ENVISAT Calibration and Validation

1. ENVISAT Calibration and Validation Presented by : Guido Levrini & Evert Attema (ESA)

2. CONTENT OF THE PRESENTATION • Calibration and Validation Program Objectives • Objectives of the Commissioning Phase and Product Release • Organisation of the Cal/Val activities • Schedule • Cal/Val Approach • ASAR • MERIS/AATSR • MIPAS/GOMOS/SCIAMACHY • RA-2/MWR, POD • Simulated Products and Product tools • Conclusions

3. CALIBRATION AND VALIDATION PROGRAM OBJECTIVES • Large number of instruments to be calibrated • Extremely large number of Envisat Products to be validated, both: • Level 1b (engineering calibrated parameters, geolocated) • Level 2 (geophysical quantities, geolocated) • Geophysical Products cover • ocean (MSL, wind/wave, chlorophyll/sediments …) • ice (boundaries and volume, sea ice monitoring ...) • atmosphere (ozone, many trace gases, temperature, water vapour ...) • land (vegetation parameters …) • 6 months Commissioning Phase • Systematic release of products for 4.5 years (including Near Real Time for Meteo Users)

4. OBJECTIVES OF THE COMMISSIONING PHASE (1/2) CALIBRATION TEAMS Complete Calibration • Full in-flight calibration and re-characterisation of the instrument. • Complete verification of the L1b processor • tuning of all parameters • regeneration of all L1b Auxiliary products • First upgrade of the Level 1b ground processor(at end of Commissioning Phase) • Routine Calibration operations starts at the end of the Commissioning Phase

5. OBJECTIVES OF THE COMMISSIONING PHASE (2/2) VALIDATION TEAMS: Preliminary Validation • Level 2 Algorithm verification (tuning of all processing parameters, first regeneration of all Level 2 Auxiliary products) • performed, essentially, by the ESL team • carried out on the basis of the: • instrument data • preliminary results of some validation campaigns • At end of the Commissioning Phase: the processor delivers products with a consistent geophysical behaviour • By the Validation Workshop (L+9m): error bar are attached to the geophysical products

6. ORGANISATION: CAL/VAL TEAMS • ASAR Calibration & Validation team • RA-2/MWR Calibration team • RA-2/MWR Validation & Cross-Calibration team (CCVT) • Precise Orbit Determination team (POD) • MERIS Calibration team • MERIS (& AATSR) Validation team (MAVT) • MIPAS Calibration & Algorithm Verification team • GOMOS Calibration & Algorithm Verification team • SCIAMACHY Calibration & Algorithm Verification team • Atmospheric Chemistry Validation team (ACVT) • AATSR Calibration & Algorithm Verification team

7. COMPOSITION OF THE CAL/VAL TEAMS Typical composition of the Calibration and of the Validation teams: • ESA staff • Expert Support Laboratory (ESL) members • Instrument Contractor representative (Cal team) • Selected AO Cal/Val Project representatives (PI) • Representative of the operational processor • One representative of the Val group (in the Cal team) • One representative of the Cal group (in the Val team) • Funding comes mostly from ESA but also from national agencies, EC, etc. • Many players  coordinated approach

8. SCHEDULE

9. PRODUCTS RELEASE: APPROACH • At end of the Commissioning Phase (L+6m): • Level 1b products shall be fully verified and distribution starts to all users • Level 2 products will only be preliminary validated, i.e.: • Complete tuning of all processing parameters • Complete processor functionality verification • Initial distribution to the AO PI’s (science category) starts • By the Validation Workshop (L+9m): • Level 2 products preliminary validation is consolidated, i.e.: • First regeneration of the Level 2 Auxiliary products • Error bars are estimated for all Level 2 products and the achieved level of “validation” is reported in the Product Handbook • Distribution starts to all users • ASAR IMAGE, WAVE, WS products released at end of Commissioning Phase • ASAR AP, GMM products released at the Validation Workshop (L+9m)

10. ASAR • Instrument calibration • Antenna gain correction factor (per beam/mode)  transponders • Antenna pattern re-computation  rain forest, module stepping • Instrument drift monitoring/compensation  transponders, module stepping • Processor Verification and Product Quality Assessment • Wave Cross-Spectra (L1b) and Wave Parameters (L2) product validation •  comparison with buoys and with ERS-2 data, model assimilation

11. MERIS / AATSR • Instrument in-flight calibration • Vicarious calibration  desert sites, clouds, rayleigh scattering over clear water, comparison with simultaneous in-situ measurements • Processor Verification (Level 1b and Level 2) • tuning of processing parameters • re-computation of Auxiliary Products • Water Products Validation  open ocean cruises, coastal water sampling, fixed buoys, comparison with other sensors • Validation of Cloud parameters, Water vapour, Atmospheric corrections, Vegetation parameters via dedicated campaigns and satellite intercomparison AATSR is AO responsibility (activities are coordinated at technical level)

12. MIPAS, GOMOS, SCIAMACHY • Instrument in-flight calibration (including pointing performance and re- characterisation of instrument in-flight performance) • SCIA is AO responsibility (activities are coordinated at technical level) • Processor Verification (Level 1b and Level 2) • tuning of processing parameters • re-computation of Auxiliary Products • Balloons and high altitude aircraft campaigns • Assimilation into models (NWP and CTM models) • Intercomparison with other satellite data • Ground-based measurements (lidars, FTS, spectrometers, radiometers, ozone sondes)

13. RA-2 / MWR - POD • Absolute range calibration (over NW Mediterranean basin) • Absolute sigma zero calibration (via dedicated transponder) • Instrument in-flight calibration (including in-flight re-characterisation of the instrument and optimisation of the on-board tracker settings) • Processor Verification (Level 1b and Level 2) • tuning of processing parameters • re-computation of Auxiliary Products • Cross-calibration with ERS-2, Jason, T/P, GFO • Product Geophysical validation and Product Quality assessment • Assessment of the Quality of the operational orbit by independent expert group (POD). Computation of short-arc best fit orbits in support of Calibration campaigns.

14. CONCLUSION • The approach to the calibration of the Envisat Instruments, to the verification of the on-ground processing chains and to the validation of the Envisat derived geophysical quantities has been presented. • The Agency is committed to deliver the Envisat data to the general user community starting six months after the launch. • The Calibration and Validation activities have been organised such to be able to reach this objective. • The size and the complexity of the mission and the number of geophysical quantities to be validated represent a major challenge to all involved