AIRCRAFT (ER-2) LASER INFRARED-ABSORPTION SPECTROMETER (ALIAS) FOR IN-SITU STRATOSPHERIC MEASUREMENTS OF HCI, N2O, CH4, NO2, AND HNO3

The Aircraft Laser Infrared Absorption Spectrometer (ALIAS) instrument is a high-resolution (0.0003 cm-1) scanning tunable-diode-laser spect rometer designed, tested, and flown more than 30 times on the National Aeronautics and Space Administration's high-altitude ER-2 aircraft in the Airborne Arctic Stratospheric Expedition of 1991-1992. Using long -path infrared laser absorption spectroscopy to detect optical absorpt ions as small as 10(-5), ALIAS provides fast, continuous in-situ measu rements of key atmospheric gases, with gas detection sensitivities oft ens of parts in 10(12). With four lasers and detectors in a single liq uid-nitrogen Dewar, simultaneous measurements of HCl, NO2, HNO3, CH4, and N2O are made using laser sources at 3.4-8 mum, injected into a 1-m -long, 80-pass Herriott cell.