Systematic Earth observation: significant progress as we enter the 21st century with Landsat 7

The Landsat Earth observation approach introduced in 1972 created a new way of monitoring land cover and land use globally. The Landsat 7 mission, successfully launched on April 15, 1999, continues those observations and demonstrates significant progress in precise numerical radiometry, spectral differentiation and seasonally repetitive monitoring as we enter the 21^st century. A long-term data acquisition plan was designed to ensure that substantially cloud-free, seasonal coverage would be recorded and archived in the U.S. for all land areas of the globe. Substantial improvements in calibration procedures have also been made to ensure long-term stability in the acquired spectral radiometry. A Landsat Science Team consisting of representatives from U.S. universities and government agencies has been addressing the technical and analytical means to process and analyze the core of this observation record. The expected outcome of these efforts is a rapid improvement in understanding the Earth system, as well as conceptual knowledge that will underpin significant advancements in the application of this technology for commercial, operational, educational and research purposes. The lessons learned from the Landsat 7 mission are expected to have a significant, positive influence on future Landsat-like missions