PLATO (PLAnetary Transits and Oscillations of stars)1 is the M3 class ESA mission dedicated to the discovery
and study of extrasolar planetary systems by means of planetary transits detection. PLATO Payload Camera
units are integrated and vibrated at CSL before being TVAC tested for thermal acceptance and performance
verification at 3 different test facilities (SRON, IAS and INTA). 15 of the 26 Flight Cameras were integrated,
tested and delivered to ESA for integration by the Prime between June 2023 and June 2024, with the remaining
flight units to be tested by the end of 2024. In this paper, we provide an overview of our serial testing approach,
some of the associated challenges, key performance results and an up-to-date status on the remaining planned
activities.
PROBA-3 is a mission devoted to the in-orbit demonstration (IOD) of precise formation flying (F2) techniques and technologies for future ESA missions. The mission includes two spacecrafts. One of them will act as an external occulter for scientific observations of the solar corona from the other spacecraft, which will hold the ASPIICS coronagraph instrument, under CSL (Centre Spatial de Liège) responsibility. The ASPIICS instrument on PROBA-3 looks at the solar corona through a refractive telescope, able to select 3 different spectral bands: Fe XIV line @ 530.4nm, He I D3 line @587.7nm, and the white-light spectral band [540;570nm]. The external occulter being located at ~ 150 meters from the instrument entrance, will allow ASPIICS to observe the corona really close to the solar limb, probably closer than any internally or externally occulted coronagraph ever observed. CSL is responsible for the optical design, integration, testing and validation of the complete ASPIICS instrument. The instrument qualification model (QM) underwent a full qualification campaign at CSL, providing confidence and assuring the performances of the coronagraph design. During the year 2021, the flight model (FM) was also successfully integrated and tested at CSL. The calibration performed at INAF during September 2021 was the last step to achieve before the instrument delivery to ESA end of 2021. This paper will present the results of the qualification campaign, the optical performances of the flight instrument and the calibration campaign. Several challenges were faced during these campaigns, amongst which are detailed the alignment of the focal plane, the alignment measurement during environmental testing and setup constraints during the calibration. The successful validation of the instrument and its final acceptance is demonstrated.
In order to characterize and calibrate the Metimage spectro-radiometer instrument response in Solar Spectral Bands, an Optical Ground Support Equipment (OGSE), a sun simulator has been designed and developed at CSL. This Sun Simulator (SUSI) is designed for wavelength ranging from 400 nm to 2300 nm. In order to reach radiance and both spatial and angular homogeneity requirements a specific design allowing mixing up to 4 plasma lamp sources has been designed and implemented. This mixing and homogenizing device is placed at the focal plane of an Off Axis parabolic mirror which will produce an 0.5° full divergence beam over a pupil of 350 mm. First the design and its challenges will be given. Simulation of SUSI performances are then proposed. Finally, experimentally measured performances of the OGSE are presented.
PLATO is an exoplanet hunting mission of the European Space Agency. It is a medium-class mission, with a launch foreseen in 2026. Its prime objective is to uncover Earth-sized planets residing in their habitable zone. The payload consists in 26 cameras with a very wide field of view. These cameras consist in a Telescope Optical Unit, aligned at ambient and characterised at the operational temperature, and a Focal Plane Array bearing the detectors, and delivered after coupling with the Front End Electronics. In this contribution, we report on the alignment of the Engineering Model camera of Plato, i.e., the input metrology, the mechanical alignment of the optical unit with the focal plane array, the test environment and the optical characterisation throughout the process until the integrity check after delivery to the cryo-vacuum testing facility where the camera underwent a thorough performance demonstration. We also give a detailed description of the bolting process and the associated error budget.
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 Liége (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 is an exoplanet hunting mission from the European Space Agency. It is a medium-class mission, with a launch foreseen in 2026. Its prime objective is to uncover Earth-sized planets residing in the habitable zone of their host star. The payload consists of 26 cameras with a very wide field-of-view. While the operational temperature of 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 the detector dark current and with the very high accuracy required from the alignment process bring a number of interesting challenges. In the present article, we review the alignment concept, present optical simulations of the measurements 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 the alignment, i.e. the definition of the best image plane at the operational temperature and the optical alignment itself, at room temperature.
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.
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