Kamlesh P. Lulla, NASA's chief scientist for Earth observation at Johnson Space Center in Houston, directs observation science activities from the Space Shuttle and the International Space Station. He says that generally the Great Wall is hard to see and hard to photograph, because the material from which it is made is about the same color and texture as the area surrounding it.
While the Great Wall of China is very difficult to see or photograph from low Earth orbit, sections of the wall can be seen readily in radar imagery.
This image of sections of the wall in a desert about 435 miles west of Beijing was made by the Spaceborne Imaging Radar flown aboard the Space Shuttle Endeavour. The wall appears as an orange line extending the length of the image.