Saturday, April 7, 2012

Image of the week : moon in 3D


It was on January 9: the first full moon of 2012.

The Pleiades satellite was there to immortalize the event, not only for the beauty of the show but because the Moon is a very interesting "target" for its in-orbit activities : free from atmospheric disturbances, it is possible to finely calibrate the instrument optical Pleiades on the seas and lunar craters.

Best of all, Pleiades has also achieved a first by taking, thanks to its agility, two stereo images of the visible face of the Moon: so here the first three-dimensional image of our natural satellite from an observation satellite Earth!

The two images were taken while the satellite Pleiades occupied two diametrically opposed positions on its orbit at 694 km altitude: two views separated by nearly 14100 km.
It is this gap that creates the differences between the red and cyan, which allows you, with appropriate spectacles, to see the Moon in 3 dimensions.

This parallax effect of the difference of views, is known since ancient astronomy: the Greeks (Aristarchus, Eratosthenes, Hipparchus, Ptolemy) used this method to measure the distance between objects in the solar system and stars.
In 1751, 'l'abbé' de Lacaille and Joseph de Lalande, in Berlin and Cape Town, performed the first accurate measurement of distance from the Earth to the Moon.

Note: Due to shooting conditions and to use the 3D glasses, the image is rotated 90 ° from the representation "usual" of the Moon: the large crater Tycho Brahe, right here, is well located in the southern hemisphere of the Moon.

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