CN112284533A - Radiometer for remote sensor on-orbit atmospheric correction - Google Patents

Abstract

The invention discloses a radiometer for remote sensor on-orbit atmospheric correction, which comprises an integrating sphere, wherein the inner surface of the integrating sphere is coated with a diffuse reflection coating; the integrating sphere is provided with a ground light gathering port, a sunlight incident port and at least one detector interface; the ground light gathering port is connected with the light gathering system, and a first electromagnetic valve is arranged between the ground light gathering port and the light gathering system; the sunlight incident port is provided with a second electromagnetic valve; the detector interface is provided with a collimation correction module and a detector module; the incident light of the ground light gathering port and the sunlight incident port enters the integrating sphere and is reflected for multiple times by the diffuse reflection coating, a uniform illumination surface is formed on the inner surface of the integrating sphere, and the uniform illumination surface is led into the detector module through the collimation correction module of the detector interface. The calibration device takes the stable known sun as a reference, eliminates the influence of self attenuation and change on the calibration precision in principle, can accurately measure the atmospheric characteristic parameters above the calibration field, and has the advantages of simple structure, good stability and reliable and effective acquired signals.

Description

A radiometer for on-orbit atmospheric correction of remote sensors

technical field

The invention relates to the technical field of spectral radiation calibration, in particular to a radiometer used for on-orbit atmospheric correction of a remote sensor.

Background technique

With the development of the national economy and science and technology, the support of aerospace remote sensing data is urgently needed in the fields of national macro-decision-making, national defense and military, land and resources survey, precision agriculture, environmental monitoring, atmospheric detection, and extreme disaster forecasting. The hyperspectral imaging technology is a remote sensing technology developed in the 1980s. Different from the traditional spectrometer, the hyperspectral imaging technology integrates the image and the spectrum (integration of the spectrum), with nano-scale hyperspectral resolution, in the acquisition of targets At the same time of two-dimensional space image information, continuous fine spectral information of the target is simultaneously obtained, which greatly improves the detection ability of space remote sensing, and can be widely used in land, atmosphere, ocean and other observations.

The ground 3D cube data obtained by the hyperspectral camera in orbit can invert the reflectivity curve of the ground object; however, due to the influence of the atmospheric characteristics over the ground object, the inverted reflectivity curve and the real reflectivity curve of the ground object exist. Due to the contribution of scattering and absorption of molecules and aerosol particles in the atmosphere, the radiation value of the target before the detector passes through the upward atmosphere and the real radiation value of the ground object are very different, and the difference varies with weather conditions. and local atmospheric parameters (such as water vapor and other absorbed gas content, atmospheric aerosols, temperature, humidity and air pressure, etc.) vary greatly. Therefore, in order to obtain high-quality hyperspectral aerospace remote sensing data traceable to SI (International Basic System of Units), and to accurately and quantitatively interpret the ground object information, it is necessary to carry out in-depth research on the earth observation work of hyperspectral imagers, and to carry out atmospheric correction. Atmospheric effects are deducted.

The existing atmospheric radiation correction methods mainly include the measurement of the actual atmospheric transmittance and the simulated calculation of the atmospheric transmittance based on the detected atmospheric parameters. However, real-time measurement of atmospheric transmittance for long-slope paths is very difficult and difficult to achieve. The computer software simulation analysis method is mainly used to correct the measured radiation signal by constructing a calculation model of atmospheric spectral transmittance. This kind of method generally uses foreign atmospheric radiation transfer software (such as MODTRAN, etc.) to calculate the standard atmospheric model. Atmospheric transmittance, the advantages of this type of method lie in the advantages of simple operation, low cost and short cycle. However, there is a big difference between the actual atmosphere and the standard atmospheric model in typical areas of my country, and it has certain limitations in calculation accuracy and calculation efficiency. Therefore, in practical engineering applications, it is still necessary to use atmospheric measuring instruments to perform actual observation and correction of atmospheric characteristic parameters at the calibration time of the measurement site. However, at present, the calibration of atmospheric characteristic parameters in practical engineering applications requires the use of multiple atmospheric measurement instruments, the measurement process is complex, and the lack of self-calibration devices and instrument attenuation self-correction functions makes it difficult to maintain long-term stability.

SUMMARY OF THE INVENTION

The invention proposes a radiometer used for atmospheric correction of remote sensors in orbit. Taking the stable and known sun as a reference, in principle, the influence of self-attenuation and change on the calibration accuracy of the calibration source can be eliminated, and the calibration can be accurately measured and calibrated. Atmospheric characteristic parameters over the field, eliminate atmospheric profile errors, and invert atmospheric parameters.

For this reason, the present invention adopts the following technical solutions:

Example 1:

A radiometer used for on-orbit atmospheric correction of a remote sensor, as shown in Figure 1, the radiometer includes an integrating sphere 1, and the inner surface of the integrating sphere 1 is coated with a diffuse reflection coating 2; the integrating sphere 1 is provided with The light concentrating port 3 to the ground, the sunlight entrance 4 and a detector interface 5; The first solenoid valve 11; the sunlight incident port 4 is provided with a second solenoid valve 12; the detector interface 5 is provided with a collimation correction module and a detector module; The incident light from port 4 enters the integrating sphere and is repeatedly reflected by the diffuse reflection coating 2 to form a uniform surface on the inner surface of the integrating sphere, and then passes through the collimation and correction module of the detector interface 5 and then enters the detector module.

The collimation and correction module includes a field diaphragm 7 and a correction collimation lens 8 . The correction and collimation lens 8 is placed in the field of view diaphragm 7 , and the light enters the correction and collimation lens 8 from the detector interface 5 The detector module is introduced; the detector module includes an optical filter 9 and a detector unit 10, and the light is introduced into the detector unit 10 after passing through the optical filter 9, and the detector unit 10 is an InGaAs detector.

Wherein, the light collecting system 6 is a reflective structure.

Wherein, the InGaAs detector is an integrated detector, which integrates at least one pixel.

Among them, the incident flux of the light concentrating port 3 on the ground is equal to the incident flux of the sunlight incident port 4, because

The sunlight incident flux is

为大气层外太阳辐照度，b_λ为带宽，θ为太阳光入射角度，D_s为太阳光入射口口径；in,

is the solar irradiance outside the atmosphere, b _λ is the bandwidth, θ is the incident angle of sunlight, and D _s is the aperture of the solar light entrance;

The incident flux to the concentrator is

为上行大气透过率，

为下行大气透过率，ρ(λ)为地面反射率，τ₀(λ)为地面观测聚光系统透过率，Ω为轨道高度与地面形成的立体角度，D_o为对地聚光口口径；in,

is the upward atmospheric transmittance,

is the downward atmospheric transmittance, ρ(λ) is the ground reflectivity, τ ₀ (λ) is the transmittance of the ground observation concentrating system, Ω is the solid angle formed by the orbit height and the ground, and D _o is the concentrating port on the ground caliber;

when

Then the relationship between the aperture of the sunlight entrance and the aperture of the concentrator on the ground is:

Embodiment 2

A radiometer used for on-orbit atmospheric correction of a remote sensor, as shown in Figure 2, the radiometer includes an integrating sphere 1, and the inner surface of the integrating sphere 1 is coated with a diffuse reflection coating 2; the integrating sphere 1 is provided with The light concentrating port 3 on the ground, the sunlight incident port 4 and the two detector interfaces 51 and 52; the light concentrating port 3 on the ground is connected to the light collecting system 6, There is a first solenoid valve 11 between them; the sunlight entrance 4 is provided with a second solenoid valve 12; the detector interfaces 51 and 52 are both provided with a collimation correction module and a detector module; The incident light from the port and the sunlight entrance enters the integrating sphere and is repeatedly reflected by the diffuse reflection coating to form a uniform surface on the inner surface of the integrating sphere, and then enters the detector through the collimation correction modules of the detector interfaces 51 and 52. module.

The first collimation and correction module at the detector interface 51 includes a first field diaphragm 71 and a first correction and collimation lens 81 , and the first correction and collimation lens 81 is placed in the first field of view diaphragm In 71, the light enters the first correcting and collimating lens 81 from the detector interface 51 and then leads to the first detector module. The first detector module includes the first filter 91 and the first detector unit 101, and the light is filtered. After the light sheet 91 is introduced into the detector unit 101, the detector unit 101 is an InGaAs detector; the second collimation correction module at the detector interface 52 includes a second field diaphragm 72 and a second correction and collimation lens 82, the second correcting and collimating lens 82 is placed in the second field of view diaphragm 82, and the light enters the second correcting and collimating lens 82 from the detector interface 52 and then is introduced into the second detector module, and the detector module includes The second filter 92 and the second detector unit 102, the light is guided to the detector unit 102 after passing through the filter 92, and the detector unit 102 is a Silicon detector.

Wherein, the InGaAs detector is an integrated detector, which integrates at least one pixel.

Wherein, the incident flux of the light concentrating port 3 and the incident flux of the solar light incident port 4 are kept equal, because the solar light incident port flux is

为大气层外太阳辐照度，b_λ为带宽，θ为太阳光入射角度，D_s为太阳光入射口口径；in,

is the solar irradiance outside the atmosphere, b _λ is the bandwidth, θ is the incident angle of sunlight, and D _s is the aperture of the solar light entrance;

The incident flux to the concentrator is

为上行大气透过率，

为下行大气透过率，ρ(λ)为地面反射率，τ₀(λ)为地面观测聚光系统透过率，Ω为轨道高度与地面形成的立体角度，D_o为对地聚光口口径；in,

is the upward atmospheric transmittance,

is the downward atmospheric transmittance, ρ(λ) is the ground reflectivity, τ ₀ (λ) is the transmittance of the ground observation concentrating system, Ω is the solid angle formed by the orbit height and the ground, and D _o is the concentrating port on the ground caliber;

when

Then the relationship between the aperture of the sunlight entrance and the aperture of the concentrator on the ground is:

A measurement method based on the above-mentioned radiometer for on-orbit atmospheric correction of a remote sensor, comprising the following:

1) Self-calibration correction of the radiometer: the mean value of the output of the radiometer to the solar observation detector when the remote sensor passes a certain solar altitude during orbital operation is the same as the radiometer when the remote sensor passed the same solar altitude during the orbital operation. The ratio of the output mean of the daily observation detector to determine the relative attenuation of the radiometer itself;

Among them, the average output of the detector is the time t from the solar altitude angle α to the solar altitude angle β of the remote sensor running in the orbit. The first solenoid valve is used to close the concentrating port on the ground, and the second solenoid valve is opened to allow sunlight to enter. For daily observation, the incident light enters the integrating sphere and is reflected multiple times by the diffuse reflection coating to form a uniform surface on the inner surface of the integrating sphere.

2) Measurement of atmospheric radiation characteristics: When the remote sensor passes over the ground calibration field, the second solenoid valve is used to close the sunlight inlet, and the first solenoid valve is opened, so that the ground concentrating system is aligned with the center reference area of the calibration field, and the The light of the calibration field is collected by the concentrating system on the ground and then enters the integrating sphere, and then is reflected multiple times by the diffuse reflection coating to form a uniform illumination surface on the inner surface of the integrating sphere. Atmospheric transmittance.

The present invention adopts the above technical scheme, and has the following advantages:

1) The present invention takes the stable and known sun as a reference, eliminates the influence of self-attenuation and change on the calibration accuracy of the calibration source in principle, can accurately measure the atmospheric characteristic parameters over the calibration field, eliminates atmospheric profile errors, and reverses the play atmospheric parameters;

2) In the present invention, a correction module is set before the light enters the detector to solve the problem that the light is refracted and enters the detector after passing through the integrating sphere. Due to the large refraction angle, the wavelength curve will be warped and widened, thereby ensuring the spectrum of the detector. Response bandwidth and make calibration of atmospheric correction radiometers more accurate;

3) Simple structure and good stability.

Description of drawings

1 is a schematic structural diagram of Embodiment 1 of a radiometer used for remote sensor on-orbit atmospheric correction according to the present invention

FIG. 2 is a schematic structural diagram of Embodiment 2 of the radiometer used for remote sensor on-orbit atmospheric correction according to the present invention

FIG. 3 is a schematic structural diagram of a light concentrating system in a specific embodiment of the present invention.

Detailed ways

In order to make the objectives, features and advantages of the present invention clearer, a specific implementation of the present invention will be described in more detail below with reference to the accompanying drawings and embodiments. In the following description, many specific details are set forth. In order to facilitate a full understanding of the present invention, the present invention is capable of being carried out in many other ways than described, and therefore, the present invention is not limited by the specific embodiments disclosed below.

The specific implementation method is given according to the structural features and functions in the present invention. The radiometer system indicators used for the on-orbit atmospheric correction of the remote sensor are as follows:

1 Inner diameter of integrating sphere 56.0mm 2 Integrating sphere thickness 10.0mm 3 Sunlight entrance size Ф0.17mm 4 The size of the concentrator on the ground Ф1.54mm 5 Detector Aperture Size Si: 5×Ф3.2mm; InGaAs: 1×Ф8.8mm 6 Detector photosensitive surface size Ф1.0mm

The light collecting system adopts a reflective structure, as shown in Figure 3, the lens is made of quartz material, and the light and miniaturization of the structure is considered at the same time, and the optical design results are shown in the following figure:

For Si detectors, 5 independent cells are used, and for InGaAs detectors, a 5-in-1 overall layout is used. The central wavelength setting of the detector and the received energy are shown in the table below:

The incident light from the solar light entrance and the ground concentrating port of the radiometer enters the integrating sphere and is repeatedly reflected by the diffuse reflection coating. After forming a uniform surface on the inner surface of the integrating sphere, it reaches the filter of the detector The incident angle will be greater than 9°, which will easily cause the wavelength curve to warp and widen, making the data obtained by the detector inaccurate. Therefore, a calibration collimator lens is used before the light enters the detector, and the distance between the collimator lens and the filter is corrected. After the light leaves the calibration collimating lens, the incident angle to the detector filter surface is controlled within 9°, thereby ensuring the spectral response bandwidth of the detector and making the calibration of the atmospheric correction radiometer more accurate.

Measurement methods for radiometers used for on-orbit atmospheric correction of remote sensors, including the following:

1) Self-calibration correction of the radiometer: the mean value of the output of the radiometer to the solar observation detector when the remote sensor passes a certain solar altitude during orbital operation is the same as the radiometer when the remote sensor passed the same solar altitude during the orbital operation. The ratio of the output mean of the daily observation detector to determine the relative attenuation of the radiometer itself;

Among them, the average output of the detector is the time when the remote sensor runs in the orbit from the sun altitude angle of -2° to the sun altitude angle of +4° (near the arctic shadow area) for 2 minutes, and the first solenoid valve is used to close the concentrating port on the ground. Open the second solenoid valve to make the sunlight entrance to observe the sun. The incident light enters the integrating sphere and is reflected by the diffuse reflection coating for multiple times, forming a uniform surface on the inner surface of the integrating sphere, and then continuously collects 10 data through the detector. average of

2) Measurement of atmospheric radiation characteristics: When the remote sensor passes over the ground calibration field, the second solenoid valve is used to close the sunlight inlet, and the first solenoid valve is opened, so that the ground concentrating system is aligned with the center reference area of the calibration field, and the The light of the calibration field is collected by the concentrating system on the ground and then enters the integrating sphere, and then is reflected multiple times by the diffuse reflection coating to form a uniform illumination surface on the inner surface of the integrating sphere. Atmospheric transmittance.

According to the relative relationship between the reference area at the center of the calibration field and the orbit, for different calibration time points, the satellite swings within the range of ±10°. Considering the influence of the drift angle, the accuracy of the roll angle is required to be better than 0.1°, that is, the positioning accuracy of the atmospheric correction radiometer collection area is better than 1.54km.

The above descriptions are only preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements and improvements made within the spirit and principles of the present invention shall be included in the protection of the present invention. within the range.

Claims (9)

1. a radiometer for remote sensor on-orbit atmospheric correction, characterized in that: the radiometer comprises an integrating sphere, and the inner surface of the integrating sphere is coated with a diffuse reflection coating; the integrating sphere is provided with a concentrating light on the ground a port, a solar light incident port and at least one detector interface; the ground-facing light-concentrating port is connected to a light-concentrating system, and a first solenoid valve is arranged between the ground-facing light-concentrating port and the light-concentrating system; the solar light incident The port is provided with a second solenoid valve; the detector interface is provided with a collimation correction module and a detector module; the incident light from the ground concentrating port and the sunlight entrance port enters the integrating sphere and passes through the diffuse reflection coating for many times. Reflect, form a uniform surface on the inner surface of the integrating sphere, and then import it into the detector module through the collimation correction module of the detector interface. 2 . A radiometer for on-orbit atmospheric correction of a remote sensor according to claim 1 , wherein the light-concentrating system is a reflective structure. 3 . 3. A radiometer for remote sensor on-orbit atmospheric correction according to claim 1, characterized in that: the collimation and correction module comprises a field diaphragm and a correction collimator lens, and the correction collimator lens It is placed in the field diaphragm, and the light enters the correction collimating lens from the detector interface and then guides into the detector module. 4. A radiometer for remote sensor on-orbit atmospheric correction according to claim 1, characterized in that: the detector module comprises a filter and a detector unit, and the light is guided into the detector after passing through the filter unit. 5 . A radiometer for on-orbit atmospheric correction of a remote sensor according to claim 4 , wherein the detector unit is an InGaAs detector. 6 . 6 . The radiometer according to claim 5 , wherein the InGaAs detector is an integrated detector, which integrates at least one pixel. 7 . 7 . A radiometer for on-orbit atmospheric correction of a remote sensor according to claim 4 , wherein the detector unit is a Silicon detector. 8 . 8. A radiometer for on-orbit atmospheric correction of a remote sensor according to claim 1, characterized in that: the incident flux of the concentrating port on the ground and the incident flux of the sunlight incident port are kept equal, because The sunlight incident flux is

in,

is the solar irradiance outside the atmosphere, b _λ is the bandwidth, θ is the incident angle of sunlight, and D _s is the aperture of the solar light entrance; The incident flux to the concentrator is

in,

is the upward atmospheric transmittance,

is the downward atmospheric transmittance, ρ(λ) is the ground reflectivity, τ ₀ (λ) is the transmittance of the ground observation concentrating system, Ω is the solid angle formed by the orbit height and the ground, and D _o is the concentrating port on the ground caliber; when

Then the relationship between the aperture of the sunlight entrance and the aperture of the concentrator on the ground is:

9. A kind of measurement method based on the described radiometer for remote sensor on-orbit atmospheric correction according to claim 1-8, is characterized in that: comprise as follows: 1) Self-calibration correction of the radiometer: the mean value of the output of the radiometer to the solar observation detector when the remote sensor passes a certain solar altitude during orbital operation is the same as the radiometer when the remote sensor passed the same solar altitude during the orbital operation. The ratio of the output mean of the daily observation detector to determine the relative attenuation of the radiometer itself; Among them, the average output of the detector is the time t from the solar altitude angle α to the solar altitude angle β of the remote sensor running in the orbit. The first solenoid valve is used to close the concentrating port on the ground, and the second solenoid valve is opened to allow sunlight to enter. For daily observation, the incident light enters the integrating sphere and is reflected multiple times by the diffuse reflection coating to form a uniform surface on the inner surface of the integrating sphere.

2) Measurement of atmospheric radiation characteristics: When the remote sensor passes over the ground calibration field, the second solenoid valve is used to close the sunlight inlet, and the first solenoid valve is opened, so that the ground concentrating system is aligned with the center reference area of the calibration field, and the The light of the calibration field is collected by the concentrating system on the ground and then enters the integrating sphere, and then is reflected multiple times by the diffuse reflection coating to form a uniform illumination surface on the inner surface of the integrating sphere. Atmospheric transmittance.

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