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O 2 A-band

Requirements Consolidation of the Near-Infrared Channel of the GMES-Sentinel-5 UVNS Instrument: Study Overview R.Siddans PM1: RAL, 9 July 2013. O 2 A-band. Sun-normalised radiance. O 2 A-band contains optically thick molecular absorption lines

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O 2 A-band

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  1. Requirements Consolidation of the Near-Infrared Channel of the GMES-Sentinel-5 UVNS Instrument:Study OverviewR.SiddansPM1: RAL, 9 July 2013

  2. O2 A-band Sun-normalised radiance • O2 A-band contains optically thick molecular absorption lines • Effective scattering altitude of photons (viewed in nadir) varies with wavelength • O2 mixing ratio known therefore measurements can be used to infer scattering profile. • Amount of information depends critically on spectral resolution but also on random and systematic instrumental and forward model errors 0.06nm resolution 0.3 nm resolution Wavelength / nm

  3. Overview • Study to consolidate requirements for Sentinel-5 NIR channel • Application areas to be addressed: • Height resolved aerosol from O2-A (and B) bands (RAL) • Scattering correction for DOAS retrievals UV/VIS/NIR (RAL) • Scattering correction for full-physics retrievals from SWIR+NIR joint retrieval (Univ Leicester) • Water vapour retrievals (Univ Bremen) • Impact of vegetation fluorescence to be taken into account in deriving requirements (and retrieval simulations) • Input from FU-Berlin consultant

  4. Consortium Retrieval Schemes • RAL height-resolved aerosol scheme • OE scheme largely developed for Eumetsat and ESA studies (MTG UVS, Capacity, Camelot) • Retrieves aerosol extinction profile, integrated to layer amounts • Instrumental errors quantified by linear mapping • Non-linear version used to test impact of realistic cloud distributions • Leicester OCO full physics retrieval scheme • Retrieves CO2, CH4 from SWIR band, jointly fitting NIR band, and internally representing aerosol as either extinction profile or parameterised profile shape. • Bremen Optimal Estimation DOAS (BESD) scheme • Devloped for full physics SWIR retrievals, to be applied for H2O from NIR, exploiting O2-B for implicit scattering correction.

  5. Treament of Cloud (errors from NIR fit on other L2) • UV/VIS species: As in Eumetsat A-band study. • Realistic cloud scenarios defined (model or CALIPSO/CloudSat) • NIR radiances simulated • Cloud parameters (fraction layer height, reflectance or optical depth) retrieved from A and/or B band. • UV/VIS AMF computed for true and retrieved state • Linear mapping used to propagate instrumental errors through 1-4. • SWIR species • Full physics approach from sub-set of UV/VIS set (cirrus, aerosol low cloud fraction) • NIR-H2O • Full physics approach from sub-set of UV/VIS set

  6. Organisation of study • Task 1: First Analysis of the NIR Band of the S-5 UVNS Instrument – Initial Trade-off. • Task2: Refinement of NIR Specifications • Task 3: Conclusions Apr May Jun Jul Aug Sep Oct Nov Dec Jan Feb Mar • NB Task 2.6 runs during Task1, to define its scope by MTR

  7. Task1: First Analysis of the NIR Band of the S-5 UVNS Instrument – Initial Trade-off. • Focus on threshold and goal requirements for spectral resolution and coverage in the region of the O2-A and O2-B(+H2O) bands. • User requirements + basic instrument performance will be taken from the MRTD + updates from ESA. • Performance for NIR-1 and NIR-2 bands reported for resolutions of 0.4,0.2,0.12 and 0.06nm, for each application. • Based on existing simulations where possible. • Limited new simulations if not. • It will be stated which L2 requirements can be met by a NIR channel which covers 685-775nm at the threshold resolution (0.4nm) • Threshold resolution for aerosol profile identified. • Output: TN1, describing the NIR band specifications linked to user service requirements. • Task limited to resolution / noise / bandwidth trade-off. • Impact of other errors only where overriding considerations identified previously.

  8. Task 2: Refinement of NIR Specifications • Task 2.1-2.4: Retrieval simulations to consolidate requirements for each application area. • Task 2.5: Co-registration requirements • Assess impact of co-registration errors on utility of NIR band scattering profile characterisation • Based on CloudSat/CALIPSO + RT calculations to generate statistics of AMF errors as fn of co-location error. • Task 2.6: Definition of geophysical scenarios and instrument assumptions • Define scope of Task 2 simulations • Geophysical scenarios • Key instrument requirements to be consolidated via retrieval simulation • Study resources limit number of different types of error to ~5 • Discussion with SWIR contractor to align simulation work & define baseline for SWIR channel to be assumed here.

  9. Deliverables • KO=April • KO + 4 months = end July’13 • TN1, describing the NIR band specifications linked to user service requirements • KO + 11 months = end Feb’14 • TN2: describing the refined NIR band specifications linked to user service requirements • KO + 12 months = end March’14 • Final Report, Executive Summary • + Technical Data Package ?

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