An improvement to the volcano-scan algorithm for atmospheric correction of CRISM and OMEGA spectral data

https://doi.org/10.1016/j.pss.2009.03.007Get rights and content

Abstract

The observations of Mars by the CRISM and OMEGA hyperspectral imaging spectrometers require correction for photometric, atmospheric and thermal effects prior to the interpretation of possible mineralogical features in the spectra. Here, we report on a simple, yet non-trivial, adaptation to the commonly-used volcano-scan correction technique for atmospheric CO2, which allows for the improved detection of minerals with intrinsic absorption bands at wavelengths between 1.9 and 2.1 μm. This volcano-scan technique removes the absorption bands of CO2 by ensuring that the Lambert albedo is the same at two wavelengths: 1.890 and 2.011 μm, with the first wavelength outside the CO2 gas bands and the second wavelength deep inside the CO2 gas bands. Our adaptation to the volcano-scan technique moves the first wavelength from 1.890 μm to be instead within the gas bands at 1.980 μm, and for CRISM data, our adaptation shifts the second wavelength slightly, to 2.007 μm. We also report on our efforts to account for a slight ∼0.001 μm shift in wavelengths due to thermal effects in the CRISM instrument.

Section snippets

Atmospheric correction with the new algorithm

The atmosphere of Mars has a composition that is 95% CO2 (Owen et al., 1977), which produces several absorption bands in the near-infrared region (1.0–4.0 μm) (Martin and Barker, 1932). One of these absorption bands is a triad of moderately-deep and narrow bands between 1.9 and 2.1 μm, which are notable in part because they interfere with the detection of broad features of surface hydration or surface H2O ice at these same wavelengths. Accurate analysis of these surface features requires removal

Time-dependent volcano-scan transmission spectra

For the CRISM spectrometer, the wavelengths shift during the course of the mission, due to thermal effects on the instrument. We have observed this shift over time while measuring a large number of volcano-scan transmission spectra during the mission. We plot the gas-band portion of 3 of the 16 volcano-scan transmission curves in Fig. 4. Note that these volcano-scan spectra effectively record the shifts in the wavelength at the times of the measurement of the transmission spectra. In Fig. 4,

Summary

First, we have proposed and tested a new method for atmospheric separation of OMEGA and CRISM data, adapting the standard volcano-scan technique for more accurate determination of spectral properties of the surface of Mars. Second, we have presented some initial tests of this new algorithm when also accounting for time-dependent shifts in wavelength in the CRISM instrument.

This new method for atmospheric correction allows for a non-zero difference in the Lambertian albedo at λ=2.007 μm relative

Acknowledgements

PCM acknowledges support from and conversations with Raymond Arvidson, Gerhard Neukum, Selby Cull, Sandra Wiseman, Kim Lichtenberg, Bethany Ehlmann, Ernst Hauber, Tom Stein, Lars Arvidson, and Margo Mueller. The work by PCM has been funded by a Robert M. Walker senior research fellowship from the McDonnell Center for the Space Sciences and by a Humboldt Research Fellowship. The authors from institutions in the USA acknowledge support from NASA funds through the Applied Physics Laboratory, under

References (21)

  • S. Erard et al.

    New composite spectra of Mars, 0.4–5.7 μm

    Icarus

    (1997)
  • G. Bellucci et al.

    Evidence for enhanced hydration on the northern flank of Olympus Mons, Mars

    Icarus

    (2007)
  • J.-P. Bibring et al.

    Mars surface diversity as revealed by the OMEGA/Mars express observations

    Science

    (2005)
  • J.L. Bishop et al.

    Phyllosilicate diversity and past aqueous activity revealed at Mawrth Vallis, Mars

    Science

    (2008)
  • Bishop, J.L., Parente, M., Weitz, C.M., Noe Dobrea, E.Z., Roach, L.A., Murchie, S.L., McGuire, P.C., McKeown, N.K.,...
  • Brown, A.J., Calvin, W.M., McGuire, P.C., Murchie, S.L., 2008. CRISM south polar mapping: first Mars year of...
  • B.L. Ehlmann et al.

    Orbital identification of carbonate-bearing rocks on Mars

    Science

    (2008)
  • Fueten, F., Racher, H., Stesky, R., MacKinnon, P., Hauber, E., McGuire, P.C., Zegers, T., Gwinner, K., 2009. Structural...
  • A. Gendrin et al.

    Sulfates in martian layered terrains: the OMEGA/Mars Express view

    Science

    (2005)
  • Y. Langevin et al.

    Sulfates in the north polar region of Mars detected by OMEGA/Mars Express

    Science

    (2005)
There are more references available in the full text version of this article.

Cited by (170)

  • Sensitivity analysis of ice/dust aerosol and phase function assumptions on Hapke spectral unmixing and band depth parameters of martian water ice

    2022, Icarus
    Citation Excerpt :

    DISORT-based atmospheric correction routines for CRISM and OMEGA have been developed and tested through numerous studies over the past decade for both analysis of atmospheric constituents (e.g., Smith et al., 2009, 2018) and correction for the atmosphere in order to analyze the planetary surface's spectral characteristics and properties (Arvidson et al., 2006; Cull et al., 2010; Liu et al., 2012; Shaw et al., 2013; Liu et al., 2016; Kreisch et al., 2017; Lapotre et al., 2017b; Liu et al., 2018). Before DISORT modeling is performed, atmospheric gas bands from CO2 were removed to first order by ratioing CRISM I/F spectra to scaled atmospheric transmission spectrum derived from the Olympus Mons high and low altitude observations, also referred to as the volcano-scan method (McGuire et al., 2009). This was done using the CAT (CRISM Analysis Tool) add-on toolbox in ENVI.

View all citing articles on Scopus
1

Formerly at: McDonnell Center for the Space Sciences, Washington University, St. Louis, MO, USA.

2

Now at: Department of the Geophysical Sciences, University of Chicago, Chicago, IL, USA.

3

Now at: GeoEye Inc., 12076 Grant St. Thornton, CO 80241, USA.

View full text