Spectroscopic challenges for high accuracy retrievals of atmospheric CO2 and the Orbiting Carbon Observatory (OCO) experiment

The space-based Orbiting Carbon Observatory (OCO) mission will achieve global measurements needed to distinguish spatial and temporal gradients in the CO 2 column. Scheduled by NASA to launch in 2008, the instrument will obtain averaged dry air mole fraction ( X CO 2 ) with a precision of 1 part per million (0.3%) in order to quantify the variation of CO 2 sources and sinks and to improve future climate forecasts. Retrievals of X CO 2 from ground-based measurements require even higher precisions to validate the satellite data and link them accurately and without bias to the World Meteorological Organization (WMO) standard for atmospheric CO 2 observations. These retrievals will require CO 2 spectroscopic parameters with unprecedented accuracy. Here we present the experimental and data analysis methods implemented in laboratory studies in order to achieve this challenging goal.