. Instrumental Capabilities

 The SMILES is equipped with a heterodyne superconductor-insulator-superconductor (SIS) receiver to be operated in the 625/650-GHz band as a limb-emission sounding radiometer. The SMILES has a mechanically scanning elliptical offset-Cassegrain antenna (ANT) with diameters of 40 cm x 20 cm to achieve an altitude resolution of about 3.5 km - 4.1 km at the tangential altitude ranging from upper troposphere (10 km) to lower mesosphere (60 km) from the orbit of the ISS.

 The atmospheric limb emission collected by the ANT is directed to Submillimeter Receiver (SRX), where the received submillimeter-wave signal is combined with a reference signal (637.32 GHz) from a submillimeter-wave local oscillator (SLO), and is directed to SIS mixers through quasioptics consisting of focusing mirrors, wire-grids, and a sideband filter. Two SIS mixers, one of which for upper sideband (USB: 649.12 GHz - 650.32 GHz) and the other for lower sideband (LSB: 624.32 GHz - 626.32 GHz), are operated for simultaneously down-converting both sidebands into the intermediate frequency (IF) band ranging between 11 GHz and 13 GHz. The IF signals are further down-converted and amplified in the Intermediate Frequency Amplification Section (IFA), and then analyzed by two acousto-optical spectrometers in the Radio Spectrometer (AOS).