SOXS at NTT: results and lesson learned during the preliminary acceptance in Europe phase from an AIV perspective

Le résumé fourni par la source

The Son Of X-Shooter (SOXS) is a single-object wide-band spectrograph for transient follow-up at the ESO New Technology Telescope (NTT), providing simultaneous spectroscopic coverage from 350 nm to 2000 nm with an average resolving power R ≈ 4500 for a 1′′ slit. In November 2024, SOXS successfully completed its Preliminary Acceptance in Europe (PAE), the final verification milestone before shipment to the observatory, demonstrating compliance with functional, performance, and safety requirements. The PAE verification campaign assessed the instrument at both subsystem and system level. Spectral resolution measurements on the UV-VIS arm confirmed R > 4500 across all four channels, while the NIR echelle spectrograph delivered R ∼ 5250–5950 across its 15 orders. Mechanical flexures induced by telescope rotation were characterised through a dedicated three-component methodology and compensated via Active Flexure Compensators (AFCs) driven by a look-up table integrated into the Instrument Control Software, yielding a residual motion below one tenth of the slit width. The cryogenic system demonstrated stable operation. Detector characterisation, calibration unit validation, pipeline verification against archival X-Shooter data, and end-to-end template execution confirmed full operational readiness. We draw lessons learned on requirement specification and early validation, safety review timing relative to design freeze, proactive engagement with review authorities, flexure mitigation strategies for Nasmyth-focus instruments, management of evolving standards in long-duration projects, and the treatment of documentation as a living process. These lessons provide guidance for future instruments undergoing the ESO acceptance framework.

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