Martian Surface Emissivity and Surface Spectral Units Results from the Thermal Emission Imaging Syst

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Martian Surface Emissivity and Surface Spectral
UnitsResults from the Thermal Emission Imaging
System

• Joshua L. Bandfield, Deanne Rogers,
• Michael D. Smith, and Philip R. Christensen
• Arizona State University and NASA Goddard Space
  Flight Center

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Overview

• Three concepts for interpretation of THEMIS data
• Constant radiance correction
• Removes temperature dependence from emissivity
  data
• Surface emissivity retrieval
• Removes atmospheric dust and water ice
  contributions
• Spectral unit mapping
• Deconvolution determines quantitative
  contributions of spectral endmembers

3
Overview

• Three concepts for interpretation of THEMIS data
• Constant radiance correction
• Removes temperature dependence from emissivity
  data
• Surface emissivity retrieval
• Removes atmospheric dust and water ice
  contributions
• Spectral unit mapping
• Deconvolution determines quantitative
  contributions of spectral endmembers

4
Overview

• Three concepts for interpretation of THEMIS data
• Constant radiance correction
• Removes temperature dependence from emissivity
  data
• Surface emissivity retrieval
• Removes atmospheric dust and water ice
  contributions
• Spectral unit mapping
• Deconvolution determines quantitative
  contributions of spectral endmembers

5
Overview

• Three concepts for interpretation of THEMIS data
• Constant radiance correction
• Removes temperature dependence from emissivity
  data
• Surface emissivity retrieval
• Removes atmospheric dust and water ice
  contributions
• Spectral unit mapping
• Deconvolution determines quantitative
  contributions of spectral endmembers

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Example Image Syrtis Major
Band 654 DCS Radiance
Surface Temperature
10 km
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Constant Radiance Correction
Band 654 DCS Emissivity

• Measured Radiance Surface Radiance
  Atmospheric Attenuation Atmospheric Emission
• Atmospheric emission is constant, rather than
  proportional to surface radiance
• This causes apparent emissivity differences

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Constant Radiance Correction
Band 654 DCS Emissivity

• Atmospheric emission can be solved for using area
  of constant emissivity, but variable temperature
• The emitted radiance for each band is subtracted
  from the entire image
• This method removes the need for atmospheric
  temperature profile

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Constant Radiance Correction
Before Correction
After Correction
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Surface Emissivity Retrieval

• Atmospheric properties are generally not highly
  variable over a THEMIS scene
• Surface emissivity is known at large scales from
  TES data
• Atmospheric opacity is solved for large areas and
  applied to individual pixels

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Surface Emissivity Retrieval
Band 654 DCS Radiance
Surface Unit Emissivity
1.00
0.98
0.96
0.94
0.92
Emissivity
0.90
0.88
0.86
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7
8
9
10
11
12
13
Wavelength (mm)
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Atmospheric Opacity Spectra
0.18
0.16
0.14
0.12
THEMIS
0.10
Opacity (t)
0.08
Opacity
0.06
Emissivity
0.04
Retrieved Dust Opacity This Method 0.165 M.
Smith 0.173
0.02
TES Dust
0
-0.02
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7
8
9
10
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12
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Wavelength (mm)
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Spectral Unit Mapping
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Spectral Unit Mapping
B654 DCS
RMS Error (0-0.01)
TES Basalt
Qtz. Monzonite
Atm. Ice
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Spectral Unit Mapping
Band 654 DCS Radiance
Surface Emissivity
Measured Modeled
Emissivity
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7
8
9
10
11
12
13
Wavelength (mm)
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Spectral Unit Mapping
Band 654 DCS Radiance
Surface Emissivity
Measured Modeled
Emissivity
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7
8
9
10
11
12
13
Wavelength (mm)
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Spectral Unit Mapping
Band 654 DCS Radiance
Surface Emissivity
Measured Modeled
Emissivity
6
7
8
9
10
11
12
13
Wavelength (mm)
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Conclusions

• Constant radiance correction removes atmospheric
  emission effects
• Necessary to make ratios and emissivity images
  accurate
• Surface emissivity retrieval provides results
  consistent with other methods
• Allows for comparison to TES and laboratory
  emissivity
• Spectral unit maps can be used to retrieve
  quantitative surface properties