The science buried in 50-year old lunar images

The scientific value of Surveyor's 87,000 television images was highlighted in a letter signed by four of the project's original co-investigators. The oldest co-investigator, Ewen Whitaker, is 92 years old. "The scientific value of this film medium cannot be underestimated, as much still remains to be researched and extracted from the images," the scientists wrote. Surveyor's cameras were primarily used for engineering investigations that helped pave the way for the upcoming Apollo landings. These included close-ups of the spacecraft's foot pads to see how deep Surveyor had sunk into the lunar soil. But there were also scientific observations, such as dozens of panoramic photographs taken under a range of lighting conditions. Additionally, the Surveyors captured shots of the constellation Orion, the lunar horizon glow, and a 26-hour timelapse of Earth—part of an experiment to see if our planet's sea state could be inferred using various polarization filters.

Philip Stooke, a geography professor at the Centre for Planetary Science and Exploration at the University of Western Ontario, said Surveyor's unseen images could be used to help with future mission planning—especially missions that involve rovers. When the sun is directly overhead, there are minimal shadows, making it difficult for rover drivers to spot hidden obstacles. Likewise, when the sun is on the horizon opposite a rover's direction of travel, shadows inside small lunar craters can be hidden from view. Stooke said the Soviet Union's Lunokhod 2 may have fallen victim to this effect in 1973, driving into a crater and banging into an outcrop, covering the rover in dust that eventually doomed it.

Stooke has done some of the most extensive—and most tedious—Surveyor panorama work to date. He said that because the original Surveyor images were processed in darkrooms, it was extremely difficult to correct for natural lighting gradients that occur in each image.

"Anytime you take an image of a landscape, there's going to be a gradient of light across it where one side is a little brighter than the other," he said. "When you stick the pieces together to try to build up a mosaic, you can see the seams between them because the dark side of one image is placed next to the light side of another image." As a result, the original panoramas resemble fish scales, where each individual image can be seen.

Around the year 2000, Stooke set out to rescan the original panoramas and correct the brightness of each individual fish scale. It took him about a year of on-and-off again work to restore a single panorama—five years total to do all five Surveyors. Buried within some of the 87,000 original unseen images are more panoramas. Since the individual images in these panoramas will be digital from the get-go, correcting for lighting variances should be easier. Better yet, making the archive publicly available means the entire space image processing community will be able to give it a try.