The Lunar Laser Ranging Experiment from the Apollo 11 mission

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. Since then, the distance between the Earth and the Moon has been measured repeatedly over a period of more than 35 years. Download high resolution version (904x913, 314 KB)The Lunar Laser Ranging Experiment from the Apollo 11 mission. ... Download high resolution version (904x913, 314 KB)The Lunar Laser Ranging Experiment from the Apollo 11 mission. ... Lasers range in size from microscopic diode lasers (top) with numerous applications, to football field sized neodymium glass lasers (bottom) used for inertial confinement fusion, nuclear weapons research and other high energy density physics experiments. ... Retroreflectors are clearly visible in a pair of bicycle shoes. ... Bulk composition of the moons mantle and crust estimated, weight percent Oxygen 42. ... July 21 is the 202nd day (203rd in leap years) of the year in the Gregorian Calendar, with 163 days remaining. ... 1969 (MCMLXIX) was a common year starting on Wednesday (the link is to a full 1969 calendar). ... Apollo 11 was the fifth human spaceflight of the Apollo program, the third human voyage to the moon, and the first manned mission to land on the Moon. ... Earth (often referred to as The Earth) is the third planet in the solar system in terms of distance from the Sun, and the fifth in order of size. ...

Two more retroreflector arrays, left by the Apollo 14 and Apollo 15 missions have contributed to the experiment. The unmanned Soviet Lunokhod 1 and Lunokhod 2 rovers carried smaller arrays. Reflected signals were received from Lunokhod 1, but then it was left in a position preventing the return of signals. Lunokhod 2's array has returned signals to Earth. (Note that NASA's NSSDC catalog confuses Lunokhod 1 and Lunokhod 2 on this issue: [1], while more accurate references can be found at [2] and [3]). Apollo 14 was the eighth manned mission in the Apollo program and the third mission to land on the moon. ... Apollo 15 was the ninth manned mission in the Apollo program and the fourth mission to land on the Moon. ... Lunokhod series Soviet Moon exploration robot vehicle A panorama shot from Lunokhod 1 A photo from Lunokhod 1 showing the Luna 17 lander The tracks of Lunokhod showing the little wheel in the center that was used for odometry. ... Lunokhod series Soviet Moon exploration robot vehicle Lunokhod 2 was the second of two unmanned lunar rovers landed on the Moon by the Soviet Union as part of the Lunokhod program. ...

The Apollo 15 array is three times the size of the arrays left by the two earlier Apollo missions. Its size made it the target of three-quarters of the sample measurements taken in the first 25 years of the experiment. Improvements in technology since then have resulted in greater use of the smaller arrays, by sites such as the McDonald Observatory and the OCA Laser-Lune telemetry station affiliated with the Côte d'Azur Observatory. Aerial view of the McDonald Observatory. ... Telemetry is a technology that allows the remote measurement and reporting of information of interest to the system designer or operator. ... The Côte dAzur Observatory (in French: Observatoire de la Côte dAzur) originated in 1988 with the merger of two observatories: Nice Observatory The CERGA (Centre dÉtudes et de Recherches Géodynamiques et Astronomiques) External links Côte dAzur Observatory official website (English version) ...

Lunar ranging also provides data useful for other experiments, including tests of general relativity designed by physicists such as Carrol Alley. For a non-technical introduction to the topic, please see Introduction to General relativity. ... Carroll Alley is an American physicist. ...

As of 2002 work is progressing on increasing the accuracy of the Earth-Moon measurements to near millimeter accuracy. For album titles with the same name, see 2002 (album). ...

Some of the results of this long-term experiment are:

• The moon is spiraling away from Earth at a rate of 3.8 cm per year, due to the Earth's ocean tides.
• The moon probably has a liquid core.
• The universal force of gravity is very stable. The experiments have put an upper limit of the change in Newton's gravitational constant G of less than 1 part in 100,000,000,000 since 1969.
• Einstein's theory of gravity and the general theory of relativity predict the moon's orbit to within the accuracy of the laser ranging measurements.

The tide is the cyclic rising and falling of Earths ocean surface caused by the tidal forces of the Moon and the Sun acting on the Earth. ... In physics, gravitation or gravity is the tendency of objects with mass to accelerate toward each other. ... Sir Isaac Newton, President of the Royal Society, (4 January 1643 – 31 March 1727) [OS: 25 December 1642 – 20 March 1727] was an English mathematician, physicist, astronomer, alchemist, chemist, inventor, and natural philosopher who is generally regarded as one of the most influential scientists and mathematicians in history. ... According to the law of universal gravitation, the attractive force between two bodies is proportional to the product of their masses and inversely proportional to the square of the distance between them. ... Albert Einstein, photographed by Yousuf Karsh in 1948. ... For a non-technical introduction to the topic, please see Introduction to General relativity. ... Two bodies with a slight difference in mass orbiting around a common barycenter. ...

See also

• Lunar distance (astronomy)

In astronomy, a lunar distance ( LD ) is a measurement of the distance from the Earth to the Moon. ...

External links and sources

• Apollo 15 Laser Ranging Retroreflector Experiment
• History of Laser Ranging
• Lunar Retroreflectors History and Position
• Station de Télémétrie Laser-Lune in Grasse, France
• 1994 article on "Measuring the Moon's Distance"
• 2002 article about "UW researcher plans project to pin down moon's distance from Earth"
• NASA: What Neil & Buzz Left on the Moon
• CNN: Apollo 11 Experiment Still Returning Results after 30 Years
• JPL: Apollo 11 Experiment Still Going Strong after 35 Years