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Laser Ranging Retroreflector

NSSDCA ID: 1969-059C-04

Mission Name: Apollo 11 Lunar Module / EASEP
Principal Investigator:Dr. Carroll O. Alley


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.

Alternate Names

  • Apollo11EASEP/LaserRangingRetroreflector
  • S078

Facts in Brief

Mass: 77 kg

Funding Agency

  • NASA-Office of Space and Terrestrial Applications (United States)


  • Planetary Science: Celestial Mechanics

Additional Information

Questions and comments about this experiment can be directed to: Dr. David R. Williams



NameRoleOriginal AffiliationE-mail
Dr. Carroll O. AlleyPrincipal InvestigatorUniversity of

Selected References

  • Alley, C. O., et al., Laser Ranging Retroreflector, in Apollo 11 Prelim. Sci. Rept., NASA SP-214, Wash., DC, 1969.

Related Information

Lunar Ranging at McDonald Observatory

Lunar Ranging at McDonald Observatory

McDonald Laser Ranging Station (University of Texas)
Current Lunar Laser Ranging Data Sets

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