  This paper defines the UK Infra-Red Telescope (UKIRT) Hemisphere Survey (UHS)
and release of the remaining ~12,700 sq.deg of J-band survey data products. The
UHS will provide continuous J and K-band coverage in the northern hemisphere
from a declination of 0 deg to 60 deg by combining the existing Large Area
Survey, Galactic Plane Survey and Galactic Clusters Survey conducted under the
UKIRT Infra-red Deep Sky Survey (UKIDSS) programme with this new additional
area not covered by UKIDSS. The released data includes J-band imaging and
source catalogues over the new area, which, together with UKIDSS, completes the
J-band UHS coverage over the full ~17,900 sq.deg area. 98 per cent of the data
in this release have passed quality control criteria, the remaining 2 per cent
being scheduled for re-observation. The median 5-sigma point source sensitivity
of the released data is 19.6 mag (Vega). The median full width at half-maximum
of the point spread function across the dataset is 0.75 arcsec. In this paper,
we outline the survey management, data acquisition, processing and calibration,
quality control and archiving as well as summarising the characteristics of the
released data products. The data are initially available to a limited
consortium with a world-wide release scheduled for August 2018.
