Submillimeter wavelength radiometry dedicated to spectral analysis of planetary atmospheres: Low noise system development at Paris Observatory

We address the development of low noise system radiometer for heterodyne detection at Terahertz frequencies for high spectral resolution instruments (typ. 107) at Observatoire de Paris PSL. This work highlights constant effort to aim at keeping state-of-the-art receiver noise performances from 300 GHz to 1200 GHz and above for molecular line and continuum detection. In this work we concentrate on the mixer element as the first active element of the radiometric chain. We present the current ongoing work for the demonstration of a low-noise 325 GHz radiometer for earth atmospheric sounding applications. Three types of mixer configurations have been optimized and some of them fabricated and measured. We discuss some, but not all, of the system related aspect and the choice of mixer parameters for best performance that will provide stability for the long-term operation.