page 1 1 of 20, crisp, oco may 2006 the orbiting carbon observatory: sampling approach and...
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Page 1 1 of 20, Crisp, OCO May 2006
The Orbiting Carbon Observatory: Sampling The Orbiting Carbon Observatory: Sampling Approach and Anticipated Data Products Approach and Anticipated Data Products
David Crisp, OCO PIDavid Crisp, OCO PIhttp://oco.jpl.nasa.gov
JPL/Caltech
May 2006
Carbon Fusion Workshop
Page 2 2 of 20, Crisp, OCO May 2006
What Processes Control Atmospheric CO2?
Carbon dioxide (CO2) is the:
Main atmospheric component of the global carbon cycle
Main man-made greenhouse gas
Only half of the CO2 produced by human activities is remaining in the atmosphere
O OC
Page 3 3 of 20, Crisp, OCO May 2006
Outstanding Questions
• Where are the sinks that are absorbing almost 50% of the CO2 that we emit?
– Land or ocean?
– Eurasia/North America?
• Why does CO2 buildup vary dramatically with nearly uniform emissions?
• How will CO2 sinks respond to climate change?
Page 4 4 of 20, Crisp, OCO May 2006
The Orbiting Carbon Observatory (OCO)
Approach: • Collect spatially resolved, high resolution
spectroscopic observations of CO2 and O2 absorption in reflected sunlight
• Use these data to resolve spatial and temporal variations in the column averaged CO2 dry air mole fraction, XCO2 over the sunlit hemisphere
• Employ independent calibration and validation approaches to produce XCO2 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 CO2 sources and sinks and quantify their variability over the seasonal cycle
Page 5 5 of 20, Crisp, OCO May 2006
Precise Measurements Needed to Constrain CO2 Surface Fluxes
• Resolve pole to pole XCO2 gradients on regional scales
• Resolve the XCO2 seasonal cycle in the Northern Hemisphere
356
364
Precisions of 1–2 ppm (0.3–0.5%) Precisions of 1–2 ppm (0.3–0.5%) on regional scales needed to: on regional scales needed to:
• Resolve (8ppm) pole to pole XCO2 gradients on regional scales
• Resolve the XCO2 seasonal cycle in the Northern Hemisphere
Page 6 6 of 20, Crisp, OCO May 2006
OCO Fills a Critical Measurement Gap
OCO will make precise global measurements of XCO2 over the range of scales needed to monitor CO2 fluxes on regional to continental scales.
Spatial Scale (km)
1
2
3
4
5
6
CO
2 E
rror
(pp
m)
1 10 100 1000 10000
OCO
FlaskSite
AquaAIRS
Aircraft
0
FluxTower
Globalview Network
NOAATOVS
ENVISATSCIAMACHY
Page 7 7 of 20, Crisp, OCO May 2006
Making Precise CO2 Measurements from Space
Clouds/Aerosols, Surface Pressure Clouds/Aerosols, H2O, TemperatureColumn CO2
O2 A-band CO2 1.61m
CO2 2.06 m
• High resolution spectra of reflected sunlight in near IR CO2 and O2 bands used to retrieve the column average CO2 dry air mole fraction, XCO2
– 1.61 m CO2 bands – Column CO2 with maximum sensitivity near the surface
– O2 A-band and 2.06 m CO2 band• Surface pressure, albedo, atmospheric
temperature, water vapor, clouds, aerosols• Why high spectral resolution?
– Enhances sensitivity, minimizes biases
Page 8 8 of 20, Crisp, OCO May 2006
OCO Observing Strategy
• Nadir Observations: tracks local nadir– + Small footprint (< 3 km2) 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
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 CO2 and O2 measurements in reflected sunlight• CO2 concentrations are near their diurnally-averaged values near noon• Maximizes opportunities of coordinated science and calibration activities
TES – T, P, H2O, O3, CH4, COMLS – O3, H2O, COHIRDLS – T, O3, H2O, CO2, CH4
OMI – O3, aerosol climatology
aerosols, polarization
CloudSat – 3-D cloud climatologyCALIPSO – 3-D aerosol climatology
AIRS – T, P, H2O, CO2, CH4
MODIS – cloud, aerosols, albedo
OCO - - CO2
O2 A-band ps, clouds, aerosols
Coordinated Observations
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
Page 11 11 of 20, Crisp, OCO May 2006
The OCO Instrument
• 3 bore-sighted, high resolution, grating spectrometers
• O2 0.765 m A-band
• CO2 1.61 m band
• CO2 2.06 m band
• Similar optics and electronics• Common 200 mm f/1.9 telescope
• Spectrometers cooled to < 0 oC
• 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)
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 1.5o
Space-based CO2 column measurements complement surface measurement network.
Chevallier et al. 2006
OCO3-Days
OCO1-Day
OCO Sampling: Clouds reduce number of usable samples
Page 13 13 of 20, Crisp, OCO May 2006
OCO Data Hierarchy
Spectral
Spa
tial
Sounding:3 Collocated Spectra
Spectrum
3
4
Frame:4 (8) Cross-Track
Soundings
Granule:All ~30,000
Soundings recorded each orbit
21
5
Pixel
Page 14 14 of 20, Crisp, OCO May 2006
OCO characterization for Key Environmental Parameters (SZA, surface type)
Averaging Kernels: Early Support forSource/sink inversions
• Study effect on XCO2 biases on CO2 source/sink inversions• Rehearsal of ingesting OCO XCO2 (early feedback on L2 product)
Page 15 15 of 20, Crisp, OCO May 2006
Example: XCO2 Averaging Kernel and Errors for a Single Orbit Track
Nadir Viewing Averaging Kernel Along Orbit Track
Single Sounding XCO2 Errors
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
Page 17 17 of 20, Crisp, OCO May 2006
• The space-based XCO2 data will be validated against the surface WMO standard for CO2 using measurements of XCO2 from ground based Fourier transform spectrometers (FTS) as a transfer standard
• XCO2 will be retrieved from the FTS and space-based instruments using same retrieval code
FTS XCO2 compared to:• Surface in situ CO2
• Tall tower in situ CO2
• Column CO2 integrated from in situ profiles
FTS XCO2 performance tracked by monitoring:• Instrument Line Shape (HCl gas cell)• Pointing (Doppler shift, telluric vs solar
features)• XO2, surface pressure and H2O
Observations at 79°N (Spitsbergen) FTSNotholt et al., GRL, 2005
WLEF FTIR
Space-based XCO2 Validation Strategy
Observations at 79°N (Spitsbergen) FTSNotholt et al., GRL, 2005
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 CO2 dry air mole fraction
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
ProductSingle Product Volume
(MBytes)Daily Volume
(Gbytes)Mission Volume
(Tbytes)Science Telemetry 4.843 3.455Housekeeping Telemetry 0.186 0.133OCO Level 0 310.281 4.406 3.141OCO Level 1A 315.429 4.479 3.193OCO Level 1B 640.184 9.090 6.480Level 2 15.922 0.226 0.161Total 23.230 16.563
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
Heliostat
Shutter
T/VAC Chamber
Solar Diffuser
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tru
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Heliostat
Shutter
T/VAC Chamber
Solar Diffuser
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