  The VISIONS public survey provides large-scale, multiepoch imaging of five
nearby star-forming regions at subarcsecond resolution in the near-infrared.
All data collected within the program and provided by the European Southern
Observatory (ESO) science archive are processed with a custom end-to-end
pipeline infrastructure to provide science-ready images and source catalogs.
The data reduction environment has been specifically developed for the purpose
of mitigating several shortcomings of the bona fide data products processed
with software provided by the Cambridge Astronomical Survey Unit (CASU), such
as spatially variable astrometric and photometric biases of up to 100 mas and
0.1 mag, respectively. At the same time, the resolution of coadded images is up
to 20% higher compared to the same products from the CASU processing
environment. Most pipeline modules are written in Python and make extensive use
of C extension libraries for numeric computations, thereby simultaneously
providing accessibility, robustness, and high performance. The astrometric
calibration is performed relative to the Gaia reference frame, and fluxes are
calibrated with respect to the source magnitudes provided in the Two Micron All
Sky Survey (2MASS). For bright sources, absolute astrometric errors are
typically on the order of 10 to 15 mas and fluxes are determined with
subpercent precision. Moreover, the calibration with respect to 2MASS
photometry is largely free of color terms. The pipeline produces data that are
compliant with the ESO Phase 3 regulations and furthermore provides curated
source catalogs that are structured similarly to those provided by the 2MASS
survey.
