org.orekit.attitudes.InertialAttitudeTest.java Source code

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Here is the source code for org.orekit.attitudes.InertialAttitudeTest.java

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/* Copyright 2002-2015 CS Systmes d'Information
 * Licensed to CS Systmes 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
 * limitations under the License.
 */
package org.orekit.attitudes;

import org.apache.commons.math3.geometry.euclidean.threed.Rotation;
import org.apache.commons.math3.geometry.euclidean.threed.Vector3D;
import org.apache.commons.math3.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));
        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().applyTo(initial.getRotation().revert());
            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));
        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().applyTo(initial.getRotation().revert());
            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));

        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.applyTo(rMinus.revert());
        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;
    }

}