Mathematical modelling of the apparatus channel of an infrared remote sensing system

This paper presents a mathematical model of the apparatus channel of an infrared remote sensing radiometric system. The latter comprises: (1) the sounded object. This may be a medium, such as a cloud or a dense aerosol layer caused by a temperature inversion; (2) background radiation; (3) the atmospheric channel, or the medium where the signal radiation from the sounded object and the background radiations propagate; (4) the apparatus channel or the infrared radiometer itself. The system described is useful for investigating, measuring or controlling objects and media. The apparatus channel modelled is proposed as a lock-in detector. The joint action of all types of noise due to the stochastic nature of the infrared radiation or to the optoelectronic and electronic conversions is discussed. The final results allow calculation of the apparatus channel output signal-to-noise ratio.