Data processing pipeline for a time-sampled imaging Fourier transform spectrometer

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Imaging Fourier transform spectrometers (IFTS) are becoming the preferred systems for remote sensing spectral imaging applications because of their ability to provide, simultaneously, both high spatial and spectral resolution images of a scene. IFTS can be operated in either step-and-integrate or rapid-scan modes, where it is common practice to sample interferograms at equal optical path difference intervals. The step-and-integrate mode requires a translation stage with fast and precise point-to-point motion and additional external trigger circuitry for the detector focal plane array (FPA), and produces uniformly position-sampled interferograms which can be analyzed using standard FFT routines. In the rapid-scan mode, the translation stage is continuously moving and interferograms are often acquired at the frame-rate of the FPA. Since all translation stages have associated velocity errors, the resulting interferograms are sampled at non-uniform intervals of optical path difference, which requires more sophisticated analysis. This paper discusses the processing pipeline which is being developed for the analysis of the non-uniform rapid-scan data produced by the Herschel/SPIRE IFTS.