GOME Spectral Line Ratio Plots

13/5/95

• One month after the launch of ERS-2, tests are still being performed on the GOME instrument (nominal operations will start in October 1995). Spectral line ratio plots provide further confirmation of the nominal functioning of the instrument.

• These maps do not show total column ozone values.

• The data used are uncalibrated raw data.

• It shows the first complete day (May 13) of atmospheric observation by the GOME instrument.

• The instrument was in nadir viewing mode (not scanning) and the coolers were not switched on.

• The ratio maps show ratio intensities measured by GOME in selected spectral lines.

• The ratio plot using the spectral lines 331 nm and 318 nm is much smoother than the plot of the summation of all pixel readouts of the GOME spectral band II B (the lines 318 and 331 are within this band). The highest intensities in the total intensity plot indicate clouds and the lowest intensities indicate no sunlight.

• The GOME spectral line ratio 331/318 nm (two ozone lines) depends on the total optical path of sunlight at the wavelengths of these lines. Values near unity (coloured blue) indicate night and at the south pole the antarctic winter. A special projection was used to move the poles more into the centre of the plot. Due to the inclination angle (98.2 degrees) of the ERS-2 orbit GOME does not scan the poles (which is possible using a certain scanning mode). The lack of plotting at the poles does not show ozone holes.

• The GOME line ratio 780/665 nm (Near Infra Red / RED) is sensitive to vegetation. High values occur over land masses (coloured red), values less than unity over the sea and values close to unity at night.

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