EphemerisSegmentPropagator.java
/* Contributed in the public domain.
* 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.files.general;
import java.util.List;
import java.util.stream.Stream;
import org.orekit.attitudes.InertialProvider;
import org.orekit.errors.OrekitException;
import org.orekit.errors.OrekitMessages;
import org.orekit.files.general.EphemerisFile.EphemerisSegment;
import org.orekit.frames.Frame;
import org.orekit.orbits.CartesianOrbit;
import org.orekit.orbits.Orbit;
import org.orekit.propagation.BoundedPropagator;
import org.orekit.propagation.Propagator;
import org.orekit.propagation.SpacecraftState;
import org.orekit.propagation.analytical.AbstractAnalyticalPropagator;
import org.orekit.time.AbsoluteDate;
import org.orekit.utils.ImmutableTimeStampedCache;
import org.orekit.utils.TimeStampedPVCoordinates;
/**
* A {@link Propagator} based on a {@link EphemerisSegment}.
*
* <p> The {@link #getPVCoordinates(AbsoluteDate, Frame)} is implemented without using the
* {@link #propagate(AbsoluteDate)} methods so using this class as a {@link
* org.orekit.utils.PVCoordinatesProvider} still behaves as expected when the ephemeris
* file did not have a valid gravitational parameter.
* @param <C> type of the Cartesian coordinates
*
* @author Evan Ward
*/
class EphemerisSegmentPropagator<C extends TimeStampedPVCoordinates> extends AbstractAnalyticalPropagator
implements BoundedPropagator {
/**
* Sorted cache of state vectors. A duplication of the information in {@link
* #ephemeris} that could be avoided by duplicating the logic of {@link
* ImmutableTimeStampedCache#getNeighbors(AbsoluteDate)} for a general {@link List}.
*/
private final ImmutableTimeStampedCache<C> cache;
/** Tabular data from which this propagator is built. */
private final EphemerisSegment<C> ephemeris;
/** Inertial frame used for creating orbits. */
private final Frame inertialFrame;
/** Frame of the ephemeris data. */
private final Frame ephemerisFrame;
/**
* Create a {@link Propagator} from an ephemeris segment.
*
* @param ephemeris segment containing the data for this propagator.
*/
EphemerisSegmentPropagator(final EphemerisSegment<C> ephemeris) {
super(new InertialProvider(ephemeris.getInertialFrame()));
this.cache = new ImmutableTimeStampedCache<>(
ephemeris.getInterpolationSamples(),
ephemeris.getCoordinates());
this.ephemeris = ephemeris;
this.ephemerisFrame = ephemeris.getFrame();
this.inertialFrame = ephemeris.getInertialFrame();
// set the initial state so getFrame() works
final TimeStampedPVCoordinates ic = cache.getEarliest();
final TimeStampedPVCoordinates icInertial = ephemerisFrame
.getTransformTo(inertialFrame, ic.getDate())
.transformPVCoordinates(ic);
super.resetInitialState(
new SpacecraftState(
new CartesianOrbit(
icInertial, inertialFrame, ephemeris.getMu()
),
getAttitudeProvider().getAttitude(
icInertial.toTaylorProvider(inertialFrame),
ic.getDate(),
inertialFrame),
DEFAULT_MASS
)
);
}
@Override
public TimeStampedPVCoordinates getPVCoordinates(final AbsoluteDate date, final Frame frame) {
final Stream<C> neighbors = this.cache.getNeighbors(date);
final TimeStampedPVCoordinates point =
TimeStampedPVCoordinates.interpolate(date, ephemeris.getAvailableDerivatives(), neighbors);
return ephemerisFrame.getTransformTo(frame, date).transformPVCoordinates(point);
}
@Override
protected Orbit propagateOrbit(final AbsoluteDate date) {
final TimeStampedPVCoordinates pv = this.getPVCoordinates(date, inertialFrame);
return new CartesianOrbit(pv, inertialFrame, this.ephemeris.getMu());
}
@Override
public AbsoluteDate getMinDate() {
return ephemeris.getStart();
}
@Override
public AbsoluteDate getMaxDate() {
return ephemeris.getStop();
}
@Override
protected double getMass(final AbsoluteDate date) {
return DEFAULT_MASS;
}
@Override
public SpacecraftState getInitialState() {
return this.basicPropagate(this.getMinDate());
}
@Override
protected void resetIntermediateState(final SpacecraftState state,
final boolean forward) {
throw new OrekitException(OrekitMessages.NON_RESETABLE_STATE);
}
@Override
public void resetInitialState(final SpacecraftState state) {
throw new OrekitException(OrekitMessages.NON_RESETABLE_STATE);
}
}