this desolate landscape haleakala crater
is located on the hawaiian island of
maui
it looks very similar to the distant
pockmarked wastelands of the moon
and it is here at the lower observatory
that nasa and the university of hawaii
are involved in work which helps us
understand the geophysical science of
the moon and the earth
lure observatory situated at the ten
thousand foot summit of mount haleakala
uses laser technology to accurately
range within one inch the two hundred
forty thousand mile distance between the
two bodies
ranging or measuring distance is
accomplished by clocking the time it
takes bursts of laser light to leave the
observatory hit one of four retro
reflectors on the moon and return to the
observatory
by measuring the continually changing
distance between the earth and moon we
are able to unlock many details relating
to the motions of both bodies
analysis of day-to-day changes in the
earth's motion help scientists better
understand the earth's rotation
continental drift
weather phenomena such as the el nino
effect and forces deep within the earth
that set off earthquakes
there are currently two other
observatories located around the world
which also participate in lunar laser
ranging but as yet neither has achieved
the level of precision of the lower
facility
much more will be learned in the future
by interpreting data from many stations
simultaneously
the accuracy of ranging has come a long
way since apollo astronauts armstrong
and aldrin placed the first
retroreflector on the moon
a member of the technical staff at the
jet propulsion laboratory working on
lunar laser ranging is dr skip new hall
the moon reflectors are composed of
array of several dozen or perhaps a few
hundred are these so-called corner
reflectors
and they have a nice feature
that
no matter what direction the light goes
in from
the it always returns out at exactly the
same direction so when we shine a laser
beam at the moon no matter how it's
oriented locally the light comes right
back out when the apollo
astronauts first put the reflectives on
the moon we got some returns back in
early 1970 and late 1969
the uncertainty in the return time was
about
equivalent of a distance of 150 to 200
meters that's around 600 feet
we have refined the time equipment the
lasers and the other associated
electronic equipment that supports this
so now
we have the uncertainties and distance
are equal to about three quarters of an
inch
which is an amazing improvement
the key to the lunar ranging operation
is a laser that can be adjusted to
create intense billion watt pulses of
energy
energy that makes its way to the moon
and back
the light energy is channeled out of the
observatory by this mirrored instrument
which keeps the laser beam continually
locked on target with the retro
reflectors on the moon
meanwhile in the observatory's main
control room the receiving telescope
which is composed of 80 lenses is
adjusted to line up visually with the
moon's apollo 15 retro reflector near
hadley real
the giant telescope acts as a collector
for the particles of laser light that
make the trip back to the observatory
the time it takes for the light
particles to reach the telescope is
calculated and fed into data banks
the information returned is analyzed
regularly by a group of scientists at
nasa's jet propulsion laboratory in
pasadena california
again dr skip newhall
we have now a means of measuring
earth and lunar phenomena geophysical
body-oriented science phenomena that
were not available by any means before
this is the only way we can measure
particularly connected with the moon
lunar laser ranging
helping scientists to learn more about
the earth and our closest celestial
neighbor the moon