  Over its 13 years of operation (1990 -- 2002), the Faint Object Camera (FOC)
on board the Hubble Space Telescope (HST) observed 26 individual active
galactic nuclei (AGNs) in ultraviolet (UV) imaging polarimetry. However, not
all of the observations have been reduced and analyzed or set within a
standardized framework. We plan to reduce and analyze the AGN observations that
have been neglected in the FOC archives using a consistent, novel, and
open-access reduction pipeline of our own. We then extend the method to the
full AGN sample, thus leading to potential discoveries in the near future. We
developed a new pipeline in Python that will be able to reduce all the FOC
observations in imaging polarimetry in a homogeneous way. Most of the
previously published reduced observations are dispersed throughout the
literature, with the range of different analyses and approaches making it
difficult to fully interpret the FOC AGN sample. By standardizing the method,
we have enabled a coherent comparison among the different observational sets.
In this first paper of a series exploring the full HST/FOC AGN sample, we
present an exhaustively detailed account of how to properly reduce the
observational data. Current progress in data-analysis is implemented in and has
provided state-of-the-art UV polarimetric maps. We compare our new maps to the
benchmark AGN case of NGC~1068 and successfully reproduce the main results
previously published, while pushing the polarimetric exploration of this AGN
futher, thanks to a finer resolution and a higher signal-to-noise ratio (S/N)
than previously reported. We also present, for the first time, an optical
polarimetric map of the radio-loud AGN IC~5063 and we examine the complex
interactions between the AGN outflows and the surrounding interstellar medium
(ISM).
