1. Retrieval of Oxygen A-band Spectra Using Airborne Measurements Vijay Natraj et al.

2. Welcome-2 OCO Mission O 2 A-band Clouds/Aerosols, Surface Pressure “strong” CO 2 band Clouds/Aerosols, H 2 O, Temperature “weak” CO 2 band Column CO 2 First global, space-based observations of column integrated dry air mole fraction, X CO2, at high accuracy (1 ppm, 0.3%) Column-integrated CO 2 abundance => Maximum contribution from surface High resolution spectroscopic measurements of reflected sunlight in near IR CO 2 and O 2 bands

3. Welcome-3 Retrieval of O’Brien (CSIRO, Australia) Spectra High precision, high resolution O 2 A-band spectra of sunlight reflected from ocean surface (O’Brien et al., J. Atmos. Oceanic Tech., Feb. 1997 and Dec. 1998) Retrieve column O 2 with precisions required for OCO Retrieval Strategy –Forward Model: multistream, multiple scattering RT model with BDRF at the surface –ILS provided by O'Brien –Inverse method based on optimal estimation theory (Rodgers, 2000) Minimises cost function involving computed and a priori states, measured and computed spectra, a priori and measurement error covariances

4. Welcome-4 Retrieval: First Cut rms residual = 8.8%

5. Welcome-5 Retrieval: Second Cut Wavelength Scaling rms residual = 2.3%

6. Welcome-6 Retrieval: Third Cut Continuum Level, Tilt, Zero Offset, ILS Width Fits rms residual = 1.4%

7. Welcome-7 Retrieval: Fourth Cut Line Mixing, Solar Feature Removal rms residual = 1.1%

8. Welcome-8 Conclusion Retrieved column O 2 with precision ~ 1% Demonstrates potential to retrieve column O 2 with precisions around 0.1% by averaging sufficient soundings End-to-end retrieval simulation tests show this precision is sufficient to retrieve X CO2 with precisions better than 0.3%