LOW-NOISE COOLED PLANAR SCHOTTKY DIODE RECEIVERS FOR GROUND-BASED SPECTRAL OZONE MEASUREMENTS AT 142 GHZ

Two new low-noise cooled receivers based on planar Schottky diode mixe rs were designed and built for the Lebedev Physics Institute (LPI) spe ctrometer for ground-based measurements of the atmospheric ozone spect ral line of 142.175 GHz central frequency. The receivers differ in the intermediate frequency (IF) bands, of around 3.7 and 1.5 GHz. Review description of the spectrometer equipped with the 3.7-GHz IF receiver is given, and its performance is compared with other millimeter-wave g round-based ozone spectrometers. Special attention was paid to design of the input Gaussian optics and the mixers. Techniques of laboratory tests of the receivers and results of the tests through all 2-mm wavel ength range are considered and discussed. SSB mixer noise temperature of 460+/-60 K was obtained at 151 GHz for room temperature mixer, and the value of 180+/-30 K was measured at 134 GHz under cooling to 85 K in liquid nitrogen cryostat. SSB mixer conversion losses were less tha n 5.5 dB in both the cases. SSB noise temperature of the spectrometer is less than 1500 K without cooling and less than 700 K at cryogenic o peration at 142 GHz. This provides sensitivity of about 0.2 and 0.1 K for the narrowest spectral channel width of 0.1 MHz and signal integra tion time of 1 hour. Using the optimized spectrum analyzers delivers d ata on high-accuracy retrieval of the ozone vertical profile in the at mosphere at altitudes about from 15 to 75 km. Examples of the ozone ob servation data are given.