  The CHaracterizing ExOPlanet Satellite (CHEOPS), to be launched in December
2019, will detect and characterize small size exoplanets via ultra high
precision photometry during transits. CHEOPS is designed as a follow-up
telescope and therefore it will monitor a single target at a time. The
scientific users will retrieve science-ready light curves of the target,
automatically generated by the CHEOPS data reduction pipeline of the Science
Operations Centre. This paper describes how the pipeline processes the series
of raw images and, in particular, how it handles the specificities of CHEOPS
data, such as the rotating field of view, the extended irregular Point Spread
Function, and the data temporal gaps in the context of the strict photometric
requirements of the mission. The current status and performance of the main
processing stages of the pipeline, that is the calibration, correction and
photometry, are presented to allow the users to understand how the
science-ready data have been derived. Finally, the general performance of the
pipeline is illustrated via the processing of representative scientific cases
generated by the mission simulator.
