Development of portable-type laser heterodyne spectrometer for the observation of the ozone hole

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The portable-type laser heterodyne spectrometer was designed in 1992 and its construction was completed in 1993. It is equipped with four tunable diode lasers for measurements of various trace gases in the wavelength region of 8-11 mu m. The weight of the optics is 70 kg. The fine adjustment of the optics is easier than the former type and the laser instability due to optical feedback is reduced. This spectrometer has realized an extremely high wavenumber resolution of 0.0013 cm^<-1> and a high signal-to-noise ratio (typically 1500 for O_3 and 500 for N_2O) for each spectrum measured every 10 minutes. These characteristics enable us to derive the altitude profiles of atmospheric minor gases in the troposphere and stratosphere from observated spectra. Many observations were performed using this portable-type laser heterodyne spectrometer. The vertical profiles of ozone, nitrous oxide, and methane were observed at Tsukuba and Sendai. In 1994, similar observations were carried out at Syowa station, Antarctica. In 1996 and 1997, observations of ozone, nitrous oxide, and methane were performed for the validation of RIS and ILAS instruments on board the ADEOS satellite. Thus, important information on the ozone depletion processes was obtained using the portable-type laser heterodyne spectrometer developed in this study.