  We describe a versatile pipeline for processing the data collected by the
Ultra-Violet Imaging Telescope (UVIT) on board Indian Multi-wavelength
astronomical satellite AstroSat.The UVIT instrument carries out simultaneous
astronomical imaging through selected filters / gratings in Far-Ultra-Violet
(FUV), Near-Ultra-Violet & visible (VIS) bands of the targeted circular sky
field (~ 0.5 deg dia). This pipeline converts the data (Level-1) emanating from
UVIT in their raw primitive format supplemented by inputs from the spacecraft
sub-systems into UV sky images (& slitless grating spectra) and associated
products readily usable by astronomers (Level-2). The primary products include
maps of Intensity (rate of photon arrival), error on Intensity and effective
Exposure. The pipeline is open source, extensively user configurable with many
selectable parameters and its execution is fully automated. The key ingredients
of the pipeline includes - extraction of drift in pointing of the spacecraft,
and disturbances in pointing due to internal movements; application of various
corrections to measured position in the detector for each photon - e.g.
differential pointing with respect to a reference frame for shift and add
operation, systematic effects and artifacts in the optics of the telescopes and
detectors, exposure tracking on the sky, alignment of sky products from
multi-episode exposures to generate a consolidated set and astrometry. Detailed
logs of operations and intermediate products for every processing stage are
accessible via user selectable options. While large number of selectable
parameters are available for the user, a well characterized standard default
set is used for executing this pipeline at the Payload Operation Centre (POC)
for UVIT and selected products are archived and disseminated by the Indian
Space Research Organization (ISRO) through its ISSDC portal.
