A Balloon-Borne Tunable Diode Laser Absorption Spectrometer for Multispecies Trace Gas Measurements

A balloon-borne tunable diode laser absorption spectrometer capable of in situ measurement of the concentrations of several stratospheric trace gases simultaneously in the same parcel of air is described. Laboratory tests show present detection limits of 1.5 ppbv for NO and 0.5 ppbv for NO2 under stratospheric conditions. This instrument was flown in July 1983 to make the first tunable diode laser measurement in the stratosphere. The concentration of NO2 at 31.4 km and a solar zenith angle of 68° were measured to be 13.4 ± 5.2 ppbv. The instrument was recovered intact. This success has led to plans to conduct additional NO/NO2 flights and to upgrade the spectrometer to measure other gas species.