Preface to Landsat Legacy Special Issue: Continuing the Landsat Legacy

Since the launch of its first satellite in 1972, the Landsat program has demonstrated the insights that can be obtained through Earth observation at a resolution sensitive to both natural and human drivers. As a result, both scientific debate and environmental policy development are increasingly aided by information from the Landsat satellites. The scientific and operational uses of Landsat data are innumerable and exhibit increasing rigor and sophistication. The US Geological Survey's (USGS) decision in 2008 to make standard data products freely available through the internet was a watershed event in the history of the program, and has led to ambitious analyses previously precluded by data costs and processing requirements. In this Special Issue of Remote Sensing of Environment, “Continuing the Landsat Legacy,” we capture the current status of the Landsat program, present information regarding the forthcoming Landsat Data Continuity Mission (Landsat-8), and document new research programs and projects that rely on Landsat data. A special emphasis is placed on the burgeoning scientific and applications opportunities enabled by free access to the US archive, including use of dense time-series data to characterize inter- and intra-annual land cover changes, new capabilities for continental-scale mapping, and applications focused upon particular information needs. The importance of free and open access to the Landsat image archive cannot be overstated. The geometric and radiometricqualityof thestandard Landsatproducts has enabled new applications. Furthermore, the ability to leverage the complete archive to track four decades of environmental and resource change on Earth has ultimatelyresultedinthefulfillmentof theoriginal visionof theLandsat program, which was first articulated in the 1960's.