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Description
Apertif is a phased-array feed system for the Westerbork Synthesis
Radio Telescope (WSRT), providing forty instantaneous beams over 300
MHz of bandwidth. This first data release includes observations in the
first year of survey operations, from 1 July 2019 through 30 June
2020. The data release includes all raw observational data for a total
of 221 observations of 160 independent target fields, covering
approximately one thousand square degrees of sky. A subset of
processed data products, meeting specified quality assessment criteria
as outlined in Adams et al. (2022), are also released. Images and
cubes are released on a per beam basis, and 3374 beams (of 7640
considered) are included in this data release. The processed data
products are only available for the upper 150 MHz of the band over the
range 1280–1430 MHz. The first 12.5 MHz of data are flagged due to
persistent RFI resulting in a nominal bandwidth of 137.5 MHz and
central frequency of 1361.25 MHz. The data products are not
primary-beam corrected, however the primary-beam images are provided
separately that may be used for mosaicking or for correction of
individual images. The raw visibility data are provided as separate
collections for the survey fields, flux calibrator and polarization
calibrator observations. The tables can be joined to identify the
associated calibrators for a target observation. This service queries
the raw visibilities for the survey fields. These are stored on tape
and are not immediately available for download. The data release
documentation should be consulted for up-to-date information on how to
access the data.
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