BaseRangeRateTroposphericDelayModifier.java
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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.TroposphericModel;
import org.orekit.propagation.FieldSpacecraftState;
import org.orekit.propagation.SpacecraftState;
import org.orekit.utils.FieldTrackingCoordinates;
import org.orekit.utils.ParameterDriver;
import org.orekit.utils.TrackingCoordinates;
/** Baselass modifying theoretical range-rate measurements with tropospheric delay.
* The effect of tropospheric correction on the range-rate is directly computed
* through the computation of the tropospheric delay difference with respect to
* time.
*
* 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 BaseRangeRateTroposphericDelayModifier {
/** Tropospheric delay model. */
private final TroposphericModel tropoModel;
/** Constructor.
*
* @param model Tropospheric delay model appropriate for the current range-rate measurement method.
* @since 12.1
*/
protected BaseRangeRateTroposphericDelayModifier(final TroposphericModel model) {
tropoModel = model;
}
/** Get the name of the effect modifying the measurement.
* @return name of the effect modifying the measurement
* @since 13.0
*/
public String getEffectName() {
return "troposphere";
}
/** Get the tropospheric delay model.
* @return tropospheric delay model
*/
protected TroposphericModel 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 rangeRateErrorTroposphericModel(final GroundStation station,
final SpacecraftState state) {
// The effect of tropospheric correction on the range rate is
// computed using finite differences.
final double dt = 10; // s
// spacecraft position and elevation as seen from the ground station
final Vector3D position = state.getPosition();
// tracking
final TrackingCoordinates trackingCoordinates1 =
station.getBaseFrame().getTrackingCoordinates(position, state.getFrame(), state.getDate());
// only consider measures above the horizon
if (trackingCoordinates1.getElevation() > 0) {
// tropospheric delay in meters
final double d1 = tropoModel.pathDelay(trackingCoordinates1,
station.getOffsetGeodeticPoint(state.getDate()),
station.getPressureTemperatureHumidity(state.getDate()),
tropoModel.getParameters(state.getDate()), state.getDate()).
getDelay();
// propagate spacecraft state forward by dt
final SpacecraftState state2 = state.shiftedBy(dt);
// spacecraft position and elevation as seen from the ground station
final Vector3D position2 = state2.getPosition();
// tracking
final TrackingCoordinates trackingCoordinates2 =
station.getBaseFrame().getTrackingCoordinates(position2, state2.getFrame(), state2.getDate());
// tropospheric delay dt after
final double d2 = tropoModel.pathDelay(trackingCoordinates2,
station.getOffsetGeodeticPoint(state.getDate()),
station.getPressureTemperatureHumidity(state.getDate()),
tropoModel.getParameters(state2.getDate()), state2.getDate()).
getDelay();
return (d2 - d1) / dt;
}
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 rangeRateErrorTroposphericModel(final GroundStation station,
final FieldSpacecraftState<T> state,
final T[] parameters) {
// Field
final Field<T> field = state.getDate().getField();
final T zero = field.getZero();
// The effect of tropospheric correction on the range rate is
// computed using finite differences.
final double dt = 10; // s
// spacecraft position and elevation as seen from the ground station
final FieldVector3D<T> position = state.getPosition();
final FieldTrackingCoordinates<T> trackingCoordinates1 =
station.getBaseFrame().getTrackingCoordinates(position, state.getFrame(), state.getDate());
// only consider measures above the horizon
if (trackingCoordinates1.getElevation().getReal() > 0) {
// tropospheric delay in meters
final T d1 = tropoModel.pathDelay(trackingCoordinates1,
station.getOffsetGeodeticPoint(state.getDate()),
station.getPressureTemperatureHumidity(state.getDate()),
parameters, state.getDate()).
getDelay();
// propagate spacecraft state forward by dt
final FieldSpacecraftState<T> state2 = state.shiftedBy(dt);
// spacecraft position and elevation as seen from the ground station
final FieldVector3D<T> position2 = state2.getPosition();
// elevation
final FieldTrackingCoordinates<T> trackingCoordinates2 =
station.getBaseFrame().getTrackingCoordinates(position2, state2.getFrame(), state2.getDate());
// tropospheric delay dt after
final T d2 = tropoModel.pathDelay(trackingCoordinates2,
station.getOffsetGeodeticPoint(state.getDate()),
station.getPressureTemperatureHumidity(state.getDate()),
parameters, state2.getDate()).
getDelay();
return d2.subtract(d1).divide(dt);
}
return zero;
}
/** Get the drivers for this modifier parameters.
* @return drivers for this modifier parameters
*/
public List<ParameterDriver> getParametersDrivers() {
return tropoModel.getParametersDrivers();
}
}