The ELT Phasing and Diagnostic Station (PDS), is a multi-purpose optomechanical system providing metrology tools to phase the segmented primary mirror of the ELT and hosting the sensors required to verify AO-assisted diffraction limited image quality at the ELT. The purpose of the PDS in the context of the ELT lifecycle is twofold. On one side, during the AIV phase of the ELT, the PDS will be the fundamental tool enabling commissioning of the telescope. On the other hand, during operation, the PDS will provide the essential metrology means to monitor performance and detect and isolate potential failures within the observatory. The project, which is one of the most important internal development endeavors at ESO, passed PDR in mid-2021 and underwent an optical final design review in late 2021, where challenges associated to the schedule were identified and more time was given to optimize the design. The project underwent a restructuring in early 2022 before starting its final design phase which has been successfully completed in 2023. In the same period all procurements concerning critical long lead items have been launched. The present contribution first introduces the project in the context of the ELT construction programme, outlining the project structure and the project management tools employed for planning and progress monitoring. Subsequently, the main system engineering processes used within the project will be described. Finally, we report on the main technical results obtained during the final design phase and the plans for the assembly, integration and test of the system.
The GRAVITY+ project includes the upgrade of the Very Large Telescope Interferometer infrastructure and of the instrument GRAVITY to improve sky coverage, high contrast capabilities, and faint science. The improved sky coverage is obtained via the implementation of one Laser Guide Star (LGS) on each Unit Telescope (UT). This first requires an upgrade of the infrastructure of each of the UTs, which was made over 18 months in 2022 and 2023. The addition of the LGS system requires the implementation of multiple components on several areas of the telescope. These areas include the top ring, the centerpiece, a new platform under the Nasmyth platform, and in the basement. The system includes pointing and aircraft avoidance cameras, the laser projector, laser and electronics cabinets, a heat exchanger, and pumps. As none of the UTs were developed with the infrastructure needed to carry such a system, the same upgrade is made for each of the three UTs. This upgrade consists of a full adaptation of the centerpiece, an upgrade of one of the altitude cable wraps, the installation of a platform under the Nasmyth platform, and the implementation of a cooling circuit running from the basement to the new sub-Nasmyth platform via the azimuth cable wrap. This upgrade requires two missions per telescope, for a total of 30 nights out of operation per telescope. The centerpiece activity also requires the removal of the M1 mirror and cell. The activities were therefore coordinated with the regular recoating of the M1 to minimize the number of nights out of operation. The upgrade required approximately 7.5 staff years of work and 36 missions from Europe to Chile, with around 60 people participating in at least one of the seven missions.
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