THz for space: The golden age

Over the past three decades interest in the unique spectral measurements offered by terahertz instruments operat-ing outside the Earth´s atmosphere has grown enormously. Since the historic flight of Cosmos 669 in 1974, satellite instruments have performed both direct detection and heterodyne spectroscopy measurements in the interstellar medium, in external galaxies, in the atmospheres of planets and comets and in the Earth´s stratosphere. Seventeen orbital instruments containing THz sensors or sources have either completed their mission objectives or are currently operational. They originate in Russia, Japan, Europe and the US and cover applications in astrophysics and cosmology; planetary and small solar system body science; and pollution, ozone and climate monitoring on the Earth. It is truly a golden age for THz space science and applications.