DETECTION OF THERMAL EMISSION FROM ATMOSPHERIC GASES BY LASER HETERODYNE RADIOMETRY

A gaseous component is considered as a self emitting source that can b e detected and characterized remotely by its thermal emission spectrum . The required spectrum analyser should have an appropriately narrow b andwidth. For an atmospheric component, with isolated absorption lines , the linewidths are about 0.1 cm-1 or 3 GHz under standard conditions . This leads to the need for a high resolution radiometer. A laser het erodyne radiometer (LHR) has been used to detect the emission of two c omponents (C2H4 and NH3) at 10 mum wavelength under atmospheric pressu re.