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 N ID: 425606
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Slide1
Next Generation Lunar Laser Ranging
Alix
Preston*, Stephen Merkowitz, Jan McGarry, Thomas ZagwodzkiLUNAR Steering Committee MeetingApril 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 NASASlide2
Hydroxide Bonding and Hollow Cubes
GSFC has been investigating in-house hollow corner cube developmentAttempting to use Hydroxide-Bonding techniques to bond mirrorsEasy: only need a small amount of hydroxide solution (typically KOH or sodium silicate)Strong: >1 MPa
in shearCan bond large surface areasWorks with a variety of materialsCan survive large temperature changesCurrently understanding how the hydroxide bond curesHow much does it change the angles between surfaces?
Two 1” mirrors bonded using the hydroxide bonding methodSlide3
Current Work
6-axis
piezo positioners that will be used to construct hollow corner cubes
1” corner cube produced using the
piezo
aligners and hydroxide bonding
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, othersSlide4
Future Work Plan
Finish improvements to far-field test bed (almost done)Make and test 2” cubesAttempt to have first cube made in JuneDetermine how the FFDP changes after thermally cyclingCompare cubes using different bonding methodsPrepare report on 2” cubes
Procure 5”-6” facetsCurrently looking into possible vendorsMake and test larger corner cubesPrepare 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