CN104457985B - A kind of in-orbit spectrum calibration method of color dispersion-type high light spectrum image-forming remote sensor - Google Patents

Abstract

The spectrum calibration method in-orbit of a kind of color dispersion-type high light spectrum image-forming remote sensor, (1) crosses extraction DN value the remote sensing images in place from high light spectrum image-forming remote sensor, and is converted to the entrance pupil spoke brightness of high light spectrum image-forming remote sensor place；(2) simultaneous ground-based measurements spectroscopic data is brought into the simulation of high-resolution atmospheric radiation transmission and calculates ultraspectral resolution entrance pupil spoke brightness；(3) each channel spectrum receptance function under different side-play amount is built according to Laboratory spectral calibration parameter；(4) by ultraspectral resolution entrance pupil spoke brightness channel spectrum receptance function convolution each under different side-play amounts, ultraspectral resolution is down to the spectral resolution of high light spectrum image-forming remote sensor, and spectrally resolved rate curve drops in the ultraspectral obtained under different side-play amount；(5) utilize entrance pupil spoke brightness curve in place in step (1) drop from the ultraspectral under different side-play amounts spectrally resolved rate curve carry out Spectral matching obtain high light spectrum image-forming remote sensor in orbit in center wavelength shift and bandwidth change.

Description

A kind of in-orbit spectrum calibration method of color dispersion-type high light spectrum image-forming remote sensor

Technical field

The present invention relates to a kind of place spectrum calibration method in-orbit based on color dispersion-type high light spectrum image-forming remote sensor, particularly to the place spectrum calibration method in-orbit of TG-1 color dispersion-type high light spectrum image-forming remote sensor.

Background technology

High light spectrum image-forming remote sensor can obtain the continuous print curve of spectrum of the various atural objects observed in the ken, and its spectral resolution can reach nanometer scale.The abundant spectral information of its offer, can determine that special spectral signature, it is achieved the fine of atural object identifies and quantitative inversion.

The reliability of high light spectrum image-forming remote sensor data and the degree of depth of application and range depend greatly on spectral calibration precision.Only could extract real object spectrum curve from image through the high light spectrum image-forming remote sensor of spectral calibration.

Spectral calibration mainly includes Laboratory Calibration, onboard process and radiometric calibration site in-orbit.Often utilizing monochromatic remote sensor to carry out spectral calibration in laboratory, calibration precision is the highest.Onboard process is similar with Laboratory Calibration, but a series of equipment of Laboratory Calibration are impossible to indiscriminately imitate to be transplanted on satellite, and must flow through and simplify the purpose reaching calibration, often selects the sun as reference light source.Decay due to onboard process remote sensor device, it is necessary to utilize In-flight calibration method to be corrected.

Summary of the invention

The technology of the present invention solves problem: solve the spectral calibration problem of place in-orbit of color dispersion-type high light spectrum image-forming remote sensor, it is provided that a kind of calibrating method that can accurately obtain high light spectrum image-forming spectrum remote sensor centre wavelength and band.This method utilizes place simultaneous observation in-orbit, carries out high light spectrum image-forming remote sensor spectral calibration in-orbit, it is possible to Simultaneous Inversion center wavelength shift amount and bandwidth variable quantity, is effectively improved spectral calibration precision in-orbit.

The technical solution of the present invention is: the spectrum calibration method in-orbit of a kind of color dispersion-type high light spectrum image-forming remote sensor, and step is as follows:

(1) cross extraction DN value the remote sensing images in place from high light spectrum image-forming remote sensor, and be converted to the entrance pupil spoke brightness of high light spectrum image-forming remote sensor place；

(2) simultaneous ground-based measurements spectroscopic data is brought into the simulation of high-resolution atmospheric radiation transmission and calculates ultraspectral resolution entrance pupil spoke brightness；

(3) each channel spectrum receptance function under different side-play amount is built according to Laboratory spectral calibration parameter；

(4) by ultraspectral resolution entrance pupil spoke brightness channel spectrum receptance function convolution each under different side-play amounts, ultraspectral resolution is down to the spectral resolution of high light spectrum image-forming remote sensor, and spectrally resolved rate curve drops in the ultraspectral obtained under different side-play amount；

(5) utilize entrance pupil spoke brightness curve in place in step (1) drop from the ultraspectral under different side-play amounts spectrally resolved rate curve carry out Spectral matching obtain high light spectrum image-forming remote sensor in orbit in center wavelength shift and bandwidth change.

Each channel spectrum receptance function S in described step (3)_i(λ,δ₁,δ₂) it is:

$S_i(\mathrm{\λ},{\mathrm{\δ}}_1,{\mathrm{\δ}}_2)=\exp [-{\left(\frac{(\mathrm{\λ}-{\mathrm{\λ}}_c\left(i\right)-{\mathrm{\δ}}_1)}{({\mathrm{\σ}}_i-{\mathrm{\δ}}_2)/2\sqrt{\ln 2}}\right)}^2]$

In formula: λ is wavelength；

λ_c(i), σ_iThe centre wavelength of each passage i respectively provided in Laboratory spectral calibration parameter and half-wave width；

δ₁, δ₂Respectively center wavelength shift amount and bandwidth variable quantity.

Described step (5) is by Spectral matching cost function χ²(δ₁,δ₂) solve minima, it is determined that spectral response functions, and then obtain center wavelength shift amount and bandwidth variable quantity, wherein χ²(δ₁,δ₂) function is as follows:

${\mathrm{\χ}}^2({\mathrm{\δ}}_1,{\mathrm{\δ}}_2)=\underset{j=N1}{\overset{N2}{\mathrm{\Σ}}}{[s_j({\mathrm{\δ}}_1,{\mathrm{\δ}}_2)-s_j]}^2$

In formula, s_j(δ₁,δ₂) it is the ultraspectral resolution entrance pupil spoke brightness resolution decreasing curve of spectrum under different side-play amount；

s_jFor the high light spectrum image-forming remote sensor entrance pupil place spectral radiance curve that place is extracted；

N1, N2 be selected characteristic absorption peaks border wave band respectively.

The present invention compared with prior art has the beneficial effect that

(1) present invention utilizes place spectrum measuring data, it is achieved that the spectral calibration in-orbit of color dispersion-type high light spectrum image-forming remote sensor.

(2) the spectral calibration algorithm of the present invention utilizes Spectral matching cost function, improves execution efficiency and the spectral calibration precision of program.

(3) present invention has successfully carried out the spectral calibration of TG-1 high light spectrum image-forming remote sensor, it is possible to effectively monitor the spectral drift problem of color dispersion-type high light spectrum image-forming remote sensor, and high-spectrum remote-sensing application is had great importance.

Accompanying drawing explanation

Fig. 1 is the inventive method flow chart.

Detailed description of the invention

Below in conjunction with accompanying drawing, the present invention is elaborated, as it is shown in figure 1, specifically comprise the following steps that

(1) high light spectrum image-forming remote sensor place Apparent radiance calculates

Radiation calibration coefficient according to high light spectrum image-forming remote sensor, obtains Apparent radiance during high light spectrum image-forming remote sensor interlude overhead, ground by formula (1).

L_i(λ)=Gain_i×DN_i+offset_i(1)

In formula: L_i(λ) for the spoke brightness of high light spectrum image-forming remote sensor respective channel；

DN_iFor the count value of respective channel on high light spectrum image-forming remote sensor interlude ground image；

Gain_i、offset_iThe respectively gain of the radiation calibration coefficient of high light spectrum image-forming remote sensor respective channel and skew.

(2) ultraspectral resolution entrance pupil spoke brightness calculation

According to the atmospheric radiative transfer equation that the sun-air-earth's surface interacts, utilize place synchro measure data, according to high-resolution atmospheric radiation transmission, obtain ultraspectral resolution Apparent radiance by formula (2) simulation.

$L_{\mathrm{TOA}}\left(\mathrm{\λ}\right)=L_0\left(\mathrm{\λ}\right)+\frac{\mathrm{\ρT}\left(\mathrm{\μ}\right)}{1-\mathrm{S\ρ}}\frac{E_d}{\mathrm{\π}}---\left(2\right)$

In formula: L_TOA(λ) it is the spectral radiance of high light spectrum image-forming remote sensor；

L₀(λ) be atmospheric path radiation produce spectral radiance；

f_B(λ) for the spectral response functions of domestic multispectral load respective channel；

ρ is the spectral reflectivity in place；

S is the hemisphere albedo that air is downward；

T (μ) is total transmitance that Top Of Atmosphere is arrived on earth's surface；

E_dIt is the incident radiation total on earth's surface when ρ=0.

(3) structure of spectral response functions under different side-play amounts

According to color dispersion-type high light spectrum image-forming remote sensor, under different side-play amounts, the available formula (3) of spectral response functions builds.

$S_i(\mathrm{\λ},{\mathrm{\δ}}_1,{\mathrm{\δ}}_2)=\exp [-{\left(\frac{(\mathrm{\λ}-{\mathrm{\λ}}_c\left(i\right)-{\mathrm{\δ}}_1)}{({\mathrm{\σ}}_i-{\mathrm{\δ}}_2)/2\sqrt{\ln 2}}\right)}^2]---\left(3\right)$

In formula: λ is wavelength；

S_i(λ,δ₁,δ₂) it is the spectral response functions under different side-play amount；

λ_c(i), σ_iThe centre wavelength of each passage respectively provided in Laboratory spectral calibration parameter and half-wave width；

δ₁, δ₂Respectively center wavelength shift amount and bandwidth variable quantity.

(4) by ultraspectral resolution entrance pupil spoke brightness and each channel spectrum receptance function convolution, ultraspectral entrance pupil spoke brightness is down to the spectral resolution of high light spectrum image-forming remote sensor；

(5) Spectral matching

Near Atmospheric Absorption peak wave band carry out Spectral matching adopt formula (4) be calculated, to function χ²(δ₁,δ₂) solve minima, obtain spectral calibration parameter (center wavelength shift amount and bandwidth variable quantity): when Spectral matching cost function reaches minima, spectral response functions is just uniquely determined, i.e. δ₁、δ₂Determine.The process minimized is actually and constantly adjusts δ₁、δ₂, so that Spectral matching cost function reaches minima.

${\mathrm{\χ}}^2({\mathrm{\δ}}_1,{\mathrm{\δ}}_2)=\underset{j=N1}{\overset{N2}{\mathrm{\Σ}}}{[s_j({\mathrm{\δ}}_1,{\mathrm{\δ}}_2)-s_j]}^2---\left(4\right)$

In formula: χ²(δ₁,δ₂) Spectral matching cost function；

s_j(δ₁,δ₂) it is the ultraspectral entrance pupil spoke brightness resolution decreasing curve of spectrum under different side-play amount, the curve namely obtained after step (4) process of convolution；

s_jFor place extract high light spectrum image-forming remote sensor entrance pupil place spectral radiance curve, step (1) result obtain；

N1, N2 are distinguished as selected characteristic absorption peaks border wave band.

The present invention is unspecified partly belongs to general knowledge as well known to those skilled in the art.

Claims (3)

1. the spectrum calibration method in-orbit of a color dispersion-type high light spectrum image-forming remote sensor, it is characterised in that step is as follows:

(1) cross extraction DN value the remote sensing images in place from high light spectrum image-forming remote sensor, and be converted to the entrance pupil spoke brightness of high light spectrum image-forming remote sensor place, and then obtain place entrance pupil spoke brightness curve；

(2) simultaneous ground-based measurements spectroscopic data is brought into the simulation of high-resolution atmospheric radiation transmission and calculates ultraspectral resolution entrance pupil spoke brightness；

(3) each channel spectrum receptance function under different side-play amount is built according to Laboratory spectral calibration parameter；

(4) by ultraspectral resolution entrance pupil spoke brightness channel spectrum receptance function convolution each under different side-play amounts, ultraspectral resolution is down to the spectral resolution of high light spectrum image-forming remote sensor, and spectrally resolved rate curve drops in the ultraspectral obtained under different side-play amount；

(5) utilize entrance pupil spoke brightness curve in place in step (1) drop from the ultraspectral under the different side-play amounts in step (4) spectrally resolved rate curve carry out Spectral matching obtain high light spectrum image-forming remote sensor in orbit in center wavelength shift and bandwidth change.

2. the spectrum calibration method in-orbit of a kind of color dispersion-type high light spectrum image-forming remote sensor according to claim 1, it is characterised in that: each channel spectrum receptance function S in described step (3)_i(λ,δ₁,δ₂) it is:

$S_i(\mathrm{\λ},{\mathrm{\δ}}_1,{\mathrm{\δ}}_2)=\exp \[-{\left(\frac{(\mathrm{\λ}-{\mathrm{\λ}}_c(i)-{\mathrm{\δ}}_1)}{({\mathrm{\σ}}_i-{\mathrm{\δ}}_2)/2\sqrt{ln2}}\right)}^2\]$

In formula: λ is wavelength；

λ_c(i), σ_iThe centre wavelength of each passage i respectively provided in Laboratory spectral calibration parameter and half-wave width；

δ₁, δ₂Respectively center wavelength shift amount and bandwidth variable quantity.

3. the spectrum calibration method in-orbit of a kind of color dispersion-type high light spectrum image-forming remote sensor according to claim 1, it is characterised in that: described step (5) is by Spectral matching cost function χ²(δ₁,δ₂) solve minima, it is determined that spectral response functions, and then obtain center wavelength shift amount and bandwidth variable quantity, wherein χ²(δ₁,δ₂) function is as follows:

${\mathrm{\χ}}^2({\mathrm{\δ}}_1,{\mathrm{\δ}}_2)=\underset{j=N1}{\overset{N2}{\Σ}}{\[s_j({\mathrm{\δ}}_1,{\mathrm{\δ}}_2)-s_j\]}^2$

In formula, s_j(δ₁,δ₂) it is the ultraspectral resolution entrance pupil spoke brightness resolution decreasing curve of spectrum under different side-play amount；

s_jFor the high light spectrum image-forming remote sensor entrance pupil place spectral radiance curve that place is extracted；

N1, N2 be selected characteristic absorption peaks border wave band respectively.