FORTE: ISON Robotic Telescope Control Software

Space surveillance has a number of important features that make it very different from most of the classical fields of observational astronomy. Among those, we can mention a demand for extremely accurate timing, complex tracking modes, dynamic scheduling, high data acquisition rate, and often unusual telescope setup that may include multiple optical channels working simultaneously. One needs to take all this into account to ensure an adequate telescope control system (TCS) software design.
Since 2011, the International Scientific Optical Network (ISON) project started a transition to the new standard TCS software called FORTE (Facility for Operating Robotic TElescopes) that is now in the course of active development and testing and that should gradually replace the obsolete ISON software throughout the whole network to overcome the numerous design flaws and limitations of the latter.
This new software has Python-based distributed client-server architecture that makes it extremely flexible an scalable to a wide range of sensor apertures and configurations. A tight integration with Apex package for astronomical image analysis helps to automate the complex calibration and maintenance tasks and provides access to stellar catalogs and orbital data. A customizable high-level object-oriented modular approach allows one to easily configure the package for use in some very peculiar sensor configurations, like a new 6-channel 3-mount barrier sensor, in a completely transparent way.
We describe the basic design principles of FORTE and show in detail how it meets these and other requirements of ground-based optical space surveillance.