Remote sensing, basic principles

Despite the fact that signals from molecules may be coming from thousands of light years away, a quantitative analysis can be performed on interstellar gas through the use of radio telescopes and their remote sensing capabilities. Such telescopes at first glance may seem an odd tool for a chemist, but these instruments basically exploit fundamental principles of molecular spectroscopy in a manner similar, but not identical, to a laboratory spectrometer. 

In this overview, the basic principle of all optical remote gas-sensing methods is introduced and is used to explain how the accuracy and sensitivity with which a target gas can be measured are defined by the spectroscopic properties of the gas itself. These properties define the region of the spectrum in which it has significant absorption features together with their strength and structure. 

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