Research On Spectrum Detection Technology With High Spectral Resolution And High Signal To Noise Ratio And Spectral-radiometric Calibration Method

Carbon emission is becoming a topic of more and more concern as global warming.There are obvious disadvantages to detect the density of the greenhouse gases with atmospheric monitoring station: the only data of the specific places can be obtained,and the distribution of the monitoring stations is very uneven.The most part is concentrated in the developed countries such as the Unites States and Europe,the ones of the other areas are few.It is hard to acquire the data about emission and absorption of the greenhouse gases on a global scale.Moreover,gas distributing information of vertical direction can not be obtained with ground-based observation.With the development of science and technology,satellite remote sensing technology has become the effective means for the environment monitoring and predicting.And it has been applied successfully in retrievals of atmospheric pressure,temperature and humidity and identification of atmospheric molecule and aerosol type.Compared with traditional monitoring method,satellite remote sensing monitoring can acquire the information of atmospheric trace gas on a global scale smoothly,economically,and repeatedly.The countries advanced in aerospace have carried out the research on space-borne infrared hyperspectral technology aimed at greenhouse gas emissions.China currently has executed “China's National Climate Change Programme”,this project implements an experimental scientific satellite for monitoring CO2 globally.Detecting atmospheric trace gas with remote sensing is based on gas absorption spectra.This paper focuses on the spectrum detection technology with high spectral resolution and high signal to noise ratio(SNR).The research mainly includes SNR improvement,laboratory spectral-radiometric calibration and on-orbit spectral correction.The details of this research were as follows: 1)Start with the main performance parameters of the High Resolution Hyper-Spectral Sensor for carbon observation Grating Spectrometer(HRHS-GS),the detailed designs of optical and imaging system were introduced.Attention is fixed on spectral resolution,special resolution and SNR,establishing theoretical basis for the model “Multiplex Merging of Spectral Pixels” and spectral-radiometric calibration.2)Polarization state of the instrument was explained,atmospheric radiative transfer model in glint mode was established,the incident energy of the instrument was discussed.The solution to weak incident energy for ocean glint observation was given.Moreover,in the light of the situation that the SNR of the two CO2 channels didn't satisfy the requirements of performance,the model “Multiplex Merging of Spectral Pixels” was established.The SNR was improved by increasing incident energy of a single spectral channel without reducing spectral sampling.The influence to transmittance spectra from spectral broadening was evaluated quantitatively through theoretical simulation and experimental results.3)Aiming at the characteristics of the HRHS-GS,a laboratory spectral-radiometric calibration system was established.Spectral calibration adopted monochromator and tunable laser to measure instrument line shape(ILS),center wavelength,and bandwidth.These two methods would be compared and verified each other for high calibration precision.Laboratory radiometric calibration adopt national radiance standard lamp,standard white board to measure the relationship between instrument output value and input radiance.4)Taking into account the on-orbit operation mode,an on-orbit spectral-radiometric calibration method was proposed to correct performance deviation due to environment changes,launch vehicle vibration and space radiation.Taking the 0.76?m O2-A band as an example,the availability of the on-orbit spectral correction was verified,satisfying the spectral calibration accuracy requirement of better than ??/10.In this paper,the spectrum detection technology with high spectral resolution and high SNR was studied.The problems of fine spectrum detecting and SNR improvement were solved.The above-mentioned study supplied theoretical basis and technical support for the retrieval of CO2 concentration.