Installed on APEX earlier this year, SEPIA is sensitive to light with wavelengths in the range 1.4-1.8 millimetres [2]. The exceptional observing conditions on the extremely dry Chajnantor Plateau in northern Chile mean that, although this light is blocked by water vapour in the atmosphere at most places on Earth, SEPIA is still able to detect the faint signals coming from space.
This wavelength region is of great interest to astronomers as signals from water in space are found here. Water is an important indicator of many astrophysical processes, including the formation of stars, and is believed to play an important role in the origin of life. Studying water in space -- in molecular clouds, in star-forming regions and even in comets within the Solar System -- is expected to provide critical clues to the role of water in the Milky Way and in the history of Earth. In addition, SEPIA's sensitivity makes it a powerful tool for also detecting carbon monoxide and ionised carbon in galaxies in the early Universe.
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