1. High Priority Science Passive Instrument Heritage Spacecraft Cost Resiliency All NASA Flight System Orbiting Carbon Observatory (OCO) Science -1 Why CO 2 ? O OC ISSUES: Carbon dioxide (CO 2 ) is the Principal atmospheric component of the global carbon cycle Primary anthropogenic driver of climate change Only half of CO 2 produced by human activities over the past 30 years has remained in the atmosphere. Where are the sinks? Will this continue? Atmosphere Human Activity LandOcean ??

3. High Priority Science Passive Instrument Heritage Spacecraft Cost Resiliency All NASA Flight System Orbiting Carbon Observatory (OCO) Science -3 The Global Carbon Cycle Natural carbon fluxes account for 300 GtC/yr and exist in near equilibrium. The ~6 GtC/yr produced by human activity represents only 2% of the carbon flux, but it may tip the balance 6 GtC/yr

4. Atmospheric levels of CO 2 have risen from ~ 270 ppm in 1860 to ~370 ppm today. Accumulation of atmospheric CO 2 has fluctuated from 1 – 6 GtC/yr despite nearly constant anthropogenic emissions. WHY? Since 1860, global mean surface temperature has risen ~1.0 °C with a very abrupt increase since 1980. “Keeling Plot” Does increasing atmospheric CO 2 drive increases in global temperature? Do increasing temperatures increase atmospheric CO 2 levels? Atmospheric CO2: the Primary Anthropogenic Driver of Climate Change

5. High Priority Science Passive Instrument Heritage Spacecraft Cost Resiliency All NASA Flight System Orbiting Carbon Observatory (OCO) Science -5 What are the relative roles of the oceans and land ecosystems in absorbing CO 2 ? Is there a Northern hemisphere land sink? –Relative roles of North America/ Eurasia What controls carbon sinks? –Why does the atmospheric buildup vary substantially with uniform emission rates? –How will sinks respond to climate change Climate prediction requires an improved understanding of natural CO 2 sinks –Future atmospheric CO 2 increases –Their contributions to global change An Uncertain Future Where are the Missing Carbon Sinks? OCO will dramatically reduce these uncertainties

6. High Priority Science Passive Instrument Heritage Spacecraft Cost Resiliency All NASA Flight System Orbiting Carbon Observatory (OCO) Science -6 An Uncertain Future: Where are the Missing Carbon Sinks? Only half of the CO 2 released into the atmosphere since 1970 years has remained there. The rest has been absorbed by land ecosystems and oceans What are the relative roles of the oceans and land ecosystems in absorbing CO 2 ? Is there a northern hemisphere land sink? What are the relative roles of North America and Eurasia What controls carbon sinks? Why does the atmospheric buildup vary with uniform emission rates? How will sinks respond to climate change? Reliable climate predictions require an improved understanding of CO 2 sinks Future atmospheric CO 2 increases Their contributions to global change

7. Atmospheric CO 2 has been monitored systematically from a network of ~100 surface stations since 1957 Over the past 20 years – only ~1/2 of the CO 2 associated with fossil and biomass fuel combustion has remained in the atmosphere – the remainder has been absorbed by the ocean and land ecosystems Carbon sinks are not well understood – Is there a Northern hemisphere land sink? Relative roles of North America/ Eurasia – What controls sources and sinks? Why does the atmospheric buildup vary from 1 - 6 GtC/year in the presence of roughly constant emission rates? How will the efficiency of these sinks evolve as the climate changes? An Integrated, global strategy needed to answer these questions. – The US Carbon Cycle Science Program USGCRP, NSF, DoE, USDA, NOAA, NASA, USGS The ~100 GLOBALVIEW-CO2 flask network stations and the 26 continental sized zones used for CO 2 flux inversions. This network is designed to measure back- ground CO 2. It can not retrieve accurate source and sink locations or magnitudes! Bousquet et al., Science 290, 1342 (2000). The Global Carbon Cycle: Many Questions

8. High Priority Science Passive Instrument Heritage Spacecraft Cost Resiliency All NASA Flight System Orbiting Carbon Observatory (OCO) Science -8 Measurements Needed to Revolutionize Our Understanding of the Global Carbon Cycle Accurate, spatially resolved global measurements of X CO2 will revolutionize our understanding of the carbon cycle if measurement can be acquired –With accuracies of 1 ppm –On regional scales (8 o X 10 o ) –On monthly time scales 1.2 0.6 0.0 Fig. F.1.3: Carbon flux errors from simulations including data from (A) the existing surface flask network, and (B) satellite measurements of XCO2 with accuracies of 1ppm on regional scales on monthly time scales Flux Retrieval Errors GtC/year/Zone 1.2 0.6 0.0 Flux Retrieval Errors GtC/year/Zone OCO FLASK SATELLITE Flux Errors Fig. F.1.2 Flux Errors vs Measurement Accuracy

9. High Priority Science Passive Instrument Heritage Spacecraft Cost Resiliency All NASA Flight System Orbiting Carbon Observatory (OCO) Science -9 Why Measure CO 2 from Space? Improved CO 2 Flux Inversion Capabilities Rayner & O’Brien, Geophys. Res. Lett. 28, 175 (2001) Current State of Knowledge Global maps of carbon flux errors for 26 continent/ocean-basin-sized zones retrieved from inversion studies Studies using data from the 56 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. Flux Retrieval Error GtC/yr/zone

10. 4  5  Why Measure CO2 from Space? Dramatically Improved Spatiotemporal Coverage The O=C=O orbit pattern (16-day repeat cycle)

11. O=C=O Measurement Objectives Objective: Characterize the geographic distribution of CO 2 sources and sinks on regional to continental scales over seasonal to interannual time scales Approach: Space-based atmospheric carbon monitoring system –Global coverage (land and ocean) high spatial resolution (4 o x 5 o ) weekly to monthly time scales –High measurement precision Column CO 2 measurement precision –~1ppm (0.3% of 370 ppm) Resolve East-West gradients as well as interhemispheric gradients in CO 2 Advanced Modeling tools used to retrieve –CO 2 column amounts from observations –Sources and sinks from global CO 2 maps Correlative Measurement Program –Validation, bias removal, diurnal cycles –Laboratory Measurements Coverage in Each 16-Day Repeat Cycle 4  5 

12. High Priority Science Passive Instrument Heritage Spacecraft Cost Resiliency All NASA Flight System Orbiting Carbon Observatory (OCO) Science -12 Proposed Sampling Strategy Addresses All Science Objectives B) Satellite OCO will provide an accurate description of X CO2 on regional scales –Atmospheric motions mix CO 2 over large areas as it is distributed through the column –Source/Sink model resolution limited to 1 o x 1 o High spatial resolution –Isolates cloud-free scenes –Provides thousands of samples on regional scales 16 Day Repeat Cycle –Provides large numbers of samples on monthly time scales 4  5  8  10  Ground tracks over the tip of South America Spatial sampling along ground track

13. High Priority Science Passive Instrument Heritage Spacecraft Cost Resiliency All NASA Flight System Orbiting Carbon Observatory (OCO) Science -13 Measurement Strategy Maximizes Information Content and Measurement Validation Opportunities Nadir Mode Target Mode Glint Mode 1:15 PM near polar orbit –15 minutes ahead of the A-Train Same ground track as AQUA –Global coverage every 16 days Science data taken on day side –Nadir mode: Highest spatial resolution –Glint mode: Highest SNR over ocean –Target mode: Validation Airmass dependence Same path as FTIR Calibration data taken on night side

14. High Priority Science Passive Instrument Heritage Spacecraft Cost Resiliency All NASA Flight System Orbiting Carbon Observatory (OCO) Science -14 OCO Spatial Sampling Strategy OCO is designed provide an accurate description of X CO2 on regional scales Atmospheric motions mix CO 2 over large areas as it is distributed through the column Source/Sink model resolution limited to 1 o x1 o OCO flies in the A-train, 15 minutes ahead of the Aqua platform 1:15 PM equator crossing time yields same ground track as AQUA Global coverage every 16 days OCO samples at high spatial resolution Nadir mode: 1 km x 1.5 km footprints Isolates cloud-free scenes Provides thousands of samples on regional scales Glint Mode: High SNR over oceans Target modes: Calibration

15. High Priority Science Passive Instrument Heritage Spacecraft Cost Resiliency All NASA Flight System Orbiting Carbon Observatory (OCO) Science -15 Will it Work? Accuracies of 1ppm needed to identify CO 2 sources and sinks. Realistic, end-to-end, Observational System Simulation Experiments Reflected radiances for a range of atmospheric/surface conditions line-by-line multiple scattering models Comprehensive description of mission scenario instrument characteristics Results: The OCO payload will meet or exceed the requirements for measuring CO 2 provide rigorous constraints on the distribution and optical properties of clouds and aerosols End-to-end retrievals of X CO2 from individual simulated nadir soundings at SZAs of 35 o and 75 o. The model atmospheres include sub-visual cirrus clouds (0.02  c  0.05), light to moderate aerosol loadings (0.05  a  0.15), over ocean and land surfaces. INSET: Distribution of X CO2 errors (ppm) for each case

16. High Priority Science Passive Instrument Heritage Spacecraft Cost Resiliency All NASA Flight System Orbiting Carbon Observatory (OCO) Science -16 Validation Program Ensures Accuracy and Minimizes Spatially Coherent Biases Ground-based in-situ measurements –NOAA CMDL Flask Network + Tower Data –TAO/Taurus Buoy Array Uplooking FTIR measurements of X CO2 –3 OCO –4 NDSC Aircraft measurements of CO 2 profile Complemented by Laboratory and on-orbit calibration Buoy Network CMDL

17. High Priority Science Passive Instrument Heritage Spacecraft Cost Resiliency All NASA Flight System Orbiting Carbon Observatory (OCO) Science -17 Rigorous Physics Based Retrieval Algorithms Level 1 Level 2 Level 3 X CO2 Retrieval Calibration Source/Sink Retrieval Inverse Models Assimilation Models Level 4

18. The Pushbroom Spectrometer Concept It is possible to obtain many ground-track spectra simultaneously if the instantaneous field of view (IFOV) is imaged onto a 2D detector array. In this case, wavelength information is dispersed across one dimension and cross-track scenes are dispersed along the other dimension. The instrument acquires spectra continuously along the ground track at a rate of 4 Hz. This results in 24 spectra/sec and 3000 spectra per 4  5  region every 16 days. 2D 1024  1024 arrays are available in Si (visible) and HgCdTe (NIR) from Rockwell Sciences.

19. Cloud and Aerosol Interference Clouds, aerosols and sub-visible cirrus (high altitude ice clouds) prevent measurement of the entire atmospheric column. An analysis of available global data suggests that a space-based instrument will see “cloud-free” scenes only ~ 10% of the time. Geographically persistent cloud cover will be especially problematic and will induce biases in the data. Number of cloud-free scenes per month anticipated for space-based sampling averaged into 3  6  (Lat  Lon) bins based on AVHRR cloud data. D. O’Brien (2001).

20. Sub-visible Cirrus Clouds Clouds, aerosols and sub-visible cirrus (high altitude ice clouds) prevent measurement of the entire atmospheric column. Sub-visible cirrus clouds are effective at scattering near infrared light because the light wavelengths and particle sizes are both ~ 1 – 2  m. An analysis of available global data suggests that a space-based instrument will see “cloud-free” scenes only ~ 10% of the time. Geographically persistent cloud cover will be especially problematic and will induce biases in the data. VISIBLE 1.38  m MODIS data

21. O=C=O Performance Improves with Spatial Averaging Accuracy of OCO X CO2 retrievals as a function of the number of soundings for optimal (red) and degraded performance (blue) for a typical case (37.5  solar zenith angle, albedo=0.05, and moderate aerosol optical depth,  a {0.76  m} = 0.15). Results from end-to-end sensitivity tests (solid lines) are shown with shaded envelopes indicating the range expected for statistics driven by SNR (N 1/2 ) and small-scale biases (N 1/4 ).

22. High Priority Science Passive Instrument Heritage Spacecraft Cost Resiliency All NASA Flight System Orbiting Carbon Observatory (OCO) Science -22 Q4 Science Impacts of X-band Failure OCO will meet its 1 ppm relative accuracy requirement under both scenarios The Baseline Science Mission will be achieved Based on Fig. F.1.10

23. High Priority Science Passive Instrument Heritage Spacecraft Cost Resiliency All NASA Flight System Orbiting Carbon Observatory (OCO) Science -23 Response: OCO requires no ancillary data to measure X CO2 X CO2 measurements are relatively insensitive to the details of the underlying terrain and surface characteristics –Observations from the high resolution O 2 A-band spectrometer will be used to characterize the topographic variability within each spatial footprint –Effects of surface albedo are discussed in Question #18 Q15 OCO Geolocation Requirements (cont.) The claimed need for 5 km geolocation (F-18) is deemed inadequate for mapping CO 2 retrievals onto terrain and surface characteristics

24. High Priority Science Passive Instrument Heritage Spacecraft Cost Resiliency All NASA Flight System Orbiting Carbon Observatory (OCO) Science -24 Question #17 Q17 Question 17: Due to the critical effect of changing surface albedo, it is essential that the entire spectra are collected simultaneously. Please clarify. Response OCO uses grating spectrometers –All wavelength information for a given spatial sample is recorded simultaneously on array detectors –Each spatial sample is read out almost simultaneously 1.4 msec per spectrum

25. High Priority Science Passive Instrument Heritage Spacecraft Cost Resiliency All NASA Flight System Orbiting Carbon Observatory (OCO) Science -25 Response: The wavelength-dependent albedo is retrieved as an independent variable in each spectral channel. Question18 Q18 Question 18: Please quantify the error in the CO 2 column measurement resulting from surface albedo variations and uncertainties. A formal, detailed error analysis is not required here. However, you do need to demonstrate that this error source, which is not explicitly considered in the proposal, is not important relative to the error budget and specified 1 ppm accuracy level.

26. High Priority Science Passive Instrument Heritage Spacecraft Cost Resiliency All NASA Flight System Orbiting Carbon Observatory (OCO) Science -26 Albedo Is Retrieved Explicitly The wavelength dependent albedo is determined from the continuum level within each spectral band as part of the simultaneous retrieval –Surface albedo changes much more slowly with wavelength than gas vibration-rotation features –The OCO spectral resolution has been chosen to resolve the spectral lines from the continuum in each band Because the entire spectrum is collected almost simultaneously in each channel, the X CO2 retrieval depends only on the spatial average of the albedo within each footprint Q18 2.06

27. High Priority Science Passive Instrument Heritage Spacecraft Cost Resiliency All NASA Flight System Orbiting Carbon Observatory (OCO) Science -27 Albedo Is Retrieved Explicitly The end-to-end retrieval simulations included wavelength-dependent albedos, which were retrieved as part of the X CO2 retrieval process. –Albedo types considered: dark ocean, desert, snow, conifer forests and snow Errors associated with uncertainties in the albedo retrieval are a small part of the total error budget –The X CO2 retrieval algorithm is only weakly dependent on the absolute value of the surface albedo (through its effects on the SNR) –Atmospheric O 2 and CO 2 columns depend on differences between the line core and continuum Q18 Demonstrate that this error source, which is not explicitly considered in the proposal, is not important relative to the error budget and specified 1 ppm accuracy level. Fig. F.1.9: End to end test of the OCO retrieval algorithm

28. High Priority Science Passive Instrument Heritage Spacecraft Cost Resiliency All NASA Flight System Orbiting Carbon Observatory (OCO) Science -28 Q20 OCO Sampling Biases: Level 3 Products Global XCO2 Maps (16-day average) 1:15 PM local sampling time chosen because –Production of CO 2 by respiration is offset by photosynthetic uptake –Instantaneous X CO2 measurement is within  0.3 ppm of the diurnal average (see figure) –Airborne measurements of CO 2 profiles from COBRA and ABLE-2B substantiate this view Atmospheric transport desensitizes OCO measurements to the clear-sky bias –Air passes through clouds on a time-scale short compared to the time needed to affect significant changes in X CO2 (no cloud bias evident in figure) –Mixing greatly reduces the influence of local events & point sources on X CO2 Fig. F.2.4: a) Calculated monthly mean, 24 hour average X CO2 (ppm) during May using the NCAR Match model driven by biosphere and fossil fuel sources of CO 2. b) X CO2 differences (ppm) between the monthly mean, 24 hour average and the 1:15 PM value X CO2 (ppm)  X CO2 (ppm) MAY

29. High Priority Science Passive Instrument Heritage Spacecraft Cost Resiliency All NASA Flight System Orbiting Carbon Observatory (OCO) Science -29 Q20 Level 4a: Inverted Sources and Sinks OCO measurements of X CO2 will not be evenly distributed in time and space. The inversion approaches incorporated into the OCO Mission Science strategy account for spatial and temporal inhomogeneity in observations. –The power of OCO in constraining sources and sinks comes from the ~10 8 new observations over a two-year period and the relatively high density of X CO2 observations in the tropics (where constraints from contemporary surface networks are weak). –Inversions of OCO data in combination with FTIR, aircraft, and flask observations, will revolutionize our understanding of the global carbon cycle. OCO Sampling Bias: Level 4a Products Geographic Distribution of CO 2 Sources & Sinks

30. High Priority Science Passive Instrument Heritage Spacecraft Cost Resiliency All NASA Flight System Orbiting Carbon Observatory (OCO) Science -30 Q20 Level 4b: Carbon Cycle Data Assimilation Data assimilation will calculate the 3-D CO 2 field by combining OCO X CO2 data with –in situ CO 2 observations –Uplooking FTIR X CO2 –Atmospheric transport model Analogous to modern weather forecasting –Spatially and temporally biased observations assimilated into a physical model to produce maps with continuous spatial and temporal information. OCO Sampling Bias: Level 4b Products Carbon Cycle Data Assimilation X CO2 Assimilation Strategy

31. High Priority Science Passive Instrument Heritage Spacecraft Cost Resiliency All NASA Flight System Orbiting Carbon Observatory (OCO) Science -31 Q21 Question # 21 Question 21: Level 2 data consists of a constellation of point measurements obtained in clear sky conditions. What are the spatial and temporal statistics of these measurements as a function of latitude? In particular, how will the geographical sampling of the instrument be affected by the relatively larger amount of cloudiness which tends to occur in the tropics relative to other latitudes? How will this degrade the quality of the Level 3 and Level 4 data, and how will this affect your science? Response: –OCO acquires 740 soundings per degree of latitude along the orbit track –With 14.65 orbits/day, and a 16 day repeat cycle, Ground tracks are separated by ~1.5 o of longitude Over a 16 day period, each 4 o x 5 o sub-region is traversed 3.3 times, yielding ~10,000 X CO2 soundings (assuming no clouds) –Only a small fraction of these samples are needed to meet the baseline science requirements

32. High Priority Science Passive Instrument Heritage Spacecraft Cost Resiliency All NASA Flight System Orbiting Carbon Observatory (OCO) Science -32 Response: –Observational System Simulation Experiments (OSSE’s) using the OCO orbit and 8 km x 8 km footprint (based on ISCCP data) –There is no strong tropical bias in the number of CO 2 soundings –High cirrus produce a sampling bias in the tropics, but their effects are compensated by the low solar zenith angle and high SNR Effects of Clouds on Sampling How will the geographical sampling of the instrument be affected by the relatively larger amount of cloudiness which tends to occur in the tropics relative to other latitudes? Average number of cloud-free hits each month in each 4 x 5 degree latitude bin, averaged over the year. Q21 Rayner et al. (2002)

33. High Priority Science Passive Instrument Heritage Spacecraft Cost Resiliency All NASA Flight System Orbiting Carbon Observatory (OCO) Science -33 Probability of Viewing Cloud-Free Scenes Increases with Spatial Resolution July 8 km x 8 km 0.00.51.0 Probability of clear-sky scene 24 km x 24 km 40 km x 40 km Rayner, Law and O’Brien III (2001) OSSE’s confirm that the probability of viewing cloud-free scenes increases as the sample footprint size decreases The high spatial resolution (1 km x 1.5 km) provided by OCO will yield more cloud free scenes Q21

34. High Priority Science Passive Instrument Heritage Spacecraft Cost Resiliency All NASA Flight System Orbiting Carbon Observatory (OCO) Science -34 Q22 Airborne Demonstration of +0.1% Retrieval Precision for Column O 2 Retrieval of tropospheric column O 2 to + 0.1% demonstrated using reflected near infrared sunlight with an airborne O 2 A-band instrument D. M. O’Brien et al., J. Atmos. Oceanic Tech. 15, 1272 (1998).

35. High Priority Science Passive Instrument Heritage Spacecraft Cost Resiliency All NASA Flight System Orbiting Carbon Observatory (OCO) Science -35 Q22 Flight Instrument Validation 1.57 1.59 1.58 Wavelength (  m) CO 2 1.58  m Band Ground-based FTIR solar spectrum in the OCO 1.58  m CO 2 band recorded at Table Mountain Facility, Wrightwood, CA (May 2002, S. Sander)

36. High Priority Science Passive Instrument Heritage Spacecraft Cost Resiliency All NASA Flight System Orbiting Carbon Observatory (OCO) Science -36 Question 8a Question 8a: Quantify the science impacts of the descope options Response: The OCO Team has identified 5 descope options 1. Relax geolocation requirement from 5 km to ~10 km 2. Leave A-Train 3. Reduce sampling rate from 4.5 to 3.0 Hz 4. Limit science observation to NADIR viewing 5. Delete 2.06  m channel Q8a

37. High Priority Science Passive Instrument Heritage Spacecraft Cost Resiliency All NASA Flight System Orbiting Carbon Observatory (OCO) Science -37 Q8a The Execution of All Descope Options Defines the Minimum Science Mission Baseline Science MissionMinimum Science Mission Provide global X CO2 measurements from space with 1 ppm relative accuracy 2.5 x 10 5 km 2 scale (4  x 5  ) 16 day interval 2 year mission Provide global X CO2 measurements from space with 1 ppm relative accuracy 1.0 x 10 6 km 2 scale (8  x 10  ) 1 month interval 2 year mission Combine X CO2 measurements with ground- based data to retrieve the geographic distribution of CO 2 sources & sinks on seasonal to interannual timescales. Use NADIR, GLINT and TARGET modes to provide independent data validation approaches Deleted Formation fly with the A-Train to allow coordinated observations and enhance data value to the ESE community Deleted Section F.2.6, pp. F-17-18 Q8a

38. High Priority Science Passive Instrument Heritage Spacecraft Cost Resiliency All NASA Flight System Orbiting Carbon Observatory (OCO) Science -38 Q8a OCO X CO2 Retrieval Performance Quantified for Baseline & Minimum Missions Minimum Mission Baseline Mission After Fig. F.1.10, p. F-8 OCO delivers global X CO2 measurements with 1 ppm relative accuracy in the Baseline Science Mission & Minimum Science Mission. Simulations conducted with the end-to-end OCO retrieval algorithm Q8a

39. High Priority Science Passive Instrument Heritage Spacecraft Cost Resiliency All NASA Flight System Orbiting Carbon Observatory (OCO) Science -39 Response: Relaxing the geolocation requirement from 5 km to ~10 km complicates the validation of the OCO data but does not affect the data accuracy. –Detailed response provided in Question 15 A relaxed geolocation requirement increases difficulty in collocating OCO validation measurements using TARGET mode. –FTIR’s located in spatially uniform areas The relaxed geolocation requirement will not affect the ability to correlate the OCO measurements with those from the A-Train –OCO swath is substantially smaller than that of A-Train instruments. Descope 1 Relaxed Geolocation Requirements Q8a

40. High Priority Science Passive Instrument Heritage Spacecraft Cost Resiliency All NASA Flight System Orbiting Carbon Observatory (OCO) Science -40 Descope 3 Reduced Sampling Rate Response: Reducing sampling rate from 4.5 Hz to 3.0 Hz will –Reduce the number of samples in each 4  x 5  region by 33% –Increases footprint area by 50% Slightly increased cloud contamination Results quantified in the response to Question 21 Q8a 33% Reduction

41. High Priority Science Passive Instrument Heritage Spacecraft Cost Resiliency All NASA Flight System Orbiting Carbon Observatory (OCO) Science -41 Descope 4 Delete TARGET & GLINT Modes Response: Deleting GLINT mode will reduce sensitivity over oceans and at high latitudes –OCO still meets its 1 ppm X CO2 relative accuracy goal operating only in NADIR mode Deleting TARGET mode decreases the number of independent validation methods Fig. F.1.9, p. F-7 OCO retrieval performance for several NADIR viewing scenarios Q8a

42. High Priority Science Passive Instrument Heritage Spacecraft Cost Resiliency All NASA Flight System Orbiting Carbon Observatory (OCO) Science -42 Descope 5 Delete 2.06  m Channel Response : Deleting the 2.06  m channel requires significantly more soundings to be averaged to meet the 1 ppm X CO2 relative accuracy goal Fig. F.1.8 quantifies the RSS errors for retrievals with all three spectrometers (c) and without the 2.06  m channel (b). Q8a

43. High Priority Science Passive Instrument Heritage Spacecraft Cost Resiliency All NASA Flight System Orbiting Carbon Observatory (OCO) Science -43 Q8a Descope 5 Delete 2.06  m Channel (con’t) The Baseline configuration reaches the 1 ppm accuracy goal in 10 – 50 soundings while it requires 50 – 10,000 soundings to achieve this goal without the 2.06  m channel. To achieve 1 ppm requires –Increasing sampling grid from 4  x 5  to 8  x 10  –Increasing interval from 16 days to 1 month Fig. F.1.10 quantifies the simulated observatory performance as a function of the number of soundings for the baseline configuration (red) and the instrument with the 2.06  m channel deleted (blue).

44. High Priority Science Passive Instrument Heritage Spacecraft Cost Resiliency All NASA Flight System Orbiting Carbon Observatory (OCO) Science -44 OCO Addresses the High Science Priorities X CO2 (ppm) OCO provides critical data for –Understanding the carbon cycle Essential for developing carbon management strategies –Predicting weather and climate Understanding sources/sinks essential for predicting CO 2 buildup O 2 A-Band will provide global surface pressure measurements OCO validates technologies critically needed for future operational CO 2 monitoring missions Climate Forcing/Response T/H 2 O/O 3 AIRS/TES/MLS CloudsCloudSat AerosolsCALIPSO CO 2 OCO