SCIAMACHY Optical Assembly Thermal Design

SCIAMACHY is a German-Dutch Earth observation instrument which is to fly aboard the Envisat-1 spacecraft It is an 8 channel spectrometer designed to analyse sun light which is scattered on higher layers of the atmosphere. Two of the channels perform measurements in the Infra-Red. For these channels a low and stable temperature level of the instrument is required (< -20 °C) to minimise the impact of IR background radiation on the measurements. Additionally, the system requirement on spectral stability requires the variation in thermal gradient to be very small. This paper presents the flow down from system to thermal requirements and gives a rationale for the Thermal Control Sub-system (TCS) design concept which was established to meet these severe requirements. Added to this are some of the analyses results which support the TCS design. The presented TCS design reflects the PDR status.