1. Page 1 1 of 14, Vijay, Ge152 The Orbiting Carbon Observatory(OCO) Mission http://oco.jpl.nasa.gov The Orbiting Carbon Observatory (OCO) Mission http://oco.jpl.nasa.gov http://oco.jpl.nasa.gov Vijay Natraj (Caltech) Ge152 May 28 2008

2. Page 2 2 of 14, Vijay, Ge152 Introduction: Carbon Sinks? Atmospheric Carbon dioxide (CO 2 ) –Primary man-made greenhouse gas –Mixing ratios increased by ~25% since 1860 –Only half of the CO 2 from fossil fuel emissions in atmosphere Outstanding Issues –Where are the CO 2 sinks? –Why does atmospheric buildup vary with uniform emission rates? –How will CO 2 sinks respond to climate change?

3. Page 3 3 of 14, Vijay, Ge152 Why Measure CO 2 from Space? Studies from GV-CO 2 stations –Flux residuals exceed 1 GtC/yr in some zones –Network is too sparse Inversion tests –Global X CO2 pseudo-data with 1 ppm accuracy –Flux errors reduced to < 0.5 GtC/yr/zone for all zones –Global flux error reduced by a factor of ~3 Courtesy: Rayner and O’Brien, 2001 1.2 0.6 0.0 Flux Residuals (Gt/yr/zone) 1.2 0.6 0.0 Flux Residuals (Gt/yr/zone)

4. Page 4 4 of 14, Vijay, Ge152 Precise CO 2 Measurements Needed Space-based X CO2 estimates will improve constraints on CO 2 fluxes –Near global coverage on monthly intervals –Precisions of 1–2 ppm (0.3–0.5%) on regional scales –No spatially coherent biases > 1–2 ppm (0.3 to 0.5%) on regional scales CO 2 Mixing Ratio (ppm) 356 360 364 Latitude 90 -90 0 356 360 364 Latitude 90 -90 0

5. Page 5 5 of 14, Vijay, Ge152 The Orbiting Carbon Observatory (OCO) Spectra of CO 2 and O 2 absorption in reflected sunlight used to estimate X CO2 Random errors and biases no larger than 1 - 2 ppm (0.3 - 0.5%) on regional scales at monthly intervals OCO will make the first space-based measurements with the precision and resolutions needed to quantify CO 2 sources and sinks and monitor their variability.

6. Page 6 6 of 14, Vijay, Ge152 OCO Fills a Critical Measurement Gap OCO will make precise global measurements of X CO2 needed to monitor CO 2 fluxes on regional to continental scales. Spatial Scale (km) 1 2 3 4 5 6 CO 2 Error (ppm) 1 10 100 100010000 OCO Flask Site Aqua AIRS Aircraft 0 Flux Tower Globalview Network NOAA TOVS ENVISAT SCIAMACHY

7. Page 7 7 of 14, Vijay, Ge152 Spectroscopy Clouds/Aerosols, Surface PressureClouds/Aerosols, H 2 O, TemperatureColumn CO 2 Column-integrated CO 2 abundance –Maximum contribution from surface Why high spectral resolution? –Enhances sensitivity, minimizes biases O 2 A-band CO 2 1.61  m CO 2 2.06  m

8. Page 8 8 of 14, Vijay, Ge152 OCO Will Fly in the A-Train OCO files at the head of the A-Train, 4 minutes ahead of the Aqua platform 1:26 Coordinated Observations GLORY 1:34

9. Page 9 9 of 14, Vijay, Ge152 Nadir Observations Observatory points instrument at local nadir –Collects science data over sunlit hemisphere at solar zenith angles < 85  Advantages + Small footprint (< 3 km 2 ) isolates cloud-free scenes and reduces biases from spatial inhomogeneities over land + Simplifies operations Liabilities  Low Signal/Noise over dark ocean

10. Page 10 10 of 14, Vijay, Ge152 Glint Observations Glint Observations: views “glint” spot –Angle of reflection equals angle of incidence of sunlight at surface:  R =  I Advantages + Improves Signal/Noise over oceans Disadvantages  More interference from clouds  Operations more complicated Local Nadir Glint Spot Ground Track  R  I

11. Page 11 11 of 14, Vijay, Ge152 Target Observations Tracks a stationary surface target (calibration site) to collect large numbers of soundings Uplooking ground-based FTS data acquired simultaneously through same slant column Acquire Target data over 1 surface validation site each day 447-m WLEF Tower Geolocation Accuracy Scan Direction Spatial Direction Along Slit

12. Page 12 12 of 14, Vijay, Ge152 Retrieval Algorithm

13. Page 13 13 of 14, Vijay, Ge152 Validation Program Ground-based in-situ measurements NOAA CMDL Flask Network + Tower Data TAO/Taurus Buoy Array Uplooking FTS measurements of X CO2 3 funded by OCO 4 upgraded NDSC Aircraft measurements of CO 2 profile Buoy Network CMDL

14. Page 14 14 of 14, Vijay, Ge152 Acknowledgments Yuk Yung David Crisp, Charles Miller Retrieval Algorithm: Denis O’Brien, Geoff Toon, Bhaswar Sen, Hartmut Boesch, Rob Spurr, Hari Nair, James McDuffie, Mick Christi Validation: Paul Wennberg, Ross Salawitch, Brian Connor Calibration: Carol Bruegge OCO Science Team