FFTSCAN: A Program for Spectral Smoothing Using Fourier Transforms

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.

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Document Details

Document Type
Technical Report
Publication Date
May 19, 1992
Accession Number
ADA264921

Entities

People

  • S. A. Clough
  • W. O. Gallery

Organizations

  • Atmospheric and Environmental Research, Inc

Tags

Communities of Interest

  • Cyber
  • Energy and Power Technologies

DTIC Thesaurus Topics

  • Abstracts
  • Accuracy
  • Computer Programs
  • Computers
  • Contracts
  • Delta Functions
  • Discrete Fourier Transforms
  • Errors
  • Fast Fourier Transforms
  • Fourier Transformation
  • Instructions
  • Radiance
  • Schematic Diagrams
  • Spectroscopy
  • Standards
  • Transmittance
  • Triangles

Readers

  • Approximation Theory.
  • Computer Science.