Overview of MSI Level 1 validation by ECVT(AO PIs) - Discussion
EarthCARE Status – May 2021
Jürgen Fischer and Rene Preusker

2nd ESA EarthCARE Validation Workshop
25-28 May 2021 (online)
ESA
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2nd

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MSI Level 1 validation proposals• MMP : Monitoring MSI/EarthCARE L1 performances using concomitantintercalibration and stand-alone approaches (Noelle SCOTT, LMD, Palaiseau, France)• GIVE : German Initiative for the Validation of EarthCARE (Ulla Wandinger, Tropos,Leipzig, FUB, Germany)• Validation of EarthCARE Product in China (Xiuqing He, National Satellite
Meteorological Center, Beijing, China)• Evaluation of EarthCARE Radiances and Fluxes with CERES Data Products (NormenLoeb, NASA Langley Research Center, USA)
• EarthCARE BBR L1 and L2 Products Assessment (Nicolas Clerbaux, Royal
Meteorological Institute of Belgium)
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MSI Level 1 validation proposals
MMP : Monitoring MSI/EarthCARE L1 performances using concomitantintercalibration and stand-alone approaches (Noelle SCOTT, LMD, Palaiseau, France)
The method relies upon two concomitant approaches:(i) a relative (sometimes referred to as inter-calibration) approach and(ii) a "stand alone" approach.
They combine observations to observations and simulations to observations
comparisons, respectively:§ All geographical regions and seasons, as well as land/sea/day/night scenes,
clear/cloudy/aerosols scenes, thus encompassing a broad range of brightness
temperatures.
§ Simulations will be performed with the 4A/OP model fed with adequate
descriptions of the atmospheric and surface state.
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MSI Level 1 validation proposals
GIVE : German Initiative for the Validation of EarthCARE (Ulla Wandinger, Tropos,Leipzig, Germany)§ Inter-comparison of different satellite aerosol products and additional radiativetransfer simulations are further used to interpret the MSI Level 1 radiancemeasurements.
§ Comparisons of validated aerosol products from OLCI and SLSTR (long operational
perspective of the European Sentinel-3 series).
§ The EarthCARE BMA-FLX product will also be compared to fluxes that are estimatedfrom MSG-SEVIRI radiance measurements

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MSI – L1 Calibration – Discussion

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MSI – L1 Calibration – what is needed ?
§ VNS is calibrated against reflectance standard (not radiance)! Selection of solar
spectrum: Continuous analysis !
Ø radiometric diffusers ageing
Ø instrument sensitivity evolution
Ø Spectral characterisation of VNS bands (not explicitly addressed so far)
§ TIR calibration
Ø Analysis of housekeeping data: Black-body evolution.
Ø Stray-light correction/orbit dependent ?
§Access to instrument data to analyse with respect to calibration procedures: Who isdoing it ?

§Geo-location accuracy for VNS and TIR (by bands)

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Inflight absolute and relative radiometric
1. Invariant Calibration Targets: Precise RTM simulations, ideally accompanied with ground-based
atmosphere characterisation. Use of established sites allows inter-satellite comparisons.
••••
•
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Rayleigh Calibration oceanic sites, offglint geometry, no clouds, only background aerosol.
Applicable only for wavelengths/geometry with significant Rayleigh signal : VIS 1.
DCC (Deep Convective Clouds): nearly perfect solar diffusers (adequate for inter-band: relative
radiometric calibration). Worldwide distributed, mainly +- 10°.
LWC (liquid water clouds, trade wind zones): good for intermediate intensities, non-linearities vsbright
Sun Glint Reflectance follows refractive index: Good for inter-band, but MSI is slightly tilted to offglint:-(SST: relatively stable, monitored by many ground based and satellite missions. Needs good RTM(water vapour)(Pseudo) Invariant Calibration Sites (PICS): mostly deserts, DOME-C…

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Inflight absolute and relative radiometric
2. SNO (Simultaneous Nadir Observations): Inter-satellite. RSR must be as
similar as possible (or RTM based transfer). Spatial variability should below. Eventually, radiometric consistency (closures) between instruments
on one platform (BBR ßàMSI) should be used.
3. Statistical Inter-comparisons (look also on higher moments of pdf’s )ESA UNCLASSIFIED - For Official Use

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RayleighChander et
al 2013
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Chander etal 2013
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Lessons learned from previous missions
1. Effort and budget should be allocated to instrument pre-launch characterization and knowledge transfer.
Some instrument features observed during operations are usually extremely difficult to be characterized andto be disentangled from each-other in-flight!! House-keeping data can support instrument characterisation(we will never use 99.5 % of the HK data, but we don’t want to miss any!)
2. “… the calibration is a never-ending process and a dedicated effort should be allocated throughout the fullmission lifetime (and beyond), this entails the need for regular reprocessing campaigns for the continuousimprovements of the level 1 dataset …“
3. Multi-sensor radiometric inter-comparison over Pseudo-Invariant Calibration Sites (PICS) is an invaluable
source, however, the uncertainty of the methods requires meticulous work to incorporate, BRDF,
atmospheric, spatial averaging and spectral effects. (RadCalNet, spectral HR sensors to establish transfer
functions, community agreed RTM, protocols, …) It is always a cooperative approach: (CEOS, GSICS)
4. Option: Orbital maneuverer provide view on moon for stability monitoring and diffusor BRDF investigations

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