BACKGROUND CONTRIBUTIONS IN DIRECT AND DIFFERENTIAL FOURIER TRANSFORM LWIR MEASUREMENTS: A COMPARATIVE ANALYSIS

In order to assess the differences between background clutter using the CATSI instrument in direct (single-beam) and differential (double-beam) mode, a survey of background measurements was undertaken. Measurements include samples of sky, mountains, forest, buildings, roads and snow during springtime in the long wave infrared using both single-beam and double-beam interferometry. It is found that background distribution and statistics in these two modes are significantly different, with the differential mode presenting less variation than the direct mode. This may impact the ability to detect atmospheric contaminants. This analysis was performed in order to better understand the difference between operating a standard and a differential FTIR instrument.