Abstract

The balloon-borne laser in situ sensor (BLISS) instrument is a microprocessor controlled high-resolution absorption spectrometer operating in the mid-infrared wavelength region.¹ Tunable lead-salt diode lasers provide IR radiation in selected wavelength regions for sensitive derivative absorption spectroscopy over a 1-km round-trip path. The TDL radiation is directed to a retroreflector which is lowered up to 500 m below the instrument gondola. A He–Ne laser and coaligned TV camera with CID imaging are used for retroreflector tracking. Currently the instrument operates with two TDLs, and the capability exists to measure four stratospheric species simultaneously: NO, NO₂, O₃, and H₂O. A selected TDL is frequency-modulated at 2 kHz and scanned in wavelength over a spectral feature of the species of interest. A cell filled with a fraction of a torr of the gas to be monitored allows a reference spectrum to be recorded for line identification and wavelength calibration.

© 1984 Optical Society of America