RelativisticClockRangeRateModifier.java
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*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
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package org.orekit.estimation.measurements.modifiers;
import java.util.Collections;
import java.util.List;
import org.orekit.estimation.measurements.EstimatedMeasurement;
import org.orekit.estimation.measurements.EstimationModifier;
import org.orekit.estimation.measurements.RangeRate;
import org.orekit.propagation.SpacecraftState;
import org.orekit.utils.Constants;
import org.orekit.utils.ParameterDriver;
/** Class modifying theoretical range-rate measurement with relativistic frequency deviation.
* <p>
* Relativistic clock correction is caused by the motion of the satellite as well as
* the change in the gravitational potential
* </p>
* @author Bryan Cazabonne
* @since 10.3
*
* @see "Teunissen, Peter, and Oliver Montenbruck, eds. Springer handbook of global navigation
* satellite systems. Chapter 19.2. Springer, 2017."
*/
public class RelativisticClockRangeRateModifier extends AbstractRelativisticClockModifier implements EstimationModifier<RangeRate> {
/** Gravitational constant. */
private final double gm;
/** Simple constructor.
* @param gm gravitational constant for main body in signal path vicinity.
*/
public RelativisticClockRangeRateModifier(final double gm) {
super();
this.gm = gm;
}
/** {@inheritDoc} */
@Override
public List<ParameterDriver> getParametersDrivers() {
return Collections.emptyList();
}
/** {@inheritDoc} */
@Override
public void modify(final EstimatedMeasurement<RangeRate> estimated) {
// Spacecraft state
final SpacecraftState state = estimated.getStates()[0];
// Relativistic frequency deviation
final double factor = -gm * getScaleFactor();
final double dfRel = factor *
(reciprocal(state.getA()) - reciprocal(state.getPVCoordinates().getPosition().getNorm()));
// Update estimated value taking into account the relativistic effect.
final double[] newValue = estimated.getEstimatedValue().clone();
newValue[0] = newValue[0] + dfRel * Constants.SPEED_OF_LIGHT;
estimated.setEstimatedValue(newValue);
}
/** Returns the inverse of the given value.
* @param value value to inverse
* @return the inverse of the value
*/
private static double reciprocal(final double value) {
return 1.0 / value;
}
}