PolynomialAccelerationModel.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.forces.empirical;
- import java.util.ArrayList;
- import java.util.Collections;
- import java.util.List;
- import org.hipparchus.CalculusFieldElement;
- import org.hipparchus.util.FastMath;
- import org.orekit.propagation.FieldSpacecraftState;
- import org.orekit.propagation.SpacecraftState;
- import org.orekit.time.AbsoluteDate;
- import org.orekit.utils.ParameterDriver;
- /** Polynomial acceleration model.
- * @since 10.3
- * @author Luc Maisonobe
- * @author Bryan Cazabonne
- */
- public class PolynomialAccelerationModel implements AccelerationModel {
- /** Acceleration scaling factor.
- * <p>
- * 2⁻²⁰ is the order of magnitude of third body perturbing acceleration.
- * </p>
- * <p>
- * We use a power of 2 to avoid numeric noise introduction
- * in the multiplications/divisions sequences.
- * </p>
- */
- private static final double ACCELERATION_SCALE = FastMath.scalb(1.0, -20);
- /** Drivers for the polynomial coefficients. */
- private final List<ParameterDriver> drivers;
- /** Reference date for computing polynomials. */
- private AbsoluteDate referenceDate;
- /** Simple constructor.
- * @param prefix prefix to use for parameter drivers
- * @param referenceDate reference date for computing polynomials, if null
- * the reference date will be automatically set at propagation start
- * @param degree polynomial degree (i.e. a value of 0 corresponds to a constant acceleration)
- */
- public PolynomialAccelerationModel(final String prefix,
- final AbsoluteDate referenceDate,
- final int degree) {
- // Reference date
- this.referenceDate = referenceDate;
- // Parameter drivers
- drivers = new ArrayList<>();
- for (int i = 0; i < degree + 1; ++i) {
- drivers.add(new ParameterDriver(prefix + "[" + i + "]", 0.0, ACCELERATION_SCALE,
- Double.NEGATIVE_INFINITY, Double.POSITIVE_INFINITY));
- }
- }
- /** {@inheritDoc} */
- @Override
- public void init(final SpacecraftState initialState, final AbsoluteDate target) {
- if (referenceDate == null) {
- referenceDate = initialState.getDate();
- }
- }
- /** {@inheritDoc} */
- @Override
- public double signedAmplitude(final SpacecraftState state,
- final double[] parameters) {
- final double dt = state.getDate().durationFrom(referenceDate);
- double amplitude = 0;
- for (int i = parameters.length - 1; i >= 0; --i) {
- amplitude += amplitude * dt + parameters[i];
- }
- return amplitude;
- }
- /** {@inheritDoc} */
- @Override
- public <T extends CalculusFieldElement<T>> T signedAmplitude(final FieldSpacecraftState<T> state,
- final T[] parameters) {
- final T dt = state.getDate().durationFrom(referenceDate);
- T amplitude = dt.getField().getZero();
- for (int i = parameters.length - 1; i >= 0; --i) {
- amplitude = amplitude.add(amplitude.multiply(dt).add(parameters[i]));
- }
- return amplitude;
- }
- /** {@inheritDoc} */
- @Override
- public List<ParameterDriver> getParametersDrivers() {
- return Collections.unmodifiableList(drivers);
- }
- }