The Satellite That Kept Looking Home

A photograph of Earth can change how people imagine the planet. A second photograph of the same place, taken later and measured consistently, can answer a different question: what changed? Landsat began turning that question into a practical method. Launched on July 23, 1972, the first satellite in the program was intended to observe the land repeatedly, building evidence rather than waiting for a single unforgettable view.

Its original name was Earth Resources Technology Satellite 1, or ERTS-1. It became Landsat 1 when the program was renamed in 1975. Unlike a crewed mission, it did not carry someone who could choose a scene through a window. Its instruments recorded broad strips of terrain along an orbital path. An eighteen-day repeat cycle brought opportunities to examine the same areas again, although cloud cover could still hide what researchers wanted to see.