Conceptual Study of Superconducting Submillimeter-Wave Limb-Emission Sounder-2 (Smiles-2) Receiver

The Superconducting Submillimeter-Wave Limb-Emission Sounder-2 (SMILES-2) is a satellite mission for observation of the stratosphere, mesosphere, and lower thermosphere with superconducting submillimeter-wave receivers, being proposed to the announcement of opportunity for M-class missions run by the Japan Aerospace Exploration Agency (JAXA). The SMILES-2 notable features are extremely high sensitivity and observation capability of atmospheric diurnal cycles. Those are requested from a scientific requirement for the investigation of the 4-D space-time structure of diurnal variations in the whole atmosphere. Such features require SMILES-2 to have 4-K cooled superconducting devices for high sensitivity and to be aboard a satellite platform on a non-sunsynchronous orbit. The mechanical 4-K cooling system is a power consuming instrument. Satellite on a non-sunsynchronous orbit gets a large sun-shade ratio in most of season, and has limitations of power supply to the mission instrument. The issue of the SMILES-2 mission design is mainly to fit the 4-K cooling system to the limited power resource of M-class satellite. This paper discusses our development status on designing the SMILES-2 mission payload. SMILES-2 will be proposed to JAXA in the beginning of the next year.