The efficient automatic planning and scheduling of astronomical observations from space and ground-based observatories has become essential for large astronomical surveys. It facilitates the coordination of multiple instruments and observatories located at different sites and enables a fast reaction to changes of the environmental conditions while maximizing the scientific return.

The main challenge for astronomical planning tools is to maximize the number of observed targets, taking into account available resources, time, and observation constraints. These constraints are mainly related to target visibility, observation cadence, the ephemerides of astronomical events, and the phase of the moon, among others. The resulting observational plans shall fulfill all the constraints and shall be optimal in terms of the telescope time used for science observations, that is to say, minimize the idle time of the instrument, and maximize the scientific return.

In this talk, we will present the STARS library (Scheduling Telescopes as Autonomous Robotic Systems), which provides the tools needed to generate optimal schedules for space and ground-based observatories. It includes the means to define the tasks to be planned, their constraints and the observational resources, the scheduling algorithms based on Artificial Intelligence techniques, and their optimization goals (figures of merit). We also provide a web-based graphical user interface to easily visualize and analyze the generated schedules. The future development plans include, among other things, the ability to generate observation schedules directly from the browser, thus providing a graphical interface throughout the scheduling process.

STARS is being successfully used in several ground and space-based observatories. The CARMENES instrument at the Calar Alto Observatory and the TJO robotic telescope at the Montsec Observatory are already in operation and using the STARS library. Additionally, the library will be employed for the operations of the CTA Observatory, the scheduler of the Ground Observations Program of the PLATO M3-ESA mission, and the planning tool for the ARIEL M4-ESA mission, all of which are currently in development.