First results of GOBELIN project: GOME Breadboard Model characterisation under ambient and vacuum conditions

In-flight monitoring of the optical response of GOME revealed a number of instrumental features that drift or change with time. Some of these observed features are related to outgassing of the instrument in space. In particular outgassing of optical coatings, e.g. the dichroic mirror in COME, can result in a change of the optical characteristics and thereby changing the response of the GOME instrument. Another feature is related to the etalon effect which results in a spectral modulation of the GOME spectra. This modulation varies in time due to a varying contamination layer, most likely ice, on the cooled detectors. Through the GOBELIN project the GOME Breadboard Model has been made available to us by ESA. The GOME Breadboard Model has been fully upgraded to represent the GOME Flight Model and therefore offers a unique opportunity to study the above phenomena under controlled laboratory conditions. First results are presented addressing in particular the effect of outgassing on instrument optical response, including the polarisation response, and the etalon effect.