MICADO is the Multi-AO Imaging Camera for Deep Observations, a first light instrument for the Extremely Large Telescope (ELT). The instrument will be assisted by a Single-Conjugate Adaptive Optics (SCAO) system and the Multiconjugate adaptive Optics Relay For ELT Observations (MORFEO). MICADO can operate in the so-called standalone mode in the absence of MORFEO with the SCAO correction alone. The Relay Optics (RO), is the optical system relaying the ELT focal plane to an appropriate position inside the MICADO cryostat for that SCAO-only stand-alone observing mode. After successfully passing the Final Design Review (FDR), the manufacturing of the RO is in full swing. We present here the current status of the ongoing assembly, integration and verification campaign (AIV), together with its upcoming challenges. The RO consists of an optical bench made of carbon fiber reinforced plastic (CFRP), an optical assembly made of three flat, motorized tip-tilt-piston mirrors (M1, M5 and M6) and three powered mirrors (M2, M3 and M4) of up to ~500 mm in diameter, the MICADO calibration assembly (MCA) including its deployable unit with a flat mirror (MDU) and a cover to protect all opto-mechanical components on top of the bench. The fabrication of the mirrors has started, while the machining of the mirror mounts is well ahead. The optical bench, as well as all other CFRP parts have been ordered and the manufacturing is completed. In order to get optimum performance and minimal wavefront error (WFE), the mirrors are tested in their mounts before carrying out the final polishing operations. Therefore, all mirror mounts are scheduled to be delivered to the mirror vendor QED Optics by the end of 2024.
MATISSE (Multi AperTure mid-Infrared SpectroScopic Experiment) is the spectro-interferometer for the VLTI of the European Southern Observatory (ESO), operating in the L-, M- and N- spectral bands, and combining up to four beams from the unit or the auxiliary telescopes (UTs or ATs). MATISSE will offer new breakthroughs in the study of circumstellar environments by allowing the mapping of the material distribution, the gas and essentially the dust. The instrument consists in a warm optical system (WOP) accepting four beams from the VLTI and relaying them after a spectral splitting to cold optical benches (COB) located in two separate cryostats, one in L-M- band, and one in N-band. The test plan of the complete instrument has been conducted at the Observatoire de la Côte d’Azur in order to confirm the compliance of the performance with the high-level requirements. MATISSE has successfully passed the Preliminary Acceptance in Europe the 12th September 2017. Following this result, ESO gave approval for the instrument to be shipped to Paranal. The Alignment, Integration and Verification phase was conducted until end of February 2018, at the end of which first observations on sky have been performed to test the operations with the VLTI and to obtain first stellar light. The two first runs of the commissioning followed, respectively in March and in May 2018. It has the goal to optimize the MATISSE-VLTI communication, the acquisition procedures and the interface parameters. The observations were performed on bright L-M- and N- stars, with four ATs located on short baselines and UTs. The limit magnitudes will be deduced.
This paper reports on the performance of the instrument measured in laboratory (results of test plan in Nice and AIV in Paranal) in terms of spectral coverage, dispersion laws and spectral resolutions, and transfer function analysis: instrumental contrast, visibility accuracy, accuracy of the differential phase, of the closure-phase and of the differential visibility. It also provides results of the first tests on sky and the planning of the on-going commissioning.
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