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this desolate landscape haleakala crater

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is located on the hawaiian island of

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maui

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it looks very similar to the distant

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pockmarked wastelands of the moon

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and it is here at the lower observatory

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that nasa and the university of hawaii

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are involved in work which helps us

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understand the geophysical science of

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the moon and the earth

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lure observatory situated at the ten

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thousand foot summit of mount haleakala

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uses laser technology to accurately

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range within one inch the two hundred

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forty thousand mile distance between the

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two bodies

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ranging or measuring distance is

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accomplished by clocking the time it

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takes bursts of laser light to leave the

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observatory hit one of four retro

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reflectors on the moon and return to the

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observatory

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by measuring the continually changing

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distance between the earth and moon we

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are able to unlock many details relating

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to the motions of both bodies

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analysis of day-to-day changes in the

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earth's motion help scientists better

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understand the earth's rotation

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continental drift

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weather phenomena such as the el nino

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effect and forces deep within the earth

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that set off earthquakes

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there are currently two other

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observatories located around the world

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which also participate in lunar laser

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ranging but as yet neither has achieved

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the level of precision of the lower

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facility

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much more will be learned in the future

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by interpreting data from many stations

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simultaneously

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the accuracy of ranging has come a long

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way since apollo astronauts armstrong

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and aldrin placed the first

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retroreflector on the moon

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a member of the technical staff at the

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jet propulsion laboratory working on

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lunar laser ranging is dr skip new hall

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the moon reflectors are composed of

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array of several dozen or perhaps a few

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hundred are these so-called corner

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reflectors

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and they have a nice feature

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that

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no matter what direction the light goes

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in from

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the it always returns out at exactly the

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same direction so when we shine a laser

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beam at the moon no matter how it's

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oriented locally the light comes right

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back out when the apollo

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astronauts first put the reflectives on

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the moon we got some returns back in

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early 1970 and late 1969

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the uncertainty in the return time was

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about

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equivalent of a distance of 150 to 200

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meters that's around 600 feet

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we have refined the time equipment the

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lasers and the other associated

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electronic equipment that supports this

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so now

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we have the uncertainties and distance

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are equal to about three quarters of an

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inch

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which is an amazing improvement

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the key to the lunar ranging operation

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is a laser that can be adjusted to

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create intense billion watt pulses of

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energy

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and back

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the light energy is channeled out of the

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observatory by this mirrored instrument

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which keeps the laser beam continually

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locked on target with the retro

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reflectors on the moon

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meanwhile in the observatory's main

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control room the receiving telescope

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which is composed of 80 lenses is

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adjusted to line up visually with the

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moon's apollo 15 retro reflector near

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hadley real

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the giant telescope acts as a collector

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for the particles of laser light that

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make the trip back to the observatory

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the time it takes for the light

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particles to reach the telescope is

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calculated and fed into data banks

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the information returned is analyzed

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regularly by a group of scientists at

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nasa's jet propulsion laboratory in

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pasadena california

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again dr skip newhall

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we have now a means of measuring

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earth and lunar phenomena geophysical

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body-oriented science phenomena that

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were not available by any means before

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this is the only way we can measure

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particularly connected with the moon

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lunar laser ranging

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helping scientists to learn more about