spaceborne interferometric infrared hyperspectral detector. The bit code threshold is set based on the signal characteristics of the interferogram observed by the instrument in orbit, and the quantization bit code of the analog-to-digital converter is adjusted in segments according to the amplitude distribution characteristics of the interferogram signal. This avoids the situation where the ground sets unreasonable thresholds such as too large or too small based on the envelope of the blackbody interferogram signal, thereby achieving the optimization of data transmission rate without loss of effective information.

[0005] To achieve the above objectives, the present invention provides the following technical solution:

[0006] To achieve the above objectives, the present invention provides a method for adjusting the quantization bit code of a spaceborne interferometric infrared hyperspectral detector, comprising the following steps:

[0007] A. Extracting the upper envelope of the interferogram: Read the interferogram, set the sliding window size, calculate the local maxima of the interferogram signal in each region within the window, use the difference function and the sign function to determine the extreme points, and connect all the extreme points to form the upper envelope;

[0008] B. Dynamically update the envelope: Traverse global observation data, iteratively compare the envelopes before and after, retain the maximum extreme points at the same location and the newly added extreme points at different locations, and form the global maximum interferogram envelope;

[0009] C. Calculate the bit trimming mask: Set the analog-to-digital converter bit trimming mask based on the global maximum interferogram envelope to form the data segmentation quantization bit code;

[0010] D. Key region bit code compensation adjustment: Add bit code to the oscillating signal region formed by atmospheric spectrum (such as the 15μm CO2 absorption spectral line region) of the sampling sequence corresponding to the optical path difference of the interferogram, and increase the bit code in the wing area near the central peak to ensure that the bit correction mask can adapt to the maximum signal fluctuation when the instrument observes the real earth scene;

[0011] E. Dynamic adjustment: Periodically update the envelope and check the bit code adaptability, triggering abnormal adjustments.

[0012] As a further aspect of the present invention, the interferogram signal is read from an interferogram data loaded into the processor memory by the bit code adjustment processor. When determining the extreme points using a combination of the difference function and the sign function, the difference function is defined as:

[0013] diff(y) = [y2-y1,...,y i -y i-1 ,...,y n -y n-1]

[0014] Wherein, n is total length of y sequence, i is y sequence serial number;

[0015] Sign function is defined as:

[0016]

[0017] First order difference sequence is defined by difference function, sign function sequence is calculated by sign function, sign function sequence is twice differentiated, and local maximum point is judged by difference result.

[0018] As further scheme of the present application, when local maximum point is judged by difference result, if a point y i is local maximum, then there must be diff(y A )=y i -y i-1 >0, sign(diff(y A ))=1, diff(y B )=y i+1 -y i <0, sign(diff(y B ))=-1; if sign(diff(y)) sequence is further differentiated, then there must be diff(sign(diff(y)))=sign(diff(y B ))-sign(diff(y A ))=-2; on the contrary, if y i is local minimum, then there must be diffI(y A )=y i -y i-1 <0, sign(diff(y A ))=-1, diff(y B )=y i+1 -y i >0, sign(diff(y B ))=1, and diff(sign(diff(y)))=sign(diff(y B ))-sign(diff(y A ))=2.

[0019] As further scheme of the present application, diff(y) is derivative calculation of y sequence, greater than 0 indicates increasing, recorded as 1; less than 0 indicates decreasing, recorded as -1; equal to 0 indicates not increasing or decreasing, is straight line, recorded as 0.

[0020] As a further scheme of the present application, the global maximum interferogram envelope covers the maximum value of the interferogram signal of all observed scenes; the first envelope construction needs to traverse the global data of a day, and the subsequent envelope is updated once every quarter.

[0021] As a further scheme of the present application, when the envelope is dynamically updated, the envelope update rule is:

[0022] The larger maximum value is taken at the same position;

[0023] The newly added extreme point is reserved at different positions to form the maximum outer envelope covering all observed scenes.

[0024] As a further scheme of the present application, when the bit trimming mask is calculated, the logarithm with base 2 of the discrete point value of the global maximum interferogram envelope is taken and rounded up: bit = ceil(log2(OutlineY)), where bit is the bit trimming mask that needs to be set for the analog-to-digital converter, ceil() is the rounding up function, and OutlineY is the corresponding value of each discrete point of the envelope. A stepwise segmented bit code mask is generated to determine the number of segmented quantization bits of the analog-to-digital converter.

[0025] As a further scheme of the present application, when the key area bit code compensation adjustment is performed, the bit code adjustment range of the CO2 absorption band is the region of the interferogram sampling serial number corresponding to an optical path difference of 0.66 cm.

[0026] As a further scheme of the present application, when the key area bit code compensation adjustment is performed, one bit of quantization bit code is added in the region of the CO2 absorption band oscillation signal near the interferogram optical path difference of 0.66 cm, and the bit code is appropriately increased in the wings near the central peak region of the interferogram (corresponding to the interval of 0.12 cm symmetrically extended to the left and right wings along the zero optical path difference of the central peak of the interferogram).

[0027] As a further scheme of the present application, when the bit code is dynamically adjusted, periodic verification is performed, and the envelope is updated every quarter by extracting one day of data. The suitability of the bit code is verified, and when the change in the bit code demand of the new envelope exceeds a preset threshold, real-time bit code adjustment is triggered. The preset threshold is ±1 bit of the current bit number.

[0028] In a second aspect, the present application provides a satellite-borne interferometric infrared hyperspectral detector data quantization bit code adjustment system, which comprises the following components:

[0029] A data reading module: used for loading interferogram data from the processor memory and reading the amplitude information of the interferogram signal;

[0030] An envelope extraction module: connected with the data reading module, used for calculating the local maximum points of the interferogram signal by sliding window segmentation, judging the extreme points by using the combination algorithm of the difference function and the sign function, and connecting all the maximum points to generate the upper envelope;

[0031] Dynamic updating module: connected with the envelope extraction module, for traversing global observation data, iteratively comparing the envelope lines before and after, retaining the larger maximum value points at the same position and the newly added extreme value points at different positions, forming a global maximum interferogram envelope line;

[0032] Bit trimming mask calculation module: connected with the dynamic updating module, for calculating the logarithm with base 2 and rounding up based on the discrete point values of the global maximum interferogram envelope line, to generate a stepped segmented bit code mask;

[0033] Key area compensation module: connected with the bit trimming mask calculation module, for dynamically adjusting the quantization bit code in the CO2 absorption band oscillation signal region corresponding to the interferogram optical path difference 0.66cm and the adjacent central peak wing area, and increasing the bit code or adjusting the coverage range;

[0034] Dynamic calibration module: for periodically updating the global maximum interferogram envelope line, verifying the bit code adaptability, and triggering abnormal adjustment;

[0035] Memory and processor: for storing program instructions and executing the functions of the above modules.

[0036] As a further scheme of the present application, in the dynamic updating module:

[0037] The envelope line updating rule is to retain the larger maximum value at the same position and to merge the newly added extreme value points at different positions;

[0038] The first global envelope line construction needs to traverse one day of global observation data, and subsequent updates are made once every quarter.

[0039] Compared with the prior art, the satellite-borne interferometric infrared hyperspectral detector data quantization bit code adjustment method proposed by the present application has the following beneficial effects:

[0040] 1. Through adaptive envelope extraction and update and intelligent compensation of key areas, dynamic adaptive optimization is realized, and the global adaptability is improved.

[0041] The present application calculates the local maximum value points by sliding window segmentation, combines the difference function and the sign function combination algorithm, accurately captures the dynamic change characteristics of the interferogram signal, generates a global maximum envelope line covering all observation scenes based on the iterative update mechanism of global observation data, ensures that the bit code allocation adapts to extreme signal fluctuations, dynamically increases the bit code in the interferogram local larger oscillation signal region formed by the CO2 absorption spectrum and the wing area near the central peak of the interferogram, avoids quantization distortion caused by signal steepness, reduces the redundant bit code in the non-key area, and realizes the optimal balance between data precision and resource occupation.

[0042] 2. By improving the data compression rate and the segmented bit code mask, the quantization error and data volume are significantly reduced.

[0043] The application generates a stepped segmented bit code mask by calculating the logarithm of the discrete point value of the envelope and rounding up, and effectively reduces the invalid data bits in the non-critical area by dynamically adjusting the quantization bit width, thereby improving the overall data volume compression under the premise of ensuring the integrity of core scientific data such as CO2 absorption band, and significantly reducing the star-ground transmission bandwidth demand.

[0044] 3. By the dynamic adjustment mechanism, the global envelope is periodically updated and combined with real-time abnormal trigger adjustment to avoid bit code adaptation failure caused by instrument aging or environmental changes, and to ensure the long-term stability of the system in orbit operation. Moreover, the segmented bit code mask directly guides the ADC quantization bit width adjustment, which also avoids the high power consumption problem caused by the full range high bit code in the traditional scheme, thereby reducing the system power consumption.

[0045] In summary, the application realizes the intelligent adjustment of the data quantization bit code of the spaceborne interferometric infrared hyperspectral detector through the whole-chain optimization design of dynamic envelope extraction-segmented bit code mask-key area compensation-periodic dynamic adjustment, and has the characteristics of high precision, low resource occupation and strong adaptability, thereby providing reliable technical support for scientific tasks such as numerical weather prediction, atmospheric parameter inversion and component monitoring, climate change research, etc.

[0046] These aspects or other aspects of the application will be more apparent in the following description of the embodiments. It should be understood that the above general description and the following detailed description are only exemplary and explanatory, and cannot limit the application. BRIEF DESCRIPTION OF DRAWINGS

[0047] In order to more clearly illustrate the technical solutions in the embodiments of the application or the related art, the following will briefly introduce the drawings needed to be used in the exemplary embodiments or the related art description. The drawings are used to provide further understanding of the application, and constitute a part of the specification. The drawings are used together with the embodiments of the application to explain the application, and do not constitute a limitation on the application. In the drawings:

[0048] Figure 1 A flow chart of a spaceborne interferometric infrared hyperspectral detector data quantization bit code adjustment method according to an embodiment of the application.

[0049] Figure 2 A schematic diagram of a maximum envelope formed by traversing the global observation interferogram data on the autumn equinox day in a spaceborne interferometric infrared hyperspectral detector data quantization bit code adjustment method according to an embodiment of the application.

[0050] Figure 3A bit trimming mask setting diagram in a satellite borne interferometric infrared hyperspectral detector data quantization bit code adjustment method of an embodiment of the present application.

[0051] Figure 4 A quantization abnormal interferogram data diagram generated by an unreasonable bit trimming mask in a satellite borne interferometric infrared hyperspectral detector data quantization bit code adjustment method of an embodiment of the present application.

[0052] Figure 5 A pseudo spectral line diagram generated by abnormal interferogram data in a satellite borne interferometric infrared hyperspectral detector data quantization bit code adjustment method of an embodiment of the present application.

[0053] Figure 6 A quantization normal interferogram data diagram generated by a bit trimming mask adjustment in a satellite borne interferometric infrared hyperspectral detector data quantization bit code adjustment method of an embodiment of the present application.

[0054] Figure 7 A pseudo spectral line disappearance diagram after interferogram data normal quantization in a satellite borne interferometric infrared hyperspectral detector data quantization bit code adjustment method of an embodiment of the present application. DETAILED DESCRIPTION

[0055] The present application will be further described below in conjunction with the drawings and specific embodiments, and it should be noted that the following described embodiments or technical features can be combined in any manner to form new embodiments without conflict.

[0056] In order to make the objectives, technical solutions and advantages of the present application clearer, further detailed description of the embodiments of the present application will be made below in conjunction with the drawings, and it should be understood that the specific embodiments described herein are only used to explain the present application and should not be used to limit the present application.

[0057] It should be noted that all the expressions of "first" and "second" in the embodiments of the present application are used to distinguish two same name non-same entities or non-same parameters, and it can be seen that "first" and "second" are only used for the convenience of description and should not be understood as a limitation of the embodiments of the present application. In addition, the terms "include" and "have" and any variations thereof are intended to cover non-exclusive inclusion, for example, other steps or units inherent to the process, method, system, product or equipment containing a series of steps or units.

[0058] With reference to the drawings, the technical solutions in the embodiments of the present application will be clearly and completely described below, obviously, the described embodiments are some of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all the other embodiments obtained by those skilled in the art without creative work belong to the scope of protection of the present application.

[0059] The flowcharts shown in the drawings are only illustrative, not necessarily including all the contents and operations / steps, and not necessarily executed in the described order. For example, some operations / steps can also be decomposed, combined or partially merged, so that the actual execution order can be changed according to the actual situation.

[0060] Some embodiments of the present application will be described in detail below with reference to the drawings. The following embodiments and features in the embodiments can be combined with each other without conflict.

[0061] In order to ensure that the infrared hyperspectral detector does not occur code overflow when observing any earth scene, and to avoid the code redundancy of the interferogram, the present application provides a data quantization code adjustment method for a spaceborne interferometric infrared hyperspectral detector, sets a code threshold based on the actual on-orbit observation interferogram signal characteristics of the instrument, adjusts the quantization code of the analog-to-digital converter according to the amplitude distribution characteristics of the interferogram signal, avoids the unreasonable threshold of setting too large or too small based on the blackbody interferogram signal envelope on the ground, and thus optimizes the data transmission rate on the premise of not losing effective information.

[0062] Referring to Figure 1 The embodiments of the present application provide a data quantization code adjustment method for a spaceborne interferometric infrared hyperspectral detector, which comprises the following steps:

[0063] Step S10, extracting the upper envelope line of the interferogram: reading the interferogram, setting the size of the sliding window, segmenting the local maximum values of the interferogram signal in the window, judging the extreme value points by using the combination of the difference function and the sign function, and connecting all the maximum value points to form the upper envelope line.

[0064] In this step, the interferogram signal is loaded from the code adjustment processor to the interferogram data read in the processor memory, and when the combination of the difference function and the sign function is used to judge the extreme value points, the difference function is defined as:

[0065] diff(y)=[y2-y1,...,y i -y i-1 ,...,y n -y n-1 ]

[0066] Wherein, n is the total length of y sequence, i is the serial number of y sequence;

[0067] The sign function is defined as:

[0068]

[0069] The first order difference sequence is defined by using the difference function, the sign function sequence is calculated by using the sign function, the sign function sequence is twice differentiated, and the local maximum point is determined by the difference result.

[0070] In this embodiment, when the local maximum point is determined by the difference result, if a point y i is the local maximum, then there must be diff(y A ) = y i -y i-1 > 0, sign(diff(y A )) = 1, diff(y B ) = y i+1 -y i < 0, sign(diff(y B )) = -1; if the sign(diff(y)) sequence is further differentiated, then diff(sign(diff(y))) = sign(diff(y B ))-sign(diff(y A )) = -2; on the contrary, if y i is the local minimum, then there must be diff(y A ) = y i -y i-1 < 0, sign(diff(y A )) = -1, diff(y B ) = y i+1 -y i > 0, sign(diff(y B )) = 1, and diff(sign(diff(y))) = sign(diff(y B ))-sign(diff(y A )) = 2.

[0071] Wherein, diff(y) is the derivative of y sequence, greater than 0 indicates increasing, recorded as 1; less than 0 indicates decreasing, recorded as -1; equal to 0 indicates not increasing or decreasing, is a straight line, recorded as 0.

[0072] After the first time of differentiating the y sequence and calculating the sign of the difference diff, the obtained sequence only has three values of 0, -1 and 1, the maximum point should be located between -1 and 1, and 1 appears first and then -1, and after diff, it is equal to -1-1=-2. Since the length of the new sequence is reduced by one after each diff, in order to correspond to the index position of the maximum point in the original sequence y, 1 should be added after the position of the twice-differentiated sequence -2 is found. For example, as shown in the following table, the y sequence has 9 elements, in which y3=3 and y8=4 are local maximum values, and y6=-1 is a local minimum value. After the y sequence is calculated by using the difference function and cooperating with the sign function according to the above-mentioned method of finding the local maximum value, the length of the once-differentiated sequence diff1 is reduced to 8, and the length of the twice-differentiated sequence diff2 is reduced to 7, in which the positions of diff2=-2 are located at the 2nd and 7th positions of the sequence, and the position of diff2=2 is located at the 5th position. Therefore, in order to obtain the positions of the maximum and minimum points of the original y sequence, only the positions of diff2=-2 or diff2=2 need to be added by 1, and the corresponding results are shown in Table 1 as follows:

[0073] Table 1: Difference result judgment local maximum value point result table

[0074] Serial number 1 2 3 4 5 6 7 8 9 y value 1 2 3 1 0 -1 3 4 2 diff1 / 1 1 -2 -1 -1 4 1 -2 sign / 1 1 -1 -1 -1 1 1 -1 diff2 / / 0 -2 0 0 2 0 -2

[0075] Finally, all the maximum value points are connected to form an envelope line on the interference graph, and the envelope line is stored in a cache or a memory, the next interference graph is sequentially read, and the upper and lower envelope lines of the interference graph are extracted according to the above-mentioned method.

[0076] Step S20, dynamically updating the envelope line: traversing the global observation data, iteratively comparing the envelope lines before and after, retaining the maximum value points at the same position and the newly added maximum value points at different positions, and forming a global maximum interference graph envelope line.

[0077] In this step, the global maximum interference graph envelope line covers the maximum values of the interference graph signals of all observation scenes; the first envelope line construction needs to traverse the global data of one day, and the subsequent envelope line is updated once every quarter.

[0078] In this embodiment, when the envelope line is dynamically updated, the envelope line updating rule is:

[0079] Taking the larger maximum value at the same position;

[0080] Retaining the newly added maximum value points at different positions to form a maximum outer envelope line covering all observation scenes.

[0081] In this embodiment, by comparing the two envelope lines before and after, after extracting all the maximum value points of an interference graph by using the local maximum value algorithm, an outer envelope line Outline is formed, which includes the numerical values (y max) and the sequence of the corresponding positions (x max ) of the envelope lines. Since the envelope line reflects the local maximum distribution position of the interferogram signal, but the interferogram signal obtained by the infrared hyperspectral detector observing different earth scenes will change with the energy of the scene, it is necessary to traverse the interferogram in a certain time to obtain the corresponding envelope, and compare each envelope line, and finally construct a maximum envelope line that can cover all the interferogram waveforms. Since the observation data of the polar orbit satellite infrared hyperspectral detector in one day can basically cover all the observation scenes in the world, the maximum envelope line can be obtained by iterating the interferogram in one day. The method of comparing the envelope lines before and after and updating the new envelope line is described as follows: Since the sizes of the two interferogram signals before and after are not the same, the extreme values and the distribution positions of the corresponding envelope lines may also be different.

[0082] When updating the envelope line, if the maximum value positions of the two envelope lines before and after appear at the same position, the maximum value of the position with the larger value is used to update the envelope line; if the maximum value positions of the two envelope lines before and after appear at different positions, that is, the position where the maximum value of the first envelope line appears is not the maximum value of the second envelope line, or the position where the maximum value of the first envelope line does not appear is the maximum value of the second envelope line, both the maximum values of the envelope lines are retained, and the newly added points of the maximum value of the second envelope line are supplemented to update the envelope line. The envelope line update is shown in the following table. The outer envelope line obtained from the first interferogram is denoted as Outline1 = [(1, 6050), (2, 6167), (4, 6125), (5, 159), (6, 6032)], and the outer envelope line of the second interferogram is denoted as Outline2 = [(1, 6045), (3, 6189), (4, 6175), (6, 6002)], wherein the positions where the maximum values of the two envelope lines appear are respectively 1, 3, 4 and 6, and the larger value at these positions is taken as the maximum value point of the new envelope line OutlineN; the maximum value point of Outline2 at position 3 is supplemented to OutlineN because Outline1 does not appear at position 3 but Outline2 appears at position 3; similarly, the maximum value points of Outline1 at positions 2 and 5 are still retained in OutlineN because Outline1 appears at positions 2 and 5 but Outline2 does not appear at positions 2 and 5. Read the new interferogram and obtain Outline3, compare Outline3 with OutlineN and update OutlineN, and iterate in this way until all the interferograms in the selected time or selected area are traversed, and the final OutlineN is the required maximum outer envelope line. The corresponding results of the maximum values of the envelope lines are shown in Table 2:

[0083] Table 2: Corresponding results of the maximum values of the envelope lines

[0084] Position serial number 1 2 3 4 5 6 Outline1 6050 6167 / 6125 6159 6032 Outline2 6045 / 6189 6175 / 6002 OutlineN 6050 6167 6189 6175 6159 6032

[0085] If the maximum points of the two envelope lines appear at the same position, the maximum value at this position is used to update the envelope line; if the maximum points of the two envelope lines appear at different positions, no matter whether the maximum value of the first envelope line appears at the position of the second envelope line or not, the maximum values of the two envelope lines are reserved and used to update the envelope line, thereby forming a new envelope line and storing it, and the above steps are repeatedly performed until all the interferogram data of the global area observed by the instrument is traversed, and the final interferogram envelope line is formed.

[0086] In step S30, a bit trimming mask is calculated based on the global maximum interferogram envelope line to form a data segmented quantization bit code.

[0087] In this step, when the bit trimming mask is calculated, the logarithm with base 2 of the discrete point values of the global maximum interferogram envelope line is taken and rounded up: bit = ceil(log2(OutlineY)), bit is the bit trimming mask to be set for the analog-to-digital converter, ceil() is a rounding up function, and OutlineY is the corresponding value of each discrete point of the envelope line, a ladder-shaped segmented bit code mask is generated, and the number of bits of the analog-to-digital converter for segmented quantization is determined.

[0088] In this embodiment, the bit trimming mask of the analog-to-digital converter is set based on the interferogram envelope line, thereby forming the bit code for data segmented quantization. The bit code range of the analog-to-digital converter is determined according to the outer envelope line, and the digital sampling-encoding resource is saved because the analog-to-digital converter quantizes and samples in binary. After the outer envelope line is determined, OutlineX is used to represent the corresponding serial number of each discrete point of the envelope line, and OutlineY is used to represent the corresponding value of each discrete point of the envelope line. The logarithm with base 2 of OutlineY is taken and rounded up: bit = ceil(log2(OutlineY)), bit is the bit trimming mask to be set for the analog-to-digital converter, and ceil() is a rounding up function.

[0089] In step S40, the bit code of the key region is compensated and adjusted. The bit code is increased in the interval of the oscillation signal formed by the atmospheric spectrum corresponding to the sampling sequence of the optical path difference (such as the 15 μm CO2 absorption spectral line region), and the bit code is increased in the wing region near the central peak, so as to ensure that the bit trimming mask can adapt to the maximum signal fluctuation when the instrument observes the real earth scene.

[0090] In this step, when the bit code of the key region is compensated and adjusted, the adjustment range of the bit code of the CO2 absorption band is the sampling serial number region corresponding to the optical path difference of 0.66 cm.

[0091] In the key area bit code compensation adjustment, the CO2 absorption band oscillation signal area near the 0.66cm optical path difference of the interferogram is increased by 1 bit quantization bit code, and the 0.12cm optical path difference interval of the two wings near the central peak area of the interferogram is increased by 1 bit bit code.

[0092] Due to the characteristics of the central amplitude and the two wings tending to be flat, the outer envelope also has such characteristics, so the quantization bit code of the two wings of the interferogram is basically the same, and the central peak area is relatively large, the OutlineX corresponding to the same bit trimming mask is extracted, and the mask segment setting position can be determined, as shown in the following formula: Figure 3 The linear segments of the step-type distribution, in addition, considering that the CO2 absorption spectrum near 15μm will form a relatively strong oscillation signal near the 0.66cm optical path difference of the two wings of the interferogram (corresponding to the regions near the sampling serial numbers 2000 and 18000 in the following formula), the bit code overflow is not prevented, and according to this prior knowledge, the bit code values of the two regions (1400-2800 and 16200-17600) can be increased by one bit code; similarly, the wing area closest to the peak of the interferogram can also have a large signal, so according to the prior knowledge, the bit code of the two segments 8000-9400 and 9850-11250 also needs to be appropriately increased, and it should be noted that the above specific values are only applicable to the interferogram measurement data of the corresponding infrared hyperspectral detector. Figure 3 Figure 3

[0093] Step S50, dynamic adjustment: periodically update the envelope and check the bit code adaptability, and trigger abnormal adjustment.

[0094] In this step, when the bit code is dynamically adjusted, periodic verification is performed, and the envelope is updated every quarter by extracting one day of data, and the bit code adaptability is verified, and when the bit code demand of the new envelope changes by more than a preset threshold, real-time bit code adjustment is triggered, and the preset threshold is ±1 bit of the current bit number.

[0095] Considering that the earth scene radiation has seasonal changes in a year, the maximum outer envelope obtained by traversing the interferogram in one day can be applicable to global scenes, but it can not be applicable to all scenes in a year, therefore, for the sake of robustness, one day of interferogram data can be traversed every quarter to check whether the bit trimming masks of each time have great differences, therefore, when the bit trimming mask is calculated according to the envelope in the foregoing step, the rounding up and the adjustment of the code value according to the prior knowledge can basically adapt to the bit code trimming of the interferogram of an instrument in the whole life cycle.

[0096] The present application is based on the actual interferogram signal characteristics of the star-borne interferometric infrared hyperspectral detector for earth observation, extracts the maximum outer envelope of the interferogram, and sets the bit code of the segmented interferogram data for digital quantization. Figure 2 ​​is the maximum envelope line formed by traversing the global earth observation interferogram data at the autumnal equinox, and from the graph, it can be determined that the maximum interferogram signal corresponding to the global highest temperature region of the earth on that day will not exceed this envelope line. In order to set a reasonable data quantization bit code according to this envelope line, and to ensure that the quantization bit code is applicable to the interferogram data quantization storage for a relatively long period of time after the autumnal equinox, the envelope line also needs to be appropriately enlarged, and the logarithm with 2 as the base is calculated as the bit trimming mask for the storage data, and the result is shown in Figure 3 .

[0097] As shown in Figure 3 , the bit trimming mask generated by the present application is well compatible with the signal characteristics of the actual earth observation interferogram, and a larger bit code is allocated to the central peak signal near the zero optical path difference (i.e. near the sampling serial number 9500 in the graph); and a smaller bit code is allocated to the lower signals on both wings, and especially for the oscillation signals near the optical path difference of 0.66 cm formed by the CO2 absorption spectrum (corresponding to the region near the sampling serial numbers 2000 and 18000 in the graph), a dynamic adjustment module is performed.

[0098] The technical progress generated by the present application can be illustrated by the following examples, Figure 4 is the result of quantizing the actual earth observation interferogram signal by the bit trimming mask set by the blackbody interferogram signal envelope. Since the bit trimming mask is not compatible with the CO2 oscillation signal near the optical path difference of 0.66 cm, the signal overflows the bit code range and forms a distorted interferogram. The spectrum obtained by Fourier transform on the distorted interferogram is shown in Figure 5 , and the CO2 absorption spectrum in the range of 650-750 cm -1 is doped with some pseudo-spectrum lines (compared with Figure 7 normal spectrum), and even the modulated oscillation noise signal appears outside the instrument band in the range of 500-600 cm -1 .

[0099] Figure 6 is the result of quantizing the actual earth observation interferogram signal by the bit trimming mask provided by the present application. As can be seen from the graph, the CO2 oscillation signal of the interferogram near the optical path difference of 0.66 cm is quantized normally, and there is no overflow bit code range phenomenon. Figure 7 is the Fourier transform spectrum corresponding to the normal interferogram, and the pseudo-spectrum lines in the range of 650-750 cm -1 have disappeared, and the noise in the range of 500-600 cm -1 has also been eliminated, showing a normal zero-mean random noise spectrum. Thus, the effectiveness of the bit trimming mask provided by the present application is verified.

[0100] It should be noted that, Figure 2is the maximum envelope line of the interferogram obtained from step 1 to step 4, the gray line in the figure is a typical atmospheric detection interferogram signal, and the black solid line is the maximum envelope line obtained by traversing the interferogram in a day, Figure 3 is the analog-to-digital converter bit trimming mask obtained from step 5. Figure 4 to Figure 7 is the measurement error caused by unreasonable setting of the bit trimming mask to data processing. Figure 4 is the flat-top distortion caused by the unreasonable setting of the bit trimming mask, which causes the CO2 oscillation signal near the optical path difference of 0.66 cm to exceed the upper limit of the bit threshold, and further causes Figure 5 the spectrum calculated from the interferogram has some pseudo-spectrum lines in the range of 650-750 cm -1 -1, and even the modulated oscillation noise signal outside the instrument bandwidth in the range of 500-600 cm -1 -1 appears; Figure 5 is the CO2 oscillation signal near the optical path difference of 0.66 cm effectively maintained after the reasonable setting of the bit trimming mask, so that Figure 7 the normal Fourier transform spectrum shown in the figure is obtained, and the pseudo-spectrum lines in the range of 650-750 cm -1 -1 have disappeared, and the noise in the range of 500-600 cm -1 -1 has also been eliminated, showing a normal zero-mean random noise spectrum. Figure 4 to Figure 7 The two comparative examples demonstrate the effectiveness of the bit trimming mask method provided by the present application.

[0101] Therefore, based on the interferogram data of the spaceborne interferometric infrared hyperspectral detector for earth observation, the maximum envelope line is extracted, and the bit trimming mask for quantization of the interferogram is calculated accordingly. The prior art is mainly based on the bit trimming mask provided by the blackbody interferogram signal envelope and the optical filter bandwidth setting when the instrument is observed in a high-temperature blackbody laboratory vacuum environment before satellite launch. Since there is a large difference between the blackbody interferogram signal characteristics and the real earth observation interferogram signal, the bit trimming mask provided before launch cannot be compatible with the real earth observation interferogram data, especially for the CO2 oscillation signal near the optical path difference of 0.66 cm. The bit trimming mask adjustment method provided by the present application solves the above problems well, ensuring normal quantization storage of the earth observation interferogram signal and normal calculation of the Fourier transform spectrum.

[0102] It should be noted that the above figures are only schematic representations of the processes included in the method according to the exemplary embodiments of the present application, and are not for limiting purposes. It is easy to understand that the processes shown in the above figures do not indicate or limit the time sequence of these processes. In addition, it is also easy to understand that these processes can be executed synchronously or asynchronously, for example, in multiple modules.

[0103] It should be understood that although the above steps are described in a certain order, these steps are not necessarily executed in the above order. Unless otherwise specified herein, the execution of these steps is not strictly limited in order, and these steps can be executed in other orders. Moreover, part of the steps of the present embodiment can include multiple steps or multiple stages, which are not necessarily executed at the same time, but can be executed at different times, and the execution order of these steps or stages is not necessarily sequential, but can be alternately executed with at least part of other steps or steps or stages in other steps.

[0104] It should be noted that the satellite-borne interferometric infrared hyperspectral detector data quantization bit code adjustment method is based on the satellite-borne interferometric infrared hyperspectral detector data quantization bit code adjustment system, which comprises the following components:

[0105] The data reading module is used to load the interferogram data from the processor memory and read the amplitude information of the interferogram signal.

[0106] The envelope extraction module is connected with the data reading module and is used to calculate the local maximum value points of the interferogram signal by sliding window segmentation, judge the extreme value points by using the combination algorithm of difference function and sign function, and connect all the maximum value points to generate the upper envelope line.

[0107] The dynamic updating module is connected with the envelope extraction module and is used to traverse the global observation data, iteratively compare the front and rear envelope lines, retain the larger maximum value points at the same position and the newly added extreme value points at different positions, and form the global maximum interferogram envelope line.

[0108] The bit trimming mask calculation module is connected with the dynamic updating module and is used to calculate the logarithm with base 2 and take the upper integer based on the discrete point value of the global maximum interferogram envelope line, to generate a ladder-shaped segmented bit code mask.

[0109] The key area compensation module is connected with the bit trimming mask calculation module and is used to dynamically adjust the quantization bit code, increase the bit code or adjust the coverage range in the CO2 absorption band oscillation signal region corresponding to the optical path difference of 0.66 cm and the adjacent central peak wing region.

[0110] The dynamic calibration module is used to periodically update the global maximum interferogram envelope line, verify the adaptability of the bit code, and trigger abnormal adjustment.

[0111] The memory and the processor are used to store program instructions and execute the functions of the above modules.

[0112] In the dynamic updating module: In the dynamic updating module:

[0113] The envelope updating rule is that a larger maximum value is kept at the same position, and new extreme points are combined at different positions.

[0114] The first global envelope construction needs to traverse global observation data in a day, and subsequent quarterly updates are performed once every quarter.

[0115] Through the above detailed steps, the satellite-borne interferometric infrared hyperspectral detector data quantization bit code adjustment system of the present application is used to execute the steps of the satellite-borne interferometric infrared hyperspectral detector data quantization bit code adjustment method in the above embodiments, which will not be described here.

[0116] The above is the exemplary embodiment disclosed by the present application, but it should be noted that various changes and modifications can be made without departing from the scope of the embodiments disclosed by the present application defined by the claims. The functions, steps and / or acts of the method claims described herein need not be performed in any particular order. Furthermore, although the elements of the embodiments disclosed by the present application can be described or claimed in individual form, unless explicitly restricted otherwise, they can also be understood as plural.

[0117] It should be understood that, as used herein, the singular forms "a", "an" and "the" are intended to include plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms "comprises", "comprising", "includes" and / or "including", as used herein, specify the presence of stated features, integers, steps, operations, elements, and / or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and / or groups thereof. The above-mentioned embodiment numbers of the embodiments disclosed by the present application are only for description, and do not represent the advantages or disadvantages of the embodiments.

[0118] Those skilled in the art should understand that the above discussion of any embodiment is only exemplary, and is not intended to imply that the scope of the embodiments disclosed by the present application (including claims) is limited to these examples; under the idea of the embodiments of the present application, the technical features of the above embodiments or different embodiments can also be combined, and there are many other changes of the above different aspects of the embodiments of the present application, which are not provided in detail for the sake of brevity. Therefore, any omissions, modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the embodiments of the present application shall be included in the scope of protection of the embodiments of the present application.

Claims

1. A method for adjusting the data quantization bit code of a spaceborne interferometric infrared hyperspectral sounder, characterized in that, The method comprises the following steps: Extracting the upper envelope of the interferogram: reading the interferogram, setting the size of the sliding window, segmenting the local maximum values of the interferogram signal in the window, using the combination of the difference function and the sign function to judge the extreme value points, and connecting all the maximum value points to form the upper envelope; Dynamic updating of the envelope: iterating and comparing the envelopes before and after, retaining the maximum extreme value points at the same position and the newly added extreme value points at different positions, and forming the global maximum interferogram envelope; Calculating the bit trimming mask: setting the bit trimming mask of the analog-to-digital converter based on the global maximum interferogram envelope to form the data segment quantization bit code; Key area bit code compensation adjustment: increasing the bit code in the oscillation signal region formed by the atmospheric spectrum corresponding to the sampling sequence of the interferogram optical path difference, and appropriately adjusting the bit code in the two wings near the central peak value to ensure that the bit trimming mask can adapt to the maximum signal fluctuation when the instrument observes the real earth scene; Dynamic adjustment: periodically updating the envelope and verifying the bit code adaptability, and triggering abnormal adjustment.

2. The method for adjusting the data quantization bit code of a space-borne interferometric infrared hyper-spectral sounder according to claim 1, wherein, The interferogram signal is loaded from the bit code adjustment processor to the interferogram data read in the processor memory, the difference function is defined as: diff(y) = [y2 - y1,..., y i - y i-1 ,..., y n - y n-1 ] Wherein, n is the total length of y sequence, and i is the serial number of y sequence; The sign function is defined as: A first-order difference sequence is defined using the difference function, a sign function sequence is calculated using the sign function, and the sign function sequence is twice differentiated to determine the local maximum value points.

3. The method for adjusting the data quantization bit code of a space-borne interferometric infrared hyper-spectral sounder according to claim 2, characterized in that, When judging the local maximum point by the difference result, if a point y i is a local maximum, then there must be diff(y A ) = y i - y i-1 > 0, sign(diff(y A )) = 1, diff(y B ) = y i+1 - y i < 0, sign(diff(y B )) = -1; if the difference operation is performed again on the sequence of sign(diff(y)), then there is diff(sign(diff(y))) = sign(diff(y B )) - sign(diff(y A )) = -2; Conversely, if y i is a local minimum, then necessarily diff(y A ) = y i - y i-1 < 0, sign(diff(y A )) = -1, diff(y B ) = y i+1 - y i > 0, sign(diff(y B )) = 1, and diff(sign(diff(y))) = sign(diff(y B )) - sign(diff(y A )) = 2.

4. The method for adjusting the data quantization bit code of a space-borne interferometric infrared hyper-spectral sounder according to claim 3, characterized in that, diff(y) is the derivative of y sequence, greater than 0 indicates increasing, recorded as 1; less than 0 indicates decreasing, recorded as-1; equal to 0 indicates no increasing or decreasing, which is a straight line, recorded as 0.

5. The method for adjusting the data quantization bit code of a space-borne interferometric infrared hyper-spectral sounder according to claim 1, wherein, The global maximum interferogram envelope covers the maximum value of the interferogram signal of all observation scenes; the first envelope construction needs to traverse the global data of one day, and the subsequent envelope is updated once every quarter.

6. The method for adjusting the data quantization bit code of a space-borne interferometric infrared hyper-spectral sounder according to claim 5, wherein, When the envelope is dynamically updated, the envelope updating rule is: The larger maximum value at the same position is taken; Different positions retain the newly added extreme value points to form the maximum envelope covering all observation scenes.

7. The method for adjusting the data quantization bit code of a space-borne interferometric infrared hyper-spectral sounder according to claim 3, wherein, When calculating the bit trimming mask, the discrete point values of the global maximum interferogram envelope are taken as the logarithm with base 2 and rounded up: bit = ceil(log2(OutlineY)), bit is the bit trimming mask of the analog-to-digital converter, ceil() is the rounding up function, OutlineY is the corresponding value of each discrete point of the envelope, a stepwise segmented bit code mask is generated, and the number of segmented quantization bits of the analog-to-digital converter is determined.

8. The method of claim 7, wherein the quantization bit code is adjusted according to the following equation: ###0001### where N is the number of quantization bit codes, and N is an integer. When the key area bit code compensation adjustment is performed, the CO2 absorption band bit code adjustment range is the interferogram sampling sequence region corresponding to the optical path difference of 0.66 cm. ​ 9. The method of claim 8, wherein the quantization bit code is adjusted according to the following equation: ###00001### where N is the number of quantization bit codes, N is the number of quantization bit codes after adjustment, and N is the number of quantization bit codes before adjustment. When the key area bit code compensation adjustment is performed, 1 bit quantization bit code is added in the CO2 absorption band oscillation signal region near the interferogram optical path difference of 0.66 cm, and the bit code is appropriately adjusted in the two wings near the central peak value of the interferogram.

10. The data quantization bit code adjustment method for a spaceborne interferometric infrared hyperspectral detector as described in claim 6, characterized in that, When the bit code is dynamically adjusted, periodic verification is performed, one day of data is updated every quarter to update the envelope, and the bit code adaptability is verified. When the bit code demand of the new envelope changes by more than the preset threshold, real-time bit code adjustment is triggered, and the preset threshold is ±1 bit of the current bit code.

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