http://www.newscientist.com/blog/space/2007/12/china-moon-photo-flawed-but-not-fake.html

Wednesday, December 05, 2007

China Moon photo flawed but not fake
The first publicly released photo from China's Chang'e 1 Moon probe is
genuine, though flawed, because it has been modified to make it more
pleasing to the eye, according to an analysis by a Planetary Society blogger.

Rumours have been circulating online that a photo released by the Chinese
government and attributed to the country's first Moon probe is actually a
copy of an image from the US defense department's Clementine probe of the
mid-1990s.

China has insisted the image it released really is from Chang'e 1. This is
confirmed by a new analysis by Planetary Society blogger Emily Lakdawalla (
which I came upon via an entry in Alan Boyle's Cosmic Log).

Clementine did image the part of the Moon that appears in the Chang'e 1
image. But the two images have differences that show the Chang'e 1 image is
not merely a copy. As Lakdawalla points out, sunlight illuminates the scene
from different angles in the two images, and the Chang'e 1 image reveals
more detail (see images above - the top one is Clementine, the bottom Chang'
e 1).

"My personal opinion, based upon the evidence I was able to dig up, is that
the Chinese do have an orbiter at the Moon, and that it is producing really
beautiful images that are a great improvement over Clementine," Lakdawalla
writes.

But she also notes that the image released to the public is actually a
composite made by stitching together 19 images, each of which shows a small
part of the scene. The edges where the images were joined together have been
smoothed to make them less apparent, Lakdawalla says.

The stitching together process also provides an explanation for an "extra"
crater seen in the Chang'e 1 image (top right) that does not appear in the
Clementine view of the same area (top left). The Chang'e 1 chief scientist
has suggested that either Clementine's camera was not sensitive enough to
see the crater or that it was gouged out by an impact after Clementine made
its observations.

But Lakdawalla says flaws in the stitching-together process simply created
an illusory duplicate of a real crater in the image. When she re-aligned the
border between the images in the composite (bottom right), it became a
close match to the Clementine image (bottom left), without the extra crater.

"However, because of the blending of the seams, this is not a product that
should be used for scientific research - including looking for new craters,"
she adds. "Some of this problem should go away once the Chang'e team
improves their knowledge of their spacecraft's orbit and of the shape of the
Moon; with more precise positional information, their mosaics will
automatically improve, having less obvious seams with smaller offsets."

David Shiga, online reporter (Top image: NASA/DOD, CAST; Bottom image, top
row: NASA/DOD, CAST; bottom row: NASA/DOD, CAST/Emily Lakdawalla)