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.
The Focal Plane Assembly (FPA) in optics is the unit located at the focal plane position of the different optical instruments. Each FPA hosts the detectors on support structures and associated interfaces (I/Fs) as quasi-static mounts which assemble them with the rest of the mechanical parts of the instrument; the electronic I/Fs as the flexi-cables connecting each detector to the Front End Electronics (FEE); and the thermomechanical I/Fs as the Thermal Straps (TS) attaching these devices in order to dissipate their heat. Due to the critical repeatability aspect of the different models (QM, FM, FS) in the space missions, each FPA must be identical with stringent specifications, which includes strict opto-mechanical positioning tolerances. These very demanding metrological requirements only can be reached under a special industrialization of alignment processes and an automatic metrology verification thanks to a high-precision, high-performance non-contact vision dimensional measurement system with micrometric or even better accuracy. After the in-lab conditions assembly activities, a better alignment attending the acquired knowledge and lessons learned of past cases have been used to implement improvements into the alignment of new large FPAs for acceptance testing. The optical metrological performances verification carried out before and after the acceptance test campaign of FPAs has been successfully passed and several Flight Models (FMs) have been assembled by the AIV Team from the Spanish Instituto Nacional de Técnica Aeroespacial (INTA) following ECSS (European Cooperation for Space Standardization) policy, and have been delivered to ESA’s subcontractors for performing the formal acceptance processes at instrument level under increasingly tight schedule constraints.
PLATO (PLAnetary Transits and Oscillation of Starts) is the third medium class mission of ESA devoted to exoplanets detection and partial characterization together to the associated star activity evaluation through its astroseismology. It is consisting on 26 telescopes mounted on the same platform, 24 called ‘normal’ and composed of four full-frame CCDs and 2 ‘fast’ composed of four frame-transfer CCDs mounted on their respective focal plane assemblies (FPAs). For completing the detection chain, they are using their front-end electronics (FEE), being the optics and opto-mechanics of the telescope optical unit (TOU) the last element of the PLATO-CAMs. In the framework of the mission development, the PLATO-CAMs, after their proper alignment and assembly, are required to be calibrated and tested on simulated working conditions. INTA is one of the European institutions (together to IAS and SRON, in France and Netherlands, respectively), in which such telescopes testing and calibration is carried out by simulating the L2 conditions corresponding to the PLATO-CAMs working environment. In this paper, the setup preparation for PLATO-CAM calibration and testing details are reported on, including design, and fabrication of the different elements, all the ground support equipment (GSE) required for the PLATO-CAMs full characterization and performance evaluation. In addition, the results on the first model tested at INTA, the engineering model (EM) are summarized.
The preparation of the different institutes (IAS, SRON and INTA at France, Netherlands and Spain, respectively) for being ready for testing the PLATO (Planetary transits and oscillation of starts) telescopes (PLATO CAMs) under working condition has been a long trip full of requirements updates and needs adaptation. For this ESA mission devoted to the Exoplanets detection and partial characterization together to the associated star activity evaluation through its astroseismology, 26 telescopes are going to be mounted on the same platform. There are 24 identical ‘normal’ and 2 ‘fast’ PLATO CAMs, all formed by four CCDs mounted on the focal plane assembly (FPA), the front end electronics (FEE) used for completing the detection chain, and optics and optomechanics that forms the telescopes optical unit (TOU). After their alignment and integration verification done at CSL, they are sent to the corresponding institute for running at the best focus temperature at which the telescope provides the best image the performance checks required for considering them properly characterized and ready to be installed in their final configuration at OHB. In this paper, a brief summary on the main details of the tests carried out at INTA on the PLATO CAM flight model (FM) number three are reported on. In addition, preliminary results obtained together to the rest of the consortium and related to the telescopes capabilities are included for the particular case of such first flight model tested at INTA.
PLATO (Planetary Transits and Oscillation of Starts) will be used for finding the hugest amount of exoplanets ever found and to characterize them together to the associated star activity evaluation through its astroseismology. For such a purpose, 26 telescopes will be mounted on the same platform: 24 of them, called ‘normal’ and composed of four full-frame CCDs and the last 2, known as ‘fast’ composed of four frame-transfer CCDs. In both cases, CCDs will be installed on their respective focal plane assemblies (FPAs). For completing the detection chain, they are using their front end electronics (FEE), being the optics and opto-mechanics of the telescope optical unit (TOU) the last element of the PLATO CAMs. As a part of the payload development and assembly and integration and test, the PLATO CAMs are required to be calibrated and tested on simulated working conditions. INTA is one of the European institutions (together to IAS and SRON, in France and Netherlands, respectively), in which such telescopes testing and calibration is carried out. As a part of the product assurance activities, a protocol for reaching safe conditions on the telescopes during TVAC testing under any unexpected and dangerous event happed was prepared. In this paper, we are describing the need of the protocol activation for answering to one of the worst events that could be present during a TVAC testing campaign: an unexpected power outage making the vacuum pumps critically fail. The room conditions recovering in a safe way is reported on.
The PLAnetary Transits and Oscillations of stars mission (PLATO) is an ESA M3 mission planned to detecting and characterizing extrasolar planetary systems as Earth-like exoplanets orbiting around the habitable zone of bright solartype stars. PLATO consists of 26 cameras (CAM) mounted on the same instrument platform in order to cover a large field of view (FoV) with the highest possible photon detection statistics. Each PLATO CAM consists of a telescope Optical Unit (TOU), the FPA, and the detector read-out Front End Electronics (FEE). The FPA is the structure located at the focal plane position of the CAM that supports four identical CCDs and the mechanical interface parts to match with the TOU and FEE. Due to the critical repeatability aspect of the mission, each FPAs must be identical with very stringent specifications which includes strict opto-mechanical positioning tolerances. Also the number of FPAs that have to be manufactured, integrated and tested at the same time requires a special space industrialization process and an optimized metrology verification due to the very restrictive design and schedule constraints. In order to solve this challenge a flight-representative QM has been developed in order to validate a manufacturing, assembly, integration and verification (AIV) on-ground processes. As well, an innovative metrology system has being developed for improving the alignment and verification under the tightly AIV requirements before, during and after a proper qualified campaign in a very demanding environment. INTA has adapted into an ISO6 cleanroom facility a high accuracy and vast performance non-contact CNC vision dimensional measuring system, and has developed a Ground Support Equipment (GSE) for a real-time alignment step in order to reach that requirements.
PLATO, PLAnetary Transits and Oscillation of stars, is an ESA mission mainly devoted to survey the Galaxy searching for and characterizing Earth-like exoplanets, and their host stars. This will be achieved using continuous and extremely accurate photometry for both exoplanetary transits and asteroseismology analysis. Current design plans to mount 26 cameras in the same instrument bench in order to cover a large field of view with the highest possible photon statistics. Each PLATO camera consists of the telescope (TOU, Telescope Optical Unit), the focal plane assembly (FPA), and the detector and camera read out electronics (FEE). Four CCDs (Charge Coupled Devices) will be included in each FPA, which implies a really delicate assembly and integration verification (AIV) process due to the stringent scientific requirements breakdown into hard engineering ones (among others, CCDs co-alignment in terms of tip and tilt and roll with respect to the optical axis). In the following lines, the FPA current opto-mechanical design is briefly presented and an integration process conceptual proposal is reported on, discussing the error budgets associated to the main requirements to be verified during FPAs AIV, and the main results obtained during the prototype first AIV round.
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