This video begins with a brief introduction of climate change and introduces ERS-1 (launched July 1999) as an Earth observation satellite that can help scientists understand better the global processes that affect our climate and environment. The rest of the video details the calibration and validation techniques used to ensure the quality of ERS-1 data. Rather than calibrate the instruments in space, the techniques were applied to data received from the Synthetic Aperture Radar, Wind Scatterometer, Radar altimeter and ATSR instruments. Some of the techniques involved various transponders at ground stations across Europe, aircraft and oil platforms. Calibration results are given in detail.