Fitting the curve in Excel®:Systematic curve fitting of laboratory and remotely sensed planetary spectra

Spectroscopy in planetary science often provides the only information regarding the compositional and mineralogical make up of planetary surfaces. The methods employed when curve fitting and modelling spectra can be confusing and difficult to visualize and comprehend. Researchers who are new to working with spectra may find inadequate help or documentation in the scientific literature or in the software packages available for curve fitting. This problem also extends to the parameterization of spectra and the dissemination of derived metrics. Often, when derived metrics are reported, such as band centres, the discussion of exactly how the metrics were derived, or if there was any systematic curve fitting performed, is not included. Herein we provide both recommendations and methods for curve fitting and explanations of the terms and methods used. Techniques to curve fit spectral data of various types are demonstrated using simple-to-understand mathematics and equations written to be used in Microsoft Excel® software, free of macros, in a cut-and-paste fashion that allows one to curve fit spectra in a reasonably user-friendly manner. The procedures use empirical curve fitting, include visualizations, and ameliorates many of the unknowns one may encounter when using black-box commercial software. The provided framework is a comprehensive record of the curve fitting parameters used, the derived metrics, and is intended to be an example of a format for dissemination when curve fitting data

Spectral characterisation of analog samples in anticipation of OSIRS-REx's arrival at Bennu: A blind test study

We present spectral measurements of a suite of mineral mixtures and meteorites that are possible analogs for asteroid (101955) Bennu, the target asteroid for NASA's Origins, Spectral Interpretation, Resource Identification, Security, Regolith Explorer (OSIRIS-REx) mission. The sample suite, which includes anhydrous and hydrated mineral mixtures and a suite of chondritic meteorites (CM, CI, CV, CR, and L5), was chosen to characterize the spectral effects due to varying amounts of aqueous alteration and minor amounts of organic material. Our results demonstrate the utility of mineral mixtures for understanding the mixing behavior of meteoritic materials and identifying spectrally dominant species across the visible to near-infrared (VNIR) and thermal infrared (TIR) spectral ranges. Our measurements demonstrate that, even with subtle signatures in the spectra of chondritic meteorites, we can identify diagnostic features related to the minerals comprising each of the samples. Also, the complementary nature of the two spectral ranges regarding their ability to detect different mixture and meteorite components can be used to characterize analog sample compositions better. However, we observe differences in the VNIR and TIR spectra between the mineral mixtures and the meteorites. These differences likely result from (1) differences in the types and physical disposition of constituents in the mixtures versus in meteorites, (2) missing phases observed in meteorites that we did not add to the mixtures, and (3) albedo differences among the samples. In addition to the initial characterization of the analog samples, we will use these spectral measurements to test phase detection and abundance determination algorithms in anticipation of mapping Bennu's surface properties and selecting a sampling site

Photometric, spectral phase and temperature effects on 4 Vesta and HED meteorites Implications for the Dawn mission

Phase angle and temperature are two important parameters that affect the photometric and spectral behavior of planetary surfaces in telescopic and spacecraft data. We have derived photometric and spectral phase functions for the Asteroid 4 Vesta, the first target of the Dawn mission, using ground based telescopes operating at visible and near infrared wavelengths 0.4 2.5 lm . Photometric lightcurve observations of Vesta were conducted on 15 nights at a phase angle range of 3.8 25.7 using duplicates of the seven narrowband Dawn Framing Camera filters 0.4 1.0 lm . Rotationally resolved visible 0.4 0.7 lm and near IR spectral observations 0.7 2.5 lm were obtained on four nights over a similar phase angle range. Our Vesta photometric observations suggest the phase slope is between 0.019 and 0.029 mag deg. The G parameter ranges from 0.22 to 0.37 consistent with previous results e.g., Lagerkvist, C. I., Magnusson, P., Williams, I.P., Buontempo, M.E., Argyle, R.W., Morrison, L.V. [1992]. Astron. Astrophys. Suppl. Ser. 94, 43 71; Piironen, J., Magnusson, P., Lagerkvist, C. I., Williams, I.P., Buontempo, M.E., Morrison, L.V. [1997]. Astron. Astrophys. Suppl. Ser. 121, 489 497; Hasegawa, S. et al. [2009]. Lunar Planet. Sci. 40. ID 1503 within the uncertainty. We found that in the phase angle range of 0 lt; a 6 25 for every 10 increase in phase angle Vesta s visible slope 0.5 0.7 lm increases 20 , Band I and Band II depths increase 2.35 and 1.5 respectively, and the BAR value increase 0.30. Phase angle spectral measurements of the eucrite Moama in the lab show a decrease in Band I and Band II depths and BAR from the lowest phase angle 13 to 30 , followed by possible small increases up to 90 , and then a dramatic drop between 90 and 120 phase angle. Temperature induced spectral effects shift the Band I and II centers of the pyroxene bands to longer wavelengths with increasing temperature. We have derived new correction equations using a temperature series 80 400 K of HED meteorite spectra that will enable interpretation of telescopic and spacecraft spectral data using laborator

The Canadian space agency planetary analogue materials suite

The Canadian Space Agency (CSA) recently commissioned the development of a suite of over fifty well-characterized planetary analogue materials. These materials are terrestrial rocks and minerals that are similar to those known or suspected to occur on the lunar or martian surfaces. These include: Mars analogue sedimentary, hydrothermal, igneous and low-temperature alteration rock suites; lunar analogue basaltic and anorthositic rock suites; and a generic impactite rock suite from a variety of terrestrial impact structures. Representative thin sections of the materials have been characterized by optical microscopy and electron probe microanalysis (EPMA). Reflectance spectra have been collected in the ultraviolet, visible, near-infrared and mid-infrared, covering 0.2-25. μm. Thermal infrared emission spectra were collected from 5 to 50. μm. Raman spectra with 532. nm excitation, and laser-induced fluorescence spectra with 405. nm excitation were also measured. Bulk chemical analysis was carried out using X-ray fluorescence, with Fe valence determined by wet chemistry. Chemical and mineralogical data were collected using a field-portable Terra XRD-XRF instrument similar to CheMin on the MSL Curiosity rover. Laser-induced breakdown spectroscopy (LIBS) data similar to those measured by ChemCam on MSL were collected for powdered samples, cut slab surfaces, and as depth profiles into weathered surfaces where present. Three-dimensional laser camera images of rock textures were collected for selected samples.The CSA intends to make available sample powders (<45. μm and 45-1000. μm grain sizes), thin sections, and bulk rock samples, and all analytical data collected in the initial characterisation study to the broader planetary science community.Aiming to complement existing planetary analogue rock and mineral libraries, the CSA suite represents a new resource for planetary scientists and engineers. We envision many potential applications for these materials in the definition, development and testing of new analytical instruments for use in planetary missions, as well as possible calibration and ground-truthing of remote sensing data sets. These materials may also be useful as reference materials for cross-calibration between different instruments and laboratories. Comparison of the analytical data for selected