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Spatial C o-Registration

Spatial C o-Registration . Jochen Landgraf and Andre Galli. The requirement. “The spatial co-registration between all channels in all bands shall be equal to or better than 0.10 ( Goal) / 0.15 (threshold) SSD (Spatial sampling distance) in a nadir view”

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Spatial C o-Registration

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  1. Spatial Co-Registration Jochen Landgraf and Andre Galli

  2. The requirement • “The spatial co-registration between all channels in all bands shall be equal to or better than 0.10 (Goal) / 0.15 (threshold) SSD (Spatial sampling distance) in a nadir view” Requirement is interpreted as an interband co-registration requirement To consolidate this requirement sub-pixel information is needed on a spatial scale of better than 0.05 SSD = 100 m Pixel inhomogeneity may be caused by variation of

  3. Cabauw Experimental Site for Atmospheric Research Water Vapour,Aerosol and Cloud Lidar (CAELI) Signal every 14 seconds at a vertical resolution of 7.5 m up to an altitude of 15 km above the surface. For a wind speed of 1 km/min this results in a spatial resolution of 125 m in one spatial dimension. Backscattered lidar signal has to be transformed to optical depth. Therefore, we assume an extinction coefficient of 0.25 km-1 (typical for mitlatitude cirrus). => uncertainty in OD 100%.

  4. Cirrus optical depth / March 28, 2011

  5. Sensitivity τ=0 as a function of Δτ

  6. Sensitivity τ=0 as a function of Δτ O2 A and SWIR-2 have strongest sensitivity and opposite in sign SWIR-1 sensitivity is smallest. Sensitivity study can be reduced to displacements in one band.

  7. Cirrus optical depth / March 28, 2011

  8. Cirrus optical depth / March 28, 2011 Cirrus has little spatial structures Δτ < 0.002

  9. 10 % misalignment SZA = 30o / March 28, 2011 dashed: CH4 / solid: CO2

  10. 10 % misalignment SZA = 50o/ March 28, 2011 ε(CO2) < 0.03 % / ε(CH4) < 0.02 % dashed: CH4 / solid: CO2

  11. Error Analysis based on five Lidar Scenes

  12. Standard Deviation for different Ranges of τcir

  13. Standard Deviation for different Ranges of τcir 0.125 % error level

  14. Conclusions • Co-alignment requirement driven by CO2 and relative misalignment between O2-A and SWIR-2 CO2 1-sigma error < 0.125 % for 10 % displacement • Misalignment error smaller for stronger filtering on cirrus optical depth and larger pixel size. • On small scales, where it is assumed to work with proxy-retrievals inter-channel co-registration becomes less critical. • The co-registration error behaves as pseudo-noise on larger temporal and spatial scales. Thus, this study supports the present MRD (v1.2) requirements (10% goal, 15% threshold) for the SWIR-2 and the O2 A band

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