Adjusting alignment of optics on volcanic gas monitoring instrument.

Scientist Christoph Kern adjusts the alignment of optics on the active long-path differential optical absorption spectroscopy (LP-DOAS) instrument. LP-DOAS sends a beam of ultraviolet or visible light to a reflector located tens to hundreds of meters away. Characteristic absorption lines of trace gases present in the light path are measured in the spectrum of returning light. The robust design and versatility of the instrument make it a promising tool for monitoring of volcanic degassing and understanding processes in a range of volcanic systems.