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    * contributor license agreements.  See the NOTICE file distributed with
    * this work for additional information regarding copyright ownership.
    * CS licenses this file to You under the Apache License, Version 2.0
    * (the "License"); you may not use this file except in compliance with
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    *
    *   http://www.apache.org/licenses/LICENSE-2.0
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   * Unless required by applicable law or agreed to in writing, software
   * distributed under the License is distributed on an "AS IS" BASIS,
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  package org.orekit.estimation.measurements.gnss;
  
  import java.util.Arrays;
  
  import org.hipparchus.analysis.differentiation.Gradient;
  import org.orekit.estimation.measurements.EstimatedMeasurement;
  import org.orekit.estimation.measurements.EstimatedMeasurementBase;
  import org.orekit.estimation.measurements.GroundReceiverCommonParametersWithDerivatives;
  import org.orekit.estimation.measurements.GroundReceiverCommonParametersWithoutDerivatives;
  import org.orekit.estimation.measurements.GroundReceiverMeasurement;
  import org.orekit.estimation.measurements.GroundStation;
  import org.orekit.estimation.measurements.ObservableSatellite;
  import org.orekit.propagation.SpacecraftState;
  import org.orekit.time.AbsoluteDate;
  import org.orekit.utils.Constants;
  import org.orekit.utils.ParameterDriver;
  import org.orekit.utils.TimeSpanMap.Span;
  import org.orekit.utils.TimeStampedPVCoordinates;
  
  /** Class modeling a phase measurement from a ground station.
   * <p>
   * The measurement is considered to be a signal emitted from
   * a spacecraft and received on a ground station.
   * Its value is the number of cycles between emission and
   * reception. The motion of both the station and the
   * spacecraft during the signal flight time are taken into
   * account. The date of the measurement corresponds to the
   * reception on ground of the emitted signal.
   * </p>
   * @author Thierry Ceolin
   * @author Luc Maisonobe
   * @author Maxime Journot
   * @since 9.2
   */
  public class Phase extends GroundReceiverMeasurement<Phase> {
  
      /** Type of the measurement. */
      public static final String MEASUREMENT_TYPE = "Phase";
  
      /** Name for ambiguity driver.
       * @deprecated as of 12.1 not used anymore
       */
      @Deprecated
      public static final String AMBIGUITY_NAME = "ambiguity";
  
      /** Driver for ambiguity. */
      private final AmbiguityDriver ambiguityDriver;
  
      /** Wavelength of the phase observed value [m]. */
      private final double wavelength;
  
      /** Simple constructor.
       * @param station ground station from which measurement is performed
       * @param date date of the measurement
       * @param phase observed value (cycles)
       * @param wavelength phase observed value wavelength (m)
       * @param sigma theoretical standard deviation
       * @param baseWeight base weight
       * @param satellite satellite related to this measurement
       * @since 9.3
       * @deprecated as of 12.1, replaced by {@link #Phase(GroundStation,
       * AbsoluteDate, double, double, double, double, ObservableSatellite,
       * AmbiguityCache)}
       */
      @Deprecated
      public Phase(final GroundStation station, final AbsoluteDate date,
                   final double phase, final double wavelength, final double sigma,
                   final double baseWeight, final ObservableSatellite satellite) {
          this(station, date, phase, wavelength, sigma, baseWeight, satellite,
               AmbiguityCache.DEFAULT_CACHE);
      }
  
      /** Simple constructor.
       * @param station ground station from which measurement is performed
       * @param date date of the measurement
       * @param phase observed value (cycles)
       * @param wavelength phase observed value wavelength (m)
       * @param sigma theoretical standard deviation
       * @param baseWeight base weight
       * @param satellite satellite related to this measurement
       * @param cache from which ambiguity drive should come
       * @since 12.1
       */
     public Phase(final GroundStation station, final AbsoluteDate date,
                  final double phase, final double wavelength, final double sigma,
                  final double baseWeight, final ObservableSatellite satellite,
                  final AmbiguityCache cache) {
         super(station, false, date, phase, sigma, baseWeight, satellite);
         ambiguityDriver = cache.getAmbiguity(satellite.getName(),
                                              station.getBaseFrame().getName(),
                                              wavelength);
         addParameterDriver(ambiguityDriver);
         this.wavelength = wavelength;
     }
 
     /** Get the wavelength.
      * @return wavelength (m)
      */
     public double getWavelength() {
         return wavelength;
     }
 
     /** Get the driver for phase ambiguity.
      * @return the driver for phase ambiguity
      * @since 10.3
      */
     public AmbiguityDriver getAmbiguityDriver() {
         return ambiguityDriver;
     }
 
     /** {@inheritDoc} */
     @Override
     protected EstimatedMeasurementBase<Phase> theoreticalEvaluationWithoutDerivatives(final int iteration,
                                                                                       final int evaluation,
                                                                                       final SpacecraftState[] states) {
 
         final GroundReceiverCommonParametersWithoutDerivatives common = computeCommonParametersWithout(states[0]);
 
         // prepare the evaluation
         final EstimatedMeasurementBase<Phase> estimated =
                         new EstimatedMeasurementBase<>(this, iteration, evaluation,
                                                        new SpacecraftState[] {
                                                            common.getTransitState()
                                                        }, new TimeStampedPVCoordinates[] {
                                                            common.getTransitPV(),
                                                            common.getStationDownlink()
                                                        });
 
         // Clock offsets
         final ObservableSatellite satellite = getSatellites().get(0);
         final double              dts       = satellite.getClockOffsetDriver().getValue(common.getState().getDate());
         final double              dtg       = getStation().getClockOffsetDriver().getValue(getDate());
 
         // Phase value
         final double cOverLambda = Constants.SPEED_OF_LIGHT / wavelength;
         final double ambiguity   = ambiguityDriver.getValue(common.getState().getDate());
         final double phase       = (common.getTauD() + dtg - dts) * cOverLambda + ambiguity;
 
         estimated.setEstimatedValue(phase);
 
         return estimated;
 
     }
 
     /** {@inheritDoc} */
     @Override
     protected EstimatedMeasurement<Phase> theoreticalEvaluation(final int iteration,
                                                                 final int evaluation,
                                                                 final SpacecraftState[] states) {
 
         final SpacecraftState state = states[0];
 
         // Phase derivatives are computed with respect to spacecraft state in inertial frame
         // and station parameters
         // ----------------------
         //
         // Parameters:
         //  - 0..2 - Position of the spacecraft in inertial frame
         //  - 3..5 - Velocity of the spacecraft in inertial frame
         //  - 6..n - station parameters (ambiguity, clock offset, station offsets, pole, prime meridian...)
         final GroundReceiverCommonParametersWithDerivatives common = computeCommonParametersWithDerivatives(state);
         final int nbParams = common.getTauD().getFreeParameters();
 
         // prepare the evaluation
         final EstimatedMeasurement<Phase> estimated =
                         new EstimatedMeasurement<>(this, iteration, evaluation,
                                                    new SpacecraftState[] {
                                                        common.getTransitState()
                                                    }, new TimeStampedPVCoordinates[] {
                                                        common.getTransitPV().toTimeStampedPVCoordinates(),
                                                        common.getStationDownlink().toTimeStampedPVCoordinates()
                                                    });
 
         // Clock offsets
         final ObservableSatellite satellite = getSatellites().get(0);
         final Gradient            dts       = satellite.getClockOffsetDriver().getValue(nbParams, common.getIndices(), state.getDate());
         final Gradient            dtg       = getStation().getClockOffsetDriver().getValue(nbParams, common.getIndices(), getDate());
 
         // Phase value
         final double   cOverLambda = Constants.SPEED_OF_LIGHT / wavelength;
         final Gradient ambiguity   = ambiguityDriver.getValue(nbParams, common.getIndices(), state.getDate());
         final Gradient phase       = common.getTauD().add(dtg).subtract(dts).multiply(cOverLambda).add(ambiguity);
 
         estimated.setEstimatedValue(phase.getValue());
 
         // Phase first order derivatives with respect to state
         final double[] derivatives = phase.getGradient();
         estimated.setStateDerivatives(0, Arrays.copyOfRange(derivatives, 0, 6));
 
         // Set first order derivatives with respect to parameters
         for (final ParameterDriver driver : getParametersDrivers()) {
             for (Span<String> span = driver.getNamesSpanMap().getFirstSpan(); span != null; span = span.next()) {
 
                 final Integer index = common.getIndices().get(span.getData());
                 if (index != null) {
                     estimated.setParameterDerivatives(driver, span.getStart(), derivatives[index]);
                 }
             }
         }
 
         return estimated;
 
     }
 
 }