Package org.orekit.propagation.events

Class InterSatDirectViewDetector

  • All Implemented Interfaces:
    EventDetector
    public class InterSatDirectViewDetector
extends AbstractDetector<InterSatDirectViewDetector>
    Detector for inter-satellites direct view (i.e. no masking by central body limb).

    As this detector needs two satellites, it embeds one coordinates provider for the secondary satellite and is registered as an event detector in the propagator of the primary satellite. The secondary satellite provider will therefore be driven by this detector (and hence by the propagator in which this detector is registered).

    In order to avoid infinite recursion, care must be taken to have the secondary satellite provider being completely independent from anything else. In particular, if the provider is a propagator, it should not be run together in a propagators parallelizer with the propagator this detector is registered in. It is fine however to configure two separate propagators PsA and PsB with similar settings for the secondary satellite and one propagator Pm for the primary satellite and then use Psa in this detector registered within Pm while Pm and Psb are run in the context of a propagators parallelizer.

    For efficiency reason during the event search loop, it is recommended to have the secondary provider be an analytical propagator or an ephemeris. A numerical propagator as a secondary propagator works but is expected to be computationally costly.

    The g function of this detector is positive when satellites can see each other directly and negative when the central body limb is in between and blocks the direct view.

    This detector only checks masking by central body limb, it does not take into account satellites antenna patterns. If these patterns must be considered, then this detector can be and combined with the logical not of field of view detectors.

    Since:
    9.3
    Author:
    Luc Maisonobe

    • Constructor Detail

      • InterSatDirectViewDetector

        public InterSatDirectViewDetector​(OneAxisEllipsoid body,
                                  PVCoordinatesProvider secondary)
        simple constructor.
        Parameters:
        body - central body
        secondary - provider for the secondary satellite

      • InterSatDirectViewDetector

        protected InterSatDirectViewDetector​(OneAxisEllipsoid body,
                                     double skimmingAltitude,
                                     PVCoordinatesProvider secondary,
                                     AdaptableInterval maxCheck,
                                     double threshold,
                                     int maxIter,
                                     EventHandler handler)
        Private constructor.
        Parameters:
        body - central body
        skimmingAltitude - skimming altitude at which events are triggered
        secondary - provider for the secondary satellite
        maxCheck - maximum checking interval
        threshold - convergence threshold (s)
        maxIter - maximum number of iterations in the event time search
        handler - event handler to call at event occurrences
        Since:
        12.0

    • Method Detail

      • getCentralBody

        public OneAxisEllipsoid getCentralBody()
        Get the central body.
        Returns:
        central body

      • getSkimmingAltitude

        public double getSkimmingAltitude()
        Get the skimming altitude.
        Returns:
        skimming altitude at which events are triggered
        Since:
        12.0

      • getSecondary

        public PVCoordinatesProvider getSecondary()
        Get the provider for the secondary satellite.
        Returns:
        provider for the secondary satellite

      • create

        protected InterSatDirectViewDetector create​(AdaptableInterval newMaxCheck,
                                            double newThreshold,
                                            int newMaxIter,
                                            EventHandler newHandler)
        Build a new instance.
        Specified by:
        create in class AbstractDetector<InterSatDirectViewDetector>
        Parameters:
        newMaxCheck - maximum checking interval (s)
        newThreshold - convergence threshold (s)
        newMaxIter - maximum number of iterations in the event time search
        newHandler - event handler to call at event occurrences
        Returns:
        a new instance of the appropriate sub-type

      • withSkimmingAltitude

        public InterSatDirectViewDetector withSkimmingAltitude​(double newSkimmingAltitude)
        Setup the skimming altitude.

        The skimming altitude is the lowest altitude of the path between satellites at which events should be triggered. If set to 0.0, events are triggered exactly when the path passes just at central body limb.

        Parameters:
        newSkimmingAltitude - skimming altitude (m)
        Returns:
        a new detector with updated configuration (the instance is not changed)
        Since:
        12.0
        See Also:
        getSkimmingAltitude()

      • g

        public double g​(SpacecraftState state)
        Compute the value of the switching function. This function must be continuous (at least in its roots neighborhood), as the integrator will need to find its roots to locate the events.

        The g function of this detector is the difference between the minimum altitude of intermediate points along the line of sight between satellites and the skimming altitude. It is therefore positive when all intermediate points are above the skimming altitude, meaning satellites can see each other and it is negative when some intermediate points (which may be either endpoints) dive below this altitude, meaning satellites cannot see each other.

        Parameters:
        state - the current state information: date, kinematics, attitude
        Returns:
        value of the switching function