Narration: Ryan Fitzgibbons


532 nanometers. That's the wavelength of a bright green color, the color of the ATLAS laser measuring the elevation of the Earth below. When ATLAS receives the photons back from Earth, it has to filter out the sunlight that naturally reflects off the Earth, which would overwhelm the detectors. So ATLAS only lets in light that is exactly 532 nanometers. Sunlight in that wavelength range will also set off ATLAS detectors, and so computer programs are needed to filter out those sunlight photons in the data.