Ground segment for ERS-2 GOME sensor at the German D-PAF

Abstract

The Global Ozone Monitoring Experiment (GOME), launched on April 21st 1995 on board the second European Remote Sensing Satellite (ERS-2), is designed to measure a range of atmospheric trace constituents, with particular emphasis on global ozone distributions. The German Remote Sensing Data Centre (DFD) plays a major role in the design, implementation and operation of the GOME Data Processor (GDP), the ground segment for the GOME sensor. Major components of the GDP are the complete GOME data archive, the earthshine spectra calibration step, the total ozone column retrieval process, and the integration into the D-PAF Data Management System. Raw GOME data are converted into calibrated radiances during the Level 0-to-1 processing by the application of a series of calibration algorithms. Calibration parameters are calculated from in-flight observations of darkness, calibration lamp, internal LED and sun measurements. Total columns of ozone and other trace gases are derived during the Level 1-to-2 processing using three main algorithms. The Initial Cloud Fitting (ICFA) determines the fractional cloud cover of the pixel scene using measurements close to and within the O 2 A-band around 760 nm. The Differential Optical Absorption Spectroscopy (DOAS) algorithm retrieves effective slant column amounts of atmospheric trace gases from spectral data in the UV and visible regions. The third algorithm calculates appropriate Air Mass Factors (AMFs), by which the slant columns are divided to yield geometry-independent vertical column amounts. In July 1996 the GDP became fully operational, with derived earthshine spectra and total ozone columns generated on a routine basis.