Current integrity concepts such as the GIC (Galileo Integrity Concept) and the SBAS integrity concept are based on integrity indicators that are computed exclusively on ground, uplink to the satellites from the Up-Link Stations (ULS) and broadcast from the satellites as originally computed in the ground segment. This paper presents two new concepts based on the possibility of intercepting the integrity information inside the satellite, the "Satellite autonomous on-board orbit monitoring" and the "Satellite autonomous on-board clock monitoring" concepts, which could be traced univocally to non-existing Space Segment functionalities and which would be in position of: • Accessing to local information, not available on ground, which could be used to detect the existence of non-nominal Signal-In-Space (SIS). Such local information includes clock environment, other local clocks, inertial measurement units, satellite thrusters control information or Clock monitoring & Control Unit (CMCU) phase noise observables. • Detecting non-nominal SIS sooner than with the current baseline, improving the time-to-alert (TTA). • Potentially using inter-satellite links observables, which implies range and doppler measurements not affected by atmospheric delays and ground local degradation (including multipath and interference). Cleaner measurements could permit to define sharper barriers or making the Signal In Space Monitoring Accuracy compatible with lower a-priori probability of non-nominal SIS. • Adding independent barriers for the detection of hazardously misleading SIS information. The new satellite on-board integrity monitoring algorithms will be described. Then, the results of the experimentation campaign, carried out with synthetic data generated with simulation tools defined and implemented by GMV and INRIM, will be presented to demonstrate the performance of the new satellite on-board monitoring algorithms. Furthermore, an introduction of 'on board clock ensemble' will be made. This clock ensemble shall offer very robust solutions, high reliability and autonomous integrity monitoring and autonomous redundancy. Since the switch-over of defective or unstable clocks of the ensemble could be made without upload of new clock model, this solution will keep the satellite operational in any conditions of clocks anomalies. Finally, the experimentation results will be to assess the capability of the new satellite autonomous integrity concepts to diminish the non-nominal Signal-In-Space "a priori" probability and to reduce the TTA; resulting as a consequence on a increase of service integrity availability.
Satellite Autonomous Integrity Monitoring (SAIM) for GNSS systems / Rodríguez, I.; García, C.; Catalán, C.; Mozo, Á.; Tavella, Patrizia; Galleani, L.; Rochat, P.; Wang, Q.; Amarillo, F.. - 3:(2009), pp. 1644-1656. (Intervento presentato al convegno ION GNSS 2009 tenutosi a Savannah, GA nel 22-25 September 2009).
Satellite Autonomous Integrity Monitoring (SAIM) for GNSS systems
TAVELLA, PATRIZIA;
2009
Abstract
Current integrity concepts such as the GIC (Galileo Integrity Concept) and the SBAS integrity concept are based on integrity indicators that are computed exclusively on ground, uplink to the satellites from the Up-Link Stations (ULS) and broadcast from the satellites as originally computed in the ground segment. This paper presents two new concepts based on the possibility of intercepting the integrity information inside the satellite, the "Satellite autonomous on-board orbit monitoring" and the "Satellite autonomous on-board clock monitoring" concepts, which could be traced univocally to non-existing Space Segment functionalities and which would be in position of: • Accessing to local information, not available on ground, which could be used to detect the existence of non-nominal Signal-In-Space (SIS). Such local information includes clock environment, other local clocks, inertial measurement units, satellite thrusters control information or Clock monitoring & Control Unit (CMCU) phase noise observables. • Detecting non-nominal SIS sooner than with the current baseline, improving the time-to-alert (TTA). • Potentially using inter-satellite links observables, which implies range and doppler measurements not affected by atmospheric delays and ground local degradation (including multipath and interference). Cleaner measurements could permit to define sharper barriers or making the Signal In Space Monitoring Accuracy compatible with lower a-priori probability of non-nominal SIS. • Adding independent barriers for the detection of hazardously misleading SIS information. The new satellite on-board integrity monitoring algorithms will be described. Then, the results of the experimentation campaign, carried out with synthetic data generated with simulation tools defined and implemented by GMV and INRIM, will be presented to demonstrate the performance of the new satellite on-board monitoring algorithms. Furthermore, an introduction of 'on board clock ensemble' will be made. This clock ensemble shall offer very robust solutions, high reliability and autonomous integrity monitoring and autonomous redundancy. Since the switch-over of defective or unstable clocks of the ensemble could be made without upload of new clock model, this solution will keep the satellite operational in any conditions of clocks anomalies. Finally, the experimentation results will be to assess the capability of the new satellite autonomous integrity concepts to diminish the non-nominal Signal-In-Space "a priori" probability and to reduce the TTA; resulting as a consequence on a increase of service integrity availability.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
