In the Optical Assembly the incident radiance and irradiance are collected and split according to wavelength and focussed on the detector modules of the two optical channels. The Optical Bench consists of a single aluminium structure in which all elements are mounted. Attached to this aluminium structure are the two Detector Modules. The Optical Assembly Thermal Hardware consists of a thermal radiator and heaters. The thermal radiator is thermally connected to the detector modules via cold-fingers and flex-links. The heaters are attached to the Optical Bench structure and the CCD detectors.
The telescope is of a wide field reflective telecentric configuration. The telescope consists of two spherical aluminium mirrors (103 and 007). Radiation from the Earth is imaged on the entrance slit (008) of the spectrometer. Between the primary and secondary mirror a polarisation scrambler (005) is positioned close to the aperture stop (006) of the telescope. The large Field Of View of 114° is in the plane perpendicular to the plane of drawing. The secondary mirror has a coating to suppress stray light from 500 nm up towards longer wavelengths. The Field Of View in the flight direction is about 1.0°.