The Optical Design Of Spectrometer With High Spectral Resolution And Wide Swath Of Greenhouse Gas Detection

Due to the emission of large amount of CO₂ and other greenhouse gases,climate problem is becoming more and more serious.As a result,greenhouse gas emission has become the focus of attention in the world.In order to detect the content of greenhouse gases in the earth's atmosphere,including two components of carbon dioxide and methane,this paper designs a device with four detection bands,wide swath space borne immersion plane diffraction grating spectrometer optical system.The four spectrometer optical systems correspond to four kinds of gas detection bands.The optical systems of the four spectrometers correspond to four kinds of gas detection bands respectively.The parameters of the four gas detection bands are as follows:1st.1.606?m band:Spectral range: 1.590?m-1.622?m;band with: 32nm;central wavelength: 1.606?m;spectral resolution: 0.08nm/20000;spatial resolution: 2km;ground swath width:500km;spectral dimension pixel number: 1000;spatial dimension number: 250;pixel size: 20?m;2nd.1.660?m band:Spectral range: 1.644?m-1.676?m;band with: 32nm;central wavelength: 1.660?m;spectral resolution: 0.08nm/20000;spatial resolution: 2km;ground swath width:500km;spectral dimension pixel number: 1000;spatial dimension number: 250;pixel size: 20?m;3rd.2.064?m band:Spectral range: 2.0435?m-2.0845?m;band with: 41nm;central wavelength:2.064?m;spectral resolution: 0.1032nm/20000;spatial resolution: 2km;ground swath width: 500km;spectral dimension pixel number: 1000;spatial dimension number: 250;pixel size: 20?m;4th.0.765?m band:Spectral range: 0.758?m-0.772?m;band with: 14nm;central wavelength: 0.765?m;spectral resolution: 0.045nm/17000;spatial resolution: 2km;ground swath width:500km;spectral dimension pixel number: 777;spatial dimension number: 250;pixel size: 20?m;The altitude of the satellite orbit is 690 km,the field of view is 2? 19.92 degrees,the instantaneous field of view is 0.166 degree.Push broom scanning mode is used.The optical system of the spectrometer consists of a front system and a lightsplitting system.The front system is designed with a transmission telescope,which consists of four lenses and one aperture.The pupil diameter is 3.8mm,the F number is1.8,the focal length is 6.9mm.The light splitting system consists of an incident slit,a collimating lens group,a immersion plane diffraction grating,a imaging lens group and an image plane.Because of the type of Littrow optical structure,the collimating lens group and the imaging lens group of this system are one combination.The MTF of the spectrometer system is better than 0.65 at Nyquist frequency.Nearly 90% of the concentration of the diffraction energy is in a single pixel size.Hyperspectral detection can be achieved.In this paper,the optical structures of four detection bands are analyzed one by one.Four additional kinds of tolerance is set up,with the default tolerance settings.Sensitivity analysis and Monte Carlo method are used to analyze the structure.The stray light analysis is carried out respectively for the grating spectrometer of four detection bands.Four kinds of structures to suppress stray light are designed,including the front hood,slit,stage 0 light trap,outer cover.The results show that the four kinds of structures can effectively prevent stray light from affecting the spectrometer system.Factors affecting the swath width of the spaceborne grating spectrometer was introduced.The principle of geometric distortion is introduced.The influential factors of spectral resolution are analyzed theoretically..