Experience with the operation of the European ALMA antennas

The 25 European antennas of ALMA were delivered by ESO to the ALMA project in Chile between April 2011 and September 2013. Their combined time of operation is already significant and allows us to draw conclusions regarding their ability to fulfil the original specification, in terms of both scientific performance and operational availability. In this paper, we will summarize the experience gained during the past five years of operation. We will characterize the performance of the antennas in routine operation and compare with the data obtained during acceptance testing. We will also describe the few technical issues experienced while operating at 5000m and the way in which these were treated during these first years of operation. We will evaluate the effective reliability obtained in service based on field data and draw some conclusions as to the way in which reliability and maintainability aspects were covered during the process which led to the final design of the antenna. We will discuss the smart use of software to handle redundancy in a flexible way and to exclude failed components without affecting overall antenna operability. The use of low-level diagnostics enabled by remote access allows us to shorten the trouble-shooting cycle and to optimise physical interventions on the antennas. Finally, the paper will cover Antenna maintenance manuals edited using an industrial interactive standard. It will be explained why this advanced and innovative concept has not achieved the success that was expected, and why the traditional form is preferred at the ALMA Observatory.