Superconducting Submillimeter-wave Limb Emission Sounder (SMILES) onboard Japanese Experimental Module (JEM) of International Space Station (ISS)

Trace gases such as ClO, BrO, HO/sub 2/, etc. in the stratosphere play important roles in the depletion of the ozone layer. Ozone, water vapor, and the trace gases in the upper troposphere are closely coupled with the radiation forces and climate change. Emission spectroscopy using a low-noise heterodyne technique in the short- to submillimeter-wave range is an effective method to remotely measure the trace gases. The spaceborne limb emission sounder can globally observe the 3D distributions of the trace gases. In order to develop and demonstrate an ultra-high sensitive detection technique of the trace gases, the authors are providing an experiment of a Superconducting Submillimeter-wave Limb Emission Sounder (SMILES) on the Exposed Facilities (EF) of the Japanese Experimental Module (JEM) of International Space Station (ISS). They have started Phase C/D Study of the JEM/SMILES from 1997. The JEM/SMILES will be operated at 640 GHz-band with 11-13 GHz IF frequencies. Superconductor-Insulator- Superconductor (SIS) mixers will be used for the ultra-high sensitive receiver. A compact 4K refrigerator for space use will achieve the operation conditions for the SIS receiver. In this experiment, the authors are also aiming to demonstrate the effectiveness of the submillimeter-wave limb emission spectrometry in observing the atmospheric environment from space. The launch of JEM/SMILES is scheduled in 2005. JEM/SMILES is a pre-phase of SMILES for an Atmospheric Chemistry and Dynamics Mission proposed in Japan.