The Lunar UV Reflectance Experiment (LURE): Exploring the Far-Ultraviolet 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:  04/01/06 – Current

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 conducted at only one reflection angle with poor wavelength sampling.

Approach - The main 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. 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, a new development funded by capital equipment for the Space Science and Engineering Division in 2006. The reflective properties of the dry lunar simulant and water frost will be measured as a function of altitude and azimuth to characterize the 2p-reflectance properties of the materials. The reflectance will be measured over 5Å intervals over the 1000 - 1800 Å range. These tests will be followed by measurements of mixtures of the lunar simulant and water ice.

Accomplishments - The reflectometer chamber that will be used to conduct the measurements is still under construction, so no reflection measurements have been made to date. The lunar simulants have been acquired, and initial ray-trace studies of the chamber have been performed.

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