Apollo 11 Experiment Still Going After 40 Years
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Apollo 11 Astronaut Buzz Aldrin, lunar module pilot, is shown here after deploying the Early Apollo Scientific Experiments Package. In the foreground is the Passive Seismic Experiment Package; beyond it is the Laser Ranging Retro-Reflector. A new look at old data spotlights how rocket landings and departures on the Moon can impact equipment. CREDIT: NASA. |
The
Apollo 11 astronauts returned from the moon 40 years ago today, but they left behind
more than footprints. An experiment they placed on the moon?s surface is still
running to this day.
The
Lunar Laser Ranging Experiment is the only moon investigation to continuously
operate since the Apollo
11 mission. The experiment studies the Earth-Moon system and beams the data
to labs around the world, including NASA's Jet Propulsion Laboratory (JPL) in
Pasadena, Calif.
"Yes,
we are still going," said James Williams, a JPL scientist involved with
the experiment, in an e-mail interview.
Data
from the ranging experiment has been used to learn ? among other things ? that
the moon has a fluid core and is moving away from the Earth, and that
Einstein's Theory of Relativity is accurate.
The
instrument itself, called a lunar laser ranging reflector, was originally
intended to accurately calculate the distance between the Earth and
moon by measuring the round-trip time of a laser fired from Earth to a
reflector on the instrument.
The
average distance from the centers of the Earth and the moon was calculated to
be 238,897 miles (384,467 km). NASA scientists say the measurement is one of
the most precise distance measurements ever made and is equivalent to
determining the distance between Los Angeles and New York to one-hundredth of
an inch.
The
accuracies will continue to improve as observatories
on Earth improve their technology.
"Technical
improvements at the observatories rejuvenate the lunar laser ranging
effort," Williams said in 2004, when the experiment turned 35.
Williams is one of four JPL scientists that analyze the data from the Lunar
Laser Ranging Experiment. "When the range accuracy improves, it is like
getting a new experiment on the Moon."
The
instrument itself does not require any power to operate on the moon (only the
lasers on Earth do), so it's likely to be in service for many years to come.
Scientists at the University of California, San Diego and the University of
Washington are working with a new lunar ranging instrument that has
significantly improved accuracy at the Apache Point Observatory in New Mexico.
"The
usefulness of continued improvements in range determinations for further
advancing our understanding of the Earth-moon system will keep the lunar
reflectors in service for years to come," Williams said.
The
lunar measuring, ongoing for 40 years now, is by no means the longest-running
experiment. Physicist Thomas Parnell set up a
slow pitch-drop experiment in 1927 that has continued long after his death,
with about one drop of the gooey stuff falling each decade. Other experiments
still underway date back to the mid-1800s.
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