AbstractShapiroBaseModifier.java
- /* Copyright 2002-2020 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 org.hipparchus.geometry.euclidean.threed.Vector3D;
- import org.hipparchus.util.FastMath;
- import org.orekit.estimation.measurements.EstimatedMeasurement;
- import org.orekit.utils.Constants;
- import org.orekit.utils.TimeStampedPVCoordinates;
- /** Class modifying theoretical range measurement with Shapiro time delay.
- * <p>
- * Shapiro time delay is a relativistic effect due to gravity.
- * </p>
- *
- * @author Luc Maisonobe
- * @since 10.0
- */
- public class AbstractShapiroBaseModifier {
- /** Shapiro effect scale factor. */
- private final double s;
- /** Simple constructor.
- * @param gm gravitational constant for main body in signal path vicinity.
- */
- public AbstractShapiroBaseModifier(final double gm) {
- this.s = 2 * gm / (Constants.SPEED_OF_LIGHT * Constants.SPEED_OF_LIGHT);
- }
- /** Modify measurement.
- * @param estimated measurement to modify
- */
- protected void doModify(final EstimatedMeasurement<?> estimated) {
- // compute correction, for one way or two way measurements
- final TimeStampedPVCoordinates[] pv = estimated.getParticipants();
- final double correction = pv.length < 3 ?
- shapiroCorrection(pv[0], pv[1]) :
- 0.5 * (shapiroCorrection(pv[0], pv[1]) + shapiroCorrection(pv[1], pv[2]));
- // update estimated value taking into account the Shapiro time delay.
- final double[] newValue = estimated.getEstimatedValue().clone();
- newValue[0] = newValue[0] + correction;
- estimated.setEstimatedValue(newValue);
- }
- /** Compute Shapiro path dilation between two points in a gravity field.
- * @param pvEmitter coordinates of emitter in body-centered frame
- * @param pvReceiver coordinates of receiver in body-centered frame
- * @return path dilation to add to raw measurement
- */
- protected double shapiroCorrection(final TimeStampedPVCoordinates pvEmitter, final TimeStampedPVCoordinates pvReceiver) {
- final Vector3D pEmitter = pvEmitter.getPosition();
- final Vector3D pReceiver = pvReceiver.getPosition();
- final double rEpR = pEmitter.getNorm() + pReceiver.getNorm();
- final double d = Vector3D.distance(pEmitter, pReceiver);
- return s * FastMath.log((rEpR + d) / (rEpR - d));
- }
- }