ELT M4 adaptive unit ready for integration

The ELT M4 is the telescope-facility adaptive unit for the European ELT. Final design and construction were awarded in 2015 to AdOptica, a consortium of Microgate and ADS International; on-site delivery is planned for 2024. The unit is based on a monolithic, structural reference body manufactured by Mersen Boostec. The flat thin mirror, controlled using the contactless voice-coil-motor based technology, is split in 6 segments produced by Safran Reosc. The M4 unit is ready for integration: we report here the results of the construction and component level testing, introducing also the forthcoming integration and system-level tests.