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

TL;DR

This paper presents an improved volcano-scan atmospheric correction method for CRISM and OMEGA spectral data, enhancing mineral detection by adjusting wavelength references within CO2 absorption bands.

Contribution

The authors adapt the volcano-scan technique by shifting reference wavelengths within CO2 absorption bands, accounting for thermal shifts, to improve mineral spectral analysis.

Findings

Enhanced detection of minerals with absorption bands at 1.9-2.1 μm.

Adjusted correction method accounts for thermal wavelength shifts.

Improved atmospheric correction accuracy for Mars spectral data.

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 CO_2, which allows for the improved detection of minerals with intrinsic absorption bands at wavelengths between 1.9-2.1 $\mu$m. This volcano-scan technique removes the absorption bands of CO_2 by ensuring that the Lambert albedo is the same at two wavelengths: 1.890 $\mu$m and 2.011 $\mu$m, with the first wavelength outside the CO_2 gas bands and the second wavelength deep inside the CO_2 gas bands. Our adaptation to the volcano-scan technique moves the first wavelength from 1.890 $\mu$m to be instead within the gas bands at 1.980 $\mu$m, and for CRISM data, our adaptation shifts the second wavelength slightly, to 2.007 $\mu$m. We also report on our efforts to account for a slight ~0.001 $\mu$m shift in wavelengths due to thermal effects in the CRISM instrument.