FREQUENCY-MODULATION-ENHANCED REMOTE-SENSING

A highly sensitive pulse amplified frequency modulation based spectros copic technique for remote sensing applications (FMRS) has been develo ped. We demonstrate that scattered light returned to a photodetector f rom distributed scattering centers permits the basic heterodyne detect ion process to be carried out. The FM photocurrent expected from scatt ering by an aerosol or cloud is sufficient for detection of atmospheri c species over ranges of up to 2 km at levels of 10(6) to 10(12) molec ules cm(-3). FMRS has the potential of being a general method for moni toring atmospheric trace gases at ambient levels.