ENVISAT Calibration and Validation

CONTENTS 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

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)

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

Routine Calibration operations starts at the end of the Commissioning Phase

Level 2 Algorithm verification (tuning of all processing parameters, firstregeneration 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 witha consistent geophysical behaviour

By the Validation Workshop (L+9m): error bar are attached to thegeophysical products

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

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

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)

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

Vicarious calibration

tuning of processing parameters

re-computation of Auxiliary Products

Water Products Validation

open ocean cruises, coastal water sampling,

Validation of Cloud parameters, Water vapour, Atmospheric corrections,

Instrument in-flight calibration

SCIA is AO responsibility (activities are coordinated at technical level)

Instrument in-flight calibration (including pointing performance and re-

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)

Absolute sigma zero calibration (via dedicated transponder)

Instrument in-flight calibration (including in-flight re-characterisation of theinstrument 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

Absolute range calibration (over NW Mediterranean basin)

The approach to the calibration of the Envisat Instruments, to theverification of the on-ground processing chains and to the validation ofthe Envisat derived geophysical quantities has been presented.

The Agency is committed to deliver the Envisat data to the general usercommunity starting six months after the launch.

The Calibration and Validation activities have been organised such to beable to reach this objective.

The size and the complexity of the mission and the number ofgeophysical quantities to be validated represent a major challenge to allinvolved

Keywords: ESA European Space Agency - Agence spatiale europeenne, observation de la terre, earth observation, satellite remote sensing, teledetection, geophysique, altimetrie, radar, chimique atmospherique, geophysics, altimetry, radar, atmospheric chemistry