Using NTT as prototype for VLT: the new NTT control system

A considerable risk is involved in developing a large complex control system, with a long lead time to integration and commissioning. To reduce this risk for VLT, ESO decided in late 1993, to make use of NTT as a testbed for the VLT control system. By upgrading the system using VLT components, e.g. standardized VME I/O boards, VLT common software, and whenever possible VLT application software, these components are tested in real-life conditions well before the start of VLT commissioning. In order to minimize disturbance to scientific operation, the strategy has been to field test subsystem by subsystem during short test periods, and afterwards restoring the original system. Each of these field tests allows an early verification of VLT control architecture and a possibility to correct direction of development. The project culminates in July 1996, when the telescope will be shut down for scientific operation and the complete control system replaced and recommissioned. The new system will then provide a VLT identical high level interface, allowing continued prototyping of operational procedures, scheduling, and science operations. The paper reports on the status of the NTT upgrade project with emphasis on how VLT has and will gain from this prototyping activity.