Abstract: Nitrogen Dioxide tropospheric (NO2 Tropo):
The Global Ozone Monitoring Experiment (GOME) was launched on April 1995 on board ESA's second European Remote Sensing Satellite (ERS-2).
This instrument can measure a range of atmospheric trace constituents, with the emphasis on global ozone distributions. Furthermore cloud properties and intensities of ultraviolet ... radiation are retrieved. These data are crucial for monitoring the atmospheric composition and the detection of pollutants.

DLR generates the operational GOME/ERS-2 level 1 and level 2 products on behalf ESA. GOME Near Real Time (NRT) products are available three hours after sensing. The NRT service was started in 1997 by setting up the GOME Data Processor at Kiruna station. Nowadays the GOME raw data is transmitted form all ERS-2 receiving stations, including the DLR Antarctic station at O'Higgins, to the DLR for further processing.

Algorithm:
The operational NO2 tropospheric column products are generated using the algorithm GDP (GOME Data Processor) version 4.x integrated into the UPAS (Universal Processor for UV/VIS Atmospheric Spectrometers) processor for generating level 2 trace gas and cloud products.
The total NO2 column is retrieved from GOME solar backscattered measurements in the visible wavelength region using the DOAS method.
An additional algorithm is applied to derive the tropospheric NO2 column: after subtracting the estimated stratospheric component from the total column, the tropospheric NO2 column is determined using an air mass factor based on monthly climatological NO2 profiles from the MOZART-2 model.
A description of the tropospheric NO2 algorithm and validation is given in the reference listed in the GOME-2 documentation pages (http://atmos.caf.dlr.de/gome2/documentation.html).

Acknowledgments:
GDP 4.x for total and tropospheric NO2 retrieval is being developed by scientists from DLR, IUP (Univ. of Bremen) and BIRA and is funded by ESA, EUMETSAT O3M-SAF and national contributions.
Contributors to the NO2 algorithm for GOME and GOME-2 are:
• BIRA: Michel Van Roozendael, Jean-Christopher Lambert, Gaia Pinardi
• DLR: Pieter Valks, Diego Loyola, Nan Hao, Walter Zimmer, Sunil Kumar Emmadi
• IUP: Hendrik Nüss, Andreas Richter