The first and second data releases of the Kilo-Degree Survey
  The Kilo-Degree Survey (KiDS) is an optical wide-field imaging survey carried
out with the VLT Survey Telescope and the OmegaCAM camera. KiDS will image 1500
square degrees in four filters (ugri), and together with its near-infrared
counterpart VIKING will produce deep photometry in nine bands. Designed for
weak lensing shape and photometric redshift measurements, the core science
driver of the survey is mapping the large-scale matter distribution in the
Universe back to a redshift of ~0.5. Secondary science cases are manifold,
covering topics such as galaxy evolution, Milky Way structure, and the
detection of high-redshift clusters and quasars.
  KiDS is an ESO Public Survey and dedicated to serving the astronomical
community with high-quality data products derived from the survey data, as well
as with calibration data. Public data releases will be made on a yearly basis,
the first two of which are presented here. For a total of 148 survey tiles
(~160 sq.deg.) astrometrically and photometrically calibrated, coadded ugri
images have been released, accompanied by weight maps, masks, source lists, and
a multi-band source catalog.
  A dedicated pipeline and data management system based on the Astro-WISE
software system, combined with newly developed masking and source
classification software, is used for the data production of the data products
described here. The achieved data quality and early science projects based on
the data products in the first two data releases are reviewed in order to
validate the survey data. Early scientific results include the detection of
nine high-z QSOs, fifteen candidate strong gravitational lenses, high-quality
photometric redshifts and galaxy structural parameters for hundreds of
thousands of galaxies. (Abridged)
