Satellite Crosslink Timing Correction for GNSS-Independent PNT
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Solution Overview
Problem
Existing satellite-based positioning and timing systems, such as GPS, are prone to failure during outages and rely on imperfect clocks, leading to disruptions in critical infrastructure and services.
Innovation Solution
A satellite system utilizing crosslinks between satellites and ground monitoring stations with a precision timing source to derive timing corrections, independent of GPS, ensuring accurate time synchronization and transfer without relying on purpose-built PNT systems.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If GPS is used as the primary source of PNT, then positioning and timing accuracy is improved, but system reliability deteriorates during GPS outages
Solution Approach 1:
The patent introduces an auxiliary satellite-based PNT system that acts as an intermediary backup when GPS becomes unavailable. This auxiliary system uses satellites equipped with clocks (though not necessarily atomic clocks) and ground monitoring stations to provide independent PNT capabilities, ensuring continuity of service during GPS outages while maintaining acceptable accuracy levels.
Solution Approach 2:
The system changes the operational parameters by switching from GPS-dependent timing to autonomous satellite clock timing when GPS is unavailable. The auxiliary system accepts degraded timing precision from non-atomic satellite clocks but maintains positioning and timing functionality through cross-links between satellites and ground stations, effectively adapting to different operational conditions.
2Device complexity
If auxiliary PNT systems use imperfect satellite clocks, then device complexity is reduced, but measurement precision deteriorates
Solution Approach 1:
The patent implements feedback mechanisms where ground monitoring stations continuously monitor the performance of satellite clocks in the auxiliary system. Timing corrections are calculated based on observed deviations and fed back to the satellites, allowing the system to maintain improved timing precision despite using simpler, non-atomic clocks on satellites.
Solution Approach 2:
The system replaces the need for complex atomic clocks on satellites with simpler electronic clocks, substituting the mechanical/physical complexity of atomic timekeeping with a more manageable system that relies on ground-based monitoring and correction algorithms to achieve the required timing precision.
3Ease of operation
If auxiliary PNT systems rely on GPS for timing correction, then ease of operation is improved, but reliability deteriorates when GPS is unavailable
Solution Approach 1:
The auxiliary PNT system is designed to be self-sufficient by implementing autonomous timing correction capabilities. Satellites in the auxiliary system use cross-links to exchange timing information and perform self-correction without requiring GPS input, enabling the system to operate independently and reliably during GPS outages while maintaining ease of operation through automated processes.
Data Source
AI summary
For global navigation satellite system (GNSS)-independent operation of auxiliary PNT systems, one or more ground stations of the auxiliary system have access to a non-GNSS source of precision timing. That source and known locations of the ground stations may be used to derive timing corrections to account for imperfect clocks in the satellites for non-purpose-built satellite systems being used for PNT. Crosslinks between satellites and/or propagation of timing correction through other ground stations are used to better control the timing and resulting precession of PNT in the PNT auxiliary system. The timing correction may be provided as a service to end users, other constellations, and/or other satellite operators.