Basic Principles of Surface-Based Remote Sensing - Surface Based Remote Sensing of the Atmospheric Boundary Layer - page 63

Fig. 3.14 Glowbar as an
infrared radiation source for
open-path FTIR
measurements
As a method working in the infrared FTIR is suited to detect trace gases which
have emission or absorption lines in this spectral range. These are especially the
greenhouse gases.
3.8 DOAS
The differential optical absorption spectroscopy (DOAS) method employs the fact
that scattering and absorption depend differently on the light frequency. Mie and
Rayleigh scattering only vary slowly with frequency while absorption varies rapidly.
DOAS is an active method requiring a well-defined light source (lamp). In the
bistatic version, lamp and receiving telescope are located several hundreds of meters
up to a few kilometres from each other. In the monostatic version, lamp and tele-
scope are in the same position and a passive retro-reflector is mounted in a respective
distance (Fig. 3.15 ). DOAS was developed in the 1980s as a standard measurement