Doppler collision has a very important issue in satellite-based navigation systems. Navigation with the Indian Constellation(NavIC) comprises seven operational satellites, among which three are geo-stationary (GEO) sa...Doppler collision has a very important issue in satellite-based navigation systems. Navigation with the Indian Constellation(NavIC) comprises seven operational satellites, among which three are geo-stationary (GEO) satellites, and the rest aregeosynchronous satellites. Due to the ’small line of sight velocities’ of GEO satellites, estimated ranges suffer from theunique challenge of Doppler collision (DC). In this study, we present an analysis of DC events in both static and dynamicconditions, particularly in aerospace applications.We utilize experimental data acquired from the Indian Regional NavigationSatellite System (IRNSS)-GPS-Satellite Based Augmentation System (SBAS) (IGS) receiver located at a low altitude stationto develop algorithms for the prediction, avoidance, and mitigation of DC events. The prediction of DC is based on themovingaverage method.We have devised an efficient algorithm to avoid the occurrence of DC, considering all possible combinationsof IRNSS GEO satellites. Additionally, we perform the mitigation of DC using a proposed hybrid approach that involves boththe space segment and user segment. The approach is based on repositioning the IRNSS 1C satellite and varying the loopbandwidth of the Delay Locked Loop (DLL). With the implementation of this proposed hybrid approach, the time durationof DC is reduced by 59.16% in static conditions and 16% in dynamic conditions.展开更多
One of the significant features that makes Indian Regional Navigation Satellite System(IRNSS)distinct from most of the other satellite navigation systems is the use of S band signal along with the L-band signals.The f...One of the significant features that makes Indian Regional Navigation Satellite System(IRNSS)distinct from most of the other satellite navigation systems is the use of S band signal along with the L-band signals.The fact that S-band signals experience lesser ionospheric delays and therefore lesser ionospheric gradients than L-band signals is of great advantage,more-so in ionospheric storm conditions.The advantage of using IRNSS S-band signal under ionospheric storm conditions for Ground Based Augmentation System(GBAS)applications is investigated in this paper.The analysis is carried out by computing a GBAS parameter namely sigma-vertical-ionospheric-gradient(σvig)using data from low-latitude stations in Hyderabad,India(17.3850°N,78.4867°E)under both quiet and storm ionospheric conditions and then estimating vertical protection levels(VPLs).It is observed that even in storm conditions,σvig is only 5.08 mm/km with S1 as against 22.80 mm/km due to L5.Also,the VPLs are 0.65 m less than those with L5 and are well within the alert limits.This work carries significance in view of GBAS being planned at several low-latitude airports.展开更多
文摘Doppler collision has a very important issue in satellite-based navigation systems. Navigation with the Indian Constellation(NavIC) comprises seven operational satellites, among which three are geo-stationary (GEO) satellites, and the rest aregeosynchronous satellites. Due to the ’small line of sight velocities’ of GEO satellites, estimated ranges suffer from theunique challenge of Doppler collision (DC). In this study, we present an analysis of DC events in both static and dynamicconditions, particularly in aerospace applications.We utilize experimental data acquired from the Indian Regional NavigationSatellite System (IRNSS)-GPS-Satellite Based Augmentation System (SBAS) (IGS) receiver located at a low altitude stationto develop algorithms for the prediction, avoidance, and mitigation of DC events. The prediction of DC is based on themovingaverage method.We have devised an efficient algorithm to avoid the occurrence of DC, considering all possible combinationsof IRNSS GEO satellites. Additionally, we perform the mitigation of DC using a proposed hybrid approach that involves boththe space segment and user segment. The approach is based on repositioning the IRNSS 1C satellite and varying the loopbandwidth of the Delay Locked Loop (DLL). With the implementation of this proposed hybrid approach, the time durationof DC is reduced by 59.16% in static conditions and 16% in dynamic conditions.
基金the project sponsored by Space Application Centre(SAC),Indian Space Research Organization(ISRO),Ahmedabad,vide sanction letter dated 23 Jan 2017(Project ID.NGP-11),under NAVICGAGAN Utilization programme.
文摘One of the significant features that makes Indian Regional Navigation Satellite System(IRNSS)distinct from most of the other satellite navigation systems is the use of S band signal along with the L-band signals.The fact that S-band signals experience lesser ionospheric delays and therefore lesser ionospheric gradients than L-band signals is of great advantage,more-so in ionospheric storm conditions.The advantage of using IRNSS S-band signal under ionospheric storm conditions for Ground Based Augmentation System(GBAS)applications is investigated in this paper.The analysis is carried out by computing a GBAS parameter namely sigma-vertical-ionospheric-gradient(σvig)using data from low-latitude stations in Hyderabad,India(17.3850°N,78.4867°E)under both quiet and storm ionospheric conditions and then estimating vertical protection levels(VPLs).It is observed that even in storm conditions,σvig is only 5.08 mm/km with S1 as against 22.80 mm/km due to L5.Also,the VPLs are 0.65 m less than those with L5 and are well within the alert limits.This work carries significance in view of GBAS being planned at several low-latitude airports.
