Identifying sampling comb changes in Fourier transform spectrometers with significant self-emission and beam splitter absorption.

For accurate calibration of Fourier transform spectrometers we must constrain or resample the interferogram data to an invariant sampling comb. This can become challenging when instrument self-emission is significant and beam splitter absorption is present. The originally-sampled interferogram center-burst position can move due not only to sampling comb changes, but also to an interaction between the strength of an external target and the so-called anomalous phase (the two ports of the interferometer contribute center-bursts at different locations, and the relative weighting of the two ports varies with the strength of the external target). We present a model of the anomalous phase to enable partitioning of changes in observed center-burst location between sampling comb changes and anomalous phase effects.