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Topic: Lunar Laser Ranging

	Laser applications - Wikipedia, the free encyclopedia
		Laser beams are focused through large telescopes on Earth aimed toward the arrays, and the time taken for the beam to be reflected back to Earth measured to determine the distance between the Earth and Moon with high precision.
		By shining particular wavelengths of laser light at the ions, it is possible to transfer momentum from the ions to the light photons, causing the ions to lose energy and to slow down, thus cooling the ions.
		The first role envisioned for the laser in military applications was as a "death ray": a hand-held device that might replace the gun as a weapon for infantry, or a vehicle-mounted "laser cannon" able to destroy tanks, ships and aircraft.
	en.wikipedia.org /wiki/Laser_applications (1632 words)

	Lunar distance - Open Encyclopedia (Site not responding. Last check: 2007-10-16)
		In celestial navigation, lunar distance is in the angle of the Moon's centre from the Sun or from the bright stars.
		Using the lunar distance and a nautical almanac it is possible to calculate the current time and thus the current longitude.
		High-precision measurements of the lunar distance are made with the help of lidar measurements of the round-trip times for light beams between lasers at Earth-based monitoring stations and retroreflectors placed on the Moon.
	open-encyclopedia.com /Lunar_distance (109 words)

	[No title] (Site not responding. Last check: 2007-10-16)
		Once the laser beam hits a reflector, scientists at the ranging observatories use extremely sensitive filtering and amplification equipment to detect the return signal, which is far too weak to be seen with the human eye.
		While the earliest ranges had accuracies of several meters (or several yards), continuing improvements in the lasers and the detection electronics have led to recent measurements that are accurate to about 3 centimeters (about 1 inch).
		From the ranging experiments, scientists know that the average distance between the centers of the Earth and the moon is 385,000 kilometers (239,000 miles), showing that modern lunar ranges have relative accuracies of better than one part in 10 billion.
	www2.jpl.nasa.gov /files/releases/lunlaser.txt (1004 words)

	Lunar Laser Ranging at McDonald
		The lunar libration in longitude, with a period of only 2.9 yr, has a 69 yr beat with another term of similar period; a third mode of that libration has a 24 yr period with respect to the node; the dissipation term and the lunar obliquity have an 18.6 yr period.
		Finally, LLR is sensitive to the relative orientation of the equator, ecliptic and lunar orbit planes, presently at the 1.5 mas level, and improving with time, due to our being on a spinning Earth while the lunar orbit precesses along the ecliptic.
		LLR, and the science it is able to accomplish, should be a source of pride to the scientific community in general.
	www.csr.utexas.edu /mlrs/dda.html (2881 words)

	Apollo Laser Ranging Experiments Yield Results (Site not responding. Last check: 2007-10-16)
		The first laser ranging retroreflector was positioned on the Moon in 1969 by the Apollo 11 astronauts.
		From the ranging experiments, scientists know that the average distance between the centers of the Earth and the Moon is 385,000 kilometers with an accuracy of better than one part in 10 billion.
		Ranging has also determined that the length of an Earth day has distinct small-scale variations of about one thousandth of a second over the course of a year, caused by the atmosphere, tides, and Earth's core.
	geophysics.ou.edu /solid_earth/readings/apollo_laser_ranging.html (607 words)

	Satellite Laser Ranging
		The primary function of Satellite Laser Ranging (SLR) is the measurement of precise distances between laser telescope and mirrors on passing satellites.
		Lunar Laser Ranging lets us study the complex motion of the moon and has even shown us that the moon is steadily moving away from the earth.
		Laser Ranging is an invaluable tool for monitoring movement of the tectonic plates and changes in the Earth's rotation.
	www.ga.gov.au /nmd/geodesy/slr/whatis.htm (361 words)

	Example of Astro-Toolbox: Lunar Laser Ranging data
		Lunar Laser Ranging supplies the positions of predefined lunar targets given in file "./data/lunar.dat" by using the DE405 ephemeris of the JPL.
		Because when the laser pulse is sent, the Moon keeps moving during the approximately 1.2 seconds which are needed to reach the target.
		As laser ranging is at the edge of nowadays technology, the range gate is set as small as possible to prevent unwanted photons to enter the photo detector.
	tau.fesg.tu-muenchen.de /~atb/examples/llr.html (554 words)

	Lunar Laser Ranging Experiment - Wikipedia, the free encyclopedia
		The ongoing Lunar Laser Ranging Experiment was first made possible by a lunar laser ranging retroreflector array planted on the Moon on July 21, 1969, by the crew of the Apollo 11.
		Lunokhod 1 also left an array, but it was poorly positioned and has not been of use to the experiment.
		Lunar ranging also provides data useful for other experiments, including tests of general relativity designed by physicists such as Carrol Alley.
	en.wikipedia.org /wiki/Lunar_Laser_Ranging_Experiment (300 words)

	Lunar Laser Ranging Experiment (Site not responding. Last check: 2007-10-16)
		The Apollo 11, Apollo 14, and Apollo 15 missions left retro-reflectors on the Moon as part of a laser ranging experiment, the Lunar Laser Ranging Experiment.
		Since then, the range from Earth to Moon has been measured at intervals, over a period of more than 30 years.
		Lunar ranging provides information that is potentially useful for a number of purposes, including providing tests of general relativity designed by physicist Carrol Alley.
	www.ceca.de /encyclopedia/l/lu/lunar_laser_ranging_experiment.html (110 words)

	Apollo 11 Experiment Continues To Return Valuable Data
		Lunar Data Support Idea That Collision Split Earth, Moon (March 17, 1999) -- Analysis of data from NASA's Lunar Prospector spacecraft has confirmed that the Moon has a small core, supporting the theory that the bulk of the Moon was ripped away from the early Earth when an...
		Scientists who analyze the data from the Lunar Laser Ranging Experiment have measured, among other things, that the Moon is moving away from the Earth and that the shape of the Earth is changing at an unprecedented accuracy level.
		Laser ranging has shown that the Moon is receding from the Earth at about 3.8 centimeters (1.5 inches) every year.
	www.sciencedaily.com /releases/1999/07/990720083540.htm (1155 words)

	JPL.NASA.GOV: Feature Stories
		Scientists from various institutions who analyze the data from the lunar laser ranging experiment have observed, among other things, that the Moon is moving away from the Earth and has a fluid core, and that Einstein's Theory of Relativity is accurate.
		The lunar laser ranging experiment is the only lunar investigation continuously operating since the Apollo project.
		To this end, a new lunar ranging instrument with significantly improved accuracy is being constructed at Apache Point Observatory in New Mexico by the University of California at San Diego and the University of Washington.
	www.jpl.nasa.gov /news/features.cfm?feature=605 (951 words)

	Abstract
		In a LLR experiment, a very short pulse of laser light is fired through a telescope at one of the retro-reflectors.
		With this scenario, the LLR is a type of experiment virtually identical to the “Two Parallel Car Metaphor.” The line between the sun and Leo is represented by the path of the two parallel cars.
		Because LLR observers frequently need to use some "trial and error" when trying to "find" the retro-reflector, their data is not accurate enough (actually for several reasons) to determine an exact number as to how "close" the gap must be.
	pages.sbcglobal.net /webster.kehr/Chapters/Chapter100-LLR.htm (5636 words)

	LUNAR (Site not responding. Last check: 2007-10-16)
		Among those devices was a laser ranging retroreflector, which, a generation later, is still yielding fundamental scientific data.
		Laser ranging has made possible a wealth of new information about the dynamics and structure of the Moon.
		The Apollo 11 and 14 laser reflector arrays are identical and consist of 100 fused silica corner cube reflectors, mounted in a 46 centimeter aluminum panel.
	ilrs.gsfc.nasa.gov /satellite_missions/list_of_satellites/lunar.html (521 words)

	LUNAR LASER RANGING OBSERVATIONS COULD FALSIFY EINSTEIN'S THEORY OF RELATIVITY
		An introduction to Lunar Laser Ranging (L.L.R.) _______________________________________ (Source) Up to the beginning of the sixties, the lunar theory, a major problem for astronomers, had reached a dead end and a breakthrough was needed.
		A rough analysis of LLR Cerga observations ____________________________________ Its aim is to illustrate the procedure which could be followed to detect the motion of the couple Earth-Moon in space.
		Only the specialists working at the LLR stations are sufficiently equipped to perform those corrections, so I had to limit myself to the determination of the orbital position of the moon at each date of observation.
	perso.wanadoo.fr /mluttgens/Ranging.htm (1480 words)

	Fundamental Physics of Space - Technical Details
		The beam enters the telescope where the eyepiece would be, and the transmitted beam is expanded to become the diameter of the main mirror, then bounced off the surface toward the reflector on the Moon.
		There is strong evidence that the Moon has a liquid core, and laser ranging has allowed us to determine with great accuracy the rate at which the Moon is gradually receding from the Earth.
		By beaming laser pulses at the reflector from Earth, scientists have been able to determine the round-trip travel time that gives the distance between the observatory and retroreflector.
	funphysics.jpl.nasa.gov /technical/grp/lunar-laser.html (397 words)

	UW researcher plans project to pin down moon's distance from Earth
		He'll employ the telescope, a laser beam and reflectors left by several lunar missions in a technique known as laser ranging to provide the most exacting measure yet of the Earth's distance from the moon.
		He will attach a laser that generates an average power of 2 watts, but that will jump to a peak power of a gigawatt (1 billion watts) long enough to generate a 1-inch "bullet" of light aimed through the telescope at the lunar surface.
		Each laser bullet will be aimed at one of five retroreflectors, banks of 100 to 300 special prisms that reflect a beam of light back to its point of origin.
	www.washington.edu /newsroom/news/2002archive/01-02archive/k011402.html (800 words)

	Joint CSTG/IERS Call for Participation in Satellite and Lunar Laser Ranging (Site not responding. Last check: 2007-10-16)
		Laser ranging to the Moon and artificial satellites was initiated in the 1960s and, during the 1970s and 1980s, matured into an operational space geodetic technique supporting a variety of scientific applications.
		Satellite laser ranging (SLR) was a significant source of tracking information for early altimeter satellites, such as GEOS-3 and SEASAT, and has provided a long time series of data from the Starlette and LAGEOS satellites since their launch in the mid-1970s.
		In the early 1980s, the SLR and Lunar Laser Ranging (LLR) communities participated in MERIT (Monitoring Earth Rotation and Intercomparison of Techniques) to demonstrate the utility of modern space techniques in determining Earth rotation parameters.
	cddisa.gsfc.nasa.gov /cstg/ilrs_cfp.html (935 words)

	NASA - Apollo 11 Science Experiment Still Running
		Lunar ranging should continue for decades, perhaps for centuries.
		Excerpts from the Apollo 11 Lunar Surface Journal describe Neil Armstrong and Buzz Aldrin's deployment of the lunar retroreflector array.
		Lunar Retroreflectors -- Retroreflectors, or corner-cube prisms, are optical devices that return any incident light back in exactly the direction from which it came.
	www.nasa.gov /lb/vision/space/features/21jul_llr.html (894 words)

	CNN - Apollo 11 experiment still returning results - July 21, 1999
		The laser beams bounce back anywhere from 2.3 to 2.6 seconds later and it is the tiny time differences that reveal the secrets of the moon's orbit and its movement over time.
		By multiplying the time the laser takes to return by the speed of light, researchers can calculate how far away the moon is at a particular point in time.
		He made a splash in the lunar science community in recent months with an analysis of lunar ranging data that showed the moon has a liquid core.
	www.cnn.com /TECH/space/9907/21/apollo.experiment (843 words)

	Apollo 14 Laser Ranging Retroreflector Experiment (Site not responding. Last check: 2007-10-16)
		It consisted of a series of corner-cube reflectors, which are a special type of mirror with the property of always reflecting an incoming light beam back in the direction it came from.
		The reflected laser beam is also observed with the telescope, providing a measurement of the round-trip distance between Earth and the Moon.
		Laser beams are used because they remain tightly focused for large distances.
	www.lpi.usra.edu /expmoon/Apollo14/A14_Experiments_LRRR.html (388 words)

	NASA - Was Galileo Wrong?
		Using lasers to ping the moon, NASA-supported researchers are testing a fundamental assumption of modern physics.
		"Lunar laser ranging is one of the most important tools we have for searching for flaws in Einstein's general theory of relativity," says Slava Turyshev, a research scientist at JPL who works with Jim Williams and others on the project.
		Right: Lunar laser ranging works by firing pulses of laser light at reflectors on the moon's surface and catching the returning photos.
	www.nasa.gov /vision/universe/solarsystem/06may_lunarranging.html (1349 words)

	IngentaConnect The isotropy of gravity from lunar laser ranging (Site not responding. Last check: 2007-10-16)
		IngentaConnect The isotropy of gravity from lunar laser ranging
		The isotropy of gravity from lunar laser ranging
		Laser ranging measurement of the lunar orbit (LLR) is examined for its ability to detect any spatial anisotropy in the gravitational interaction.
	api.ingentaconnect.com /content/iop/cqg/1996/00000013/00000006/art00005 (189 words)

	Moonbeams Shine On Einstein, Galileo And Newton
		The Lunar Laser Ranging experiment confirms that the Moon and Earth "fall toward" the Sun at the same rate, even though Earth has a large iron core below its rocky mantle, while the Moon is mostly rocky with a much smaller core.
		"Lunar laser ranging can conduct very accurate tests of gravity and fundamental physics," said Williams, who pointed out that small variations in gravity are difficult to study because the force is weak, unless very large masses are used.
		Lunar laser ranging measurements are helping future human and robotic missions to the Moon.
	www.spacedaily.com /news/gravity-05d.html (974 words)

	The International Laser Ranging Service
		The basic observable is the precise time-of-flight of an ultrashort laser pulse to and from a satellite, corrected for atmospheric delays.
		In the field of relativity, LLR is used for the verification of the equivalence principle, estimation of geodetic precession, and examination of the relative change in G. The ILRS Central Bureau (CB) is responsible for the daily coordination and management of ILRS activities.
		The new state-of-the-art Matera Laser Ranging Observatory (MLRO) with both SLR and lunar ranging capability has now been installed at Matera and is presently undergoing final acceptance testing.
	geodesy.eng.ohio-state.edu /iag_sectionII/ilrs.htm (2751 words)

	Laser Ranging Newsletter
		A critical part of the HMC experiment is the use of laser ranging techniques to compare time kept by the space maser with time kept by clocks on the earth.
		Velocity aberration caused by the satellite movement is compensated by the effects of the curved mirror and the spoiled dihedral angles between the curved mirror and the plane mirrors[1].
		The transmitted laser beam is expanded into a ring, enters the telescope through a coude path and leaves it concentrically around the secondary mirror.
	www.dgfi.badw-muenchen.de /edc/ilrs/ilrs.gsfc.nasa.gov/reports/slrnews_9506.html (15527 words)

	Was Galileo Wrong?
		Current lunar laser ranging can measure the distance to the Moon--roughly 385,000 km--with an error of about 1.7 cm.
		The speed of light is known--it's about 300,000 km per second--so measuring the time of flight for the laser pulse tells scientists the distance between the APOLLO telescope and the mirror sitting on the surface of the Moon.
		Right: Lunar laser ranging works by firing pulses of laser light at reflectors on the Moon's surface and catching the returning photons.
	science.nasa.gov /headlines/y2004/06may_lunarranging.htm (1409 words)

	APOLLO
		We will measure the round-trip travel time of laser pulses bounced off the lunar retroreflectors to a precision of a few picoseconds, corresponding to about one millimeter of precision in range to the moon.
		A total of four lunar retroreflectors are functional: three Apollo reflectors from Apollo 11, 14, and 15 (three times bigger), and one French-built, Soviet landed (unmanned) unit from the Luna 21 mission.
		A significant part of the challenge of lunar range modeling is converting this point-to-point measurement into a distance between the center-of-mass of the earth and the center-of-mass of the moon.
	physics.ucsd.edu /%7Etmurphy/apollo/apollo.html (955 words)

	[56.03] Apache Point Observatory Lunar Laser-ranging Operation (APOLLO) (Site not responding. Last check: 2007-10-16)
		Lunar Laser Ranging (LLR) is currently the best means available for testing Einstein's Strong Equivalence Principle, on which general relativity rests.
		LLR also provides the strongest limits to date on variability of the gravitational constant, the best measurement of the de Sitter precession rate, and is relied upon to generate accurate astronomical ephemerides.
		These factors together will move LLR into a new regime of millimeter precision, pushing tests of gravity into a range where violations of general relativity are motivated by the introduction of scalar fields.
	www.aas.org /publications/baas/v36n5/aas205/686.htm (297 words)

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