| Risultati della ricerca nelle immagini - "Airy" |
Craters-Airy_Crater-The_Prime_Meridian-0.JPGMars' Prime Meridian, such as: Longitude "0" (1 - Original NASA/MGS/MSSS CTX b/w Frame)63 visiteOn Earth, the Longitude of the Royal Observatory in Greenwich, England is defined as the "Prime Meridian" or the 0 point of Longitude. Locations on Earth are measured in degrees East or West from this position.
The Prime Meridian was defined by an International Agreement in 1884 as the position of the Transit Circle: a large telescope located in the Observatory's Meridian Building. The Transit Circle was built by Sir George Biddell Airy, the 7th Astronomer Royal, in 1850. While visual observations with Transit were the basis of navigation until the space age, it is interesting to note that the current definition of the Prime Meridian is in reference to orbiting satellites and Very Long Baseline Interferometry (VLBI) measurements of distant radio sources such as quasars.
However, said "International Reference Meridian" is now about 100 mt East of the Transit Circle at Greenwich.
For Mars, the Prime Meridian was first defined by German astronomers W. Beer and J. H. Mädler in 1830-32.
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Craters-Airy_Crater-The_Prime_Meridian-1.JPGMars' Prime Meridian, such as: Longitude "0" (2 - Original NASA/MGS/MSSS CTX b/w Frame)56 visiteBeer and Mädler used a small circular feature, which they designated "a" as a reference point to determine the rotation period of Mars. The Italian astronomer G. V. Schiaparelli, in his 1877 map of Mars, used this feature as the 0 point of Longitude. It was subsequently named Sinus Meridiani ("Middle Bay") by Camille Flammarion.
When Mariner 9 mapped the Planet at about 1 Km (0,62 mile) resolution in 1972, an extensive control net of locations was computed by Merton Davies of the RAND Corporation. Davies designated a 0,5-Km-wide crater, subsequently named Airy-0 (within the large crater Airy in Sinus Meridiani) as the Longitude 0 point.
Airy-0 was imaged once by Mariner 9 and once by the Viking 1 orbiter in 1978, and these 2 images were the basis of the Martian Longitude System for the rest of the 20th Century. The MGS has attempted to take a picture of Airy-0 on every close overflight since the beginning of the mapping of Mars.
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