NASA Technique for Manipulating Satellite Photos Now Reveals Ancient Images

Algorithm NASA first applied to satellite imagery is now used to peer into antiquity. NASA Technique for Manipulating Satellite Photos Now Reveals Ancient Images. Thousands of visitors pass these images daily without noticing, because they’re faded to the point of invisibility.

They were discovered between 2010 and 2012, along with about 200 other paintings throughout the complex, by an archaeologist using a method conceived at NASA’s Jet Propulsion Laboratory in Southern California. The technique, known as decorrelation stretch, heightens contrasts in digital imagery, making features easier to spot. It is especially popular for studying ancient rock art, partly due to the chance intersection of one man’s hobby with his professional background.

Around 2005, rock art enthusiast Jon Harman saw NASA images depicting the Martian surface with and without the application of decorrelation stretch. Seeing how much detail the technique revealed, Harman, now retired in Pacifica, California, understood the implication for studying ancient, faded images. “I Googled it and found a NASA paper that explained how to do the algorithm,” he said.

“I knew from my medical imaging experience that I could do it, so I did.” The paper was written in 1996 by Ronald Alley, a JPL employee developing applications for the Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER), a Japanese imaging instrument on NASA’s Terra satellite.