A 5-mm Wavelength-Range Spectroradiometer for Studying the Atmosphere and Underlying Surface

The results of the development of a mobile solid-state microwave spectroradiometer that operates in the 5-mm absorption band of molecular oxygen are presented. The spectroradiometer consists of a superheterodyne receiver with a low-noise input amplifier and an eight-channel spectrum analyzer. The noise temperature of the device is 1000–1300 K. A solid-state modulator–calibrator based on Schottky-barrier GaAs diodes is used to provide the automatic internal intensity calibration of received radio emission. The design of the spectroradiometer antenna system is a Teflon lens with an antireflection coating and a conical corrugated horn. The instrument is equipped with an automated digital system for controlling the measurement, calibration, and a data preprocessing procedure. Examples of the measurement results of the atmospheric emission spectra and the radiative characteristics of the earth’s surface that were obtained with this instrument are presented. The spectroradiometer is designed for remote studies of the atmosphere and the underlying surface.