METimage Calibration Pepe Phillips GSICS Data Research Working

METimage Calibration Pepe Phillips GSICS Data & Research Working Groups Meeting, 24 March 2014 EUM/RSP/VWG/14/751012 METimage Calibration 24/03/2014

Contents • • • Introduction to EPS-SG Introduction to METimage performances Calibration of the solar channels Calibration of thermal channels Plans for in-orbit monitoring EUM/RSP/VWG/14/751012 METimage Calibration Slide 24/03/2014

EPS-SG (Second Generation) Payload Instrument (and Provider) IASI-NG (CNES) Predecessor on Metop IASI (CNES) Microwave Sounding (MWS) MWS (ESA) AMSU-A (NOAA) MHS (EUM) Visible-infrared Imaging (VII) METImage (DLR) AVHRR (NOAA) RO (ESA) Sentinel-5 (Copernicus, ESA) GRAS (ESA) Satellite-A Missions Infrared Atmospheric Sounding (IAS) Radio Occultation (RO) UV/VIS/NIR/SWIR Sounding (UVNS) Multi-viewing, -channel, -polarisation Imaging (3 MI) 3 MI (ESA) GOME-2 (ESA) -/- Instrument (and Provider) Predecessor on Metop Scatterometer (SCA) SCA (ESA) ASCAT Radio Occultation (RO) RO (ESA) GRAS (ESA) Microwave Imaging for Precipitation (MWI) MWI (ESA) -/- ICI (ESA) -/- Argos-4 (CNES) A-DCS Satellite-B Missions Ice Cloud Imager (ICI ) Advanced Data Collection System (ADCS) EUM/RSP/VWG/14/751012 METimage Calibration 24/03/2014

Introduction to METimage EUM/RSP/VWG/14/751012 METimage Calibration Slide 24/03/2014

VII primary observations Products to be derived from the VII mission are: Cloud observations including microphysical analysis Water-vapour imagery Aerosol observations Polar Atmospheric Motion Vectors (AMVs) Earth surface albedo Vegetation Cryosphere (snow, sea and land ice imagery) Fire detection Surface temperature (land sea) EUM/RSP/VWG/14/751012 METimage Calibration Slide 24/03/2014

Cloud Observations • • Cloud optical thickness: 670 nm over land, 1. 24 µm over snow and sea ice, 865 nm over ocean. Cloud drop/particle effective radius: 2. 25 µm and 3. 75 µm. Cloud imagery: red (670 nm) / green (555 nm) / blue (443 nm) /near infrared (NIR) (865 nm) / thermal infrared (TIR) (10. 8 µm) cloud imagery composites. Cirrus clouds: 1. 37 µm (land during daytime) and 8. 5 µm (nighttime). Snow/cloud discrimination: 1. 6 µm and 3. 75 µm. Cloud phase at the cloud top: 1. 6 µm, 8. 5 µm and 10. 8 µm. Cloud top temperature, 763 nm oxygen-A band channels (daytime), 12. 02 µm and 13. 3 µm (CO 2 absorption) in combination with infrared sounding data at 13 -15 µm. EUM/RSP/VWG/14/751012 METimage Calibration Slide 24/03/2014 Cloud vortices, MODIS RGB imagery (courtesy NASA)

VII performance specifications • The need for more sophisticated parameterisation of clouds and surface boundary conditions drives the spectral and spatial resolution of the VII. • In comparison to AVHRR on EPS: Number Channels Spatial resolution AVHRR 6 1 km VII 500 m 20 Comparison between AVHRR (left) and MODIS (right) imagery (courtesy NASA) EUM/RSP/VWG/14/751012 METimage Calibration Slide 24/03/2014

VII Spectral Channels Cloud top Water height vapour Aerosol Cirrus Vegetation X X X X X X X X Surface temp (nm) Δ (nm) Cloud 443 555 670 752 763 865 914 1, 240 30 20 20 10 10 20 50 20 X X X X 1, 365 40 X X 1, 630 2, 250 3, 740 3, 959 4, 040 20 50 180 60 60 X X X 6, 725 370 X X Water vapour imagery and polar winds 7, 325 290 X X Water vapour imagery and polar winds 8, 540 290 X X 10, 690 500 X X X X 12, 020 500 X X X X 310 X X 13, 345 X X EUM/RSP/VWG/14/751012 METimage Calibration Slide 24/03/2014 X X Primary observations Clouds and aerosol Clouds, aerosol and vegetation Cloud and aerosol height assignment Clouds, aerosol and vegetation Water vapour Clouds, aerosol and vegetation High level clouds and aerosol and water vapour imagery Cloud phase and surface properties Cloud microphysical analysis SST and fire SST Cirrus clouds Split window for clouds and surface parameters Cloud top height.

Performance specifications (cont) Bias error < 5% (solar), < 0. 5 K @ Ttyp (thermal) Stability < 1% (solar), < 0. 15 K @ Ttyp (thermal) Inter-spatial homogeneity < 1% (solar), < 0. 1 K @ 280 K (thermal) Inter-channel homogeneity < 1% (solar), < 0. 1 K @ 280 K (thermal) MTF > 0. 3 @ Nyquist Geolocation accuracy Sub-pixel (~100 m @ nadir) Polarisation sensitivity < 5% (solar), < 11% (thermal) Channel co-registration > 80% all channels EUM/RSP/VWG/14/751012 METimage Calibration Slide 24/03/2014

METimage calibration concept Calibration concept addresses accuracy, stability and spectral and spatial homogeneity. Accuracy is achieved using on-board 2 -point linear calibration by viewing cold space as the low dynamic range reference and a target at known temperature/radiance for the high dynamic range reference -> solar diffuser (solar channels) and black body (thermal channels). Non-linearity corrections shall also be considered (TBC). Thermal channels: Offset and gain corrections performed by viewing cold space and a black body at instrument temperature every scan line - > recalibration interval of approx 3 s. Solar channels: Offset and gain corrections performed by viewing cold space once per scan line and a solar diffuser once per orbit - > recalibration interval of approx 100 mins. EUM/RSP/VWG/14/751012 METimage Calibration Slide 24/03/2014

Solar diffuser monitor • Due to the main diffuser degradation, METimage shall carry a second diffuser plate that shall be used only periodically to monitor the degradation of the main solar diffuser. • The diffuser monitor shall be deployed at regular intervals (approx once every 2 weeks). Else it remains hidden away to reduce UV exposure and contamination which are the main sources of diffuser degradation. • At end of mission, the degradation of the monitor shall be small enough that the lifetime stability requirement (1%) for the solar channels is met. EUM/RSP/VWG/14/751012 METimage Calibration Slide 24/03/2014

METimage Calibration – Lunar calibration • Lunar calibration has been successfully used for MODIS and VIIRS to monitor in-orbit performance including: • Channel dependant degradation of the solar diffuser • Reflection versus scan angle (RVS) correction of primary scan mirror • Band to band registration • Cross-talk • MTF • The role of the moon for stability monitoring is currently being considered for METimage. To use lunar calibration we need: • Lunar visibility without platform manoeuvres (except during commisioning) • Regular incidences of (full) lunar intrusions (several times per year) • Bright enough (and as constant as possible) lunar phase angle EUM/RSP/VWG/14/751012 METimage Calibration Slide 24/03/2014

Lunar calibration METimage – way forward • Plan for as many lunar calibrations as possible during commisioning/start of operation (helps curve fit to stability trending as decay steepest at start of mission). • Ensure the space view is: • Large enough to view the full moon • Where possible, optimise position of space view (simulations ongoing) • Ensure lunar intrusions suitable for calibration are achievable without spacecraft manoeuvres (no operational outage). EUM/RSP/VWG/14/751012 METimage Calibration Slide 24/03/2014