A cryogenically operated laser diode spectrometer for airborne measurement of stratospheric trace gases

A cryogenically operated laser diode spectrometer (COLD) for the airborne measurement of carbon monoxide is described. The instrument is designed, and fully qualified, for operation on a high-altitude aircraft and the scientific mission is the in situ measurement of trace gases in the upper troposphere and lower stratosphere. Sensitivities achieved so far during in-flight operation are a few ppbV with a time resolution of 4 s, coupled with a good reliability. Airborne data, obtained by COLD during research campaigns in Australia and Brazil in the frame of international projects, are also presented to demonstrate COLD in-flight performance.