The Institute - December 2019 - 16


When planning the Apollo 11 mission to
the moon, NASA researchers decided to
perform a few experiments. The LURE
was meant to investigate fundamental aspects of gravitation. The agency
hired two contractors, Spacerays and
KORAD Laser Systems, to build the
high-powered laser system that would
be used for the experiment.
In an article on the website of the University of California, Santa Cruz, Joseph
Wampler, a liaison between NASA and
the Lick Observatory, said the former
was worried that when the Apollo astronauts left the moon, their rocket exhaust
would leave the retroreflector array covered with dust. Because of that concern,
between the two companies, four teams
were given a laser system in hopes that
one of them would be able to complete
the experiment successfully.
KORAD hired Hildreth "Hal" Walker Jr.,
a power electronics engineer, to manage
one of its teams. Walker, who worked for
Union Carbide's laser systems division,
was an expert in testing and manufacturing high-voltage and high-powered
The two Spacerays teams were located
at the McDonald Observatory, owned
by the University of Texas at Austin and
located near Fort Davis, and the Haleakala Observatory, owned by the University of Hawaii and located in Kula.
KORAD's laser teams were located at the
Lick Observatory.
On 20 July 1969, the Apollo 11 astronauts landed on the moon and mounted
the mirror array in the Sea of Tranquility.
According an article by Brian J. Hagerty
in Optics & Photonics News, the array's
exact coordinates in the Sea of Tranquility were unknown. Therefore, the four
teams began to shoot lasers from their
respective sites at what they estimated
was the correct location, hoping to hit
the retroreflectors.
Walker's KORAD team encountered a
problem with its laser system. According


DEC 2019



to the Optics & Photonics
article, it failed due to the
effects of the laser on the
surrounding air. The air
disturbance "fried" the
electronics, Hagerty said.
Walker drove from the Lick Observatory including in France, Germany, Italy, and
to KORAD's headquarters in Santa Monica, the United States.
Calif., and back-more than 500 kilometers
According to an article published in
each way-to pick up replacement parts. July on the NASA Jet Propulsion LaboraDuring the attempts to complete the tory website, the data gathered from the
experiment, it became apparent to the experiment continues to give researchers
U.S. scientists scrutinizing the Sea of insight into the moon as well as Earth. In
Tranquility that someone else on Earth 1989, for example, researchers discovalso was firing a laser at the moon and ered that the lunar core is fluid-which
attempting to hit the LURE array, accord- suggests that the moon once might have
ing to Hagerty.
generated and maintained its own mag"Those rogue laser shots, it turned out, netic field, just as the Earth does.
were from a team of Soviet scientists who
NASA has approved a new generahoped to achieve an end run around the tion of reflectors to be placed on the
U.S. groups," he wrote.
lunar surface, according to the article.
A few days after the equipment failure, That would allow researchers to further
on 1 August, Walker's team detected a investigate the moon's history, study
handful of photons that reflected back the fluid core, and help support future
from the retroreflector array, dramati- human exploration.
cally improving the accuracy of the meaA plaque honoring LURE, mounted in
sured distance between the Earth and the lobby of the Shane Dome at the Lick
the moon. It took about 2.4 seconds for Observatory, reads:
those photons to make the round trip.
Approximately 300 people attended
On 1 August 1969, Lick Observatory
the IEEE Milestone ceremony, organized
made the first Earth-to-Moon distance
by Brian Berg, IEEE Region 6 history chair
measurement with centimeter accuand milestone coordinator. They heard
racy. The researchers fired a gigawatt
from several speakers, including Walker.
ruby laser at a retroreflector array
"The IEEE Milestone dedication highplaced on the Moon by Apollo 11 astrolighted the little-known story of Walker,
nauts, and measured the time delay
who was a hidden figure who installed,
in detecting the reflected pulse. This
operated, and fired the gigawatt-powered
was the first experiment using a handweapons-grade laser that produced the
placed extraterrestrial instrument.
first accurate measurement of the distance from the Earth to the moon," Berg
This article was written with assistance
told The Institute. "It also honored the from the IEEE History Center, which is
many individuals who came together funded by donations to the IEEE Founfor this experiment, which achieved dation's Realize the Full Potential of
its first success 12 days after man first IEEE campaign.
walked on the moon."

The LURE is still performed today in
observatories all around the world,

This article originally appeared online as
"One Apollo 11 Experiment Is Still Going 50
Years Later."

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