DOI: 10.5285/fcd80bf1-bd69-4054-826c-a4727af8096a
title: Laboratory spectral reflectance measurements at VNIR-SWIR wavelengths of 17 rock samples from Mount Murphy, West Antarctica

description: This dataset consists of spectral reflectance measurements in the visible to shortwave infrared wavelength range (0.35 - 2.5 micrometer) of 17 rock samples from Mount Murphy, a volcanic edifice in the Amundsen Sea Embayment of West Antarctica. These spectral measurements provide ground validation for satellite-based geologic mapping of the Mt Murphy edifice and surrounding nunataks. Samples measured for spectral reflectance were collected during the 1990-1991, 1992-1993 and 2015-2016 Antarctic Field Seasons.

Funding source: Natural Environment Research Council (NERC) Grants NE/S006710/1, NE/S006753/1 and NE/K012088/1 and studentship to JRA. The dataset is a component of the "Geological History Constraints" project of the NERC-NSF funded International Thwaites Glacier Collaboration (ITGC).
description: Rock samples from which spectral reflectance measurements were obtained were collected on expeditions to Mt Murphy in the 2015-16, and 1990-91 field seasons as part of the ANiSEED and SPRITE projects. Most samples were collected during the more recent ANiSEED field season by Dr. Joanne Johnson and Dr. Stephen Roberts. The position of each sample was recorded using a Trimble 5700 GPS receiver set at the same height as the sample's upper surface. Sample reflectance spectra were measured using a Spectral Evolution PSR 3500+ spectroradiometer by Dr. Jonathan Adams in a dark optical calibration laboratory at the NERC (Natural Environment Research Council) Field Spectroscopy Facility (FSF). Measurements were taken using a contact probe attachment with a stabilized quartz-tungsten-halogen lamp. The effective spot sampling size was a circle of diameter 1.2 cm. With the contact probe positioned over the sample, the reflected radiance of the illuminated area was measured (Lsample). This radiance was then compared to that of a NIST-traceable calibrated 99% reflectance Spectralon(R) reference panel (Labsphere, USA) (Lreference). A ratio of Lsample to Lreference was taken to arrive at a relative reflectance value. The absolute reflectance value, rho-sample, was determined by correcting the relative reflectance value with the calibration coefficients of the reference panel. Post-processing of laboratory spectra was performed using SpectraGryph - optical spectroscopy software Version 1.2, and Python 3 - Jupyter Notebook. Spectral measurements from difference parts of a sample surface were compared to investigate the spectral profiles of weathered and fresh surfaces. A representative average reflectance value for each sample was calculated, generating 17 reflectance profiles which were compiled into a new spectral library for Mt Murphy. The original orientation of each sample had been documented in the field permitting generation of 17 averaged reflectance profiles from the top of each sample. These data were used to validate satellite-based spectral mapping observations and are included as a separate .csv file. Equipment setup, training and support for the spectral measurements was provided by Dr. Robbie Ramsay (FSF).
description: Trimble 5700 GPS receiver
Spectral Evolution PSR 3500+ spectroradiometer (Spectral Evolution, USA)
Spectralon(R) reference panel, 99% (Labsphere, USA)
Software:
SpectraGryph - optical spectroscopy software Version 1.2
Python 3 - Jupyter Notebook
description: Reflectance spectra were acquired over the 0.35 - 2.5 um spectral range. The spectral interval and average resolution of the instrument were, respectively, 1.5 nm and 3.0 nm between 350 nm - 1000 nm; 3.8 nm and 10.0 nm between 1000 nm - 1890 nm; 2.5 nm and 8.0 nm between 1890 nm - 2500 nm. All reflectance values are interpolated to a 1 nm interval using cubic-spline interpolation. Radiance measurements of the illuminated sample were compared to radiance measurements of an illuminated reference panel, and ratioed to arrive at a reflectance value. The Spectralon(R) reference panel was post calibrated at FSF to NIST traceable standards. Calibration data is provided as a separate .csv file.