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Next Generation Lunar Laser Ranging. Alix Preston * , Stephen Merkowitz, Jan McGarry, Thomas Zagwodzki LUNAR Steering Committee Meeting April 12, 2011.
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Next Generation Lunar Laser Ranging Alix Preston*, Stephen Merkowitz, Jan McGarry, Thomas Zagwodzki LUNAR Steering Committee Meeting April 12, 2011 *supported in part by an appointment to the NASA Posdoctoral Program at Goddard Space Flight Center, administered by Oak Ridge Associated Universities through contract with NASA
Hydroxide Bonding and Hollow Cubes • GSFC has been investigating in-house hollow corner cube development • Attempting to use Hydroxide-Bonding techniques to bond mirrors • Easy: only need a small amount of hydroxide solution (typically KOH or sodium silicate) • Strong: >1 MPa in shear • Can bond large surface areas • Works with a variety of materials • Can survive large temperature changes • Currently understanding how the hydroxide bond cures • How much does it change the angles between surfaces? Two 1” mirrors bonded using the hydroxide bonding method
Current Work • Fabricated fixture to make corner cubes • Can accommodate larger facets already • 2” fused silica facet flats have been ordered (arrive in May) • Alignment procedures/test protocols will be established once the cubes are made • Zerodur facets will be ordered when this is completed • Optimizing the bonding process is underway • a few variations have been found already • Improvements were made to the far-field test bed • Transmit /receive optics simplified, fiber replaced spatial filter, larger off axis parabola with longer focal length, others 6-axis piezopositioners that will be used to construct hollow corner cubes 1” corner cube produced using the piezo aligners and hydroxide bonding
Future Work Plan • Finish improvements to far-field test bed (almost done) • Make and test 2” cubes • Attempt to have first cube made in June • Determine how the FFDP changes after thermally cycling • Compare cubes using different bonding methods • Prepare report on 2” cubes • Procure 5”-6” facets • Currently looking into possible vendors • Make and test larger corner cubes • Prepare report on larger cube results FFDP of an optical flat (left) and spare LAGOES 2 corner cube (right) using the improved setup. Quality is limited by air currents and vibrations Construction of the light-tight enclosure to reduce air turbulence