Significant progress has been made in the performance, qualification and validation of Active Remote Sensing systems to address complex questions in climate science from satellites in low earth orbit. During the past year, ITT has completed the design, qualified the components, and validated the performance of sophisticated Tunable Diode Laser Absorption Spectroscopy systems for airborne and space missions. ITT has shown that measurement of total column CO2 to an accuracy of 0.5% can be readily achieved using a 5 watt laser, 1 meter telescope and digital signal processing techniques to reject sunlight and noise. Furthermore, the design exploits the proven high reliability of photonic components developed by the telecom industry. ITT testing validated that these components survive launch and multi-year operation in space without significant degradation. Using a scaled sensor, the ground based validation campaign demonstrated the ability to accurately retrieve the CO2 diurnal cycle as well the automotive induced variations in CO2 observed in urban settings. These data validate the end-end sensor performance model and retrieval algorithms, which have previously been used to design a space based CO2 sensor proposed to NASA. ITT will discuss the application of these technologies to other atmospheric constituents. Combined, these results serve to demonstrate that laser based remote sensing of key components of the atmosphere which address global climate change can be achieved from low earth orbit without further development.© (2002) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.