Package org.orekit.ssa.collision.shorttermencounter.probability.twod

Class Laas2015

  • All Implemented Interfaces:
    ShortTermEncounter2DPOCMethod
    public class Laas2015
extends AbstractShortTermEncounter2DPOCMethod
    Compute the probability of collision using the method described in : "SERRA, Romain, ARZELIER, Denis, JOLDES, Mioara, et al. Fast and accurate computation of orbital collision probability for short-term encounters. Journal of Guidance, Control, and Dynamics, 2016, vol. 39, no 5, p. 1009-1021.".

    It is one of the recommended methods to use.

    It assumes :

    • Short encounter leading to a linear relative motion.
    • Spherical collision object.
    • Uncorrelated positional covariance.
    • Gaussian distribution of the position uncertainties.
    • Deterministic velocity i.e. no velocity uncertainties.

    The following constants are defined when using the empty constructor :

    • A default absolute accuracy of 1e-30.
    • A maximum number of computed terms of 37000.

    This implementation has been translated from python from the provided source code of Romain SERRA on the following github account

    Since:
    12.0
    Author:
    Vincent Cucchietti, Romain Serra

    • Field Detail

      • DEFAULT_SCALING_THRESHOLD

        public static final double DEFAULT_SCALING_THRESHOLD
        Default scaling threshold to use when sum becomes large.
        See Also:
        Constant Field Values

    • Constructor Detail

      • Laas2015

        public Laas2015()
        Default constructor.

        It uses a default absolute accuracy of 1e-30 and a maximum number of terms of 37000 which is the max number of terms computed based on Romain SERRA's observation (p.56 of "Romain Serra. Opérations de proximité en orbite : * évaluation du risque de collision et calcul de manoeuvres optimales pour l’évitement et le rendez-vous. Automatique / * Robotique. INSA de Toulouse, 2015. Français. NNT : 2015ISAT0035. tel-01261497") about Alfano test case 5 where he explains that 37000 terms were enough to meet the required precision of 5 significant digits.

      • Laas2015

        public Laas2015​(double absoluteAccuracy,
                int maxNumberOfTerms)
        Simple constructor.
        Parameters:
        absoluteAccuracy - absolute accuracy of the result
        maxNumberOfTerms - max number of terms to compute

    • Method Detail

      • compute

        public final ProbabilityOfCollision compute​(double xm,
                                            double ym,
                                            double sigmaX,
                                            double sigmaY,
                                            double radius)
        Compute the probability of collision using arguments specific to the rotated encounter frame.

        The rotated encounter frame is define by the initial encounter frame (defined in ShortTermEncounter2DDefinition) rotated by the rotation matrix which is used to diagonalize the combined covariance matrix.

        Specified by:
        compute in interface ShortTermEncounter2DPOCMethod
        Specified by:
        compute in class AbstractShortTermEncounter2DPOCMethod
        Parameters:
        xm - other collision object projected position onto the collision plane in the rotated encounter frame x-axis (m)
        ym - other collision object projected position onto the collision plane in the rotated encounter frame y-axis (m)
        sigmaX - square root of the x-axis eigen value of the diagonalized combined covariance matrix projected onto the collision plane (m)
        sigmaY - square root of the y-axis eigen value of the diagonalized combined covariance matrix projected onto the collision plane (m)
        radius - sum of primary and secondary collision object equivalent sphere radii (m)
        Returns:
        probability of collision

      • compute

        public final <T extends CalculusFieldElement<T>> FieldProbabilityOfCollision<T> compute​(T xm,
                                                                                        T ym,
                                                                                        T sigmaX,
                                                                                        T sigmaY,
                                                                                        T radius)
        Compute the probability of collision using arguments specific to the rotated encounter frame.

        The rotated encounter frame is define by the initial encounter frame (defined in ShortTermEncounter2DDefinition) rotated by the rotation matrix which is used to diagonalize the combined covariance matrix.

        Specified by:
        compute in interface ShortTermEncounter2DPOCMethod
        Specified by:
        compute in class AbstractShortTermEncounter2DPOCMethod
        Type Parameters:
        T - type of the field elements
        Parameters:
        xm - other collision object projected position onto the collision plane in the rotated encounter frame x-axis (m)
        ym - other collision object projected position onto the collision plane in the rotated encounter frame y-axis (m)
        sigmaX - square root of the x-axis eigen value of the diagonalized combined covariance matrix projected onto the collision plane (m)
        sigmaY - square root of the y-axis eigen value of the diagonalized combined covariance matrix projected onto the collision plane (m)
        radius - sum of primary and secondary collision object equivalent sphere radii (m)
        Returns:
        probability of collision