Submillimeter-wave coherent and incoherent sensors for space applications

Abstract

Most of the radiation in the Universe is emitted at wavelengths longer than 10 microns (30 THz), and this peaks at about 100 microns (3 THz), if we exclude contributions from the cosmic microwave background (CMB). Radiation in these wavelengths highlights warm phenomena, processes of change such as star formation, formation of planetary systems, and galaxy evolution; atmospheric constituents and dynamics of the planets and comets and tracers for global monitoring and the ultimate health of the earth. Sensors at far-infrared and submillimeter wavelengths provide unprecedented sensitivity for astrophysical, planetary, earth observing, and ground-based imaging instruments. Very often, for spaced based platforms where the instruments are not limited by atmospheric losses and absorption, the overall instrument sensitivity is dictated by the sensitivity of the sensors themselves. Moreover, some of the cryogenic sensors at submillimeter wavelengths provide almost quantum-limited sensitivity. Frequency sources at submillimeter wavelengths with adequate output power for transmitters and local oscillators are not easily available, and pose the greatest challenge for advancement of this field. This article provides an overview of the state-of-the-art of submillimeter-wave sensors for a variety of space-borne applications and their performance and capabilities. © 2008 Springer-Verlag Berlin Heidelberg.