VVV DR1: The First Data Release of the Milky Way Bulge and Southern
  Plane from the Near-Infrared ESO Public Survey VISTA Variables in the Via
  Lactea
  The ESO Public Survey VISTA Variables in the Via Lactea (VVV) started in
2010. VVV targets 562 sq. deg in the Galactic bulge and an adjacent plane
region and is expected to run for ~5 years. In this paper we describe the
progress of the survey observations in the first observing season, the
observing strategy and quality of the data obtained. The observations are
carried out on the 4-m VISTA telescope in the ZYJHKs filters. In addition to
the multi-band imaging the variability monitoring campaign in the Ks filter has
started. Data reduction is carried out using the pipeline at the Cambridge
Astronomical Survey Unit. The photometric and astrometric calibration is
performed via the numerous 2MASS sources observed in each pointing. The first
data release contains the aperture photometry and astrometric catalogues for
348 individual pointings in the ZYJHKs filters taken in the 2010 observing
season. The typical image quality is ~0.9-1.0". The stringent photometric and
image quality requirements of the survey are satisfied in 100% of the JHKs
images in the disk area and 90% of the JHKs images in the bulge area. The
completeness in the Z and Y images is 84% in the disk, and 40% in the bulge.
The first season catalogues contain 1.28x10^8 stellar sources in the bulge and
1.68x10^8 in the disk area detected in at least one of the photometric bands.
The combined, multi-band catalogues contain more than 1.63x10^8 stellar
sources. About 10% of these are double detections due to overlapping adjacent
pointings. These overlapping multiple detections are used to characterise the
quality of the data. The images in the JHKs bands extend typically ~4 mag
deeper than 2MASS. The magnitude limit and photometric quality depend strongly
on crowding in the inner Galactic regions. The astrometry for Ks=15-18 mag has
rms ~35-175 mas.
