Protection of spaceborne and terrestrial passive sensors to observe trace gasses from 200 to 700 GHz

Spaceborne and terrestrial passive sensors using 200-700 GHz are very important for measuring atmospheric constituents. However, these spectra are not properly protected. One agenda item 1.16 of the World Radio Conference 2000 (WRC-2000) is to consider allocation of frequency bands above 71 GHz to the Earth exploration-satellite (passive) and radio astronomy services. Spectra above 275 GHz are not allocated. Definition of Earth-based passive sensors in ITU is not clear. It is necessary to protect such services by allocating spectra and defining proper protection criteria. In this paper, the outline of spaceborne and terrestrial passive sensors are described and protection criteria are estimated. In order to measure trace gasses related with Ozone depletion, NASDA and CRL are developing SMILES (Superconducting Submillimeter-Wave Limb-Emission Sounder) in collaboration with NAO (National Astronomical Observatory) which will be launched in 2004 by HTV (H-II Transfer Vehicle) and attached to JEM (Japanese Experiment Module) of ISS (International Space Station). This project is the first to use a superconductive low-noise receiver with SIS mixer and a mechanical 4K refrigerator. The JEM/SMILES is a submillimeter-wave limb-sounding spectrometer operating at 624-629GHz and 649-654 GHz band for observing spontaneous radiation emitted by important minor constituents of the stratospheric atmosphere