CN103674237A - A method for calibrating cross radiance of an infrared fixed star and a sky background - Google Patents

Abstract

The invention relates to a method for calibrating cross radiance of an infrared fixed star and a sky background. Firstly, two infrared standard fixed stars are selected. The radiance responsivity of a device is calibrated. Because a foundation observation apparatus is a multiunit detector, a five-point multi-data-acquisition method is utilized. Then, a sky background with a high elevation angle is measured and single-point radiation calibration is performed. A corresponding relation (calibration equation) between irradiance and output gray scale of a calibrating source at a foundation observation apparatus entrance pupil site is established. A calibrating coefficient is solved in order to give a deviation case between an observation apparatus calibrating curve and a laboratory calibration coefficient before and after a target is measured. The method has a low test site requirement, does not need extra calibrating devices, and is easy to implement.

Description

A kind of infrared fixed star and sky background cross radiance Calibration Method

Technical field

The present invention relates to a kind of infrared fixed star and sky background cross radiance Calibration Method, particularly relate to infrared fixed star and the sky background cross radiance Calibration Method in a kind of objective optics characteristic research field.

Background technology

When ground observation equipment is carried out the measurement of extraterrestrial target radiation characteristic, to accurately complete quantitative measurment and analysis to institute's research object, need carry out the calibration of radiometric response degree to equipment, set up the strict corresponding relation of detector input quantity (voltage, electric current, gray scale etc.) and output quantity (radiance, radiation flux etc.).The measuring accuracy of data depends on stated accuracy to a great extent, and therefore, oneself becomes one of important step in the development of radiation characteristic measuring system, use calibration process.

Although having carried out accurate indoor detection to its responsiveness when dispatching from the factory, demarcates by measuring equipment, but in actual use, environmental change, device be the factor such as stability change in time, cause the response curve of measuring equipment to change, need to carry out test forward and backward, or interim calibration measurement, the output response variance causing because of factors such as service time, environmental changes in order to calibration.

Through investigation, collect related data: current domestic ground radiation of equipment calibration technology adopts black matrix to add the method for collimating optical system more, and the method can realize the precise calibration to equipment, and shortcoming is high to the environmental requirement of testing ground.

Therefore need badly a kind of novel infrared fixed star and sky background cross radiance Calibration Method are provided.

Summary of the invention

The technical problem to be solved in the present invention is to provide a kind of need increases extra calibration facility, and easy infrared fixed star and the sky background cross radiance Calibration Method that is easy to realization of Calibration Method.

For solving the problems of the technologies described above, a kind of infrared fixed star of the present invention and sky background cross radiance Calibration Method, comprise the following steps successively:

Step 1, under the cloudless weather condition of clear sky, in infrared standard star catalogue, choose an infrared standard star and measure, make fixed star image in respectively detector Si Jiaohe center, carry out n time and measure, obtain the gray-scale value DN of each imaging pixel of measuring _1i;

Obtain equipment gray-scale value DN ₁;

${\mathrm{DN}}_1=\frac{1}{n}\underset{1}{\overset{n}{\mathrm{\Σ}}}{\mathrm{DN}}_{1i};$

Obtain the radiant illumination E outside stellar atmosphere layer ₀₁; Calculate the atmospheric path radiation E ' in observation path ₁with transmitance t ₁;

Obtain the radiant illumination E of equipment entrance pupil place ₁;

E ₁＝E ₀₁·t ₁+E ₁′；

Step 2, under the cloudless weather condition of clear sky, in infrared standard star catalogue, choose second infrared standard star and measure, make fixed star image in respectively detector Si Jiaohe center, carry out n time and measure, obtain the gray-scale value DN of each imaging pixel of measuring _2i;

Obtain equipment gray-scale value DN ₂;

${\mathrm{DN}}_2=\frac{1}{n}\underset{1}{\overset{n}{\mathrm{\Σ}}}{\mathrm{DN}}_{2i};$

Obtain the radiant illumination E outside stellar atmosphere layer ₀₂; Calculate the atmospheric path radiation E ' in observation path ₂with transmitance t ₂;

Obtain the radiant illumination E of equipment entrance pupil place ₂;

E ₂＝E ₀₂·t ₂+E ₂′；

Step 3, obtain radiometric response coefficient A;

$A=\frac{E_1-E_2}{{\mathrm{DN}}_1-{\mathrm{DN}}_2};$

Step 4, select fine cloudless air as calibration source, calculate the radiant illumination E of equipment entrance pupil place ₃, while recording unit gray-scale value DN ₃; Obtain radiometric response coefficient B ';

B'＝E ₃-A·DＮ ₃；

Step 5, obtain the calibration equation of the radiant illumination E of equipment entrance pupil place; DN is the gray-scale value of imaging pixel;

E＝A·DN+B′。

The present invention is by measuring infrared standard fixed star and sky background radiation, set up calibration source at the radiant illumination at ground based observa tion equipment entrance pupil place and the corresponding relation of output gray level (calibration equation), solve calibration coefficient, can be forward and backward at target measurement, provide the deviation situation of scope calibration curve and Laboratory Calibration coefficient.The present invention is low to the environmental requirement of testing ground, does not need to increase extra calibration facility, and easy being easy to of Calibration Method realized.

Embodiment

The present invention chooses two infrared standard fixed stars, and radiation of equipment responsiveness is carried out to calibration, because ground based observa tion equipment is multiunit detector, therefore, adopts 5 repeatedly collecting methods.Next measures high elevation angle sky background, carries out single-point radiation calibration.Concrete steps are followed successively by:

Step 1, under the cloudless weather condition of clear sky, in infrared standard star catalogue, choose an infrared standard star and measure, make fixed star image in respectively detector Si Jiaohe center, carry out n time and measure, obtain the gray-scale value DN of each imaging pixel of measuring _1i;

Obtain equipment gray-scale value DN ₁;

${\mathrm{DN}}_1=\frac{1}{n}\underset{1}{\overset{n}{\mathrm{\Σ}}}{\mathrm{DN}}_{1i};$

Obtain the radiant illumination E outside stellar atmosphere layer ₀₁; By MORTRAN software, calculate the atmospheric path radiation E ' in observation path ₁with transmitance t ₁;

Obtain the radiant illumination E of equipment entrance pupil place ₁;

E ₁＝E ₀₁·t ₁+E ₁′；

Step 2, under the cloudless weather condition of clear sky, in infrared standard star catalogue, choose second infrared standard star and measure, make fixed star image in respectively detector Si Jiaohe center, carry out n time and measure, obtain the gray-scale value DN of each imaging pixel of measuring _2i;

Obtain equipment gray-scale value DN ₂;

${\mathrm{DN}}_2=\frac{1}{n}\underset{1}{\overset{n}{\mathrm{\Σ}}}{\mathrm{DN}}_{2i};$

Obtain the radiant illumination E outside stellar atmosphere layer ₀₂; By MORTRAN software, calculate the atmospheric path radiation E ' in observation path ₂with transmitance t ₂;

Obtain the radiant illumination E of equipment entrance pupil place ₂;

E ₂＝E ₀₂·t ₂+E ₂′；

Step 3, obtain radiometric response coefficient A;

$A=\frac{E_1-E_2}{{\mathrm{DN}}_1-{\mathrm{DN}}_2};$

Step 4, select fine cloudless air as calibration source, using measuring condition as MORTRAN software input parameter, calculate the radiant illumination E of equipment entrance pupil place ₃, while recording unit gray-scale value DN ₃; Obtain radiometric response coefficient B ';

B'＝E ₃-A·DN ₃；

Step 5, obtain the calibration equation of the radiant illumination E of equipment entrance pupil place; DN is the gray-scale value of imaging pixel;

E＝A·DN+B′。

Claims (1)

1. infrared fixed star and a sky background cross radiance Calibration Method, comprise the following steps successively:

Step 1, under the cloudless weather condition of clear sky, in infrared standard star catalogue, choose an infrared standard star and measure, make fixed star image in respectively detector Si Jiaohe center, carry out n time and measure, obtain the gray-scale value DN of each imaging pixel of measuring _1i;

Obtain equipment gray-scale value DN ₁;

${\mathrm{DN}}_1=\frac{1}{n}\underset{1}{\overset{n}{\mathrm{\Σ}}}{\mathrm{DN}}_{1i};$

Obtain the radiant illumination E outside stellar atmosphere layer ₀₁; Calculate the atmospheric path radiation E ' in observation path ₁with transmitance t ₁;

Obtain the radiant illumination E of equipment entrance pupil place ₁;

E ₁＝E ₀₁·t ₁+E ₁′；

Step 2, under the cloudless weather condition of clear sky, in infrared standard star catalogue, choose second infrared standard star and measure, make fixed star image in respectively detector Si Jiaohe center, carry out n time and measure, obtain the gray-scale value DN of each imaging pixel of measuring _2i;

Obtain equipment gray-scale value DN ₂;

${\mathrm{DN}}_2=\frac{1}{n}\underset{1}{\overset{n}{\mathrm{\Σ}}}{\mathrm{DN}}_{2i};$

Obtain the radiant illumination E outside stellar atmosphere layer ₀₂; Calculate the atmospheric path radiation E ' in observation path ₂with transmitance t ₂;

Obtain the radiant illumination E of equipment entrance pupil place ₂;

E ₂＝E ₀₂·t ₂+E ₂′；

Step 3, obtain radiometric response coefficient A;

$A=\frac{E_1-E_2}{{\mathrm{DN}}_1-{\mathrm{DN}}_2};$

Step 4, select fine cloudless air as calibration source, calculate the radiant illumination E of equipment entrance pupil place ₃, while recording unit gray-scale value DN ₃; Obtain radiometric response coefficient B ';

B'＝E ₃-A·DＮ ₃；

Step 5, obtain the calibration equation of the radiant illumination E of equipment entrance pupil place; DN is the gray-scale value of imaging pixel;

E＝A·DＮ+B′。