Within the ESA PLATO M3 mission, the Telescope Optical Unit (TOU), i.e. the opto-mechanical unit, is a fully refractive optical system. The 26 TOU Flight Models (FM) to be delivered to the upper level, the PLATO Camera, make it a series production. The first Flight Models production faced many initial challenges from a Product Assurance point of view, mostly related to MAIT activities, while moving forward these challenges decreased. Discrepancies and nonconformities associated with, mainly, but not only, materials and processes, cleanliness and contamination control, safety, qualifications and validations, are the object of this proceeding. Thus, showing that serial production adds one more variable to possible failures, but at the same time, when root causes are corrected and solved, yields less difficulties in subsequent FMs MAIT and final production. Product Assurance, in monitoring the product in failure-proofing aspects, aims at mitigating criticalities and arranging for corrective and preventive actions that allow improving the likelihood of success of the mission.
The ESA M size mission PLATO (PLAnetary Transits and Oscillation of stars) is planned to be launched in the 2026, with the aim of discover exoplanets that will be characterized with unprecedented precision. The optical elements of PLATO are 26 small telescopes, the TOUs (Telescope Optical Units), that using partially overlapping Fields of View will permit instantaneous sky coverage larger than 2100 square degrees. Each TOU has an aperture of 120 mm diameter assured by an internal stop, and it is composed by 6 lenses, the frontal one having an aspherical surface and the last acting as field flattener. The mechanical structure is realized mainly in AlBeMet. We here describe the optical design, summarizing several optical properties (materials, coatings, etc.), and report on nominal performances of the TOU system.
KEYWORDS: Contamination, Manufacturing, Cameras, Space operations, Picture Archiving and Communication System, Optics manufacturing, Materials processing, Telescopes, Inspection, Contamination control
The TOU is the Telescope Optical Unit for the PLATO ESA mission, consisting of the opto-mechanical unit for each of the 26 Cameras of which PLATO is composed. The TOU is currently in the manufacturing, assembly, integration and testing (MAIT) phase for the Proto Flight Model (PFM) and for Flight Models (FMs). We present the design processes as seen from the Product Assurance (PA) point of view: PA aims at monitoring the design and addresses specific issues related to, among others, materials and processes (these shall be suitable for the purpose and for the life-time of the mission), cleanliness and contamination control (to limit the loss of optical performance), safety, monitoring of qualifications/validations. PA supports the project in failure-proofing aspects to mitigate criticalities, e.g. in the elaboration of non-conformances and deviations that can arise during the design and MAIT process, and/or are highlighted during the reviews for manufacturing, test, and delivery of the related hardware. PA ensures early detection of potential problems and risks for the TOU and arranges for corrective actions that aim at improving the likelihood of success of the mission.
PLATO (PLAnetary Transits and Oscillation of stars) is the ESA Medium size dedicated to exo-planets discovery and cataloguing, adopted in the framework of the Cosmic Vision 2015-2025. The PLATO launch is planned in 2026 and the mission will last at least 4 years in the Lagrangian point L2. The primary scientific goal of PLATO is to discover and characterize a large amount of exo-planets hosted by bright nearby stars. The PLATO strategy is to split the collecting area into 24(+2) identical 120 mm aperture diameter fully refractive cameras with partially overlapped Field of View delivering an overall instantaneous sky covered area of about >2100 square degrees. The opto-mechanical sub-system of each camera, namely Telescope Optical Unit (TOU), is basically composed by a 6 lenses fully refractive optical system, presenting one aspheric surface on the front lens, and by a mechanical structure made in AlBeMet. In this paper we will update on the current working status of the TOUs.
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