Experiences in atmospheric emitted radiance measurements suggest that detector non-linearity be one of the most commonly-seen measurement uncertainties in mid-IR measurements, and which is of particular concern when the signals of interest are from the cold upper troposphere and are therefore weak in magnitude. Traditional instrumentation with one or two calibration blackbodies, in addition, has no provision of assessing measurement uncertainties in flight.

Recent airborne measurements by an FTS with redundant calibration blackbodies (three, thus permitting self-assessment of performance in flight) and multiple detectors (three, made of different materials or operated at different physical principles) covering the same or having significant overlapped bands, are intercalibrated and intercompared. Results from a field mission based on the NASA WB-57 high-altitude research aircraft are presented.