KEYWORDS: Equipment, Charge-coupled devices, Fluorescence, Signal detection, Astronomical imaging, Frequency modulation, Fermium, Design and modelling, Light sources and illumination, Data modeling
The FLuorescence EXplorer (FLEX) European Space Agency (ESA) mission with its payload, the FLuORescence Imaging Spectrometer (FLORIS), aims at performing quantitative measurements of the solar induced chlorophyll fluorescence from space, with the purpose of improving the monitoring of the health of Earth vegetation. The retrieval of a faint signal, such as the one from chlorophyll fluorescence, requires very low Stray-Light (SL) levels. The SL reduction in FLORIS implied constraints impacting the design, by means of using low roughness optical components, the integration, through a strict contamination control, but also the data processing with the need of a very accurate correction strategy making use of numerical models well correlated with experimental data, to be acquired during the On Ground Calibration (OGC) activities. In order to assess and validate the correction strategy, an accurate SL characterization has been anticipated during the FLORIS Optical Model Refurbished (OMR) campaign. Different methods, such as out-of-field and out-of-band measurements, have been investigated in order to avoid the detector blooming affecting measurements with high input signals. By combining the results from the different approaches, it has been possible to achieve up to 9-10 decades of explored dynamic range. The model, correlated with measurements, has finally proved to be capable to correct SL with a reduction factor <10, down to a level less than 40% of the required fluorescence error (10% of a fluorescence level of about 2 mW/m2/sr/nm). Additional presentation content can be accessed on the supplemental content page.
Leonardo SpA is leading an Italian Space Industry Team, funded by ASI, collaborating to the ESA mission PLATO program for the development of the 26 telescopes, that will fly on a single platform, aimed to discover, observe and analyze the exoplanets. The mission is based on a challenging telescope design with peculiar optical performance to be assured at very low operative temperature. The “large” number of telescopes is quite unusual for the production of scientific payload; therefore, it has imposed a change with respect the prototypical manufacturing and test approach as standard for a few Flight Models, addressing the implementation of smart and fast methodologies for the aligning and focusing of the telescopes based on simulation of the as-built data. The paper describes that approach.
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.
.We describe the main tasks of the Product Assurance process for the Telescope Optical Unit (TOU) of the ESA PLATO mission, that starts from the design phase and proceeds through all phases, up to the final product, with the aim of improving the likelihood of success of the mission. When dealing with the opto-mechanical components of the TOU, several aspects regarding safety and performance have to be analyzed and tracked. From the PA point of view, we focus in this paper on materials and processes selection that shall be suitable and robust enough for the space environment. Cleanliness and contamination control is needed to overcome loss of optical performance. Validations and qualifications on prototypes is fundamental to assess the reliability of the instrument for its purpose and for the lifetime of the mission.
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