/* Copyright 2002-2017 CS Systèmes d'Information
* Licensed to CS Systèmes d'Information (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
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package org.orekit.attitudes;
import org.hipparchus.geometry.euclidean.threed.Rotation;
import org.hipparchus.geometry.euclidean.threed.RotationConvention;
import org.hipparchus.geometry.euclidean.threed.Vector3D;
import org.hipparchus.util.FastMath;
import org.junit.After;
import org.junit.Assert;
import org.junit.Before;
import org.junit.Test;
import org.orekit.Utils;
import org.orekit.errors.OrekitException;
import org.orekit.frames.FramesFactory;
import org.orekit.orbits.KeplerianOrbit;
import org.orekit.orbits.Orbit;
import org.orekit.orbits.PositionAngle;
import org.orekit.propagation.Propagator;
import org.orekit.propagation.SpacecraftState;
import org.orekit.propagation.analytical.KeplerianPropagator;
import org.orekit.time.AbsoluteDate;
import org.orekit.time.DateComponents;
import org.orekit.time.TimeComponents;
import org.orekit.time.TimeScalesFactory;
public class InertialAttitudeTest {
private AbsoluteDate t0;
private Orbit orbit0;
@Test
public void testIsInertial() throws OrekitException {
InertialProvider law = new InertialProvider(new Rotation(new Vector3D(0.6, 0.48, 0.64), 0.9, RotationConvention.VECTOR_OPERATOR));
KeplerianPropagator propagator = new KeplerianPropagator(orbit0, law);
Attitude initial = propagator.propagate(t0).getAttitude();
for (double t = 0; t < 10000.0; t += 100) {
Attitude attitude = propagator.propagate(t0.shiftedBy(t)).getAttitude();
Rotation evolution = attitude.getRotation().compose(initial.getRotation().revert(),
RotationConvention.VECTOR_OPERATOR);
Assert.assertEquals(0, evolution.getAngle(), 1.0e-10);
Assert.assertEquals(FramesFactory.getEME2000(), attitude.getReferenceFrame());
}
}
@Test
public void testCompensateMomentum() throws OrekitException {
InertialProvider law = new InertialProvider(new Rotation(new Vector3D(-0.64, 0.6, 0.48), 0.2, RotationConvention.VECTOR_OPERATOR));
KeplerianPropagator propagator = new KeplerianPropagator(orbit0, law);
Attitude initial = propagator.propagate(t0).getAttitude();
for (double t = 0; t < 10000.0; t += 100) {
Attitude attitude = propagator.propagate(t0.shiftedBy(t)).getAttitude();
Rotation evolution = attitude.getRotation().compose(initial.getRotation().revert(),
RotationConvention.VECTOR_OPERATOR);
Assert.assertEquals(0, evolution.getAngle(), 1.0e-10);
Assert.assertEquals(FramesFactory.getEME2000(), attitude.getReferenceFrame());
}
}
@Test
public void testSpin() throws OrekitException {
AbsoluteDate date = new AbsoluteDate(new DateComponents(1970, 01, 01),
new TimeComponents(3, 25, 45.6789),
TimeScalesFactory.getUTC());
AttitudeProvider law = new InertialProvider(new Rotation(new Vector3D(-0.64, 0.6, 0.48), 0.2, RotationConvention.VECTOR_OPERATOR));
KeplerianOrbit orbit =
new KeplerianOrbit(7178000.0, 1.e-4, FastMath.toRadians(50.),
FastMath.toRadians(10.), FastMath.toRadians(20.),
FastMath.toRadians(30.), PositionAngle.MEAN,
FramesFactory.getEME2000(), date, 3.986004415e14);
Propagator propagator = new KeplerianPropagator(orbit, law);
double h = 100.0;
SpacecraftState sMinus = propagator.propagate(date.shiftedBy(-h));
SpacecraftState s0 = propagator.propagate(date);
SpacecraftState sPlus = propagator.propagate(date.shiftedBy(h));
// check spin is consistent with attitude evolution
double errorAngleMinus = Rotation.distance(sMinus.shiftedBy(h).getAttitude().getRotation(),
s0.getAttitude().getRotation());
double evolutionAngleMinus = Rotation.distance(sMinus.getAttitude().getRotation(),
s0.getAttitude().getRotation());
Assert.assertEquals(0.0, errorAngleMinus, 1.0e-6 * evolutionAngleMinus);
double errorAnglePlus = Rotation.distance(s0.getAttitude().getRotation(),
sPlus.shiftedBy(-h).getAttitude().getRotation());
double evolutionAnglePlus = Rotation.distance(s0.getAttitude().getRotation(),
sPlus.getAttitude().getRotation());
Assert.assertEquals(0.0, errorAnglePlus, 1.0e-6 * evolutionAnglePlus);
// compute spin axis using finite differences
Rotation rMinus = sMinus.getAttitude().getRotation();
Rotation rPlus = sPlus.getAttitude().getRotation();
Rotation dr = rPlus.compose(rMinus.revert(), RotationConvention.VECTOR_OPERATOR);
Assert.assertEquals(0, dr.getAngle(), 1.0e-10);
Vector3D spin0 = s0.getAttitude().getSpin();
Assert.assertEquals(0, spin0.getNorm(), 1.0e-10);
}
@Before
public void setUp() {
try {
Utils.setDataRoot("regular-data");
t0 = new AbsoluteDate(new DateComponents(2008, 06, 03), TimeComponents.H12,
TimeScalesFactory.getUTC());
orbit0 =
new KeplerianOrbit(12345678.9, 0.001, 2.3, 0.1, 3.04, 2.4,
PositionAngle.TRUE, FramesFactory.getEME2000(),
t0, 3.986004415e14);
} catch (OrekitException oe) {
Assert.fail(oe.getMessage());
}
}
@After
public void tearDown() {
t0 = null;
orbit0 = null;
}
}