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17 package org.orekit.estimation.measurements.generation;
18
19 import java.util.SortedSet;
20
21 import org.hipparchus.linear.MatrixUtils;
22 import org.hipparchus.linear.RealMatrix;
23 import org.hipparchus.random.CorrelatedRandomVectorGenerator;
24 import org.hipparchus.random.GaussianRandomGenerator;
25 import org.hipparchus.random.RandomGenerator;
26 import org.hipparchus.random.Well19937a;
27 import org.hipparchus.util.FastMath;
28 import org.junit.Assert;
29 import org.junit.Before;
30 import org.junit.Test;
31 import org.orekit.estimation.Context;
32 import org.orekit.estimation.EstimationTestUtils;
33 import org.orekit.estimation.Force;
34 import org.orekit.estimation.measurements.InterSatellitesRange;
35 import org.orekit.estimation.measurements.ObservableSatellite;
36 import org.orekit.estimation.measurements.ObservedMeasurement;
37 import org.orekit.estimation.measurements.modifiers.Bias;
38 import org.orekit.orbits.KeplerianOrbit;
39 import org.orekit.orbits.Orbit;
40 import org.orekit.orbits.OrbitType;
41 import org.orekit.orbits.PositionAngle;
42 import org.orekit.propagation.Propagator;
43 import org.orekit.propagation.SpacecraftState;
44 import org.orekit.propagation.analytical.KeplerianPropagator;
45 import org.orekit.propagation.conversion.NumericalPropagatorBuilder;
46 import org.orekit.propagation.events.InterSatDirectViewDetector;
47 import org.orekit.time.AbsoluteDate;
48 import org.orekit.time.FixedStepSelector;
49 import org.orekit.time.TimeScalesFactory;
50 import org.orekit.utils.PVCoordinates;
51
52 public class InterSatellitesRangeBuilderTest {
53
54 private static final double SIGMA = 0.5;
55 private static final double BIAS = -0.01;
56
57 private MeasurementBuilder<InterSatellitesRange> getBuilder(final RandomGenerator random,
58 final ObservableSatellite receiver,
59 final ObservableSatellite remote) {
60 final RealMatrix covariance = MatrixUtils.createRealDiagonalMatrix(new double[] { SIGMA * SIGMA });
61 MeasurementBuilder<InterSatellitesRange> isrb =
62 new InterSatellitesRangeBuilder(random == null ? null : new CorrelatedRandomVectorGenerator(covariance,
63 1.0e-10,
64 new GaussianRandomGenerator(random)),
65 receiver, remote, true, SIGMA, 1.0);
66 isrb.addModifier(new Bias<>(new String[] { "bias" },
67 new double[] { BIAS },
68 new double[] { 1.0 },
69 new double[] { Double.NEGATIVE_INFINITY },
70 new double[] { Double.POSITIVE_INFINITY }));
71 return isrb;
72 }
73
74 @Test
75 public void testForward() {
76 doTest(0xc82a56322345dc25l, 0.0, 1.2, 2.8 * SIGMA);
77 }
78
79 @Test
80 public void testBackward() {
81 doTest(0x95c10149c4891232l, 0.0, -1.0, 2.6 * SIGMA);
82 }
83
84 private Propagator buildPropagator() {
85 return EstimationTestUtils.createPropagator(context.initialOrbit, propagatorBuilder);
86 }
87
88 private void doTest(long seed, double startPeriod, double endPeriod, double tolerance) {
89 Generator generator = new Generator();
90 generator.addPropagator(buildPropagator());
91 generator.addPropagator(buildPropagator());
92 ObservableSatellite receiver = generator.addPropagator(buildPropagator());
93 generator.addPropagator(buildPropagator());
94 final Orbit o1 = context.initialOrbit;
95
96 final Orbit o2 = new KeplerianOrbit(new PVCoordinates(o1.getPVCoordinates().getPosition(),
97 o1.getPVCoordinates().getVelocity().negate()),
98 o1.getFrame(), o1.getDate(), o1.getMu());
99 ObservableSatellite remote = generator.addPropagator(new KeplerianPropagator(o2));
100 final double step = 60.0;
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107 generator.addScheduler(new EventBasedScheduler<>(getBuilder(new Well19937a(seed), receiver, remote),
108 new FixedStepSelector(step, TimeScalesFactory.getUTC()),
109 generator.getPropagator(receiver),
110 new InterSatDirectViewDetector(context.earth, new KeplerianPropagator(o2)),
111 SignSemantic.FEASIBLE_MEASUREMENT_WHEN_POSITIVE));
112
113 final double period = o1.getKeplerianPeriod();
114 AbsoluteDate t0 = o1.getDate().shiftedBy(startPeriod * period);
115 AbsoluteDate t1 = o1.getDate().shiftedBy(endPeriod * period);
116 SortedSet<ObservedMeasurement<?>> measurements = generator.generate(t0, t1);
117
118
119 Propagator propagator1 = buildPropagator();
120 Propagator propagator2 = new KeplerianPropagator(o2);
121
122 double maxError = 0;
123 AbsoluteDate previous = null;
124 AbsoluteDate tInf = t0.compareTo(t1) < 0 ? t0 : t1;
125 AbsoluteDate tSup = t0.compareTo(t1) < 0 ? t1 : t0;
126 for (ObservedMeasurement<?> measurement : measurements) {
127 AbsoluteDate date = measurement.getDate();
128 double[] m = measurement.getObservedValue();
129 Assert.assertTrue(date.compareTo(tInf) >= 0);
130 Assert.assertTrue(date.compareTo(tSup) <= 0);
131 if (previous != null) {
132
133
134
135 Assert.assertTrue(date.durationFrom(previous) >= 0.999999 * step);
136 }
137 previous = date;
138 double[] e = measurement.estimate(0, 0,
139 new SpacecraftState[] {
140 propagator1.propagate(date),
141 propagator2.propagate(date)
142 }).getEstimatedValue();
143 for (int i = 0; i < m.length; ++i) {
144 maxError = FastMath.max(maxError, FastMath.abs(e[i] - m[i]));
145 }
146 }
147 Assert.assertEquals(0.0, maxError, tolerance);
148 }
149
150 @Before
151 public void setUp() {
152 context = EstimationTestUtils.eccentricContext("regular-data:potential:tides");
153
154 propagatorBuilder = context.createBuilder(OrbitType.KEPLERIAN, PositionAngle.TRUE, true,
155 1.0e-6, 300.0, 0.001, Force.POTENTIAL,
156 Force.THIRD_BODY_SUN, Force.THIRD_BODY_MOON);
157 }
158
159 Context context;
160 NumericalPropagatorBuilder propagatorBuilder;
161
162 }