Accession Number : ADA264921


Title :   FFTSCAN: A Program for Spectral Smoothing Using Fourier Transforms


Descriptive Note : Technical rept.,


Corporate Author : ATMOSPHERIC AND ENVIRONMENTAL RESEARCH INC CAMBRIDGE MA


Personal Author(s) : Gallery, W O ; Clough, S A


Full Text : https://apps.dtic.mil/dtic/tr/fulltext/u2/a264921.pdf


Report Date : 19 May 1992


Pagination or Media Count : 25


Abstract : FFTSCAN is a computer program which uses Fourier Transforms to convolve a spectrum with an instrument spectral scanning function. This technique mimics the operation of Fourier transform spectroscopy and preserves the full extent of the scanning function, which is particulary important for functions with large side lobes, like sin(x)/x. Five scanning functions commonly used in Fourier transform spectroscopy are available: sinc, sinc2, Beer, Hamming, and Hanning, plus triangle and gauss. The program is specifically adapted to process spectra created by the atmospheric transmittance/radiance program FASCODE. A special, disk-based Fourier transform routine allows FFTSCAN to handle spectra of any size. FFTSCAN is more accurate and as or more efficient that the existing equivalent FASCODE routines. This report describes the mathematical basis for spectral smoothing in the Fourier domain and gives the user instructions for FFTSCAN. It gives examples of spectral smoothing, including estimates of error limits and computational times, and provides guidance on implementing the program on different computers.


Descriptors :   *FOURIER TRANSFORMATION , *SPECTRA , *EARTH ATMOSPHERE , *FOURIER SPECTROSCOPY , SCANNING , RADIANCE , INTERFEROMETERS , FOURIER SPECTROMETERS , SPECTROMETERS , RADIATION , COMPUTER PROGRAMS


Subject Categories : Atmospheric Physics
      Numerical Mathematics
      Atomic and Molecular Physics and Spectroscopy


Distribution Statement : APPROVED FOR PUBLIC RELEASE