Research On The Return Signals Simulation Of Spaceborne Atmosphere Detection Lidar

The atmospheric detection lidar emits laser pulses and receives backscattered return signals from clouds,aerosols,and atmospheric molecules.It is an internationally recognized best method for measuring the vertical distribution of aerosols and thin cirrus clouds.With the steady development of ground-based lidar technology in China,the technological level of lidar key devices such as laser and discriminator has been significantly improved.At present,spaceborne multi-wavelength,high-spectrum resolution“wind-aerosol-cloud”joint detection lidar is being developed.The simulation of the return signals and environment noise of the spaceborne atmospheric detection lidar provides a better detection capability of the system and minimizing the noise of return signals.In this paper,we analyze the influence of atmospheric components?molecules and aerosols?on return signals and the magnitude of solar noise of return signals at different satellite passing times.The main work is divided into the following two aspects:?1?Firstly,extinction effects of atmospheric gases?e.g.,H₂O,CO₂,and O₃?and six types of aerosols?clean continental,clean marine,dust,polluted continental,polluted dust,and smoke?on return signals of space-based lidar system at 355 nm,532 nm,1064 nm,and 2051 nm channels,based on a robust lidar return signal simulator in combination with the line-by line radiative transfer model?LBLRTM?.The results show that 2051 nm wavelength channel is suitable for retrieving CO₂ due to the transmittance of CO₂ at the wavelength of 2051 nm is close to 0,while the transmittances of H₂O and O₃ are both100%.spectral transmittance also reveals another possible window for CO₂ and H₂O detection at 2051.6 nm,since their transmittance both near 0.5.Moreover the corresponding Doppler return signals at 2051.6 nm channel can be used to retrieve wind field.Thus we suggest 2051 nm channel may better be centered at 2051.6 nm.By analyzing the signal-to-noise?SNR?,it concludes that as the wavelength increases,the upper and lower limits of the detection range are decreasing.The results clearly show that high SNR values can be seen ubiquitously in the atmosphere ranging from the height of aerosol layer top to 25 km at 355 nm,it can be found at 2051.6 nm in the lower troposphere that highly depends on aerosol distribution scenario in the vertical.This indicates that the Doppler space-based lidar system with a double-channel joint detection mode is able to retrieve atmospheric wind field or profile from 0 to 25 km.?2?solar angles are calculated after satellite orbits with different transit time are simulated by STK?satellite tools kit?,then the solar radiances are simulated by LBLRTM and the solar background noise can be calculated.We analyze the distribution characteristics of solar background noise and the effect of solar background noise at different transit times on the return signals.The results show that there is a clear seasonal difference in the distribution of solar zenith angles.The solar zenith angles of the January and July is smaller solar zenith angles than the angles of April and October.The satellite transit times of 22:30 and 13:30 are selected for the orbital altitudes of 400km and 705km,respectively,and the solar background noise of lidar return signal are smaller.