  The Zwicky Transient Facility (ZTF) is a new robotic time-domain survey
currently in progress using the Palomar 48-inch Schmidt Telescope. ZTF uses a
47 square degree field with a 600 megapixel camera to scan the entire northern
visible sky at rates of ~3760 square degrees/hour to median depths of g ~ 20.8
and r ~ 20.6 mag (AB, 5sigma in 30 sec). We describe the Science Data System
that is housed at IPAC, Caltech. This comprises the data-processing pipelines,
alert production system, data archive, and user interfaces for accessing and
analyzing the products. The realtime pipeline employs a novel
image-differencing algorithm, optimized for the detection of point source
transient events. These events are vetted for reliability using a
machine-learned classifier and combined with contextual information to generate
data-rich alert packets. The packets become available for distribution
typically within 13 minutes (95th percentile) of observation. Detected events
are also linked to generate candidate moving-object tracks using a novel
algorithm. Objects that move fast enough to streak in the individual exposures
are also extracted and vetted. The reconstructed astrometric accuracy per
science image with respect to Gaia is typically 45 to 85 milliarcsec. This is
the RMS per axis on the sky for sources extracted with photometric S/N >= 10.
The derived photometric precision (repeatability) at bright unsaturated fluxes
varies between 8 and 25 millimag. Photometric calibration accuracy with respect
to Pan-STARRS1 is generally better than 2%. The products support a broad range
of scientific applications: fast and young supernovae, rare flux transients,
variable stars, eclipsing binaries, variability from active galactic nuclei,
counterparts to gravitational wave sources, a more complete census of Type Ia
supernovae, and Solar System objects.
