Simulation studies for comparative evaluation of alternative spectral regions for the sensing of CO2 and O2 suitable for the ASCENDS Mission

We have carried out comparative simulation studies to establish the advantages and limitations of alternative spectral regions and measurement wavelengths being investigated by different groups for the sensing of CO₂ and O₂ for potential use in the ASCENDS mission implementation. Our studies are based on the lidar modeling framework we developed specifically for ASCENDS which may be further applied to similar missions relying on the active sensing approach from space or aircraft. The modeling framework performs standard lidar sensitivity calculations, and also includes analysis of weighting functions and the effects of laser wavelength instabilities. As such, the factors considered in the analysis include the general LIDAR sensitivity, shapes of the weighting functions, as well as the added error due to the laser wavelength jitter in the selected spectral bands and wavelength regions. In particular, the studies were performed for the 1.26 – 1.27 micron and the A-band of oxygen, as well as the 1.57 and 2.06 micron bands of carbon dioxide. Additionally, the analysis is based on a range of satellite datasets and models to also take into account a variety of spacial and temporal variations in surface and atmospheric parameters. The results of our comparative studies for alternative spectral bands will be presented including the quantitative estimates of required constraints on selected system parameters to achieve the desired accuracy of ~0.3% in XCO₂ measurements.