| Popis: |
In the last decades, the growing in-orbit population of resident objects has become one of the main concerns for space agencies and institutions worldwide, and several initiatives have been promoted to tackle this issue. In the resulting Space Surveillance and Tracking (SST) services, ground-based sensors (optical or radar) are typically used to track orbiting objects. Within this framework, the Italian Space Operation Centre (ISOC) has recently upgraded its systems to the ISOC 2.0 Suite, an integrated platform providing multiple functions and services in the SST domain. It is a web-based platform giving users the ability to connect and use the system both locally and remotely. The software has been designed and implemented in partnership with industry and academia. The present work describes the orbit determination module developed for the ISOC 2.0 Suite thanks to a collaboration involving the Italian Air Force, Leonardo Company and Politecnico di Milano. After the definition of the software architecture, its prototypal version has been developed and then translated to C++ language to be used in the operational environment, guaranteeing the highest performances in terms of computational times. The process starts correlating the observation data reported in Tracking Data Message (TDM) files to objects contained in the catalogue, which can be provided in one of the Consultative Committee for Space Data Systems (CCSDS) formats. The correlation is evaluated according to a statistical correlation index quantifying the probability that a candidate object is related to the input TDM. If the index is above a pre-defined threshold, the object is discarded, otherwise it is added to a list of possible correlated objects. If the process correlates the measurements to a catalogued object, an orbit determination refinement is run, by using either a sequential or a batch filter and exploiting the available ephemerides as first guess. Instead, if the correlation process does not link observation data to any catalogued object, an initial orbit determination (IOD) is performed with the available measurements. If both angular coordinates and slant range are available, a radar IOD is run, which first computes the orbital position for each observation epoch and then matches them to derive the orbital state. If instead only angular coordinates are provided, an optical IOD process is run, which first tries to retrieve the range associated to the observation by means of orbital geometry and dynamics. Then, the orbital state is computed either similarly to the radar IOD process, or by exploiting the range rate derived from the computed range. Finally, the compliance between the determined orbital state and the measurements is tested against the same statistical index as in the correlation process, both for ROD and IOD. The performance of the resulting software is assessed and provided on both synthetic and real data. |
