183 GHz radiometer for the Microwave Limb-Sounder

The Microwave Limb Sounder (MLS) is designed to measure atmospheric thermal emission from selected molecular species at millimetre wavelengths and is due to fly on the Upper Atmosphere Research Satellite. From the intensity and spectral characteristics of this emission, and its variation as the field-of-view is scanned vertically, the atmosphere profiles of geophysical parameters will be inferred. The authors give the frequency of the spectral lines which will be observed by MLS and the geophysical parameters to be inferred over the indicated altitude range. The UK is contributing the 183 GHz radiometer which is briefly described. The 183 GHz radiometer is a quasioptical Gaussian beam from the optical multiplexer. This is combined with a local oscillator signal in a quasioptical coupler and fed into a single ended mixer