Development Of Superconducting Submillimeter-Wave Limb Emission Sounder (Jem/Smiles) Aboard The International Space Station

A submillimeter wave limb emission sounder, that is to be aboard the Japanese Experiment Module (JEM, dubbed as "KIBO") at the International Space Station, has been designed. This payload, Superconducting Submillimeter-wave Limb Emission Sounder (SMILES), is aimed at global mappings of stratospheric trace gasses by means of the most sensitive submillimeter receiver ever operated in space. Such sensitivity is ascribed to a Superconductor-Insulator-Superconductor (SIS) mixer, which is operated at 4.5 K in a dedicated cryostat combined with a mechanical cooler. SMILES will observe ozone-depletion-related molecules such as ClO, HCl, HO(2), HNO(3), BrO and O(3) in the frequency bands at 624.32 - 626.32 GHz, and 649.12 - 650.32 GHz. A scanning antenna will cover tangent altitudes from 10 to 60 km in every 53 seconds,, while tracing latitudes from 38S to 65N along its orbit. This global coverage makes SMILES a useful tool of observing the low- and mid-latitudinal areas as well as the Arctic peripheral region. The molecular emissions will be detected by two units of acousto-optic spectrometers (AOS), each of which has coverage of 1.2 GHz with a resolution of 1.8 MHz. This high-resolution spectroscopy will allow us to detect weal emission lines attributing to less-abundant species.