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Modern Lunar Laser Ranging data can be fit with a 1 cm weighted rms residual. The center of Earth to center of Moon distance is computed by a program that numerically integrates the lunar and planetary orbits accounting for the gravitational attraction of the Sun, planets, and a selection of asteroids. [36] [23]
In contrast, the Lunar distance (LD or ), or Earth–Moon characteristic distance, is a unit of measure in astronomy. More technically, it is the semi-major axis of the geocentric lunar orbit . The average lunar distance is approximately 385,000 km (239,000 mi), or 1.28 light-seconds ; this is roughly 30 times Earth's diameter .
In celestial navigation, lunar distance, also called a lunar, is the angular distance between the Moon and another celestial body. The lunar distances method uses this angle and a nautical almanac to calculate Greenwich time if so desired, or by extension any other time. That calculated time can be used in solving a spherical triangle.
Lunar distance LD ≈ 384 402 km. [15] Average distance between the center of Earth and the center of the Moon. astronomical unit au. Defined as 149 597 870 700 m. [16] Approximately the distance between the Earth and Sun. light-year ly ≈ 9 460 730 472 580.8 km. The distance that light travels in a vacuum in one Julian year. [17]
To determine the distance to the reflector to 1 mm precision, or 7 ps, by averaging, the measurement needs at least (400/7) 2 ≈ 3000 photons. This explains why a much larger system is needed to improve the existing measurements—the pre-APOLLO 2 cm RMS range precision required only about 10 photons, even at the worst-case orientation of the ...
The Lunar Traverse Gravimeter was a lunar science experiment, deployed by astronauts on the lunar surface in 1972 as part of Apollo 17.The goal of the experiment was to use relative gravity measurements to infer potential attributes about the geological substrata near the Apollo 17 landing site.
The astronomical unit of length is now defined as exactly 149 597 870 700 meters. [4] It is approximately equal to the mean Earth–Sun distance. It was formerly defined as that length for which the Gaussian gravitational constant (k) takes the value 0.017 202 098 95 when the units of measurement are the astronomical units of length, mass and ...
[36] [37] To determine this value, Ptolemy started by measuring the Moon's parallax, finding what amounted to a horizontal lunar parallax of 1° 26′, which was much too large. He then derived a maximum lunar distance of 64 + 1 / 6 Earth radii. Because of cancelling errors in his parallax figure, his theory of the Moon's orbit, and ...