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

2Lunar Ranging – LUNAR Steering Committee Meeting – 9/21/09

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

3Lunar Ranging – LUNAR Steering Committee Meeting – 9/21/09

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, others

4Lunar Ranging – LUNAR Steering Committee Meeting – 9/21/09

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