SNOS: automatic optimal observations scheduling for sensor networks
Creators: name:  N. FARACO 
name:   G. PURPURA 
name:   P. DI LIZIA 
name:   M. MASSARI 
Publisher: name: Proceedings of  the 9th European Conference for Aerospace Sciences. Lille, France, 27 June - 1 July, 2022
Year: 2022
Subjects: SPACE DEBRIS
OBSERVATION
ORBIT DETERMINATION
ACTIVE DEBRIS REMOVAL

description: Space Surveillance and Tracking (SST) is growing more and more important in the Space operations and mission analysis field, given how much the crowded environment building up near Earth can hamper them. Italy is involved in SST operations, collaborating with partners both within and outside the EU. The Italian Space Operation Centre (ISOC) has recently upgraded its systems to the ISOC 2.0 Suite, an integrated web-based platform providing multiple functions and services in the SST/SSA domain. The present work describes its sensor tasking module, called SNOS (Sensors Network Optimal Scheduler), developed thanks to a collaboration involving the Italian Air Force, the Leonardo Company and Politecnico di Milano. After the definition of the software architecture, its prototype version has been developed in Python and then translated to C++ language to grant the highest performances in the operational environment. Given the list of available sensors together with their characteristics, the time window in which the observations must be scheduled and the catalogue of objects to be observed, SNOS is able to generate a user specified number of schedules, optimized both in terms of catalogue coverage and expected quality of the measurements. The results are provided to the sensor operation authority as a JSON file conveying all the information needed for the correct execution of the task and as a Tracking Data Message (TDM), which is the Consultative Committee for Space Data Systems (CCSDS) standard for this kind of operations. SNOS can handle optical sensors as well as mono- or bi-static radar and laser sensors. The process starts from the analysis of Two Line Elements (TLE) or Orbit Ephemeris Message (OEM) representing the state of the catalogued objects to identify the visible passes, i.e. the portions of their orbits which are visible from any of the sensors of the network. These are subdivided based on the priority assigned to the related object and conflicting situations are identified, such as the ones in which multiple passes from different objects are simultaneously visible by the same sensor. The candidate solutions are then gradually built by selecting passes (or portions of them) with a heuristic optimization approach. The generated schedules are assigned a score based on the catalogue coverage and the expected quality of the measurements, which weights factors such as the elevation of the object, the distance from the observer, and the duration of the pass. The scheduler also grants the possibility to modify an already ongoing schedule to allocate tasks for unforeseen necessities highlighted by the sensor authority, while still retaining the optimality of the solution. Finally, SNOS can compute the necessary sensor pointing sequence for different kind of tasks, namely tracking tasks and various survey modes of practical interest, such as the one for the surveillance of the GEO belt and the ones designed for the identification of new debris through the inspection of areas along the orbit of an object which is expected to have suffered fragmentation. The SNOS software is currently successfully employed to run the network managed by the ISOC centre.