How NASA Proved Astronauts Really Could See Roads From Orbit

During the Mercury-Atlas 9 mission in May 1963, astronaut L. Gordon Cooper Jr. took 29 color photographs of Earth and reported he could see vehicles on dirt roads, smoke-belching trains and the tops of houses from about 100 miles up. Vision experts doubted this was possible, assuming astronauts with 20/20 vision could not clearly see objects smaller than 150 feet across from orbit; some psychiatrists even speculated that weightlessness was causing hallucinations, according to a report in Air Force and Space Digest.

To settle the question, NASA and its partners developed two visual acuity experiments flown on the crewed Gemini V and Gemini VII missions. One had astronauts look through a binocular-like optical device at rectangles in various positions and contrast levels and identify their orientation. The other used giant terrestrial eye charts, nicknamed the "Eye-Q" chart, made of white rectangles 150 to 600 feet long built by the Dow Chemical Corporation and placed on dark tilled soil near Laredo, Texas, and near Carnarvon, Australia.

Cloudy skies, sunlight scattered by the spacecraft window, and unfavorable orbital passes limited the views, but astronauts on both missions were able to see portions of the Laredo site during some orbits. Combined with results from the binocular-style tests conducted before, during and after flight, the experiments showed astronauts could indeed see roads and ships with their wakes from orbit, and that vision did not deteriorate over a two-week spaceflight.

The findings mattered well beyond settling astronauts' sanity: scientific interest in what could be seen and photographed from orbit motivated NASA and partners including the U.S. Geological Survey, the Office of Naval Research and the U.S. Department of Agriculture to advocate for dedicated Earth-observing instruments, leading to the Earth Resources Technology Satellite launched in 1972 and later renamed Landsat 1, whose imagery was used to monitor crops, oceans and natural disasters.