1. Sentinel-4 and -5 Status and Level-2 Products
Ben Veihelmann, Jörg Langen, Dirk Schüttemeyer, Paul Ingmann
ESA/ESTEC
OMI Science Team Meeting 18
March 2014, KNMI, De Bilt, The Netherlands

2. Overview Sentinel-4: mission implementation and Level-2 products
AROMAT campaign: preparation of future validation

3. The Sentinel Missions for Copernicus Atmosphere Services
GEOstationary (GEO)
Hourly revisit time over Europe
Mainly air quality
Diurnal cycle of tropospheric composition
Sentinel-4
Low Earth Orbit (LEO)
Daily revisit time global coverage
Climate, air quality, ozone & UV
Tropospheric & stratospheric composition
Sentinel-5
Sentinel-5 Precursor

4. Sentinel-4/-5/-5P Mission Implementation
Instrument
Utilization of data from
Imager
Infrared sounder
Other
Sentinel-4
UVN spectrometer (1)
FCI (2)
IRS (1)
LI (2,*)
Sentinel-5
UVNS spectrometer (3)
VII (3)
IAS (3)
3MI (3)
Sentinel-5 Precursor
UVNS spectrometer TROPOMI (4)
VIIRS (5)
CRIS (5,*)
OMPS (5,*)
(1) on MTG sounder (GEO)
(2) on MTG imager (GEO)
(3) on MetOp-SG (LEO)
(4) on dedicated platform (LEO)
(5) on SNPP/JPSS (LEO)
(*) synergy on higher data level
UVN = Ultraviolet + Visible + Near infrared
FCI = Flexible Combined Imager
IRS = InfraRed Sounder
LI = Lightning Imager
UVNS = UVN + Short wave infrared
VII = Visible/Infrared Imager (MetImage)
IAS = Infrared Atmospheric Sounder (IASI-NG)
3MI = Multi-viewing, -channel, -polarisation Imager
TROPOMI = TROPOspheric Monitoring Instrument
VIIRS = Visible Infrared Imaging Radiometer Suite
CrIS = Cross-track Infrared Sounder
OMPS = Ozone Mapping Profiler Suite
MTG = Meteosat Third Generation
MetOp-SG = MetOp-Second Generation
SNPP = Suomi National Polar-orbiting Partnership
JPSS = Joint Polar Satellite System

5. Sentinel-4/UVN Instrument
Courtesy Astrium 5

6. Sentinel-4/UVN Instrument Characteristics
Radiometric accuracy 1.8% ( nm), 2.3% elsewhere
Polarisation sensitivity <0.7%
Spectral features <0.05%
Signal-to-Noise Ratio compliant
Spatial Sampling 8 km at 45˚N
Geographic Coverage Area (GCA) Europe + Sahara
Repeat Cycle 1 h over Reference Area (RA)
Spectral
Band
range [nm]
resolution [nm]
sampling ratio UV
0.5 3
VIS
NIR
0.12
400
600
800
500
700
300
UV-vis
NIR
Wavelength (nm)

7. Sentinel-4 Level-2 Products
Application
Comment
Air
Quality
Climate
Surface UV
O3 total & tropospheric column X
O3 enhanced sensitivity to lower troposphere
Synergy with infrared data from IRS
NO2 total & trop. column
SO2 total column
Also for volcanic eruption monitoring
CHOCHO total column
By-product
CH2O total column
Aerosol extinction coeff. profile, column optical depth / type / index
Also auxiliary for other S4 products
Synergy with imager data from FCI
Cloud optical thickness, fraction, altitude
Mainly auxiliary for other S4 products
Surface reflectance daily map
Who takes care of IRS alone products such as CO, HNO3?

8. Sentinel-4 Level-2 Performance Estimate (IUP, RAL, Noveltis)
Assumptions
polluted scenario at 50˚N, 15h local time
radiometric offset error small, spectral calibration successful
cloud fraction up to 20%
Tropospheric column
O3 [%]
NO2 [%]
CH2O [%]
SO2 [%]
Error type
Ran.
Sys.
Instrument 3 7 13 5 10
Scene (clear) 9 20 21 27 12
Scene (cloudy) 22 11 26 34 19 36
Total (clear) 25 31
Total (cloudy) 24 29 37 42
User req.
10-25
15-25
20-50

9. Sentinel-4 Level-2 Performance Estimate (IUP, RAL, Noveltis)
Assumptions: European background aerosol profile
Valuable aerosol data from O2A band
in morning/afternoon expected
requirement
User
Aerosol Optical Depth Noise Error
Column
Total
Boundary
Layer
06h h h 15h h
R. Siddans, STFC Rutherford Appleton Laboratory

10. Sentinel-4 Level-2 Processor Development Challenges
Tropospheric NO2 diurnal variation
good precision and accuracy
avoid diurnal biases!
 need to account for
surface anisotropy
tropospheric profile
stratospheric sub-column
aerosol vertical distribution
aerosol phase function
Aerosol layer height
from O2A band
little heritage
spectroscopy
pseudo-noise mitigation
spectral calibration
computational speed
Aerosol & surface characteristics
joint retrieval from aggregated data
little heritage
processor architecture
computational speed

11. Bi-directional Reflectance Factor, 440 nm, various surface types
Sentinel-4 Level-2 Pre-development SURMACED (BIRA, GC, LOA, IM) GPGPU (LOA, Catalyst)
Objective
Aerosol & surface reflectance from temporally aggregated radiance
Application to real satellite measurements
Validation based on real measurement
Approach
SURMACED (finalised): GRASP algorithm, performance demonstrated for favourable illumination conditions (summer), driver NO2 retrieval
GPGPU (ongoing): Proxy data from GOCI, reference from AERONET and PARASOL
GOCI on
COMS
Bi-directional Reflectance Factor, 440 nm, various surface types

12. Sentinel-4 Level-2 Pre-development AEROPRO (KNMI)
Objectives
Aerosol layer height retrieval from O2A-band
Application to real satellite measurements
Validation based on collocated measurements
Status
GOSAT (0.016 nm) + airborne lidar  finalised
GOME-2 (0.5 nm) + ground based lidar  almost finalised
poster Bram Sanders
GOME-2 on
MetOp
TANSO on
GOSAT
Lidar on FAAM
CarbonExp Campaign 2011
Collocated
GOSAT target mode
airborne lidar
CarbonExp Campaign 2011
CarbonExp Campaign 2011

13. Sentinel-4 Level-2 Processor Development
ITT early 2014
Build on heritage
Challenges
Consortium formation now!

14. Mission Elements: Sentinel–5 LEO Atmospheric Mission
Applications:
air quality, climate forcing and stratospheric ozone, tropospheric chemistry
Instrumentation:
UV-VIS-NIR-SWIR spectrometer
Use of thermal IR sounder, cloud
imager and polarisation imager
UV-Visible ( nm)
NIR ( nm)
SWIR (1590–1675nm; nm)
Spectrometers with spectral resolutions between 0.25 nm and 1.0 nm
Spatial sampling with 50 (T)/15 (G) km < 300nm and 15 (T)/5(G) km > 300 nm
Global daily coverage
Sun-synchronous Low Earth Orbit platform at 824 km mean altitude
Embarked on EPS-SG, operated by EUMETSAT

15. Possible Level-2 Products from Sentinel-5 UVNS
species
priority
applications
O3 vertical profile 1
SO, AQ, CL
O3 total column SO
NO2 total & trop. col. AQ
CH4 total column CL
CO total column
AQ, CL
SO2 total column
1 (1)
HCHO total col.
BrO total column 2
H2O total column
CHOCHO total col.
CO2 total column
species
priority
applications
Cloud optical depth, fraction, height
1 (2)
auxiliary
Aerosol absorption index 2
AQ, CL
Aerosol optical depth, type
1/2 (3)
Aerosol vertical profile
1/2 (2)
Surface reflectance
Vegetation fluorescence
science
SO = stratospheric ozone
AQ = air quality
CL = climate
(1) Only observed in strongly polluted areas (volcanic eruptions, major power plants)
(2) Priority 1 not as geophysical product itself, but for use in correcting retrievals of other products
(3) Priority 2 for instrument development; priority 1 for Level-2 product development

16. Possible Sentinel-5-relevant Level-2 Products from other instruments on Metop-SG
IAS (IASI-NG)
O3 and CO profiles
SO2, NH3, CH3OH, HCOOH
CH4, H2O, HNO3, PAN
C2H2, HCN
CFC-11, CFC-12, C2H4, N2O, HONO, CO2, volcanic ash
3MI
aerosol/cirrus optical depth
aerosol single scattering albedo, effective radius, refractive index
surface reflectance
VII (MetImage)
aerosol type, effective radius, single scattering albedo
cloud characterisation

17. Sentinel–5 scientific study activities
Consolidation of requirements
radiometric errors (offset, scaling, spectrally varying)
spatial co-registration (cloud, surface albedo impact), spatial resolution
spectral resolution vs. SNR
knowledge of slit function
added value of O2-B band
Performance assessment
error budget
band trade-offs (eg. 2-band vs. 3-band CH4 retrieval)
vertically resolved aerosol product
spectroscopic errors
fluorescence

18. AROMAT (Airborne ROmanian Measurements of Aerosols and Trace gases)
Objectives
To combine airborne, satellite and coincident ground activities
To investigate consistency and complementarity of different measurement approaches
Targets
NO2, SO2, and aerosols in exhaust plumes of large power stations (Turceni and Rovinari) and around the Bucharest urban area.
Setup
2 imaging DOAS, scanning lidar, NO2 sondes
high pollution levels and strong gradients

19. Sentinel-4 and -5 Status and L2 Products
Ben Veihelmann, Jörg Langen, Dirk Schüttemeyer, Paul Ingmann
ESA/ESTEC
Thanks for listening!
OMI Science Team Meeting 18
March 2014, KNMI, De Bilt, The Netherlands

20. Backup slides

21. Preliminary spectral fit-windows per Level-2 product
UV-Visible band
Near Infrared band

22. Sentinel-4 Instrument on Meteosat Third Generation (MTG)
MTG-Sounder
InfraRed Sounder (IRS)
Sentinel-4/UVN (S4/UVN)
Consecutive launches
FCI flexible combined imager
LI lightning imager
IRS infrared sounder
MTG-Imager
Flexible Combined Imager (FCI)
Lighting Imager (LI)
UVN = UV + Visible + Near infrared