  The $K^+\rightarrow \pi^+ \nu \bar \nu$ decay is theoretically one of the
cleanest meson decays and so a good place to look for indirect effects of new
physics complementary to LHC searches. The NA62 experiment at CERN is designed
to measure the branching ratio of this decay with 10\% precision. NA62 was
commissioned in October 2014, took data in pilot runs in 2014 and 2015. The
NA62 experimental setup is illustrated and data quality is reported.
