Study of target imaging features and signal to noise ratio for space-based laser warning system

Features of target image and signal to noise ratio(SNR) are important performance parameters for system design,threaten laser detection and attack event determination of space-based laser warning system.Based on the introduction of the warning system architecture,the imaging spots of threaten laser by near infrared detector of system are analyzed and verified by experiments.The background light radiation environment of system is discussed and the solar irradiance at the pupil of camera in system operating waveband is obtained.The calculation formula of SNR is derived and the SNR of system for threaten laser is given.The results show that the spot size of threaten laser is about 26.5 μm for normal incidence.The profile of imaging spot is changing from circle to ellipse with the incident angle increasing,and the spot area are becoming larger due to the blooming effects for the high energy intensity of laser.The main background light radiation of the warning system is the sunlight reflected by earth in the short wave infrared spectral range.Solar light of the system optical pass band exposure the detector focal plane,and generate uniform image background.The SNR of system depends on the solar zenith angle,the power density of threaten laser and the filter transmission function.The minimum of SNR are 40 dB and 60 dB for blinding laser and damage laser separately.