LEONARDO SpA is leading an Italian Space Industry Team, funded by ASI, collaborating to the ESA mission PLATO (PLAnetary Transits and Oscillation of stars). Its aim is the study of extrasolar planetary systems, with a focus on the discovery of exo-planets hosted by bright, nearby stars. PLATO is composed by 26 fully dioptric designed cameras, each composed of a telescope optical unit (TOU) and a focal plane array (FPA). The FPA is integrated with the TOU at ambient temperature by other Partners of the PLATO CAM-Team, although we determine the best image plane (BIP) of each TOU during test at cryo-vacuum operative conditions. This poses a metrology challenge at TOU manufacturing and testing facilities, with relatively high production rate of the flight units. At cold temperature (-80°C), the orientation and location of the FPA is found out as the BIP, meanwhile at ambient temperature, them are co-registered by using Hartmann masks. The results of this approach show a correspondence between the two analysis methods and give an input for subsequent FPA integration at PLATO CAM level.
Leonardo SpA is leading an Italian Space Industry Team, funded by ASI, collaborating to the ESA mission PLATO program for the realization of the 26 telescopes, which 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 (-80°C). The “large” number of telescopes, produced in high rate (up to 3 telescopes every 2 months), is quite unusual for the production of scientific payloads. It has imposed a change with respect the prototypical manufacturing and test approach, generally a few flight units for space equipment, addressing the implementation of smart and fast methodologies for aligning and focusing each telescope, based on simulation of the peculiar “as-built” data. The opto-mechanical design of the telescope has been optimized to implement an industrial approach for all the manufacturing, assembly, integration and test (MAIT) phases. The number, production rate and the performance results of the flight units so far delivered by Leonardo to the PLATO Consortium, are validating the selected design solutions and all the selected MAIT processes. All the units already delivered present very similar performance, full specs and very close to the theoretical design.
KEYWORDS: Sensors, Modulation transfer functions, Point spread functions, Stars, Telescopes, Detection and tracking algorithms, Cameras, Imaging systems, Exoplanets, Data modeling
The ESA M-size mission PLATO (PLAnetary Transits and Oscillation of stars) is scheduled for launch in 2026. During its 4-year mission orbiting Sun-Earth L2 is aimed at the discovery of exo-planets in nearby star systems. Its 26 cameras will be looking toward deep space, covering a wide area of the sky. Each camera is based on a fully dioptric design. Each camera is composed of a telescope optical unit (TOU) and a focal plane array (FPA). Here the procedure for the characterization of the best imaging plane (BIP) for each TOU is described. Camera manufacturing activity faces the challenge, by design, of locating the BIP for each TOU with high precision (±30 μm). Strict tolerances for accommodating the FPA are in fact in place in terms of inter-distances with respect to the mechanical mounts and tilts. Localization of the BIP will be carried out by mathematical optimization of the enclosed energy performances that will be evaluated at a pre-defined set of 45 field positions. Given the relatively big field-of-view of each camera (1037 deg2 for 24 normal-type and 610 deg2 for the 2 fast-type), this poses a challenge for a single service detector. Instead, an approach based on stitching single views of a smaller active area detector will be carried out. To circumvent performance limitations of detectors, for example, image degradation due to finite-size pixel sampling, dithering will be performed by leveraging a very precise mechanical positioner (hexapods) on which the detector is mounted.
PLATO (PLAnetary Transits and Oscillation of stars) is the ESA M-size mission aimed to the discovery of exo-planets hosted by bright, nearby stars. The launch of PLATO spaceship is scheduled for 2026. It will orbit Sun-Earth L2 for 4 years, looking towards deep space and covering a wide (2132 deg 2 total) area of space. To do so, PLATO will use 26 fully dioptric designed cameras, each composed of a telescope optical unit (TOU) and a focal plane array (FPA). For manufacturing purposes, the FPA will be assembled at ambient temperature, although the best image plane (BIP) of the TOU will be determined during test at cryo-vacuum conditions (-80°C). This poses a metrology challenge at TOU manufacturing and testing and at FPA integration facilities. To this extent, the procedures for the precise characterization and localization of the BIP during TOU tests are presented. In order to circumvent the thermal effects of contraction of the fixture, which in part operate at ambient and in part are cooled at -80°C (operation temperature), the final measurement will be derived by the repeated assessment of the coordinates of a set of fiducials at ambient and operation temperature. Compliance with a strict error budget is achieved by using a combination of sensors (confocal, focusvariation), mounted on very precise and repeatable hexapods. Hartmann masks are also used to co-register the position and orientation of mounting of the FPA between facilities.
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.
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