The Lunar UV Reflectance Experiment (LURE): Exploring the Far-UV Signature of Water Ice on Planetary Surfaces, 15-R9626

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Principal Investigators
Michael W. Davis
G. Randall Gladstone
Kurt D. Retherford
David C. Slater
S. Alan Stern

Inclusive Dates:  05/14/08 – 11/15/08

Background - A key observational technique in planetary astronomy is the measurement of the spectrum of sunlight reflected from rocky surfaces; this technique is commonly referred to as reflectance spectroscopy. The composition and texture of terrains may be determined from remote distances with this method. Laboratory measurements of the ultraviolet spectral signatures of many common minerals, ices, and returned surface samples are either few in number or do not exist. This lack of measurements limits the opportunities for both research funding using ultraviolet datasets and the variety of spacecraft ultraviolet surface studies funded by NASA. The measurements that do exist were only conducted at one reflection angle with poor wavelength sampling. The objective of this project is to remedy this knowledge gap by conducting a laboratory study of the far ultraviolet reflectance of various mixtures of water ice (a prevalent volatile throughout the solar system) and lunar regolith simulant.

Approach - The experiment measures the far ultraviolet reflectivity and light-scattering properties (via the bidirectional reflection distribution function) of water ice and lunar simulant samples at different angles and temperatures. These measurements take place in the Southwest Ultraviolet Reflectometer Chamber (SwURC), a new capability added to SwRI in 2006. The reflective properties of the dry lunar simulant and water frost are measured as a function of altitude to characterize the 2π -reflectance properties of the materials. The reflectance is measured over 5Å intervals over the 1,100 to 1,800 Å range. These tests are followed by measurements of mixtures of the lunar simulant and water ice.

Accomplishments - The SwURC had to be rebuilt after the detector and light source were not sufficient to properly measure reflectivity levels. The chamber rebuild is still under way, and should be completed by early 2010.

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