A NASA-developed technique for enhancing satellite images has uncovered ancient artwork hidden in the central tower of Angkor Wat, a vast temple complex in Cambodia. The newly revealed images depict horseback riders and a traditional musical ensemble, but they are nearly invisible to the naked eye due to fading over time. Thousands of visitors walk past these images daily without realizing they exist. The discovery was made between 2010 and 2012 by an archaeologist using a method originally designed at NASA’s Jet Propulsion Laboratory (JPL) in Southern California. The technique, called decorrelation stretch, enhances the contrast in digital images, making faint or faded features more visible. It has become especially valuable in the study of ancient rock art, thanks to a unique convergence of interests. Around 2005, Jon Harman, a rock art enthusiast and retired resident of Pacifica, California, became fascinated with how the technique revealed hidden details in NASA images of the Martian surface. Harman had a background in medical imaging, which helped him understand how to apply the technique to ancient artwork. He found a 1996 NASA paper explaining the algorithm and, using his technical skills, developed a version of it for public use. The original decorrelation stretch method was developed by Ronald Alley, a JPL employee, for use with ASTER, a Japanese imaging instrument aboard NASA’s Terra satellite. Alley recognized the potential of the technique to extract information from satellite imagery. Harman adapted the method for use with ImageJ, an open-source image analysis program developed by the National Institutes of Health. He also created smartphone apps that mimic the technique, which have been downloaded thousands of times. Researchers have since published studies highlighting Dstretch’s usefulness in archaeology, from uncovering ancient carvings in Norway to examining tattoos on mummified remains. Harman was not surprised that the technique gained traction in the rock art community, but he was impressed by the wide range of applications it has found. From identifying buried ruins of ancient Greek buildings to analyzing faded paintings in Egyptian tombs, Dstretch has proven to be a versatile tool. Its ability to reveal hidden details in various fields has made it a valuable resource for researchers and enthusiasts alike.