1. Page 1 1 of 20, Crisp, OCO May 2006 The Orbiting Carbon Observatory: Sampling Approach and Anticipated Data Products David Crisp, OCO PI http://oco.jpl.nasa.gov JPL/Caltech May 2006 Carbon Fusion Workshop

2. Page 2 2 of 20, Crisp, OCO May 2006 What Processes Control Atmospheric CO 2 ? Carbon dioxide (CO 2 ) is the: Main atmospheric component of the global carbon cycle Main man-made greenhouse gas Only half of the CO 2 produced by human activities is remaining in the atmosphere O OC

3. Page 3 3 of 20, Crisp, OCO May 2006 Outstanding Questions Where are the sinks that are absorbing almost 50% of the CO 2 that we emit? –Land or ocean? –Eurasia/North America? Why does CO 2 buildup vary dramatically with nearly uniform emissions? How will CO 2 sinks respond to climate change?

4. Page 4 4 of 20, Crisp, OCO May 2006 The Orbiting Carbon Observatory (OCO) Approach: Collect spatially resolved, high resolution spectroscopic observations of CO 2 and O 2 absorption in reflected sunlight Use these data to resolve spatial and temporal variations in the column averaged CO2 dry air mole fraction, X CO2 over the sunlit hemisphere Employ independent calibration and validation approaches to produce X CO2 estimates with random errors and biases no larger than 1 - 2 ppm (0.3 - 0.5%) on regional scales at monthly intervals OCO will acquire the space-based data needed to identify CO 2 sources and sinks and quantify their variability over the seasonal cycle

5. Page 5 5 of 20, Crisp, OCO May 2006 Precise Measurements Needed to Constrain CO 2 Surface Fluxes Resolve pole to pole X CO2 gradients on regional scales Resolve the X CO2 seasonal cycle in the Northern Hemisphere 356 364 Precisions of 1–2 ppm (0.3–0.5%) on regional scales needed to: Resolve (8ppm) pole to pole X CO2 gradients on regional scales Resolve the X CO2 seasonal cycle in the Northern Hemisphere

6. Page 6 6 of 20, Crisp, OCO May 2006 OCO Fills a Critical Measurement Gap OCO will make precise global measurements of X CO2 over the range of scales 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 20, Crisp, OCO May 2006 Making Precise CO 2 Measurements from Space Clouds/Aerosols, Surface PressureClouds/Aerosols, H 2 O, TemperatureColumn CO 2 O 2 A-band CO 2 1.61  m CO 2 2.06  m High resolution spectra of reflected sunlight in near IR CO 2 and O 2 bands used to retrieve the column average CO 2 dry air mole fraction, X CO2 –1.61  m CO 2 bands – Column CO 2 with maximum sensitivity near the surface –O 2 A-band and 2.06  m CO 2 band Surface pressure, albedo, atmospheric temperature, water vapor, clouds, aerosols Why high spectral resolution? –Enhances sensitivity, minimizes biases

8. Page 8 8 of 20, Crisp, OCO May 2006 OCO Observing Strategy Nadir Observations: tracks local nadir –+ Small footprint (< 3 km 2 ) isolates cloud-free scenes and reduces biases from spatial inhomogeneities over land -Low Signal/Noise over dark ocean Glint Observations: views “glint” spot + Improves Signal/Noise over oceans -More interference from clouds Target Observations –Tracks a stationary surface calibration site to collect large numbers of soundings Data acquisition schedule: alternate between Nadir and Glint on 16-day intervals Acquire ~1 Target observation each day Local Nadir Glint Spot Ground Track

9. Page 9 9 of 20, Crisp, OCO May 2006 1:18 OCO Will Fly in the A-Train OCO files at the head of the A-Train, 12 minutes ahead of the Aqua platform 1:18 PM equator crossing time yields same ground track as AQUA Near noon orbit yields high SNR CO 2 and O 2 measurements in reflected sunlight CO 2 concentrations are near their diurnally-averaged values near noon Maximizes opportunities of coordinated science and calibration activities TES – T, P, H 2 O, O 3, CH 4, CO MLS – O 3, H 2 O, CO HIRDLS – T, O 3, H 2 O, CO 2, CH 4 OMI – O 3, aerosol climatology aerosols, polarization CloudSat – 3-D cloud climatology CALIPSO – 3-D aerosol climatology AIRS – T, P, H 2 O, CO 2, CH 4 MODIS – cloud, aerosols, albedo OCO - - CO 2 O 2 A-band p s, clouds, aerosols Coordinated Observations

10. Page 10 10 of 20, Crisp, OCO May 2006 Mission Architecture Project Management (JPL) Science & Project Team Systems Engineering, Mission Assurance Ground Data System Single Instrument (Hamilton Sundstrand) 3 high resolution grating spectrometers Dedicated Bus (Orbital Sciences) LEOstar2: GALEX, SORCE, AIM Dedicated Launch Vehicle (Orbital Taurus 3110) September 2008 Launch from Vandenberg AFB Mission Operations (JPL/Orbital Sciences) NASA Ground Network, Poker Flats, Alaska

11. Page 11 11 of 20, Crisp, OCO May 2006 The OCO Instrument 3 bore-sighted, high resolution, grating spectrometers O 2 0.765  m A-band CO 2 1.61  m band CO 2 2.06  m band Similar optics and electronics Common 200 mm f/1.9 telescope Spectrometers cooled to < 0 o C Resolving Power ~18,000/21,000 Common electronics for focal planes Existing Designs For Critical Components Detectors: WFC-3, Deep Impact (RSC) Cryocooler: TES flight spare (NGST)

12. Page 12 12 of 20, Crisp, OCO May 2006 OCO Sampling over a 16-Day Repeat Cycle Prevailing Winds OCO Sampling Rate/Coverage 12-24 samples/second collected along track over land and ocean Glint: +75o SZA Nadir: +85o SZA Longitude resolution 1.5 o Space-based CO 2 column measurements complement surface measurement network. Chevallier et al. 2006 OCO 3-Days OCO 1-Day OCO Sampling: Clouds reduce number of usable samples

13. Page 13 13 of 20, Crisp, OCO May 2006 OCO Data Hierarchy Spectral Spatial Sounding: 3 Collocated Spectra Spectrum 3 4 Frame: 4 (8) Cross-Track Soundings Granule: All ~30,000 Soundings recorded each orbit 21 5 Pixel

14. Page 14 14 of 20, Crisp, OCO May 2006 OCO characterization for Key Environmental Parameters (SZA, surface type) Averaging Kernels: Early Support for Source/sink inversions Study effect on X CO2 biases on CO 2 source/sink inversions Rehearsal of ingesting OCO X CO2 (early feedback on L2 product)

15. Page 15 15 of 20, Crisp, OCO May 2006 Example: X CO2 Averaging Kernel and Errors for a Single Orbit Track Nadir Viewing Averaging Kernel Along Orbit Track Single Sounding X CO2 Errors

16. Page 16 16 of 20, Crisp, OCO May 2006 Spatial/Temporal Sampling Constraints Factors Limiting Sampling Density Orbit ground track Clouds and Aerosols –OCO can collect usable samples only in regions where the cloud and aerosol optical depth < 0.3 Low Surface Albedo Others? MISR Aerosol MODIS Cloud

17. Page 17 17 of 20, Crisp, OCO May 2006 The space-based X CO2 data will be validated against the surface WMO standard for CO 2 using measurements of X CO2 from ground based Fourier transform spectrometers (FTS) as a transfer standard X CO2 will be retrieved from the FTS and space- based instruments using same retrieval code FTS X CO2 compared to: Surface in situ CO 2 Tall tower in situ CO 2 Column CO 2 integrated from in situ profiles FTS X CO2 performance tracked by monitoring: Instrument Line Shape (HCl gas cell) Pointing (Doppler shift, telluric vs solar features) XO 2, surface pressure and H 2 O Observations at 79°N (Spitsbergen) FTS Notholt et al., GRL, 2005 WLEF FTIR Space-based X CO2 Validation Strategy Observations at 79°N (Spitsbergen) FTS Notholt et al., GRL, 2005

18. Page 18 18 of 20, Crisp, OCO May 2006 Summary of Data Products Four major products –Level 0 – Time-ordered science and housekeeping data Raw data, excluding spacecraft packet information for data transfer to ground –Level 1A - Parsed and merged science and instrument housekeeping telemetry Data subdivided into discretely named elements Data from all three spectrometers correlated in a single frame Corresponding temperature and voltage measures from housekeeping merged into appropriate frame –Level 1B - Spatially ordered, Geolocated, calibrated spectra –Level 2 - Geolocated retrieved state vectors with column averaged CO 2 dry air mole fraction

19. Page 19 19 of 20, Crisp, OCO May 2006 OCO Data Product Volumes The above estimates assume that the GDS retains just a single copy of each data product –If multiple versions of the data are maintained, the estimated volume required for OCO products could exceed 30 TBytes. –Level 2 Product volume reflects the size of the distributable product Additional “expert products: will be generated for OCO Science team use will require an additional ~55.7 Gbytes per orbit, or about 0.79 Gbytes per day

20. Page 20 20 of 20, Crisp, OCO May 2006 7/2001: Step-1 Proposal Submitted 2/2002: Step-2 Proposal Submitted 7/2003: Selected for Formulation 7/2004: System PDR 5/2005: Mission Confirmed for Implementation 10/2005: Instrument CDR 2/2006: Spacecraft CDR 7/2006: MOS/GDS CDR 8/2006: System CDR 2-4/2007: Instrument Testing 5/2007: Instrument Delivery to SC 10/2007: Observatory Integration begins 6/2008: Launch Vehicle Integration begins 9/2008: Launch from VAFB 10/2010: End of Nominal Mission < ESA 3 rd Party Mission OCO Schedule