  The Ring Imaging Cherenkov detector is crucial for the identification of
charged particles in the NA62 experiment at the CERN SPS. The detector
commissioning was completed in 2016 by the precise alignment of mirrors using
reconstructed tracks. The alignment procedure and measurement of the basic
performance are described. Ring radius resolution, ring centre resolution,
single hit resolution and mean number of hits per ring are evaluated for
positron tracks. The contribution of the residual mirror misalignment to the
performance is calculated.
