Research On The Instrument Line Shape Of High Resolution Time Interference Spectrometer

High resolution interferometric spectrometer has an important application prospect in the field of spaceborne hyperspectral remote sensing,in which the instrument line shape is an important characterization parameter in the process of quantitative application of this type of remote sensor data.At present,with the rapid development of hyperspectral satellite payload in China,higher requirements are put forward for the spectral calibration accuracy of instruments.Therefore,the calibration method of linear function proposed in this paper is of great significance to improve the spectral accuracy.The main contents of this paper are as follows:first,the influence of abnormal points,phase errors,fringe counting errors on spectrum and instrument line shape are studied,and then the interference error is corrected;Secondly,the influence of the finite field of view angle,off-axis effect and laser wavelength on the linear function of the instrument is studied;Third,combining with the factors affecting the linear function of the instrument,the paper puts forward the correction method of instrument line shape for rectangular and circular probe elements,and improves the spectral accuracy.In order to reduce the influence of interferogram error on the research of instrument line shape,this paper first completes the simulation research of the influence of interferogram error on the spectrum,and makes clear the specific influence of interferogram error on the spectrum.At the same time,the related interferogram error is corrected,and the abnormal points of interferogram are eliminated by threshold detection after filtering.The phase error caused by the asymmetry of interferogram is aligned with the blackbody interference data to eliminate the phase error.The phase error of fringe counting error is detected by linear function fitting,and then the error is corrected.For the rectangular and circular probe elements,the influence factors of the corresponding instrument line shape are studied.For the circular and rectangular probe elements,the probe element size will affect the field of view,and then lead to the spectral frequency offset,which has a linear correlation with the probe element size;the off-axis effect is positively correlated with the off-axis distance of the probe element,and negatively correlated with the focal length of the collimator,respectively,but they are not collimated at the same change distance The influence of mirror focal length is only about two thousandths of off-axis distance,and off-axis distance is the primary factor.Especially,for the rectangular probe,the off-axis effect of the probe along the diagonal direction is the smallest,while the off-axis effect of the probe along the transverse and longitudinal direction is the largest.The change of laser sampling wavelength affects the spectral frequency offset,and its jitter will seriously affect the shape of the spectral line.Based on the analysis of influence factors and formula derivation,a calibration method of instrument line shape is proposed,which is suitable for both ground and orbit instruments,including the calibration of circular and rectangular probe elements.The correction method improves the matrix correction method to improve the accuracy of on orbit spectral calibration.For circular probe,by comparing with the reference spectrum,it iterates the focal length of the instrument collimator and the off-axis distance of the probe,obtains the actual value of the instrument parameters,updates the correction matrix,and completes the correction of the linear function error of the instrument;for rectangular probe,it corrects the focal length of the instrument collimator and the transverse distance of the probe After iteration of ordinate,the actual value is obtained and the matrix is updated to complete the correction.The calibration accuracy of 0.11 ppm can be achieved for circular probe simulation data,0.23ppm can be achieved for rectangular probe,and 0.39ppm can be achieved for load data.The results show that the calibration method proposed in this paper is reasonable and feasible.By correcting the instrument linear shape error,high-precision spectral calibration can be achieved.This paper has a certain reference significance for the actual spectral calibration research and engineering.