Star Tracking Convex Hull Area Pattern Matching
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Solution Overview
Problem
Conventional star tracking systems face challenges such as confusion from sunlight and exhaust gas, optical errors, and difficulty in accurately identifying dim stars due to noise and environmental interference, leading to inaccurate attitude determination in navigation systems.
Innovation Solution
The method involves capturing star images, selecting the brightest stars, forming a convex hull to generate a spherical polygon, computing its area and higher order moments, and pattern matching these features against a database to identify stars, enhancing signal-to-noise ratio and improving image centroiding for accurate star identification and attitude determination.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional star tracking systems use standard pattern matching methods, then the system can identify stars, but the system becomes confused by sunlight reflected from the platform and exhaust gas plumes, leading to inaccurate star identification
Solution Approach 1:
The patent segments the star identification process into multiple stages: initial star detection, convex hull formation, area calculation, and hierarchical pattern matching. This segmentation allows the system to progressively filter out false detections caused by sunlight and exhaust gas, improving reliability by breaking down the complex identification task into manageable steps that can eliminate interference at each stage.
Solution Approach 2:
The patent introduces a new dimensional approach by calculating the area of the convex hull formed by detected stars and using this area as an additional feature for pattern matching. This adds a geometric dimension to the identification process beyond simple stellar intensity and position, enabling the system to distinguish true stars from interference sources like sunlight reflections and exhaust gas plumes that do not form valid convex hull patterns.
2Measurement precision
If the system processes all detected stars for pattern matching, then complete star catalog matching is achieved, but processing time and computational complexity increase significantly
Solution Approach 1:
The patent performs preliminary actions by calculating the area of the convex hull formed by detected stars before attempting full pattern matching against the star catalog. This preliminary calculation serves as a fast filter that eliminates many false candidates early in the process, allowing the system to achieve complete star catalog matching with significantly reduced processing time by avoiding exhaustive comparison of all detected stars.
Solution Approach 2:
The patent uses partial action by selecting only the most promising star patterns for complete catalog matching based on the convex hull area criterion. Instead of processing all detected stars equally, the system applies excessive filtering to identify a subset of high-probability candidates, achieving accurate star position measurement with minimal processing time by focusing computational resources on the most likely matches.
3Reliability
If the system uses only brightest stars for tracking, then signal-to-noise ratio is improved, but the system loses ability to determine attitude in certain orientations where bright stars are not visible
Solution Approach 1:
The patent creates a universal star identification system that can handle both bright and dim stars through the convex hull area method. The system maintains high signal-to-noise ratio when bright stars are visible while simultaneously retaining the ability to identify dim stars when bright stars are not visible, achieving multi-functional adaptability across different platform orientations and environmental conditions.
Solution Approach 2:
The patent changes the identification parameter from relying solely on stellar intensity (brightness) to using the geometric parameter of convex hull area. This parameter change enables the system to maintain reliability with bright stars while gaining the versatility to identify dim stars, as the convex hull area remains a valid identification feature regardless of stellar brightness or platform orientation.
4Device complexity
If conventional pattern matching is used without geometric features, then the matching process is simpler, but the system cannot effectively distinguish between stars with similar intensity patterns
Solution Approach 1:
The patent adds a geometric dimension to pattern matching by incorporating the convex hull area of detected stars as a discriminative feature. This new dimension allows the system to distinguish between stars with similar intensity patterns by comparing their spatial geometric properties, significantly improving star discrimination accuracy while maintaining relatively simple matching logic through area comparison.
Data Source
AI summary
A system and method for star tracking includes: capturing an image of stars; detecting and selecting visible stars from the captured image; extracting features from the selected stars by forming a convex hull from the selected stars to generate a spherical polygon; computing the area and higher order moments of the spherical polygon; and pattern matching the extracted feature against a database of star catalog. The pattern matching includes matching the area of the spherical polygon to a plurality of polygon areas stored in the database and when the number of the matching candidates is more than one, matching a next extracted higher order moment with a respective higher order moment in the database, and repeating said matching of the next extracted higher order moment until the number of the matching candidates is equal to one.