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PLATO is an exoplanet hunting mission from the European Space Agency. It is a medium-class mission, with alaunch foreseen in 2026. Its prime objective is to uncover Earth-sized planets residing in the habitable zone of theirhost star. The payload consists of 26 cameras with a very wide field-of-view. While the operational temperatureof the cameras will be−80◦C, the focal plane of each camera will be integrated with its telescope assembly(bearing the optics) at room temperature. The degradation of the optical quality at ambient, combined with thedetector dark current and with the very high accuracy required from the alignment process bring a number ofinteresting challenges. In the present article, we review the alignment concept, present optical simulations of themeasurements at ambient along with their analysis, and present an error budget for the optical measurements.The derivation of this error budget is easily applicable to all optical measurements to be performed during thealignment, i.e. the definition of the best image plane at the operational temperature and the optical alignmentitself, at room temperature.

A fiber fed, wide beam collimator was developed as a tool to support the Assembly, Integration and Verification (AIV) tasks associated to the integration of the ESA-PLATO telescope unit (TOU) to the focal plane, for the 26 cameras that are going to be assembled at the Centre Spatial de Liege (CSL). This collimator will work as source for the alignment process at ambient temperature, providing a white light beam that must comply with a series of critical requirements, namely high spatial uniformity over an clear aperture of 150 mm (better than 85%), Wavefront Error associated to focus aberration at the level of λ/30 rms and high flux stability over time (2% in 24h). This paper will present the steps taken towards the development, manufacture and integration of this collimator, as well as the tests devised to evaluate requirements compliance.

NOMAD is a spectrometer suite on board ESA’s ExoMars trace gas orbiter due for launch in January 2016. NOMAD consists of two infrared channels and one ultraviolet and visible channel allowing the instrument to perform observations quasi-constantly, by taking nadir measurements at dayside and nightside, and during solar occultations. In this paper, the design, manufacturing, and testing of the two infrared channels are described. We focus upon the optical working principle in these channels, where an echelle grating, used as a diffractive element, is combined with an acousto-optical tunable filter, used as a diffraction order sorter.