Spectral noise due to sampling errors in Fourier-transform spectroscopy

An assessment is made of the spectral noise in Fourier-transform spectrosco py caused by sampling errors in the interferogram acquisition. Numerical ev aluations are performed in the case of the REFIR (radiation explorer in the far infrared) instrument developed for the measurement of the long-wavelen gth Earth emissions from satellite platforms. In this case the slow respons e of a room-temperature pyroelectric detector, the relatively short acquisi tion time, the broadband operation, and the wish for a relaxed requirement of the mirror drive accuracy make sampling error an important issue. Differ ent sampling methods can be considered for reduction of the spectral noise induced by sampling errors. The effects of different sampling methods are q uantified and discussed for the selection of the most-suitable option for t his instrument. We find that only sampling methods that introduce some comp ensation (either analog or digital) of the frequency dependence of amplitud e and phase components of the acquisition-system responsivity provide satis factory results. In particular, the equal time sampling followed by a digit al filter and numerical resampling has been examined minutely with a simula tion model used to perform sensitivity tests of the main parameters that ch aracterize the procedure. (C) 2001 Optical Society of America.