MASERATI: a rocketborne tunable diode laser absorption spectrometer

The MASERATI (middle-atmosphere spectrometric experiment on rockets for ana lysis of trace-gas influences) instrument is, to our knowledge, the first r ocket-borne tunable diode laser absorption spectrometer that was developed for in situ measurements of trace gases in the middle atmosphere. Infrared absorption spectroscopy with lead salt diode lasers is applied to measure w ater vapor and carbon dioxide in the altitude range from 50 to 90 km and 12 0 km, respectively. The laser beams are directed into an open multiple-pass absorption setup (total path length 31.7 m) that is mounted on top of a so unding rocket and that is directly exposed to ambient air. The two species are sampled alternately with a sampling time of 7.37 ms, each corresponding to an altitude resolution of approximately 15 m. Frequency-modulation and lock-in techniques are used to achieve high sensitivity. Tests in the labor atory have shown that the instrument is capable of detecting a very small r elative absorbance of 10(-4)-10(-5) when integrating spectra for 1 s. The i nstrument is designed and qualified to resist the mechanical stress occurri ng during the start of a sounding rocket and to be operational during the c ruising phase of the flight when accelerations are very small. Two almost i dentical versions of the MASERATI instrument were built and were launched o n sounding rockets from the Andoya Rocket Range (69 degrees N) in northern Norway on 12 October 1997 and on 31 January 1998. The good technical perfor mance of the instruments during these flights has demonstrated that MASERAT I is indeed a new suitable tool to perform rocket-borne in, situ measuremen ts in the upper atmosphere. (C) 1999 Optical Society of America. OCIS codes : 010.1280, 120.6200, 140.2020, 300.1030, 300.6260.