Package org.orekit.propagation.covariance

Class FieldStateCovariance<T extends CalculusFieldElement<T>>

java.lang.Object
org.orekit.propagation.covariance.FieldStateCovariance<T>
Type Parameters:
T - type of the field elements
All Implemented Interfaces:
FieldTimeStamped<T>
public class FieldStateCovariance<T extends CalculusFieldElement<T>> extends Object implements FieldTimeStamped<T>
This class is the representation of a covariance matrix at a given date.

Currently, the covariance only represents the orbital elements.

It is possible to change the covariance frame by using the changeCovarianceFrame(FieldOrbit, Frame) or changeCovarianceFrame(FieldOrbit, LOF) method. These methods are based on Equations (18) and (20) of Covariance Transformations for Satellite Flight Dynamics Operations by David A. SVallado.

Finally, covariance orbit type can be changed using the changeCovarianceType(FieldOrbit, OrbitType, PositionAngle) method.

Since:
12.0
Author:
Bryan Cazabonne, Vincent Cucchietti

  • Constructor Details

    • FieldStateCovariance

      public FieldStateCovariance(FieldMatrix<T> orbitalCovariance, FieldAbsoluteDate<T> epoch, LOF lof)
      Constructor.
      Parameters:
      orbitalCovariance - 6x6 orbital parameters covariance
      epoch - epoch of the covariance
      lof - covariance LOF type

    • FieldStateCovariance

      public FieldStateCovariance(FieldMatrix<T> orbitalCovariance, FieldAbsoluteDate<T> epoch, Frame covarianceFrame, OrbitType orbitType, PositionAngleType angleType)
      Constructor.
      Parameters:
      orbitalCovariance - 6x6 orbital parameters covariance
      epoch - epoch of the covariance
      covarianceFrame - covariance frame (inertial or Earth fixed)
      orbitType - orbit type of the covariance (CARTESIAN if covarianceFrame is not pseudo-inertial)
      angleType - position angle type of the covariance (not used if orbitType is CARTESIAN)

  • Method Details

    • getDate

      public FieldAbsoluteDate<T> getDate()
      Get the date..
      Specified by:
      getDate in interface FieldTimeStamped<T extends CalculusFieldElement<T>>
      Returns:
      date attached to the object

    • getMatrix

      public FieldMatrix<T> getMatrix()
      Get the covariance matrix.
      Returns:
      the covariance matrix

    • getOrbitType

      public OrbitType getOrbitType()
      Get the covariance orbit type.
      Returns:
      the covariance orbit type

    • getPositionAngleType

      public PositionAngleType getPositionAngleType()
      Get the covariance angle type.
      Returns:
      the covariance angle type

    • getFrame

      public Frame getFrame()
      Get the covariance frame.
      Returns:
      the covariance frame (can be null)
      See Also:

    • getLOF

      public LOF getLOF()
      Get the covariance LOF type.
      Returns:
      the covariance LOF type (can be null)
      See Also:

    • changeCovarianceType

      public FieldStateCovariance<T> changeCovarianceType(FieldOrbit<T> orbit, OrbitType outOrbitType, PositionAngleType outAngleType)
      Get the covariance matrix in another orbit type.

      The covariance orbit type cannot be changed if the covariance matrix is expressed in a local orbital frame or a non-pseudo inertial frame.

      As this type change uses the jacobian matrix of the transformation, it introduces a linear approximation. Hence, the current covariance matrix will not exactly match the new linearized case and the distribution will not follow a generalized Gaussian distribution anymore.

      This is based on equation (1) to (6) from "Vallado, D. A. (2004). Covariance transformations for satellite flight dynamics operations."

      Parameters:
      orbit - orbit to which the covariance matrix should correspond
      outOrbitType - target orbit type of the state covariance matrix
      outAngleType - target position angle type of the state covariance matrix
      Returns:
      a new covariance state, expressed in the target orbit type with the target position angle
      See Also:

    • changeCovarianceFrame

      public FieldStateCovariance<T> changeCovarianceFrame(FieldOrbit<T> orbit, LOF lofOut)
      Get the covariance in a given local orbital frame.

      Changing the covariance frame is a linear process, this method does not introduce approximation unless a change in covariance orbit type is required.

      This is based on equation (18) to (20) "from Vallado, D. A. (2004). Covariance transformations for satellite flight dynamics operations."

      Parameters:
      orbit - orbit to which the covariance matrix should correspond
      lofOut - output local orbital frame
      Returns:
      a new covariance state, expressed in the output local orbital frame

    • changeCovarianceFrame

      public FieldStateCovariance<T> changeCovarianceFrame(FieldOrbit<T> orbit, Frame frameOut)
      Get the covariance in the output frame.

      Changing the covariance frame is a linear process, this method does not introduce approximation unless a change in covariance orbit type is required.

      This is based on equation (18) to (20) "from Vallado, D. A. (2004). Covariance transformations for satellite flight dynamics operations."

      Parameters:
      orbit - orbit to which the covariance matrix should correspond
      frameOut - output frame
      Returns:
      a new covariance state, expressed in the output frame

    • shiftedBy

      public FieldStateCovariance<T> shiftedBy(Field<T> field, FieldOrbit<T> orbit, T dt)
      Get a time-shifted covariance matrix.

      The shifting model is a linearized, Keplerian one. In other words, it is based on a state transition matrix that is computed assuming Keplerian motion.

      Shifting is not intended as a replacement for proper covariance propagation, but should be sufficient for small time shifts or coarse accuracy.

      Parameters:
      field - to which the elements belong
      orbit - orbit to which the covariance matrix should correspond
      dt - time shift in seconds
      Returns:
      a new covariance state, shifted with respect to the instance

    • toStateCovariance

      public StateCovariance toStateCovariance()
      Get new state covariance instance.
      Returns:
      new state covariance instance.