Merge branch 'issue-922' into develop

src/main/java/org/orekit/estimation/measurements/BistaticRange.java

+/* Copyright 2002-2022 Mark Rutten
+ * Licensed to CS GROUP (CS) under one or more
+ * contributor license agreements.  See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * Mark Rutten licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License.  You may obtain a copy of the License at
+ *
+ *   http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.orekit.estimation.measurements;
+
+import java.util.Arrays;
+import java.util.Collections;
+import java.util.HashMap;
+import java.util.Map;
+
+import org.hipparchus.analysis.differentiation.Gradient;
+import org.hipparchus.analysis.differentiation.GradientField;
+import org.hipparchus.geometry.euclidean.threed.FieldVector3D;
+import org.orekit.frames.FieldTransform;
+import org.orekit.propagation.SpacecraftState;
+import org.orekit.time.AbsoluteDate;
+import org.orekit.time.FieldAbsoluteDate;
+import org.orekit.utils.Constants;
+import org.orekit.utils.ParameterDriver;
+import org.orekit.utils.TimeStampedFieldPVCoordinates;
+import org.orekit.utils.TimeStampedPVCoordinates;
+
+/**
+ * Class modeling a bistatic range measurement using
+ * an emitter ground station and a receiver ground station.
+ * <p>
+ * The measurement is considered to be a signal:
+ * <ul>
+ * <li>Emitted from the emitter ground station</li>
+ * <li>Reflected on the spacecraft</li>
+ * <li>Received on the receiver ground station</li>
+ * </ul>
+ * The date of the measurement corresponds to the reception on ground of the reflected signal.
+ * <p>
+ * The motion of the stations and the spacecraft during the signal flight time are taken into account.
+ * </p>
+ *
+ * @author Mark Rutten
+ * @since 11.2
+ */
+public class BistaticRange extends AbstractMeasurement<BistaticRange> {
+
+    /**
+     * Ground station from which transmission is made.
+     */
+    private final GroundStation emitter;
+
+    /**
+     * Ground station from which measurement is performed.
+     */
+    private final GroundStation receiver;
+
+    /**
+     * Simple constructor.
+     *
+     * @param emitter     ground station from which transmission is performed
+     * @param receiver    ground station from which measurement is performed
+     * @param date        date of the measurement
+     * @param range       observed value
+     * @param sigma       theoretical standard deviation
+     * @param baseWeight  base weight
+     * @param satellite   satellite related to this measurement
+     * @since 11.2
+     */
+    public BistaticRange(final GroundStation emitter, final GroundStation receiver, final AbsoluteDate date,
+                         final double range, final double sigma, final double baseWeight,
+                         final ObservableSatellite satellite) {
+        super(date, range, sigma, baseWeight, Collections.singletonList(satellite));
+        addParameterDriver(emitter.getClockOffsetDriver());
+        addParameterDriver(emitter.getEastOffsetDriver());
+        addParameterDriver(emitter.getNorthOffsetDriver());
+        addParameterDriver(emitter.getZenithOffsetDriver());
+        addParameterDriver(emitter.getPrimeMeridianOffsetDriver());
+        addParameterDriver(emitter.getPrimeMeridianDriftDriver());
+        addParameterDriver(emitter.getPolarOffsetXDriver());
+        addParameterDriver(emitter.getPolarDriftXDriver());
+        addParameterDriver(emitter.getPolarOffsetYDriver());
+        addParameterDriver(emitter.getPolarDriftYDriver());
+
+        addParameterDriver(receiver.getClockOffsetDriver());
+        addParameterDriver(receiver.getEastOffsetDriver());
+        addParameterDriver(receiver.getNorthOffsetDriver());
+        addParameterDriver(receiver.getZenithOffsetDriver());
+        addParameterDriver(receiver.getPrimeMeridianOffsetDriver());
+        addParameterDriver(receiver.getPrimeMeridianDriftDriver());
+        addParameterDriver(receiver.getPolarOffsetXDriver());
+        addParameterDriver(receiver.getPolarDriftXDriver());
+        addParameterDriver(receiver.getPolarOffsetYDriver());
+        addParameterDriver(receiver.getPolarDriftYDriver());
+
+        this.emitter = emitter;
+        this.receiver = receiver;
+    }
+
+    public GroundStation getEmitterStation() {
+        return emitter;
+    }
+
+    public GroundStation getReceiverStation() {
+        return receiver;
+    }
+
+    /**
+     * {@inheritDoc}
+     */
+    @Override
+    protected EstimatedMeasurement<BistaticRange> theoreticalEvaluation(final int iteration,
+                                                                        final int evaluation,
+                                                                        final SpacecraftState[] states) {
+
+        final SpacecraftState state = states[0];
+
+        // Range 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 - measurements parameters (clock offset, station offsets, pole, prime meridian, sat clock offset...)
+        int nbParams = 6;
+        final Map<String, Integer> indices = new HashMap<>();
+        for (ParameterDriver driver : getParametersDrivers()) {
+            if (driver.isSelected()) {
+                indices.put(driver.getName(), nbParams++);
+            }
+        }
+        final FieldVector3D<Gradient> zero = FieldVector3D.getZero(GradientField.getField(nbParams));
+
+        // Coordinates of the spacecraft expressed as a gradient
+        final TimeStampedFieldPVCoordinates<Gradient> pvaDS = getCoordinates(state, 0, nbParams);
+
+        // transform between station and inertial frame, expressed as a gradient
+        // The components of station's position in offset frame are the 3 last derivative parameters
+        final FieldTransform<Gradient> offsetToInertialRx =
+                receiver.getOffsetToInertial(state.getFrame(), getDate(), nbParams, indices);
+        final FieldAbsoluteDate<Gradient> downlinkDateDS = offsetToInertialRx.getFieldDate();
+
+        // Station position in inertial frame at end of the downlink leg
+        final TimeStampedFieldPVCoordinates<Gradient> stationReceiver =
+                offsetToInertialRx.transformPVCoordinates(new TimeStampedFieldPVCoordinates<>(downlinkDateDS,
+                        zero, zero, zero));
+
+        // Compute propagation times
+        // (if state has already been set up to pre-compensate propagation delay,
+        //  we will have delta == tauD and transitState will be the same as state)
+
+        // Downlink delay
+        final Gradient tauD = signalTimeOfFlight(pvaDS, stationReceiver.getPosition(), downlinkDateDS);
+
+        // Transit state & Transit state (re)computed with gradients
+        final Gradient delta = downlinkDateDS.durationFrom(state.getDate());
+        final Gradient deltaMTauD = tauD.negate().add(delta);
+        final SpacecraftState transitState = state.shiftedBy(deltaMTauD.getValue());
+        final TimeStampedFieldPVCoordinates<Gradient> transitStateDS = pvaDS.shiftedBy(deltaMTauD);
+
+        // transform between secondary station topocentric frame (east-north-zenith) and inertial frame expressed as gradients
+        // The components of secondary station's position in offset frame are the 3 last derivative parameters
+        final FieldAbsoluteDate<Gradient> transitDate = downlinkDateDS.shiftedBy(tauD.negate());
+        final FieldTransform<Gradient> offsetToInertialTxApprox =
+                emitter.getOffsetToInertial(state.getFrame(), transitDate, nbParams, indices);
+
+        // Secondary station PV in inertial frame at transit time
+        final TimeStampedFieldPVCoordinates<Gradient> transmitApprox =
+                offsetToInertialTxApprox.transformPVCoordinates(new TimeStampedFieldPVCoordinates<>(transitDate,
+                        zero, zero, zero));
+
+        // Uplink time of flight from secondary station to transit state of leg2
+        final Gradient tauU = signalTimeOfFlight(transmitApprox, transitStateDS.getPosition(), transitStateDS.getDate());
+
+        // Total time of flight
+        final Gradient tauTotal = deltaMTauD.negate().add(tauU);
+
+        // Absolute date of transmission
+        final FieldAbsoluteDate<Gradient> transmitDateDS = downlinkDateDS.shiftedBy(tauTotal);
+        final FieldTransform<Gradient> transmitToInert =
+                emitter.getOffsetToInertial(state.getFrame(), transmitDateDS, nbParams, indices);
+
+        // Secondary station PV in inertial frame at rebound date on secondary station
+        final TimeStampedFieldPVCoordinates<Gradient> stationTransmitter =
+                transmitToInert.transformPVCoordinates(new TimeStampedFieldPVCoordinates<>(transmitDateDS,
+                        zero, zero, zero));
+
+        // Prepare the evaluation
+        final EstimatedMeasurement<BistaticRange> estimated = new EstimatedMeasurement<>(this,
+                iteration, evaluation,
+                new SpacecraftState[] {
+                    transitState
+                },
+                new TimeStampedPVCoordinates[] {
+                    stationReceiver.toTimeStampedPVCoordinates(),
+                    transitStateDS.toTimeStampedPVCoordinates(),
+                    stationTransmitter.toTimeStampedPVCoordinates()
+                });
+
+        // Range value
+        final Gradient tau = tauD.add(tauU);
+        final Gradient range = tau.multiply(Constants.SPEED_OF_LIGHT);
+
+        estimated.setEstimatedValue(range.getValue());
+
+        // Range partial derivatives with respect to state
+        final double[] derivatives = range.getGradient();
+        estimated.setStateDerivatives(0, Arrays.copyOfRange(derivatives, 0, 6));
+
+        // set partial derivatives with respect to parameters
+        // (beware element at index 0 is the value, not a derivative)
+        for (final ParameterDriver driver : getParametersDrivers()) {
+            final Integer index = indices.get(driver.getName());
+            if (index != null) {
+                estimated.setParameterDerivatives(driver, derivatives[index]);
+            }
+        }
+
+        return estimated;
+    }
+
+}

src/main/java/org/orekit/estimation/measurements/generation/BistaticRangeBuilder.java

+/* Copyright 2002-2022 Mark Rutten
+ * Licensed to CS GROUP (CS) under one or more
+ * contributor license agreements.  See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * Mark Rutten licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License.  You may obtain a copy of the License at
+ *
+ *   http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.orekit.estimation.measurements.generation;
+
+import org.hipparchus.random.CorrelatedRandomVectorGenerator;
+import org.orekit.estimation.measurements.BistaticRange;
+import org.orekit.estimation.measurements.EstimationModifier;
+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.ParameterDriver;
+
+
+/** Builder for {@link BistaticRange} measurements.
+ * @author Pascal Parraud
+ * @author Mark Rutten
+ * @since 11.2
+ */
+public class BistaticRangeBuilder extends AbstractMeasurementBuilder<BistaticRange> {
+
+    /** Emitter ground station. */
+    private final GroundStation emitter;
+
+    /** Receiver ground station. */
+    private final GroundStation receiver;
+
+    /** Simple constructor.
+     * @param noiseSource noise source, may be null for generating perfect measurements
+     * @param emitter emitter ground station
+     * @param receiver receiver ground station, from which measurement is performed
+     * @param sigma theoretical standard deviation
+     * @param baseWeight base weight
+     * @param satellite satellite related to this builder
+     */
+    public BistaticRangeBuilder(final CorrelatedRandomVectorGenerator noiseSource,
+                                final GroundStation emitter, final GroundStation receiver,
+                                final double sigma, final double baseWeight,
+                                final ObservableSatellite satellite) {
+        super(noiseSource, sigma, baseWeight, satellite);
+        this.emitter  = emitter;
+        this.receiver = receiver;
+    }
+
+    /** {@inheritDoc} */
+    @Override
+    public BistaticRange build(final SpacecraftState[] states) {
+
+        final ObservableSatellite satellite = getSatellites()[0];
+        final double sigma                  = getTheoreticalStandardDeviation()[0];
+        final double baseWeight             = getBaseWeight()[0];
+        final SpacecraftState[] relevant    = new SpacecraftState[] { states[satellite.getPropagatorIndex()] };
+
+        // create a dummy measurement
+        final BistaticRange dummy = new BistaticRange(emitter, receiver, relevant[0].getDate(),
+                                                      Double.NaN, sigma, baseWeight, satellite);
+        for (final EstimationModifier<BistaticRange> modifier : getModifiers()) {
+            dummy.addModifier(modifier);
+        }
+
+        // set a reference date for parameters missing one
+        for (final ParameterDriver driver : dummy.getParametersDrivers()) {
+            if (driver.getReferenceDate() == null) {
+                final AbsoluteDate start = getStart();
+                final AbsoluteDate end   = getEnd();
+                driver.setReferenceDate(start.durationFrom(end) <= 0 ? start : end);
+            }
+        }
+
+        // estimate the perfect value of the measurement
+        double range = dummy.estimate(0, 0, relevant).getEstimatedValue()[0];
+
+        // add the noise
+        final double[] noise = getNoise();
+        if (noise != null) {
+            range += noise[0];
+        }
+
+        // generate measurement
+        final BistaticRange measurement = new BistaticRange(emitter, receiver, relevant[0].getDate(),
+                                                            range, sigma, baseWeight, satellite);
+        for (final EstimationModifier<BistaticRange> modifier : getModifiers()) {
+            measurement.addModifier(modifier);
+        }
+        return measurement;
+
+    }
+
+}

src/main/java/org/orekit/estimation/measurements/modifiers/BaseRangeIonosphericDelayModifier.java

+/* Copyright 2002-2022 CS GROUP
+ * Licensed to CS GROUP (CS) under one or more
+ * 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
+ * the License.  You may obtain a copy of the License at
+ *
+ *   http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.orekit.estimation.measurements.modifiers;
+
+import java.util.List;
+
+import org.hipparchus.CalculusFieldElement;
+import org.orekit.estimation.measurements.GroundStation;
+import org.orekit.frames.TopocentricFrame;
+import org.orekit.models.earth.ionosphere.IonosphericModel;
+import org.orekit.propagation.FieldSpacecraftState;
+import org.orekit.propagation.SpacecraftState;
+import org.orekit.utils.ParameterDriver;
+
+/** Base class modifying theoretical range measurement with ionospheric delay.
+ * The effect of ionospheric correction on the range is directly computed
+ * through the computation of the ionospheric delay.
+ *
+ * The ionospheric delay depends on the frequency of the signal (GNSS, VLBI, ...).
+ * For optical measurements (e.g. SLR), the ray is not affected by ionosphere charged particles.
+ * <p>
+ * Since 10.0, state derivatives and ionospheric parameters derivates are computed
+ * using automatic differentiation.
+ * </p>
+ * @author Joris Olympio
+ * @since 11.2
+ */
+public abstract class BaseRangeIonosphericDelayModifier {
+
+    /** Ionospheric delay model. */
+    private final IonosphericModel ionoModel;
+
+    /** Frequency [Hz]. */
+    private final double frequency;
+
+    /** Constructor.
+     *
+     * @param model Ionospheric delay model appropriate for the current range-rate measurement method.
+     * @param freq frequency of the signal in Hz
+     */
+    protected BaseRangeIonosphericDelayModifier(final IonosphericModel model, final double freq) {
+        this.ionoModel = model;
+        this.frequency = freq;
+    }
+
+    /** Get the ionospheric delay model.
+     * @return ionospheric delay model
+     */
+    protected IonosphericModel getIonoModel() {
+        return ionoModel;
+    }
+
+    /** Compute the measurement error due to Ionosphere.
+     * @param station station
+     * @param state spacecraft state
+     * @return the measurement error due to Ionosphere
+     */
+    protected double rangeErrorIonosphericModel(final GroundStation station, final SpacecraftState state) {
+        // Base frame associated with the station
+        final TopocentricFrame baseFrame = station.getBaseFrame();
+        // delay in meters
+        final double delay = ionoModel.pathDelay(state, baseFrame, frequency, ionoModel.getParameters());
+        return delay;
+    }
+
+    /** Compute the measurement error due to Ionosphere.
+     * @param <T> type of the elements
+     * @param station station
+     * @param state spacecraft state
+     * @param parameters ionospheric model parameters
+     * @return the measurement error due to Ionosphere
+     */
+    protected <T extends CalculusFieldElement<T>> T rangeErrorIonosphericModel(final GroundStation station,
+                                                                               final FieldSpacecraftState<T> state,
+                                                                               final T[] parameters) {
+        // Base frame associated with the station
+        final TopocentricFrame baseFrame = station.getBaseFrame();
+        // delay in meters
+        final T delay = ionoModel.pathDelay(state, baseFrame, frequency, parameters);
+        return delay;
+    }
+
+    /** Get the drivers for this modifier parameters.
+     * @return drivers for this modifier parameters
+     */
+    public List<ParameterDriver> getParametersDrivers() {
+        return ionoModel.getParametersDrivers();
+    }
+
+}

src/main/java/org/orekit/estimation/measurements/modifiers/BaseRangeTroposphericDelayModifier.java

+/* Copyright 2002-2022 CS GROUP
+ * Licensed to CS GROUP (CS) under one or more
+ * 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
+ * the License.  You may obtain a copy of the License at
+ *
+ *   http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.orekit.estimation.measurements.modifiers;
+
+import java.util.List;
+
+import org.hipparchus.CalculusFieldElement;
+import org.hipparchus.Field;
+import org.hipparchus.geometry.euclidean.threed.FieldVector3D;
+import org.hipparchus.geometry.euclidean.threed.Vector3D;
+import org.orekit.estimation.measurements.GroundStation;
+import org.orekit.models.earth.troposphere.DiscreteTroposphericModel;
+import org.orekit.propagation.FieldSpacecraftState;
+import org.orekit.propagation.SpacecraftState;
+import org.orekit.utils.ParameterDriver;
+
+/** Base class modifying theoretical range measurements with tropospheric delay.
+ * The effect of tropospheric correction on the range is directly computed
+ * through the computation of the tropospheric delay.
+ *
+ * In general, for GNSS, VLBI, ... there is hardly any frequency dependence in the delay.
+ * For SLR techniques however, the frequency dependence is sensitive.
+ *
+ * @author Joris Olympio
+ * @since 11.2
+ */
+public abstract class BaseRangeTroposphericDelayModifier {
+
+    /** Tropospheric delay model. */
+    private final DiscreteTroposphericModel tropoModel;
+
+    /** Constructor.
+     *
+     * @param model  Tropospheric delay model appropriate for the current range measurement method.
+     */
+    protected BaseRangeTroposphericDelayModifier(final DiscreteTroposphericModel model) {
+        tropoModel = model;
+    }
+
+    /** Get the tropospheric delay model.
+     * @return tropospheric delay model
+     */
+    protected DiscreteTroposphericModel getTropoModel() {
+        return tropoModel;
+    }
+
+    /** Compute the measurement error due to Troposphere.
+     * @param station station
+     * @param state spacecraft state
+     * @return the measurement error due to Troposphere
+     */
+    public double rangeErrorTroposphericModel(final GroundStation station,
+                                              final SpacecraftState state) {
+
+        // spacecraft position and elevation as seen from the ground station
+        final Vector3D position = state.getPVCoordinates().getPosition();
+        final double elevation  = station.getBaseFrame().getElevation(position,
+                                                                      state.getFrame(),
+                                                                      state.getDate());
+
+        // only consider measures above the horizon
+        if (elevation > 0) {
+            // tropospheric delay in meters
+            final double delay = tropoModel.pathDelay(elevation, station.getBaseFrame().getPoint(),
+                                                      tropoModel.getParameters(), state.getDate());
+
+            return delay;
+        }
+
+        return 0;
+    }
+
+
+    /** Compute the measurement error due to Troposphere.
+     * @param <T> type of the element
+     * @param station station
+     * @param state spacecraft state
+     * @param parameters tropospheric model parameters
+     * @return the measurement error due to Troposphere
+     */
+    public <T extends CalculusFieldElement<T>> T rangeErrorTroposphericModel(final GroundStation station,
+                                                                             final FieldSpacecraftState<T> state,
+                                                                             final T[] parameters) {
+        // Field
+        final Field<T> field = state.getDate().getField();
+        final T zero         = field.getZero();
+
+        // spacecraft position and elevation as seen from the ground station
+        final FieldVector3D<T> position = state.getPVCoordinates().getPosition();
+        final T elevation               = station.getBaseFrame().getElevation(position,
+                                                                              state.getFrame(),
+                                                                              state.getDate());
+
+        // only consider measures above the horizon
+        if (elevation .getReal() > 0) {
+            // tropospheric delay in meters
+            final T delay = tropoModel.pathDelay(elevation, station.getBaseFrame().getPoint(field),
+                                                 parameters, state.getDate());
+
+            return delay;
+        }
+
+        return zero;
+    }
+
+    /** Get the drivers for this modifier parameters.
+     * @return drivers for this modifier parameters
+     */
+    public List<ParameterDriver> getParametersDrivers() {
+        return tropoModel.getParametersDrivers();
+    }
+
+}

src/main/java/org/orekit/estimation/measurements/modifiers/BistaticRangeIonosphericDelayModifier.java

+/* Copyright 2002-2022 Mark Rutten
+ * Licensed to CS GROUP (CS) under one or more