Continuum definition for ∼3.1, ∼3.4 and ∼4.0 µm absorption bands in Ceres spectra and evaluation of effects of smoothing procedure in the retrieved spectral parameters
| Autor: | Andrea Raponi, Mauro Ciarniello, Andrea Longobardo, Filippo Giacomo Carrozzo, A. Galiano, Angelo Zinzi, Fabrizio Dirri, M. C. De Sanctis, Ernesto Palomba |
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| Rok vydání: | 2018 |
| Předmět: |
Physics
Atmospheric Science 010504 meteorology & atmospheric sciences Continuum (measurement) business.industry Aerospace Engineering Hyperspectral imaging Astronomy and Astrophysics Astrophysics 01 natural sciences Spectral line Wavelength Geophysics Optics Impact crater Space and Planetary Science Linear continuum 0103 physical sciences General Earth and Planetary Sciences business 010303 astronomy & astrophysics Image resolution Smoothing 0105 earth and related environmental sciences |
| Zdroj: | Advances in Space Research. 62:2342-2354 |
| ISSN: | 0273-1177 |
| DOI: | 10.1016/j.asr.2017.10.039 |
| Popis: | NASA’s Dawn spacecraft acquired images and hyperspectral data of Ceres by means of FC and VIR instruments, and identified some widespread bright areas or bright spots (BS). The most peculiar BS is inside Occator crater and it is characterized by spectral properties very dissimilar from the rest of Ceres’ surface. To perform a mineralogical analysis, absorption bands in reflectance spectra must be properly isolated by removal of continuum, and related descriptors (such as band centers and band depths) can be computed. The method for continuum removal must be applicable to all Ceres spectra, relative to different areas, so that a comparison among spectral parameters can be made and mineralogical interpretation can be achieved. This work focuses on the definition of the most appropriate continuum to isolate absorption bands located at ∼3.1, ∼3.4 and ∼4.0 µm. The ∼3.1 µm feature is related to ammoniated phyllosilicates, while the ∼3.4 and ∼4.0 µm absorption bands are indicative of carbonates. Thermal emission affects the continuum for these bands in the VIR spectral range, which extends up to 5.1 µm, moreover all thermal-removed reliable data stop at 4.2 µm. This implies that the shoulder of bands at longer wavelength cannot be identified. We therefore defined alternative continua, i.e., a linear and two polynomial ones, able to describe spectra of any area (i.e. bright or dark) and regardless of spatial resolution. We found that the linear definition satisfies these requirements best. For the first time, we performed an error evaluation on band depths and band centers introduced by the applied method, which is relevant for comparison of spectral parameters of Ceres regions and to better interpret mineralogy and photometric effects. |
| Databáze: | OpenAIRE |
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