Satellite Orbit Propagation Using AIS Data Validation
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Solution Overview
Problem
Conventional satellite orbit propagators face challenges in acquiring observation data when GPS receivers malfunction or GPS signal reception rates decrease, limiting their ability to determine satellite positions and velocities accurately.
Innovation Solution
The proposed solution involves using ship automatic identification system (AIS) data, which is acquired, validated, and converted into an inertial coordinate system to estimate satellite positions and velocities, even when GPS data is unreliable, by implementing a method that includes circular dispersion and number of ships as validation criteria.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If GPS receiver is used for satellite orbit propagation, then measurement precision is improved, but reliability deteriorates when GPS signal reception rate decreases or GPS receiver malfunctions
Solution Approach 1:
The patent introduces AIS data as an intermediary observation source to bridge the gap when GPS data becomes unavailable. The orbit propagator selectively uses AIS data from multiple ships as a mediator to estimate satellite position and velocity, ensuring continuous operation even when GPS reception deteriorates or the receiver malfunctions.
Solution Approach 2:
The system dynamically changes the observation data parameter from GPS satellite signals to AIS ship position data based on signal quality and availability conditions. When GPS measurement precision deteriorates below acceptable thresholds, the system transitions to using AIS data with different measurement parameters (ship positions, velocities, and timing data) to maintain orbit determination capability.
2Reliability
If AIS data is used instead of GPS data, then reliability is improved, but measurement precision deteriorates
Solution Approach 1:
The patent merges data from multiple independent AIS sources (multiple ships) to compensate for the lower precision of individual measurements. By combining observations from multiple ships at different positions and angles, the system achieves sufficient measurement precision while maintaining the reliability advantage of AIS data availability.
Solution Approach 2:
The system collects excessive AIS data from more ships than the minimum required for orbit determination, then applies validation tests to select the most suitable subset. This partial use of available data ensures that even though individual AIS measurements have lower precision, the aggregated and validated data provides reliable orbit estimates.
3Measurement precision
If validation tests with multiple criteria are performed on AIS data, then measurement precision is improved, but device complexity increases
Solution Approach 1:
The patent performs preliminary validation tests on AIS data before using it for orbit propagation. The system pre-establishes selection criteria including circular dispersion thresholds and minimum ship count requirements, then applies these tests in advance to filter and validate AIS data, ensuring only quality data proceeds to the orbit estimation process.
Solution Approach 2:
The validation process is segmented into distinct test stages: circular dispersion calculation, ship count verification, and suitability determination. Each segment handles a specific aspect of data quality assessment independently, making the overall complex validation process more manageable and systematic while improving measurement precision through multi-criteria evaluation.
Data Source
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Figure 2B
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AI summary
The present disclosure relates to a satellite orbit propagator using ship automatic identification information and a control method thereof, including acquiring automatic identification system (AIS) data during a predetermined period of time, performing a validation test on the AIS data acquired during the predetermined period of time, converting the AIS data determined to be suitable through the validation test, from an earth coordinate system into an inertial coordinate system, and estimating a position and a velocity of a satellite by using the AIS data converted into the inertial coordinate system and a predetermined orbit propagator model. According to the present disclosure, there is an advantage in that the orbit can be determined using the AIS data when a satellite-mounted GPS receiver malfunctions or a GPS satellite signal reception rate decreases. In particular, while the precision is lower than that of the existing GPS-based orbit propagator, there is an advantage that it is useful for determining the initial orbit after launching a satellite.