Yasuko J. Kasai

Submillimeter Limb-emission Sounder JEM/SMILES aboard the Space Station

A submillimeter 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 gases 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, HO2, HNO3, BrO and O3 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 the latitudes form 38 S to 65 N 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 weak emission lines attributing to less-abundant species.

Submillimeter-wave spectroscopic performance of JEM/SMILES

An acousto-optical spectrometer (AOS) is employed in order to meet scientific mission objectives of submillimeter-wave limb-emission sounder (SMILES) to be aboard the Japanese Experiment Module (JEM) of the International space station (ISS). The capability of multi channel detection with AOS is suitable for observing multi chemical species in a wide frequency region. Wide noise dynamic range enables us to obtain the spectra without unnecessary increase of system noise, suggesting a good combination of AOS with low noise front end system of SMILES> Several technical concerns relating to important instrumental characteristics of AOS are discussed and expected performance of the spectrometers to be used in the JEM/SMILES mission are over viewed.

JEM/SMILES limb-sounding of stratospheric trace species II: simulation results for JEM/SMILES observations

JEM/SMILES (superconducting SubMIllimeter-wave Limb-Emission Sounder) is currently under development to demonstrate a submillimeter-wave sounder with extremely high sensitivity on the platform of the Japanese Experiment Module (JEM). In the submillimeter region, this is the first mission in space using a low-noise 4K cooled receiver, which is expected to give new observations for radicals in the stratosphere such as BrO. One of the most unique characteristics of the JEM/SMILES observation is its high sensitivity in detecting atmospheric limb emissions in the submillimeter wave range. The purpose of SMILES is global monitoring of the radicals which play important roles in the stratospheric system. We are now using the newly developed JEM/SMILES simulator to model observed spectra (including the characteristics of the SMILES sensor) and simulate the retrieval performance. Some preliminary results of the simulation are obtained in view of the scientific targets of JEM/SMILES.

JEM/SMILES limb-sounding of stratospheric trace species I: retrieval algorithm and simulator

In order to estimate measurement capability of the Superconducting Submillimter-Wave Limb-Emission Sounder (SMILES) on the Japanese Experiment Module (JEM) of the International Space Station (ISS) and to clarify the scientific impacts of the JEM/SMILES, we are developing the JEM/SMILES simulator. The simulator consists of the forward model and the inversion model. The forward model calculates a brightness temperature by applying the radiative transfer formula to a limb sounding geometry and simulates the effects of the JEM/SMILES sensor characteristics including optics superconductor-insulator-superconductor (SIS) mixers, Acousto-Optical Spectrometer (AOS), and so on, to it. Because it is important to estimate the effects of the sensor for the retrieval, we develop carefully simulated sensor model. The forward model also calculates weighting functions of molecular, the temperature, the pressure and so on. This paper describes how the brightness temperature and weighting functions are calculated in the forward model and how the effects of the sensor are taken into account in the simulator, and finally shows how the optical estimation method (OEM) is applied to our retrieval model.

Demonstration of superconducting sub-millimeter-wave limb emission sounder (SMILES) for observing trace gases in the middle atmosphere using the exposed facility of the Japanese experimental module (JEM) of the international space station

The sub-millimeter wavelength region is advantageous for high-precision observations of trace species in the stratosphere. A Superconducting Sub-Millimeter-wave Limb Emission Sounder (SMILES) is scheduled to demonstrate the measurements of extremely faint sub-millimeter-wave emissions of the atmospheric trace gases on the Exposed Facility (EF) of the Japanese Experimental Module (JEM) of the International Space Station in 2003. The applications of superconductivity and mechanical 4K-refrigerator in space will be demonstrated in the experiment. JEM/SMILES obtains the diurnal and seasonal variability in the global three-dimensional distributions of the stratospheric trace gases for quantitative understanding of the stratospheric ozone depletion and its effect on the climate change with respect to the relationships among chemical reaction processes and their relationships with atmospheric dynamics. JEM/SMILES utilizes the 640GHz band to measure the vertical profiles of trace gases involved in the stratospher...

Plan for the development of retrieval algorithm and ground segment of JEM/SMILES

Superconducting sub-millimeter-wave limb-emission sounder (SMILES) using 4K Superconductor-Insulator-Superconductor (SIS) detector for ISS/JEM is under development. Spectrum of 600 GHz regions will be acquired using acousto-optics spectrometer (AOS). The high sensitivity of SMILES will enable us to measure O3, ClO without enhancement, BrO, Hcl, HO2, HNO3 from 10 to 60 km. This paper describes a current plan of data retrieval algorithms (L0, L1, L2 and L3), ground data system, data validation and data distribution.