An unprecedented enterprise began 40 years ago when the Earth Resources Technology Satellite—later renamed Landsat—was launched. Five more Landsat spacecraft would reach orbit during the next 27 years. All were launched from Vandenberg Air Force Base, Calif. into near-polar orbits, allowing them to image the entire Earth, one slice at a time, as it rotated below, and Lockheed Martin built every spacecraft at its Valley Forge, Pa., facility.