Astronomers are expecting valuable information from the submillimeter window, frequencies from 300 GHz to 3 THz, where numerous important molecular and atomic species uniquely express through their spectral lines. Heterodyne detection is employed for submillimiter signals. One mixes the astronomical signal with a stable local oscillator to translate the signal to a much lower frequency, in the 1-10 GHz range. In this frequency range amplifiers and high resolution spectrometers are available. Cryogenic conditions are necessary, both for the high frequency mixers and the low noise amplifiers.
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