A typical GOME orbit had duration of about 100 minutes. Half of that time was spent in the night side of the Earth, when GOME carried out sequences of calibration measurements, i.e. dark current and LED measurements (pixel-to-pixel gain).
Once a day, solar irradiance measurements were carried out when the satellite crossed the terminator in the North polar region coming from the night side. A mean solar spectrum was constructed from the series of measurements during full disc solar viewing.