Superconducting Submillimeter-Wave Limb-Emission Sounder Research Articles

Evaluation of Voigt algorithms for the ISS/JEM/SMILES L2 data processing system

We present a calculation of the accuracy and speed of the Voigt function of various algorithms (Armstrong (1967), Hui et al. (1978), Humlicek (1982) and improved version of Kuntz (1997) developed in this study) for making the faster and higher accuracy forward model required for the Superconducting Submillimeter-Wave Limb-Emission Sounder (SMILES) Level 2 (L2) data processing system. The maximum relative error of the improved Kuntz’s and Armstrong’s algorithm is ϵ max ∼ 2.52 × 10 - 5 in the high-altitude range ( y < 1 ) and a minimum value of ϵ max ∼ 9.38 × 10 - 5 compared to the other results in the mid- and low-altitude range ( y > 1 ) , which meet a required precision of the SMILES L2 data processing system. The improved algorithm also shows the fastest calculation time compared to the other algorithms over the observable altitudes of SMILES. It is therefore concluded that the improved algorithm should be applied for the SMILES L2 data processing system.

Operational retrieval algorithms for JEM/SMILES level 2 data processing system

To measure the thermal emission from stratospheric minor species with high sensitivity, the Superconducting Submillimeter-wave Limb-Emission Sounder (SMILES) aboard the Japanese Experiment Module (JEM) of the International Space Station (ISS) carries 4 K cooled Superconductor–Insulator–Superconductor (SIS) mixers. The major feature of the SMILES is its high-sensitive measurement ability with low system noise temperature less than 700 K. As a part of the ground system for the SMILES, a level 2 data processing system (DPS-L2) has been developed. It retrieves the density distributions of the target species from calibrated spectra in near-real-time. The retrieval process consists of two parts: the forward model, which computes radiative transfer, and the inverse model, which deduces atmospheric states. Since the forward model must provide the most accurate basis for results and be implemented under limited computing resources, the forward model algorithm for an operational system has to be accurate and fast. Hence, the algorithm is improved (1) by designing accurate instrument functions such as the instrumental field of view (FOV), sideband rejection ratio of sideband separator, and spectral responses of acousto-optic spectrometer (AOS) and (2) by optimizing radiative transfer calculation. This paper presents the development of the DPS-L2 along with the details on its algorithm and the algorithm performance. The accuracy of this algorithm is better than 1%, and the processing time for single-scan spectra is less than 1 min with eight parallel processings using a 3.16-GHz Quad-Core Intel Xeon processor. Thus, this algorithm is suitable for the SMILES measurement.

Measurement and Evaluation of Submillimeter-Wave Antenna Quasioptical Feed System by a Phase-Retrieval Method in the 640-GHz Band

A phase-retrieval method is applied to the quasioptical feed system of the offset Cassegrain antenna of the Superconducting Submillimeter-Wave Limb-Emission Sounder (JEM/SMILES) to be aboard the International Space Station for evaluating the beam alignment by estimating the phase pattern from the beam amplitude pattern measurements. As the result, the application of the phase retrieval method is demonstrated to be effective for measuring and evaluating the quasioptical antenna feed system. It is also demonstrated that the far-field radiation pattern of the antenna main reflector can be estimated from the phase-retrieved beam pattern of the feed system.

Mechanical coolers operating below 4.5 K for space application

This paper reports the 4 K- and 1 K-class mechanical coolers developed for space use. The 4 K-class cooler has been developed for Superconducting Submillimeter-Wave Limb-Emission Sounder (SMILES), which is to be operated onboard the International Space Station (ISS). The cooling capacity is 20 mW at 4.5 K, with the total input power of approximately 120 W. The 1 K-class cooler has been developed for cooling far-infrared detectors to 1.7 K in the Space Infrared Telescope for Cosmology and Astrophysics (SPICA). The cooling capacity is 10 mW at 1.7 K and the total input power to the cooler is about 180 W. A future possible cryogen-free cooling system for temperature below 0.1 K is also presented, which uses these coolers as a pre-cooler.

Stratospheric ozone and ClO measurement using Balloon-Borne submillimeter limb sounder

Stratospheric O/sub 3/ and ClO were simultaneously observed off the northeastern coast of Japan by the Balloon-Borne Superconducting Submillimeter-Wave Limb-Emission Sounder (BSMILES) developed at National Institute of Information and Communications Technology. BSMILES is a highly sensitive submillimeter radiometer that exploits the superconductor-insulator-superconductor (SIS) technology for atmospheric research. This paper presents the first BSMILES spectra, and describes the details of the calibration process. The vertical profiles of O/sub 3/ and ClO have been also retrieved. In spite of some calibration uncertainties the obtained profiles are in relatively good agreement with previous and other available measurements.

Submillimeter-wave SIS receiver system for JEM/SMILES

Abstract A 640-GHz heterodyne superconductor-insulator-superconductor (SIS) receiver will be installed in Superconducting Submillimeter-wave Limb Emission Sounder (SMILES) on the Japanese Experiment Module of the International Space Station. SMILES will simultaneously detect twelve emission lines of stratospheric molecules in the limb sounding method. The SIS receiver is operating in single sideband (SSB) mode, and we employ a new type of Martin-Puplett interferometer consisting of two sets of a wire grid and a flat mirror for the SSB filter. The SIS mixers and intermediate-frequency low noise amplifiers will be cooled to 4.5 K and 20 K, respectively, by a Stirling refrigerator combined with a Joule-Thomson circuit used for the first time in space.