A Radiometer for Ground-Based Detection of Stratospheric Ozone at 110 GHz

A low noise superheterodyne receiver has been designed and constructed for ground-based monitoring of stratospheric ozone. The receiver measures the ozone spectral line at 110.836 GHz with a total bandwidth of 1.0 GHz. The receiver front end is cooled to a physical temperature of 20 K. The low noise front end, which consists of a whisker contacted Schottky diode mixer, a HEMT-amplifier as the first IF stage and a phase-locked Gunn-oscillator as LO, is followed by a dual acousto-optical spectrum analyzer with 85 kHz resolution near the band center. A novel low-reflection cold load has been designed in order to minimize the standing waves in the quasi-optical feed. A new feature in the inversion the spectral line is the use of the Backus-Gilbert algorithm together with singular value decomposition (SVD).