Apollo Lunar Surface
Experiment Package (ALSEP)
Laser Ranging Retroreflector
(LRRR or LR3 or LR cubed)
.
.
Apollo 11 LR3 at Tranquility Base. The black dust cover
is still in place over the prisms to maintain the cleanliness of the optics.
Note the stereo camera in background at
right.
.
.
Left - Apollo 14 LR3 at Fra Mauro. The dust cover is
the red object in right background
Right - Apollo 15 LR3. Note the sun compass at top center
.
.
Left - Diagram of Apollo 11 LR3
Right - Diagram of Apollo 15 LR3. Note added section
of prisms
Click here to download
the article Lunar Laser Range Finding The
Legacy of Apollo
and the Observatorie de
la Côte D’Azur
By Barry Davidoff
(MS Word document)
Thanks, Barry!!
Apollo Experiment Number: S 078
Apollo Missions: 11, 14, 15
Wt: A-11 23.59 kg,
A-14 20.41 kg
A-15 36.20 kg
Dim: A-11: 29.2 cm x 68.6 x 66.0
A-14: 30.0
cm x 63.8 x 64.8
A-15: 30.0
cm x 69.5 x 64.8 (30.0 cm x 105.2 x 64.8 deployed)
Essentially a large number of prisms set in a frame,
the LR3 was one of the simplest and most successful of the ALSEP experiments.
It had no moving parts or electronics. Its' function was merely to relect
laser pulses shot at it from earth back to the source of the pulses. By
measuring the round trip time of these laser pulses, it was possible to
determine within a very close margin (I heard 6 inches) the exact distance
between the source of the pulse and the moon. From these data, it was then
possible to measure such things as geologic plate tectonic movement and
the wobble of the earth's spin about its' axis.
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