Search

ispartof: SPACE TELESCOPES AND INSTRUMENTATION 2022: OPTICAL, INFRARED, AND MILLIMETER WAVE vol:12180 ispartof: Conference on Space Telescopes and Instrumentation - Optical, Infrared, and Millimeter Wave location:CANADA, Montreal date:17 Jul - 22 Jul 2022 status: published

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.

PLATO (PLAnetary Transits and Oscillation of stars) is a medium-class space mission part of the ESA Cosmic vision program. Its goal is to find and study extrasolar planetary systems, emphasizing on planets located in habitable zone around solar-like stars. PLATO is equipped with 26 cameras, operating between 500 and 1000nm. The alignment of the focal plane assembly (FPA) with the optical assembly is a time consuming process, to be performed for each of the 26 cameras. An automatized method has been developed to fasten this process. The principle of the alignment is to illuminate the camera with a collimated beam and to vary the position of the FPA to search for the position which minimizes the RMS spot diameter. To reduce the total number of measurements which is performed, the alignment method is done by iteratively searching for the best focus, decreasing at each step the error on the estimated best focus by a factor 2. Because the spot size at focus is similar to the pixel, it would not be possible with this process alone to reach an alignment accuracy of less than several tens of microns. Dithering, achieved by in-plane translation of the focal plane and image recombination, is thus used to increase the sampling of the spot and decrease the error on the merit function.

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.

A new compact spaceborne high-resolution spectrometer developed for the European Space Agency's Venus Express spacecraft is described. It operates in the IR wavelength range of 2.2 to 4.3 microm and measures absorption spectra of minor constituents in the Venusian atmosphere. It uses a novel echelle grating with a groove density of 4 lines/mm in a Littrow configuration in combination with an IR acousto-optic tunable filter for order sorting and an actively cooled HgCdTe focal plane array of 256 by 320 pixels. It is designed to obtain an instrument line profile of 0.2 cm(-1). First results on optical and spectral properties are reported.