A space-based optical observation method and system suitable for northeast black soil regions

Abstract

The application discloses a space-based optical observation method and system suitable for a northeast black soil area, and relates to the technical field of space-based observation.The method comprises the following steps: step 1, calculating the range of the solar elevation angle according to the latitude of the observation range of the northeast black soil area; step 2, calculating the signal-to-noise ratio requirement range of a specific spectral band according to the inversion requirement of soil or crops; step 3, calculating the descending speed multiple according to the signal-to-noise ratio; step 4, calculating the integration time in the sub-satellite point observation area according to the descending speed multiple; and step 5, calculating the integration time requirement under side swing according to the satellite side swing and width in different observation areas, and iteratively calculating the line frequency and satellite maneuver requirement.The system comprises a solar elevation angle calculation module, a spectral radiation brightness calculation module, a descending speed multiple calculation module, an integration time calculation module and an iteration module.The application can meet the high signal-to-noise ratio requirement of the northeast black soil area observation satellite, and ensures the high signal-to-noise ratio of imaging.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of space-based observation, and particularly relates to a space-based optical observation method and system suitable for northeast black soil regions. BACKGROUND

[0002] The push-broom mode is commonly used for earth spectrum observation satellites, and the signal-to-noise ratio is related to the instrument, the atmospheric transmission model and the observation mode. The northeast region of China has a high latitude and a low solar elevation angle, and the surface coverage is complex, which restricts the improvement of the signal-to-noise ratio of the spectrum observation in the northeast black soil region. SUMMARY

[0003] Therefore, the present application provides a space-based optical observation method and system suitable for northeast black soil regions to solve the problems of low signal-to-noise ratio and poor image quality in the prior art.

[0004] The specific technical scheme of the present application is as follows:

[0005] A space-based optical observation method suitable for northeast black soil regions, comprising the steps of:

[0006] Step 1: calculating the range of the solar elevation angle according to the latitude of the observation range of the northeast black soil region;

[0007] Step 2: calculating the signal-to-noise ratio requirement range of a specific spectral band according to the inversion requirement of soil or crops;

[0008] Step 3: calculating the descending rate multiple according to the signal-to-noise ratio;

[0009] Step 4: calculating the integration time in the sub-satellite point observation area according to the descending rate multiple;

[0010] Step 5: calculating the side-swing integration time requirement according to the satellite side-swing and the width of different observation areas, and iteratively calculating the line frequency and the satellite maneuver requirement.

[0011] Specifically, the calculation formula involved in step 1 is

[0012]

[0013] Wherein, θ is the solar elevation angle of the observation area; L1 is the low latitude of the northeast black soil region; L2 is the high latitude of the northeast black soil region; [L1, L2] represents the latitude range of the northeast black soil region; is the latitude value of the measurement area; δ is the solar declination; τ is the local hour angle of the observation area.

[0014] Specifically, step 2 comprises: step 2.1, calculating spectral radiance according to the range of surface reflectivity and solar elevation angle; step 2.2, calculating signal-to-noise ratio according to the spectral radiance.

[0015] Specifically, the calculation formula involved in step 2.1 is

[0016] S(r, θ) = a0 + a1*r + a2*r 2 +a3*r 3 +b1*θ+b2*θ 2 +b3*θ 3

[0017] Wherein, r is the surface reflectivity, which is obtained according to the statistical characteristics of ground objects; θ is the solar elevation angle of the observed ground, which is obtained by step 1 calculation; a0, a1, a2, a3, b1, b2, b3 are fitting coefficients, which are obtained by using atmospheric radiation transfer program MODTRAN4 to estimate the spectral radiance of the ground target to the top of the atmosphere under different solar elevation angles and different reflectivity.

[0018] Specifically, the calculation formula involved in step 2.2 is

[0019]

[0020] Wherein, S is the spectral radiance; t is the integration time; n is the noise characteristic; n1 is the photon shot noise; n2 is the dark current noise; n3 is the fixed pattern noise; n4 is the reset noise; n5 is the circuit readout noise; n6 is the quantization noise.

[0021] Specifically, the calculation formula involved in step 3 is

[0022] x = INT(SNR min (S, n)*v / a)

[0023] v = v G *f / H

[0024] Wherein, x is the descending speed multiple, which is an integer; INT represents rounding; SNR is the signal-to-noise ratio, SNR min is the signal-to-noise ratio that meets the minimum classification characteristic requirement; S is the spectral radiance; n is the noise characteristic; v is the image plane moving speed, v is related to the sub-satellite point speed v G , the focal length f of the camera optical system and the orbit height H; a is the pixel size.

[0025] Specifically, the calculation formula involved in step 4 is

[0026] t = x*a / v

[0027] Wherein, t is integral time; x is the multiple of the descending ground speed, taking integer; a is the pixel size; v is the image plane moving speed, v is related to the sub-satellite point speed v G , the focal length f of the camera optical system, the orbit height H.

[0028] A space-based optical observation system suitable for the northeast black soil region, comprising a solar elevation angle calculation module, a spectral radiance calculation module, a descending ground speed multiple calculation module, an integral time calculation module and an iteration module.

[0029] The solar elevation angle calculation module calculates the range of the solar elevation angle according to the latitude of the observation range in the northeast black soil region.

[0030] The spectral radiance calculation module calculates the signal-to-noise ratio requirement range of a specific spectral band using the inversion requirements of soil or crops.

[0031] The descending ground speed multiple calculation module calculates the descending ground speed multiple according to the signal-to-noise ratio.

[0032] The integral time calculation module calculates the integral time in the sub-satellite point observation area according to the multiple of the descending ground speed.

[0033] The iteration module calculates the integral time requirement under side swing according to the satellite side swing and width of different observation areas, and iteratively calculates the line frequency and satellite maneuvering requirement.

[0034] The beneficial effects of the present application are as follows:

[0035] The present application proposes a space-based optical observation method and system suitable for the northeast black soil region, which meets the high signal-to-noise ratio requirement of the northeast black soil region observation satellite and ensures high signal-to-noise ratio imaging. Using the present application, the sub-satellite point ground speed and line frequency of the satellite can be dynamically adjusted to form high signal-to-noise ratio output to meet the remote sensing inversion requirements of the black soil region. BRIEF DESCRIPTION OF DRAWINGS

[0036] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the following will briefly introduce the drawings needed to be used in the embodiments or prior art description. Obviously, the drawings in the following description are only some embodiments of the present application, and other drawings can be obtained by those skilled in the art without creative labor.

[0037] Figure 1 The flowchart of the space-based optical observation method suitable for the northeast black soil region proposed by the present application. DETAILED DESCRIPTION

[0038] In order to make the technical problems, technical solutions and beneficial effects of the present application clearer, the present application will be further described in detail below in combination with the drawings and examples. It should be understood that the specific examples described herein are only used to explain the present application and not to limit the present application.

[0039] The present application proposes a space-based optical observation method suitable for the northeast black soil region, comprising the steps of:

[0040] Step 1, according to the latitude of the observation range of the northeast black soil region, the range of the solar elevation angle is calculated. The corresponding calculation formula is

[0041]

[0042] Wherein, θ is the solar elevation angle of the observation site; L1 is the low latitude of the northeast black soil region; L2 is the high latitude of the northeast black soil region; [L1, L2] represents the latitude range of the northeast black soil region; is the latitude value of the measurement area; δ is the solar declination; τ is the local time angle of the observation area.

[0043] Step 2, according to the inversion requirements of soil or crops, the signal-to-noise ratio requirement range of specific spectral band is calculated. Specifically, first, according to the surface reflectivity and the range of solar elevation angle, the spectral radiance S is calculated, and the corresponding calculation formula is S(r, θ) = a0 + a1*r + a2*r 2 +a3*r 3 +b1*θ+b2*θ 2 +b3*θ 3

[0044] Wherein, r is the surface reflectivity, which is obtained according to the statistical characteristics of the ground object; θ is the solar elevation angle of the observation site, which is obtained by calculation in step 1; a0, a1, a2, a3, b1, b2, b3 are fitting coefficients, which are obtained by estimating the spectral radiance of the ground target reaching the top of the atmosphere under different solar elevation angles and different reflectivity using the atmospheric radiation transfer program MODTRAN4.

[0045] Then, according to the spectral radiance S, the signal-to-noise ratio SNR is calculated, and the corresponding calculation formula is

[0046]

[0047] Wherein, S is the spectral radiance; t is the integration time; n is the noise characteristic; n1 is the photon shot noise; n2 is the dark current noise; n3 is the fixed pattern noise; n4 is the reset noise; n5 is the circuit readout noise; n6 is the quantization noise.

[0048] Step 3, according to the signal-to-noise ratio, the ground speed reduction multiple is calculated. The corresponding calculation formula is

[0049] x = INT(SNR min (S, n) * v / a)

[0050] v = v G *f / H

[0051] wherein x is a descending ground speed multiple, and is an integer; INT represents rounding; SNR is a signal-to-noise ratio, SNR min is a signal-to-noise ratio meeting a minimum classification characteristic requirement; S is spectral radiance; n is a noise characteristic; v is an image plane moving speed, v is related to a sub-satellite point speed v G , a focal length f of a camera optical system, and an orbital height H; and a is a pixel size.

[0052] Step 4, integral time in a sub-satellite point observation area is calculated according to the descending ground speed multiple.

[0053] t = x * a / v

[0054] wherein t is integral time; x is a descending ground speed multiple, and is an integer; a is a pixel size; and v is an image plane moving speed, v is related to a sub-satellite point speed v G , a focal length f of a camera optical system, and an orbital height H.

[0055] Step 5, integral time requirement under satellite yaw is calculated according to satellite yaw and width in different observation areas, and line frequency and satellite maneuver requirement are iteratively calculated.

[0056] The application further provides a space-based optical observation system suitable for a northeast black soil area, which comprises a solar elevation angle calculation module, a spectral radiance calculation module, a descending ground speed multiple calculation module, an integral time calculation module and an iteration module.

[0057] The application has the following beneficial effects:

[0058] The application is directed to the characteristics of space-based spectral observation in the black soil region of northeast China, and proposes a space-based optical observation method and system suitable for the black soil region of northeast China, which meets the demand of high signal-to-noise ratio of the observation satellite in the black soil region of northeast China and guarantees high signal-to-noise ratio of imaging. By using the application, the subsatellite point ground speed and line frequency of the satellite can be dynamically adjusted to form high signal-to-noise ratio output, so as to meet the demand of remote sensing inversion in the black soil region.

Claims

1. A method for space-based optical observation suitable for the Northeastern Black Soil Region, characterized in that, The method comprises the steps of: Step 1, calculating the range of the solar elevation angle according to the latitude of the observation range of the northeast black soil region; Step 2, calculating the signal-to-noise ratio requirement range of a specific spectral band according to the inversion requirement of soil or crops; Step 3, calculating the ground speed reduction multiple according to the signal-to-noise ratio; Step 4, calculating the integration time in the sub-satellite point observation area according to the ground speed reduction multiple; Step 5, calculating the integration time requirement under side swing according to the satellite side swing and width of different observation areas, and iteratively calculating the line frequency and satellite maneuver requirement.

2. The sky-based optical observation method according to claim 1, characterized by, The calculation formula involved in the step 1 is Wherein, θ is the solar elevation angle of the observation area; L1 is the low latitude of the northeast black soil area; L2 is the high latitude of the northeast black soil area; [L1, L2] represents the latitude range of the northeast black soil area; is the latitude value of the measurement area; δ is the solar declination; τ is the local time angle of the observation area.

3. The sky-based optical observation method according to claim 1, characterized by, The step 2 comprises: step 2.1, calculating the spectral radiance according to the ground reflectivity and the range of the solar elevation angle; and step 2.2, calculating the signal-to-noise ratio according to the spectral radiance.

4. The sky-based optical observation method according to claim 3, characterized by, The calculation formula involved in the step 2.1 is S(r, 0) = a0 + a1 * r + a2 * r 2 + a3 * r 3 + b1 * 0 + b2 * 0 2 + b3 * 0 3 Wherein, r is the ground reflectivity, which is obtained according to the ground object characteristics statistics; θ is the solar elevation angle of the observation ground, which is obtained by calculation according to the step 1; a0, a1, a2, a3, b1, b2, b3 are fitting coefficients, which are obtained by estimating the spectral radiance of the ground target reaching the top of the atmosphere at different solar elevation angles and different reflectivities by using the atmospheric radiation transfer program MODTRAN4.

5. The sky-based optical observation method according to claim 3, wherein The calculation formula involved in the step 2.2 is Wherein, S is the spectral radiance; t is the integration time; n is the noise characteristic; n1 is the photon shot noise; n2 is the dark current noise; n3 is the fixed pattern noise; n4 is the reset noise; n5 is the circuit readout noise; and n6 is the quantization noise.

6. The sky-based optical observation method according to claim 1, wherein The calculation formula involved in the step 3 is x = INT(SNR min (S,n)*v / a) v = v G *f / H Wherein, x is the descending speed multiple, taking integer; INT represents rounding; SNR is the signal-to-noise ratio, SNR min The minimum classification characteristic requirement signal-to-noise ratio; S is the spectral radiance; n is the noise characteristic; v is the image plane moving speed, v is related to the sub-satellite point speed v G The focal length f of the camera optical system, the orbit height H, a is the pixel size.

7. The sky-based optical observation method according to claim 1, wherein The calculation formula involved in the step 4 is t=X*a / v Wherein, t is the integral time; x is the multiple of the descending speed, taking the integer; a is the pixel size; v is the image plane moving speed, v is related to the sub-satellite point speed v G , the focal length f of the camera optical system, the orbit height H.

8. A space-based optical observation system suitable for use in the Northeastern Black Soil Region, characterized by: The method comprises a solar elevation angle calculation module, a spectral radiance calculation module, a ground speed reduction multiple calculation module, an integration time calculation module and an iteration module. The solar elevation angle calculation module calculates the range of the solar elevation angle according to the latitude of the observation range of the northeast black soil region; The spectral radiance calculation module calculates the signal-to-noise ratio requirement range of a specific spectral band according to the inversion requirement of soil or crops; The ground speed reduction multiple calculation module calculates the ground speed reduction multiple according to the signal-to-noise ratio; The integration time calculation module calculates the integration time in the sub-satellite point observation area according to the ground speed reduction multiple; The iteration module calculates the integration time requirement under side swing according to the satellite side swing and width of different observation areas, and iteratively calculates the line frequency and satellite maneuver requirement.

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