  The Square Kilometre Array (SKA, https://skatelescope.org) will be the
world's largest radio telescope. SKA Science Data Challenges will be regularly
issued to the community as part of the science preparatory activities. The
purpose of these challenges is to inform the development of the data reduction
workflows, to allow the science community to get familiar with the standard
products the SKA will deliver, and optimise their analyses to extract science
from them. These challenges may consist of real data from currently operating
radio facilities or of simulated SKA data. The purpose of this document is to
provide information on how the SKA Science data challenge #1 (SDC1) has been
produced and to set the challenge for the community. For more information on
how to take part in the challenge and to download the data see
https://astronomers.skatelescope.org/ska-science-data-challenge-1/
