The Decades of Observation

THE VIEW FROM ABOVE

William Pecora, director of the U.S. Geological Survey, spent six years arguing that a civilian satellite should photograph Earth's resources in the open, on a repeating schedule, and publish everything it saw. He died four days before that satellite, Landsat 1, reached orbit on 23 July 1972. Landsat has flown, in one generation or another, on nearly every day since.

What Pecora could not have specified in advance was what fifty years of repetition would eventually reveal. A single photograph of a glacier or a lake proves nothing about direction. The same location photographed every 16 days for five decades turns into a measurement, visible only because nobody let the record stop.

That record was never inevitable, and it was never only American. It survived a privatization experiment that nearly shut it down in 1989, a launch failure in 1993, and a sensor failure in 2003 that still shows up as gaps in every image since. It was joined by NASA's MODIS, flying twice a day rather than once every sixteen, by Europe's Sentinel satellites, by India's, Japan's, and China's own civil programs, and eventually by a commercial industry willing to treat a satellite as disposable.

This chapter follows that history in order: why nations first pointed cameras at their own planet, how orbital mechanics decided what those cameras could see and when, which agencies built and nearly lost the resulting archives, how the instruments actually work, how the same orbits carry navigation and communications traffic alongside imagery, and how a fifty-year government project was eventually joined by a private industry willing to bet on volume over permanence.