SPHERE-IRDIS assembly, integration and testing: from bits and metal to a planet-hunting machine

SPHERE, a second-generation instrument for the VLT, is currently under performance validation before shipping to Chile. The IRDIS sub-system, an Infra-Red Dual-Imager and Spectrograph, was integrated on the SPHERE bench last December, and this paper tells the story of the 12 months preceding this milestone: the Assembly, integration and Tests (AIT) performed at Laboratoire d'Astrophysique de Marseille (LAM). Key points of the AIT strategy are then presented, and the successes and failures---human, technical, and managerial---of this adventure are discussed. We also report on the excellent optical quality achieved, paramount to guarantee ultimate performance of the SPHERE instrument, thanks to high-quality optical manufacture and a successfully applied alignment strategy.