An improvement to the volcano-scan algorithm for atmospheric correction of CRISM and OMEGA spectral data
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
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2022, IcarusCitation 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.
- 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.