Package org.orekit.utils

Class SecularAndHarmonic

java.lang.Object
org.orekit.utils.SecularAndHarmonic
public class SecularAndHarmonic extends Object
Class for fitting evolution of osculating orbital parameters.

This class allows conversion from osculating parameters to mean parameters.

Author:
Luc Maisonobe

  • Constructor Details

    • SecularAndHarmonic

      public SecularAndHarmonic(int secularDegree, double... pulsations)
      Simple constructor.
      Parameters:
      secularDegree - degree of polynomial secular part
      pulsations - pulsations of harmonic part

  • Method Details

    • resetFitting

      public void resetFitting(AbsoluteDate date, double... initialGuess)
      Reset fitting.
      Parameters:
      date - reference date
      initialGuess - initial guess for the parameters
      See Also:

    • setConvergenceRMS

      public void setConvergenceRMS(double convergenceRMS)
      Set RMS for convergence.

      The RMS is the square-root of the sum of squared of the residuals, divided by the number of measurements.

      Parameters:
      convergenceRMS - RMS below which convergence is considered to have been reached
      Since:
      10.3

    • setMaxIter

      public void setMaxIter(int maxIter)
      Set maximum number of iterations.
      Parameters:
      maxIter - maximum number of iterations
      Since:
      10.3

    • addPoint

      public void addPoint(AbsoluteDate date, double osculatingValue)
      Add a fitting point.

      The point weight is set to 1.0

      Parameters:
      date - date of the point
      osculatingValue - osculating value
      See Also:

    • addWeightedPoint

      public void addWeightedPoint(AbsoluteDate date, double osculatingValue, double weight)
      Add a weighted fitting point.
      Parameters:
      date - date of the point
      osculatingValue - osculating value
      weight - weight of the points
      Since:
      12.0

    • getReferenceDate

      public AbsoluteDate getReferenceDate()
      Get the reference date.
      Returns:
      reference date
      See Also:

    • getSecularDegree

      public int getSecularDegree()
      Get degree of polynomial secular part.
      Returns:
      degree of polynomial secular part
      Since:
      12.0

    • getPulsations

      public double[] getPulsations()
      Get the pulsations of harmonic part.
      Returns:
      pulsations of harmonic part
      Since:
      12.0

    • getHarmonicAmplitude

      public double getHarmonicAmplitude()
      Get an upper bound of the fitted harmonic amplitude.
      Returns:
      upper bound of the fitted harmonic amplitude

    • fit

      public void fit()
      Fit parameters.
      See Also:

    • getFittedParameters

      public double[] getFittedParameters()
      Get a copy of the last fitted parameters.
      Returns:
      copy of the last fitted parameters.
      See Also:

    • osculatingValue

      public double osculatingValue(AbsoluteDate date)
      Get fitted osculating value.
      Parameters:
      date - current date
      Returns:
      osculating value at current date

    • osculatingDerivative

      public double osculatingDerivative(AbsoluteDate date)
      Get fitted osculating derivative.
      Parameters:
      date - current date
      Returns:
      osculating derivative at current date

    • osculatingSecondDerivative

      public double osculatingSecondDerivative(AbsoluteDate date)
      Get fitted osculating second derivative.
      Parameters:
      date - current date
      Returns:
      osculating second derivative at current date

    • meanValue

      public double meanValue(AbsoluteDate date, int degree, int harmonics)
      Get mean value, truncated to first components.
      Parameters:
      date - current date
      degree - degree of polynomial secular part to consider
      harmonics - number of harmonics terms to consider
      Returns:
      mean value at current date

    • meanDerivative

      public double meanDerivative(AbsoluteDate date, int degree, int harmonics)
      Get mean derivative, truncated to first components.
      Parameters:
      date - current date
      degree - degree of polynomial secular part to consider
      harmonics - number of harmonics terms to consider
      Returns:
      mean derivative at current date

    • approximateAsPolynomialOnly

      public double[] approximateAsPolynomialOnly(int combinedDegree, AbsoluteDate combinedReference, int meanDegree, int meanHarmonics, AbsoluteDate start, AbsoluteDate end, double step)
      Approximate an already fitted model to polynomial only terms.

      This method is mainly used in order to combine the large amplitude long periods with the secular part as a new approximate polynomial model over some time range. This should be used rather than simply extracting the polynomial coefficients from getFittedParameters() when some periodic terms amplitudes are large (for example Sun resonance effects on local solar time in sun synchronous orbits). In theses cases, the pure polynomial secular part in the coefficients may be far from the mean model.

      Parameters:
      combinedDegree - desired degree for the combined polynomial
      combinedReference - desired reference date for the combined polynomial
      meanDegree - degree of polynomial secular part to consider
      meanHarmonics - number of harmonics terms to consider
      start - start date of the approximation time range
      end - end date of the approximation time range
      step - sampling step
      Returns:
      coefficients of the approximate polynomial (in increasing degree order), using the user provided reference date

    • meanSecondDerivative

      public double meanSecondDerivative(AbsoluteDate date, int degree, int harmonics)
      Get mean second derivative, truncated to first components.
      Parameters:
      date - current date
      degree - degree of polynomial secular part
      harmonics - number of harmonics terms to consider
      Returns:
      mean second derivative at current date