Frequency-controlled sources of far-infrared radiation for spaceborne applications

Among the difficulties in developing far-infrared (FIR) technology, a perennial lack of frequency-controlled sources has kept this spectral region's technology far behind that of the surrounding spectral regions. However, as is the case in other spectral regions, astronomers and atmospheric scientists drive much of the cutting-edge technology development in the FIR. The dramatic attenuation of FIR radiation by water and other constituents of the Earth's atmosphere forces many of the scientists' measurement platforms above the atmosphere, into space. Therefore, there is a strong correlation between the development of new FIR technology and spaceborne instrumentation. In this paper, we address the needs of the FIR space-flight community, providing an introduction to the common heterodyne receiver configurations and the state of technology for various front-end components. We make frequent reference to the added challenges of producing such receivers for space environments.