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Space technology uncovers old masterworks
   PASADENA, Calif. (UPI) _ Computer methods used by space scientists
to analyze photographs of other planets are now being used to uncover
possible old masterpieces hidden beneath known paintings.
   The same space imaging technique used by Jet Propulsion Laboratory
scientists to analyze photographs beamed from Mars, Jupiter and Saturn
is also being used to determine the condition of a priceless Leonardo da
Vinci sketch.
   Planetary scientists working with art conservators at the Los
Angeles County Art Museum developed the method to separate X-ray images
of paintings where two or more pictures are believed to exist in
different layers on the same surface.
   Don Lynn, a former JPL scientist who developed the process, said
Monday that computer enhancement of images began with NASA's Ranger
project in 1962-63 and was also used in the Mariner, Viking and Voyager
projects.
    "Very simply, what we do is obtain images of the painting through
X-ray,"  said Lynn  "The X-ray reveals both the over-painting and the
under-painting.
    "Then we move it around and try to subtract the major part of the
upper painting from the two combined pictures. The net result is a
reasonably good view _ or an excellent view _ of the painting and the
surface beneath." 
   The intensity or brightness of light values of the two images are
then converted to digital numbers, the language of the computer.
    "The computer can manipulate those numbers,"  he explained,  "and
we express the over-painting in one series of numbers and the
under-painting in another series." 
   In the final step of the process, the first set of numbers is
subtracted and the second set is coverted by the computer into light
intensity values that produce an image of the hidden painting _ possibly
a masterwork that has been covered for centuries.
   The art project began when William Leisher, head of conservation at
the art museum, asked JPL to separate and enhance a painting found
beneath a 17th century painting of the crucifixion by an unidentified
Flemish artist.
   Lynn worked with an astronomer and computer analyst from JPL and
museum officials and experts to bring out the hidden painting in
detail.
   They discovered that the surface painting was on paper and the
covered picture, on a wooden base, portrayed a man and woman in 17th
Century attire sitting at a table in a room lighted by sunshine coming
through a window.
   The process also is being used to examine the condition of the
priceless Codex Hammer, the Leonardo da Vinci manuscript on the nature
of water that was purchased in 1980 by billionaire industrialist Armand
Hammer.
   The 470-year old manuscript had for more than 250 years been known
as the Codex Leicester and was owned by the family of the Earl of
Leicester who put it on auction to pay inheritance taxes.
   The diary, which da Vinci began in 1508, was written and sketched
backwards, so that it is readable only by reflection. Hammer has donated
the manuscript to the County Museum.
   
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   Lynn worked with an ast