Hosts, Guests and Shadows: Scheduling the SKA Telescopes

The Square Kilometre Array (SKA) will be the world's most advanced radio telescope, designed to explore some of the biggest questions in astronomy today, such as the epoch of re-ionization, the nature of gravity and the origins of cosmic magnetism. The first phase of SKA construction, SKA1, is currently being designed by a large team of experts world-wide. SKA1 comprises two telescopes: a 200-element dish interferometer in South Africa and a 30000-element dipole antenna aperture array in Australia. The planning of observations in the SKA is of particular importance, to ensure the optimal use of the facilities and the maximum science output. In addition to the common data acquisition resources the planning tools must plan the use of the data processing system for each telescope. Because of the data rates involved the data processing forms a fully integrated part of the SKA telescopes, without which they cannot function, so the plan for its use can dictate use of the other resources, even though processing lags behind data taking. Along with the particular requirements of commensal (shared-data) observing and use of multiple parallel execution of sub-arrays, the planning of observing with the SKA1 telescopes presents some unique challenges. In this paper these challenges are described, along with the currently suggested solutions.