Abstract: An apparatus directed to a signal processing circuit for combining data from several spectral bands to enhance the signal-to-background ratio of a target detection system. Two spectral bands, with separate sensing arrays, receive analog signals which are fed to separate multiplexer units. From the multiplexers, the analog signals are applied to a comparator where they are compared with each other and also separately applied to shift registers where the signals are retained for further processing. If, during comparison, the ratio of the two bands is less than a threshold, there is an absence of cloud return and the signals stored in both shift registers are combined in a final output register. If the ratio of the two bands is more than a threshold, the band having the most cloud return is not used and the shift register containing the greater percentage of target return is processed through the output register.