Development of a Fabry–Perot interferometer for ultra-precise measurements of column CO₂

Progress on a passive Fabry–Perot-based instrument for detecting column CO₂ through absorption measurements at 1.58 µm is described. In this design, solar flux reaches the instrument platform and is directed through two channels. In the first channel, transmittance fringes from a Fabry–Perot interferometer are aligned with CO₂ absorption lines so that absorption due to CO₂ is primarily detected. The second channel encompasses the same frequency region as the first, but is comparatively more sensitive to changes in the solar flux than absorption due to CO₂. The ratio of these channels is sensitive to changes in the total CO₂ column, but not to changes in solar flux. This inexpensive instrument will offer high precision measurements (error <1%) in a compact package. Design of this instrument and preliminary ground-based measurements of column CO₂ are presented here as well as strategies for deployment on aircraft and satellite platforms.