Landsat: Yesterday, today, and tomorrow

Landsat, first placed in orbit in 1972, established the U.S. as the world leader in land remote sensing. The Landsat system has contributed significantly to the understanding of the Earth's environment, spawned revolutionary uses of space-based data by the commercial value-added industry, and encouraged a new generation of commercial satellites that provide regional, high-resolution spatial images. This PE&RS Special Issue provides an update to the 1997 25th Landsat anniversary issue, particularly focused on the contribution of Landsat-7 to the 34+ year history of the Landsot mission. In this overview paper, we place the Landsat-7 system in context and show how mission operations have changed over time, increasingly exploiting the global monitoring capabilities of the Landsat observatory. Although considerable progress was made during the Landsat-7 era, there is much yet to learn about the historical record of Landsat global coverage: a truly valuable national treasure. The time to do so is now, as the memories of the early days of this historic program are fading as we speak.