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.RotationOrder; 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.bodies.OneAxisEllipsoid; import org.orekit.errors.OrekitException; import org.orekit.errors.OrekitMessages; import org.orekit.frames.Frame; import org.orekit.frames.FramesFactory; import org.orekit.frames.LOFType; import org.orekit.orbits.CircularOrbit; import org.orekit.orbits.KeplerianOrbit; 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.IERSConventions; public class LofOffsetPointingTest { // Computation date private AbsoluteDate date; // Body mu private double mu; // Reference frame = ITRF 2005C private Frame frameItrf; // Earth shape OneAxisEllipsoid earthSpheric; /** Test if both constructors are equivalent */ @Test public void testLof() throws OrekitException { // Satellite position final CircularOrbit circ = new CircularOrbit(7178000.0, 0.5e-4, -0.5e-4, FastMath.toRadians(0.), FastMath.toRadians(270.), FastMath.toRadians(5.300), PositionAngle.MEAN, FramesFactory.getEME2000(), date, mu); // Create lof aligned law //************************ final LofOffset lofLaw = new LofOffset(circ.getFrame(), LOFType.VVLH); final LofOffsetPointing lofPointing = new LofOffsetPointing(circ.getFrame(), earthSpheric, lofLaw, Vector3D.PLUS_K); final Rotation lofRot = lofPointing.getAttitude(circ, date, circ.getFrame()).getRotation(); // Compare to body center pointing law //************************************* final BodyCenterPointing centerLaw = new BodyCenterPointing(circ.getFrame(), earthSpheric); final Rotation centerRot = centerLaw.getAttitude(circ, date, circ.getFrame()).getRotation(); final double angleBodyCenter = centerRot.applyInverseTo(lofRot).getAngle(); Assert.assertEquals(0., angleBodyCenter, Utils.epsilonAngle); // Compare to nadir pointing law //******************************* final NadirPointing nadirLaw = new NadirPointing(circ.getFrame(), earthSpheric); final Rotation nadirRot = nadirLaw.getAttitude(circ, date, circ.getFrame()).getRotation(); final double angleNadir = nadirRot.applyInverseTo(lofRot).getAngle(); Assert.assertEquals(0., angleNadir, Utils.epsilonAngle); } @Test public void testMiss() throws OrekitException { final CircularOrbit circ = new CircularOrbit(7178000.0, 0.5e-4, -0.5e-4, FastMath.toRadians(0.), FastMath.toRadians(270.), FastMath.toRadians(5.300), PositionAngle.MEAN, FramesFactory.getEME2000(), date, mu); final LofOffset upsideDown = new LofOffset(circ.getFrame(), LOFType.VVLH, RotationOrder.XYX, FastMath.PI, 0, 0); final LofOffsetPointing pointing = new LofOffsetPointing(circ.getFrame(), earthSpheric, upsideDown, Vector3D.PLUS_K); try { pointing.getTargetPV(circ, date, circ.getFrame()); Assert.fail("an exception should have been thrown"); } catch (OrekitException oe) { Assert.assertEquals(OrekitMessages.ATTITUDE_POINTING_LAW_DOES_NOT_POINT_TO_GROUND, oe.getSpecifier()); } } @Test public void testSpin() throws OrekitException { AbsoluteDate date = new AbsoluteDate(new DateComponents(1970, 01, 01), new TimeComponents(3, 25, 45.6789), TimeScalesFactory.getUTC()); 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); final AttitudeProvider law = new LofOffsetPointing(orbit.getFrame(), earthSpheric, new LofOffset(orbit.getFrame(), LOFType.VVLH, RotationOrder.XYX, 0.1, 0.2, 0.3), Vector3D.PLUS_K); 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.assertTrue(spin0.getNorm() > 1.0e-3); Assert.assertEquals(0.0, spin0.subtract(reference).getNorm(), 1.0e-10); } @Before public void setUp() { try { Utils.setDataRoot("regular-data"); // Computation date date = new AbsoluteDate(new DateComponents(2008, 04, 07), TimeComponents.H00, TimeScalesFactory.getUTC()); // Body mu mu = 3.9860047e14; // Reference frame = ITRF frameItrf = FramesFactory.getITRF(IERSConventions.IERS_2010, true); // Elliptic earth shape earthSpheric = new OneAxisEllipsoid(6378136.460, 0., frameItrf); } catch (OrekitException oe) { Assert.fail(oe.getMessage()); } } @After public void tearDown() { date = null; frameItrf = null; earthSpheric = null; } }