Data processing: vehicles – navigation – and relative location – Navigation – Employing position determining equipment
Reexamination Certificate
1999-08-12
2001-11-27
Cuchlinski, Jr., William A. (Department: 3661)
Data processing: vehicles, navigation, and relative location
Navigation
Employing position determining equipment
C250S203100, C244S003180
Reexamination Certificate
active
06324475
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention concerns a method for recognizing in a pre-established catalog of stars in the sky some or all of the stars detected by a star sensor, for a processing system using star recognition.
2. Background of the Invention
If recognition is successful, it is possible, for example, to estimate the attitude of the frame of reference of the star sensor or, using additional means, to refine an estimate, from which it is then possible to work back to the attitude of the vehicle, for example an aircraft or a submarine, on which the star sensor is mounted.
Prior art star recognition methods include methods in which:
some stars are selected from the sensed stars, the stars selected in this way being referred to hereinafter as “detected” stars;
the detected stars are combined two by two into “detected doublets”;
“likely doublets” are identified, i.e. doublets of stars from the catalog which are in the vicinity of the detected doublets in a common characterization space;
pairs are created each comprising a star of a likely doublet and a detected star, and
at least one list of such pairs is supplied to the processing system.
One such process is described in the paper “Autonomous Star Tracker Development” by R. W. H. van Bezooijen published in the proceedings of the Automatic Control In Aerospace IFAC Symposium, Tsukuba, Sep. 7, 1992.
SUMMARY OF THE INVENTION
The invention aims to improve the success rate of of prior art recognition methods and to minimize the calculation time.
The present invention achieves this by means of a method as defined hereinabove and characterized in that:
the stars from the catalog are grouped into classes, two stars being considered to belong to the same class if and only if they are coincident or there is a path which links them, a path being a series of likely doublets such that any pair of consecutive doublets of the series has at least one star in common,
lists are established class by class by matching some or all of the stars of a class with detected stars to constitute a list, and
at least one of these lists is selected and supplied to the processing system.
The invention therefore creates a set of subcatalogs such that the stars actually present in the field of view have an infinitesimal chance of being divided between more than one subcatalog, the stars in which have a particularly high chance of having been present in the field of view, those which are too weakly linked having been eliminated by a process of purging.
The method of the invention makes the matches on the basis of very small purged subcatalogs and usually this more than adequately compensates the increase in the computation time caused by the multiplicity of subcatalogs.
The invention also consists in a matching method such that, for equivalent performance of the star sensor, the recognition success rate is greatly improved compared to prior art methods.
REFERENCES:
patent: 5508932 (1996-04-01), Achkar et al.
Groth, E.J., “A Pattern-Matching Algorithm for Two-Dimensional Coordinate Lists”, Astronomical Journal, May 1986, USA, vol. 91, No. 5, ISSN 0004-6256, pp. 1244-1248, XP002044901.*
Scholl, M.S., “Six-Feature Star-Pattern Identification Algorithm”, Applied Optics, vol. 33, No. 20, Jul. 10, 1994, pp. 4459-4464, XP000455186.*
“Autonomous Star Tracker Development”, R.W.H. van Bezooijen, Proceedings of the Automatic Control In Aerospace IFAC Symposium, pp. 513-518, Tsukuba, Sep. 7, 1992.
Centre National d'Etudes Spatiales
Cuchlinski Jr. William A.
Lerner David Littenberg Krumholz & Mentlik LLP
Pipala Edward
LandOfFree
Method for identifying in a pre-established catalogue stars... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Method for identifying in a pre-established catalogue stars..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Method for identifying in a pre-established catalogue stars... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2590296