Diurnal variations of stratospheric/mesospheric trace species, ClO, BrO, and HO2 derived from 4K cooled submm limb sounder ISS/JEM/SMILES

The Superconducting Submillimeter-Wave Limb-Emission Sounder (SMILES) is one of the first instruments to use 4K mechanical cooler in space. It was successfully launched and attached to the Japanese Experiment Module (JEM) on the International Space Station (ISS) on September 25, 2009. It has been making atmospheric observations since October 12, 2009 with the 4-K cooled superconducting mixers for submillimeter limb-emission sounding in the frequency bands of 624.32-626.32 GHz and 649.12-650.32 GHz. Unfortunately, SMILES observations have been suspended since April 21, 2010 due to the failure of a critical component. On the basis of the observed spectra, the data processing has been retrieving vertical profiles for the atmospheric minor constituents and trace free radicals in the middle atmosphere, such as O3 with isotopes, HCl, ClO, HO2, BrO, and HNO3. It is well known that the trace species, such as ClO, BrO, HOCl, HO2, are controlling the photochemistry of stratosphere and mesosphere with diurnal variation. Observations of these species have been difficult due to reasons; 1) weak signals require integration for satellite observations, 2) limited local time from sun-synchronous satellites, and/or 3) limited space/time coverage from balloon instruments with enough sensitivity. The sensitivity of SMILES can provide opportunity to derive single scan retrieval of ClO, BrO, HOCl, and HO2. By plotting these species over 30-45 days, it is possible to derive diurnal variation of these species in the stratosphere and/or mesosphere.