Forward modeling of linear mixing in thermal IR ground leaving radiance spectra

Lee K. Balick*, Alan R. Gillespie, Matthew F. McCabe, Amit Mushkin

*Corresponding author for this work

Research output: Chapter in Book/Report/Conference proceedingConference contributionpeer-review


Hyperspectral thermal IR remote sensing is an effective tool for the detection and identification of gas plumes and solid materials. Virtually all remotely sensed thermal IR pixels are mixtures of different materials or temperatures. As sensors improve and hyperspectral thermal IR remote sensing becomes more quantitative, the concept of homogeneous pixels becomes inadequate. The contributions of the constituents to the pixel spectral ground leaving radiance are weighted by their spectral emissivity as well as their temperature, or more correctly, temperature distributions, because real pixels are rarely thermally homogeneous. Planck's Law defines a relationship between temperature and radiance that is strongly wavelength dependent, even for blackbodies. Spectral ground leaving radiance (GLR) from mixed pixels is temperature and wavelength dependent and the relationship between observed radiance spectra from mixed pixels and library emissivity spectra of mixtures of 'pure' materials is indirect. This paper presents results from a simple model of linear mixing of pixel spectral GLR. A pixel consists of one or more materials each with a temperature distribution and an emissivity spectrum. Temperature distributions consistent with high resolution thermal images are used as inputs to the model. The impact of spatial-temporal fluctuation of skin temperature on skin temperature variability will be discussed. The results show the strong sensitivity of spectral GLR at shorter wavelengths to temperature and significant variation of radiance mixture proportions with wavelength in the mid-infrared (3-5 μm). Spectral GLR of mixtures in the 8-12 μm domain are more modestly impacted but the impact of subpixel mixing and variability is still significant. A demonstration of the effects of linear mixing on linear un-mixing is also presented.

Original languageEnglish (US)
Title of host publicationElectro-Optical Remote Sensing II
ISBN (Print)0819464945, 9780819464941
StatePublished - 2006
Externally publishedYes
EventElectro-Optical Remote Sensing II - Stockholm, Sweden
Duration: Sep 13 2006Sep 14 2006

Publication series

NameProceedings of SPIE - The International Society for Optical Engineering
ISSN (Print)0277-786X


OtherElectro-Optical Remote Sensing II


  • Hyperspectral
  • Linear mixing
  • Model
  • Remote sensing
  • Spectral
  • Thermal IR

ASJC Scopus subject areas

  • Electronic, Optical and Magnetic Materials
  • Condensed Matter Physics
  • Applied Mathematics
  • Electrical and Electronic Engineering
  • Computer Science Applications


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