Earth Observation system (EOS) is a coordinated series of airborne and spaceborne platforms equipped with a variety of sensors for long-term observations of the land surface, biosphere, solid Earth, atmosphere, and oceans. This course will describe the history, challenges and developments in these systems. Topics covered include definition and physics of basic electromagnetic radiation properties, energy-matter relationships, spectral signatures of surfaces and the atmosphere, the reduction of atmospheric effects, optical and microwave sensor concepts, an introduction to data processing, enhancement, image interpretation and presentation of results. Selected from hundreds of satellite missions, Landsat, Satellite Pour l'Observation de la Terre (SPOT), and European Remote Sensing (ERS) will be briefly introduced, as well as future earth observing satellite constellations. The variety of satellite and airborne platforms, and the greater access to imagery, now make it possible to use earth observation systems to address a wide range of applications including climate change. The diverse and ever-growing applications will be reviewed.