title: Application of a nonuniform spectral resampling transform in Fourier-transform spectrometry.
abstract: We describe a nonuniform spectral resampling transform (NUSRT) that resamples a frequency-scaled spectrum that has been measured by a Fourier-transform spectrometer (FTS). Frequency scaling of a spectrum can arise from measurements made with off-axis detectors and Doppler shift induced by motion of a spaceborne FTS relative to an input radiation source. In addition, a spectrum may need to be rescaled in frequency to match spectral lines for applications such as the retrieval of atmospheric state parameters. The NUSRT is cast as a linear algebraic expression that relates a nonuniformly sampled interferogram to an input spectrum. A polynomial approximation is applied to this expression that reduces the inverse of the NUSRT to a series of Fourier transforms that can be implemented as fast Fourier transforms (FFTs). We show that this NUSRT algorithm requires on the order of 6N log N flops, which reduces the computational cost of rescaling by more than 1 order of magnitude compared with conventional FFT-based Shannon interpolation techniques while comparable accuracy is maintained.
authors.affiliation: Jet Propulsion Laboratory, California Institute of Technology, MS:183-301, 4800 Oak Grove Drive, Pasadena, California 91109, USA. edwin.sarkissian@jpl.nasa.gov
authors.forename: Edwin
authors.initials: E
authors.lastname: Sarkissian
authors.forename: Kevin W
authors.initials: KW
authors.lastname: Bowman