High Resolution Atmospheric and Astronomic Sensing at THz Frequencies

Abstract

The Terahertz (THz) part of the electromagnetic spectrum bears an amazing scientific potential in astronomy and atmospheric research. Many fundamental absorption and emission lines of astrophysical and atmospheric important molecules and atoms occur in this spectral region. Up to now more than one hundred molecules and atons habe been detected in space. There are fairly simple molecules such as CO but also molecules consisting og ten or more atoms have been detected. High resolution heterodyne spectroscopy of molecular rotational lines and fine structure lines of atoms or ions is a powerful tool which allows obtaining valuable information about the observed object such as temperature and dynamical processes as well as density and distribution of particular species. Among future astronomy missions equipped with THz heterodyne receivers are the Herschel Space Observatory and the Stratospheric Observatory for Infrared Astronomy. An instrument devoted to the investigation of the Earth's atmosphere is TELIS, the balloon borne THz and submm limb sounder. Applications and requirements for such receivers as well some key components are discussed. This includes local oscillators based on optically pumped gas lasers or solid-state lasers and low noise superconducting hot-electron bolometric mixers.