Sub-MM limb observation of stratosphere and mesosphere using ISS/JEM/SMILES

Performance of Superconducting Submillimeter-Wave Limb Emission Sounder (SMILES) onboard International Space Station was discussed from the analysis of random errors of Chlorine monoxide (ClO) in the stratosphere and mesosphere. Some lessons learned from the SMILES operation in space are discussed.

1. INTRODUCTION

Superconducting Submillimeter-Wave Limb Emission Sounder (SMILES) had observed chemical species (0₃, H³⁵CI, H³⁷CI, ³⁵CIO, HO₂, HO³⁵CI, O¹⁷00, ¹⁷000, 18₀₀₀, HNO₃, CH₃CN, and temperature) in the stratosphere and mesosphere from the Japanese Experiment Module (JEM) of the International Space Station (ISS) from Oct. 12, 2009 to Apr. 21, 2010 when the sub-mm local oscillator stopped. SMILES was jointly developed by JAXAA and National Institute of Information and Communications Technology (NICT) [1]–[3]. SMILES measured chemical species at the sub-mm wavelength regions (624.32–626.32 GHz and 649.12–650.32 GHz) with the 0.8 MHz frequency interval. SMILES have utilized 4 K mechanical cooler system [4] to achieve high sensitivity to the detect minor species such as CIO, H0₂, HOCI etc. The 4 K cooled SIS (Superconductor-Insulator-Superconductor) mixer gave very low system temperature to the SMILES observation, which means one order higher detection capability compared to the previous mm/sub-mm instruments (Aura/MLS [5] and Odin/SMR [6]).