Java tutorial
/* 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.Assert; import org.junit.Before; import org.junit.Test; import org.orekit.Utils; import org.orekit.errors.OrekitException; import org.orekit.frames.Frame; 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; import org.orekit.utils.AngularCoordinates; import org.orekit.utils.PVCoordinates; public class FixedRateTest { @Test public void testZeroRate() throws OrekitException { AbsoluteDate date = new AbsoluteDate(new DateComponents(2004, 3, 2), new TimeComponents(13, 17, 7.865), TimeScalesFactory.getUTC()); final Frame frame = FramesFactory.getEME2000(); FixedRate law = new FixedRate(new Attitude(date, frame, new Rotation(0.48, 0.64, 0.36, 0.48, false), Vector3D.ZERO, Vector3D.ZERO)); PVCoordinates pv = new PVCoordinates(new Vector3D(28812595.32012577, 5948437.4640250085, 0), new Vector3D(0, 0, 3680.853673522056)); Orbit orbit = new KeplerianOrbit(pv, frame, date, 3.986004415e14); Rotation attitude0 = law.getAttitude(orbit, date, frame).getRotation(); Assert.assertEquals(0, Rotation.distance(attitude0, law.getReferenceAttitude().getRotation()), 1.0e-10); Rotation attitude1 = law.getAttitude(orbit.shiftedBy(10.0), date.shiftedBy(10.0), frame).getRotation(); Assert.assertEquals(0, Rotation.distance(attitude1, law.getReferenceAttitude().getRotation()), 1.0e-10); Rotation attitude2 = law.getAttitude(orbit.shiftedBy(20.0), date.shiftedBy(20.0), frame).getRotation(); Assert.assertEquals(0, Rotation.distance(attitude2, law.getReferenceAttitude().getRotation()), 1.0e-10); } @Test public void testNonZeroRate() throws OrekitException { final AbsoluteDate date = new AbsoluteDate(new DateComponents(2004, 3, 2), new TimeComponents(13, 17, 7.865), TimeScalesFactory.getUTC()); final double rate = 2 * FastMath.PI / (12 * 60); final Frame frame = FramesFactory.getEME2000(); FixedRate law = new FixedRate(new Attitude(date, frame, new Rotation(0.48, 0.64, 0.36, 0.48, false), new Vector3D(rate, Vector3D.PLUS_K), Vector3D.ZERO)); PVCoordinates pv = new PVCoordinates(new Vector3D(28812595.32012577, 5948437.4640250085, 0), new Vector3D(0, 0, 3680.853673522056)); Orbit orbit = new KeplerianOrbit(pv, FramesFactory.getEME2000(), date, 3.986004415e14); Rotation attitude0 = law.getAttitude(orbit, date, frame).getRotation(); Assert.assertEquals(0, Rotation.distance(attitude0, law.getReferenceAttitude().getRotation()), 1.0e-10); Rotation attitude1 = law.getAttitude(orbit.shiftedBy(10.0), date.shiftedBy(10.0), frame).getRotation(); Assert.assertEquals(10 * rate, Rotation.distance(attitude1, law.getReferenceAttitude().getRotation()), 1.0e-10); Rotation attitude2 = law.getAttitude(orbit.shiftedBy(-20.0), date.shiftedBy(-20.0), frame).getRotation(); Assert.assertEquals(20 * rate, Rotation.distance(attitude2, law.getReferenceAttitude().getRotation()), 1.0e-10); Assert.assertEquals(30 * rate, Rotation.distance(attitude2, attitude1), 1.0e-10); Rotation attitude3 = law.getAttitude(orbit.shiftedBy(0.0), date, frame).getRotation(); Assert.assertEquals(0, Rotation.distance(attitude3, law.getReferenceAttitude().getRotation()), 1.0e-10); } @Test public void testSpin() throws OrekitException { AbsoluteDate date = new AbsoluteDate(new DateComponents(1970, 01, 01), new TimeComponents(3, 25, 45.6789), TimeScalesFactory.getUTC()); final double rate = 2 * FastMath.PI / (12 * 60); AttitudeProvider law = new FixedRate(new Attitude(date, FramesFactory.getEME2000(), new Rotation(0.48, 0.64, 0.36, 0.48, false), new Vector3D(rate, Vector3D.PLUS_K), Vector3D.ZERO)); 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 = 0.01; 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); Vector3D spin0 = s0.getAttitude().getSpin(); Vector3D reference = AngularCoordinates.estimateRate(sMinus.getAttitude().getRotation(), sPlus.getAttitude().getRotation(), 2 * h); Assert.assertEquals(0.0, spin0.subtract(reference).getNorm(), 1.0e-14); } @Before public void setUp() { Utils.setDataRoot("regular-data"); } }