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        <li>Wednesday, 16 September 2026</li>
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<div id="contentwrapper"><div id="rightcontent"><div id="headimage"><img height="100" width="530" alt="NASA Space Science Data Coordinated Archive Header" src="/logo/nssdca_header.jpg"/></div><h1>Laser Ranging Retroreflector</h1><p><strong>NSSDCA ID:</strong> 1969-059C-04</p><strong>Mission Name:</strong> Apollo 11 Lunar Module / EASEP<br/><strong>Principal Investigator:</strong>Dr. Carroll O. Alley<br/><div class="twocol"><div class="urone"><h2>Description</h2><p><p>The laser ranging retroreflector (LRRR), which was left on the lunar surface by the Apollo 11 crew, was a retroreflector array with a folding support structure for aiming and aligning the array toward earth. The array was built of cubes of fused silica. Laser ranging beams from earth were reflected back to their point of origin for precise measurement of earth-moon distance, motion of the moon's center of mass, lunar radius, and earth geophysical information.</p></p></div><div class="urtwo"><h2>Alternate Names</h2><ul><li>Apollo11EASEP/LaserRangingRetroreflector</li><li>S078</li></ul><h2>Facts in Brief</h2><p><strong>Mass:</strong> 77 kg<br/></p><h2>Funding Agency</h2><ul><li>NASA-Office of Space and Terrestrial Applications (United States)</li></ul><h2>Discipline</h2><ul><li>Planetary Science: Celestial Mechanics</li></ul><h2>Additional Information</h2><ul><li><a href="/nmc/spacecraft/display.action?id=1969-059C">Apollo 11 Lunar Module / EASEP</a></li><li><a href="/nmc/dataset/query.action?spacecraftName=Apollo+11+Lunar+Module+%2F+EASEP&amp;experimentName=Laser+Ranging+Retroreflector">Data collections from this experiment</a></li></ul><h2/><p>
          Questions and comments about this experiment can be directed to:
          <a href="mailto:gsfc-dl-nssdca-request@mail.nasa.gov?Subject=NMC+Comment%2FQuestion%3A+Laser+Ranging+Retroreflector+%281969-059C-04%29">Coordinated Request and User Support Office</a></p></div></div><div class="clear"> </div><h2>Personnel</h2><table cellspacing="0" class="alternate"><thead><tr><th>Name</th><th>Role</th><th>Original Affiliation</th><th>E-mail</th></tr></thead><tbody><tr><td>Dr. Carroll O. Alley</td><td>Principal Investigator</td><td>University of Maryland</td><td>coa@kelvin.umd.edu</td></tr></tbody></table><h2>Selected References</h2><ul><li>Alley, C. O., <em>et al.</em>, Laser Ranging Retroreflector,
    in <em> Apollo 11 Prelim. Sci. Rept.</em>, NASA SP-214, Wash., DC, 1969.</li></ul><h2>Related Information</h2>

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  <a href="/planetary/image/lunar_ranging.jpg"><img src="/planetary/thumbnail/lunar_ranging.gif" alt="Lunar Ranging at McDonald Observatory" width="71" height="100" /></a>
  <p>Lunar Ranging at McDonald Observatory</p>
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<a href="http://www.csr.utexas.edu/mlrs/">McDonald Laser Ranging Station</a> (University of Texas)<br/>
<a href="ftp://ilrs.gsfc.nasa.gov/pub/slr/slrql/moon/">Current Lunar Laser Ranging Data Sets</a> 
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