Envisat: Kalibrierung MERIS-Spektrometer und Validierung der geophysikalischen Datenprodukte

• Research unit: SER
• Project number: 3600.308 Envisat MERIS

Key words (German)

ESA, ENVISAT, Erdbeobachtung, MERIS, Uni ZH, RSL

Short description (German)

Kalibration und Validation des MERIS-Spektrometers durch Ausmessung von bestimmten Bodenzielflächen in unterschiedlichen Vegetationszonen mit terrestrischen und flugzeuggestützten Instrumenten (Sonnenphotometer, Spektralradiometer). Quervergleiche durch den Einsatz unterschiedlicher Messmethoden.

Project aims (German)

- absolute Kalibration über bekannten Bodenflächen
- Abgleichung mit MODIS-Daten (inkl. Atmosphärenkorrektur)
- Überprüfung der Extrapolation auf andere Bodenflächen
- Erstellen eines Validierungshandbuches zur Qualitätssicherung von Daten

Abstract (English)

A vicarious calibration experiment of MERIS, imaging spectrometer on ESA's ENVISAT, was performed. The purpose of this experiment was the acquisition of in-situ measurements of surface and atmospheric conditions over a bright, uniform target. These data were then correlated with the MERIS TOA radiances (Level 1b product), to determine the in-flight radiometric response of the on-orbit sensor. The in-situ estimations of top-of-atmosphere radiances lie within less than 6% of the MERIS measurements, except for band 760 nm and band 900 nm. The absolute uncertainty of the experiment is estimated to be less than 3.36%. No recommendation to update the MERIS calibation may be given.

Transfer and application (English)

The reported uncertainties achieved with this calibration are in the range of the MERIS pre-launch calibration and confirm the excellent performance of MERIS.

This calibration activity has raised significant interest at ESA level, in particular with the quality assurance group of MERIS.

Based on the experience gained in this project, we are about to propose a continuation of the project, jointly with CNES (F), TNO-TPD (NL), EUMETSAT (D), and The Swiss Embassy in Libya in a very large and spectrally homgeneous area (e.g. Erg Murzuk (CNES site Libya), Algerian Sahara (DLR site), Dasht-e Kevir (Iran), Chott el Cherid (Tunisia)).