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The second European Remote-Sensing Satellite (ERS 2) will follow the first one, which was successfully launched in July 1991. GOME is the only new experiment on board of ERS 2, which will be launched in 1994. ERS 2 will fly on a sun synchronous polar orbit in about 785 km with a descending equator crossing time at 10:30 local time. GOME is a nadir-viewing spectrometer which observes solar radiation transmitted through or scattered from the earth atmosphere or the surface. In normal operation mode the scene is scanned across track in 3 periods of 1.5 sec and a backward scan of 1.5 sec. The instantaneous field of view of 2.8 deg x 0.14 deg is swept in this period through a default optical angle of +/- 31 deg, resulting in a ground swath of 960 km. In the ERS-2 orbit a global coverage will be possible every three days. The spectrometer covers a wavelength range from 240 to 790 nm with a spectral resolution of 0.2 to 0.4 nm. This range will be recorded by 4 RETICON diode arrays, simultaneously. Additionally broadband polarization detectors are included. Using the differential optical absorption spectroscopy technique the detection of column densities of several tropospheric and stratospheric trace gases (e.g., ozone, nitrogendioxide, water vapor, oxygen/oxygen dimer, bromine oxide) will be possible without an absolute radiometric calibration. However, an absolute calibration is possible and hence the advantage to switch the instrument in a SBUV mode for comparison with this technique.
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